Radio-Television-Electronic Dictionary

Radio-Television-Electronic Dictionary
Radio -Television -Electronic
IX -2
You will find this Radio and Electronic Dictionary
a valuable reference text. Keep it handy. As you
advance in your Course and come across a term that
you know was explained in an earlier book but whose
meaning has begun to fade, just look it up. In reading
magazine or other radio articles or in discussions when
you find new, strange expressions, look them up, too.
Do not be concerned, as you glance through this reference book for the first time, if you find many new
and strange words and expressions. Later on, they will
have greater meaning. Do not try to memorize the
definitions given, nor try to read this book as a regular
text. This would lead only to confusion.
Remember, a technical dictionary is not an encyclopedia, so don't look for complete explanations which
belong in the Course itself. Nor will you expect to find
definitions of non -technical words for which you should
turn to an ordinary dictionary.
Properly used, your Radio Dictionary will save you
time and prove its value many times over.
The N.
R. I.
Printed in U.
Course prepares you to become
(Registered U. S. Patent Office)
(Registered U. S. Potent Office)
Radio -Television -Electronic Dictionary
erence line along which abscissa values
are indicated on a graph.
absolute value-The numerical value of a
number without regard for sign. Thus,
the absolute values of +9 and -9 are
both 9. In algebraic expressions, vertical
lines on each side of a quantity are used
to specify that the absolute value is to
be used. Example The absolute value
of is specified as IA .
absolute units-Units of measurement derived from the centimeter -gram -second
(C.G.S.) system of specifying length,
mass and time. Seldom used in radio.
absorption-Dissipation or loss of electromagnetic energy (radio waves) or acoustic energy (sound waves) in the medium
through which the energy travels, or dissipation of electrical energy in one circuit which is inductively coupled to another. Thus, radio waves lose energy and
hence strength in traveling through the
atmosphere, the earth or through objects.
Sound waves lose energy due to absorption when traveling through the atmosphere, the earth and particularly through
non -rigid materials like rugs :1 nd drapes.
A-Notation used to identify the filament
circuit or filament voltage supply of a
vacuum tube. Abbreviation for antenna,
ammeter, ampere or area.
A- -Notation used to designate the nega-
tive filament supply terminal of a vacuum
tube circuit or the negative terminal of an
A battery or other filament voltage source.
Pronounced "A minus."
A+-Notation used to designate the positive
filament supply terminal of a vacuum tube
or the positive terminal of an A battery
or other filament voltage source. Pronounced "A plus."
abampere-The unit of current flow in the
absolute system of electromagnetic units
(e.m.u.). One abampere is equal to 10
A battery-The single dry cell, combination
of dry cells or storage battery which furnishes filament current for the tubes in a
battery -operated vacuum tube circuit.
A.B.C., a.b.c. or ABC-Automatic bass compensation.
abcoulomb-The unit of quantity of electricity in the absolute system of electromagnetic units (e.m.u.) . One abcoulomb is
equal to 10 coulombs.
aberration-A lens defect in which the light
rays coming from a single point are not
brought to the same focal point. See
chromatic aberration and spherical aber-
abfarad-The unit of capacity in the absolute system of electromagnetic units
(e.m.u.). One abfarad is equal to 10"
abohm-The unit of resistance in the absolute system of electromagnetic units
( e.m.u.)
One abohm is equal to 10-9
absorption coefficient-A measure of the
ability of a material to absorb sound.
absorption modulation-Modulation effected
by absorption of signal power from the
antenna or r.f. system of a transmitter
AB power
abvolt-The unit of potential in the absolute
by a closely coupled a.f. system.
pack-A combination of batteries
or devices in a single housing, used to
supply A and B voltages for receivers, especially portable sets.
abrasive-The grinding material sometimes
incorporated in phonograph recorda for
the purpose of shaping the needle point
to fit the groove properly.
abscissa-The coordinate value which specifies distance in a horizontal direction
from the vertical reference line on an
ordinary graph. Also, the horizontal ref" 10-" is
the shorthand method of writing
system of electromagnetic units (e.m.u.).
One abvolt is equal to 10-8 volt.*
a.c., A.C. or AC-Alternating current.
accelerating anode-In a Farnsworth dissector tube, the electrode which draws
electrons away from the photosensitive
accelerating electrode-A cathode ray tube
electrode operated at a high positive potential and serving to increase the velocity of the electrons in the beam.
" 10-9 is the shorthand method of writing .00000001.
acceleration-The rate of increase of ve-
acoustic feedback-Transfer of sound waves
from a loudspeaker to any previous part,
such as a microphone, in the same amplifying or broadcasting system. It can
cause howling and overloading of tubes.
Acoustimator-Trade name for a special
tone control circuit used in some Motorola
a.c. plate resistance-The opposition offered
by the plate -cathode path of a tube to the
flow of alternating current. The a.c. plate
resistance is equal to the change in plate
voltage divided by the resulting change
in plate current, or is equal to the a.c.
plate voltage divided by the a.c. plate
a.c. receiver-A receiver designed to operate
only from an a.c. power source.
acute angle-An angle that is less than a
right angle (less than 90°).
adapter-Any device used for changing
temporarily or permanently the terminal
connections of a circuit or part, for test
purposes or to permit use of auxiliary apparatus.
addition-The process of finding the numerical sum of two or more quantities or
adjacent -channel selectivity-The ability of
a receiver to reject the signals of stations
on either side of the channel carrying
the desired station signal.
adjustable resistor-A wire-wound fixed resistor which has the resistance wire
partly exposed, so the amount of resistance in use can be adjusted occasionally
by loosening a screw, moving a contact
lug, and retightening the screw.
adjustable voltage divider-A wire -wound
fixed resistor having one or more movable
extra terminals which can be clamped at
desired points along the length of the resistor. Used in voltage divider applications.
admittance-The reciprocal of impedance,
measured in mhos. A measure of the
ease with which an alternating current
flows In a circuit. The word mho is ohm
spelled backwards, indicating it is a re-
acceptor circuit-A series resonant circuit
which offers minimum impedance at its
resonant frequency, and high impedance
to all other frequencies.
A.C.C.W.-Alternating-current modulated
continuous waves.
a.c.-d.c. receiver-A receiver which will
operate either from an a.c. or d.c. power
source. It does not have a power transformer, and is often called a universal
acetate disc-A phonograph record made of
an acetate compound.
a.c. generator-Any device which produces
an a.c. voltage, such as an oscillator or a
dynamoelectric generator.
acorn tube-Name applied to the small
tubes used for ultra -high frequency applications, up to about 400 megacycles.
Their shape and size are similar to that
of an acorn.
acoustic-Pertaining to sound and hearing.
acoustimeter-A device for the electrical
measurement of sound, having an output
indicator calibrated in db or directly in
units of sound intensity. More often
called a sound level meter.
Acoustical Labyrinth-Trade name used by
Stromberg-Carlson to describe the method
by which they prevent cavity resonance,
prevent standing waves, produce a low
cut-off frequency and reinforce bass response in loudspeaker systems.
Acoustic Clarifier-Trade name used by
Philco to describe free mounted cones attached to a regular loudspeaker baffle.
These cones vibrate on sudden loud
sounds and absorb undesired peaks in the
advance ball-The rounded support (often
sapphire) which rides on the disc adjacent to the recording stylus of a sound
recorder. It maintains even depth of cut
by correcting for small irregularities in
the surface of the dise.
aerial-An antenna.
a.f.-Audio frequency.
a.f.c.-Automatic frequency controL
a.h.-Ampere hour.
A.I.E.E.-American Institute of Electrical
acoustics-The science of sound. The study
of the cause and effect of audible vibrations. The characteristics of a room or
space which affect sound propagation and
sound travel.
air -cell battery-A non -rechargeable wet cell battery which delivers about 2.5 volts
when new, for use chiefly in 2-volt batteryoperated home radio receivers. Its car-
algebraic subtraction-To subtract one number from another algebraically, change the
sign of the number subtracted (the subtrahend), then add algebraically. Examples To subtract 7 from 10, change
7 to -7 and add algebraically to get 3.
To subtract 14 from -20, change 14 to
-14, then add -14 and -20 algebraically
to get -34. To subtract -7 from 40,
change -7 to 7 and add, getting 47.
algebraic sum-The sum obtained by adding
numbers with regard for their signs, according to the rules of addition in algebra.
These rules are To add numbers having
like signs, find the sum of their absolute
values and place the common sign in front
of the result. Example : The algebraic
sum of -3, -5, -1 and -10 is -19. To
add two numbers having unlike signs,
find the difference of their absolute values,
and place the sign of the larger absolute
value in front of the result. Example :
The algebraic sum of 7 and -3 is 4 ; the
algebraic sum of -33 and 11 is -22.
When three or more numbers, some
having different signs, are to be added
algebraically, find the sum of the positive
numbers first, then find the sum of the
negative numbers. Finally, add the partial sums algebraically to get the total
algebraic sum. Example The algebraic
sum of 17, -3, -10 and +4 is the algebraic sum of 21 and -13, which is 8.
align-To bring into line, such as to align
tuning circuits so they all respond to the
same frequency. Also, to align holes in
two or more parts so a bolt can be passed
through the holes, or align parts by, positioning so all are in a straight line.
aligning tool-A small screwdriver or socket
wrench, constructed partly or entirely
from non-metallic materials. Used for
making neutralizing or aligning adjustments in radio receivers. It eliminates
body capacity which would affect the accuracy of the adjustments if an ordinary metal wrench or screwdriver were
bon electrodes are porous, and absorb
oxygen from the air during use. Rated
life in normal radio use is 500 to 1500
hours, depending upon battery size and
current drain.
air condenser-A condenser having air as
its dielectric material.
air core-A term used to describe a magnetic circuit which consists only of air
and other non-magnetic materials (no
iron). Air -core construction is used
chiefly in r.f. circuits.
air-core transformer-A transformer having
a core (magnetic circuit) consisting only
of air or other non-magnetic materials,
so that the magnetic lines of force travel
only through these non-magnetic ma-
air gap-A path for electrical or magnetic
energy through air between two objects,
such as between the electrodes of a spark
gap or between core sections of an iron core transformer.
airplane dial-popular name for a circular shaped radio receiver dial with :i rotating
pointer, resembling the dials :ni,i pointers
of airplane instruments.
airport runway beacon-A radio beacon used
for marking the location of one or more
approaches to an airport.
Alexanderson alternator-A high frequency
high -power a.c. dynamoelectric generator
used in the early days of radio to produce
radio waves.
algebra-A continuation of arithmetic in
which letters and symbols are used to represent definite quantities whose actual
values may or may not be known.
algebraic expression-An expression which
states a number in terms of the signs and
symbols of algebra. A numerical algebraic expression consists entirely of numbers and signs. Example: 75 -(6 + 2)2
represents the number 11. A literal
algebraic expression also contains general numbers or letters. Examples : 2a11I.
represents the number of ohms of inductive reactance ; I2R represents the number
of watts of power.
alignment-The process of adjusting the
tuning circuits in a radio receiver or
transmitter so all respond to the same
alignment chart-A chart giving manufacturer's alignment instructions. Also,
a chart on which equations can be solved
graphically by placing a ruler on the two
known values and reading the answer
where the ruler intersects the scale for
the Federal Communications Commission.
Amateur band limits are changed from
time to time by government order.
amateur operator-A person holding a valid
license issued by the F.C.C. authorizing
him to operate licensed amateur stations.
amateur station-A radio station used by
an amateur for personal communication
with other amateurs.
amateur station call letters-Identifying
call signal assigned to a licensed amateur
operator to identify his station. Amateur calls in a given country begin with a
one or two -letter prefix (W for U. S., and
K for U. S. possessions) , followed by a
location -indicating numeral and two or
more additional letters.
ambient temperature-The temperature of
the air immediately surrounding a radio
American Morse Code-A dot-and -dash code
which is commonly used for telegraphic
communication over wires. It differs considerably from the International Morse
Code which is used in radio.
the unknown value. Also called nomogram or nomograph.
alive-A term used to describe a wire or dr cuit which is energized and therefore
has a voltage.
alligator clip-A long -nose clip with spring
controlled meshing jaws, used on test
leads for making quick temporary connections.
all -metal tube-A vacuum or gaseous tube
having a metal envelope or housing, with
electrode connections being made through
glass beads fused into the metal envelope.
Usually called a metal tube.
alloy-A mixture of two or more metals.
Thus, copper and zinc are mixed together
to form a brass alloy.
all -wave antenna-A receiving antenna designed to pick up stations reasonably well
over a wide range of carrier frequencies,
including short-wave bands as well as
the broadcast band. It may be a single
doublet antenna or a combination of two
or more doublets.
all -wave oscillator-An all -wave signal generator. A test instrument.
all -wave receiver-A receiver capable of
tuning from 550 kilocycles to at least
20,000 kilocycles.
all -wave signal generator-A test instrument capable of generating with satisfactory accuracy any of the radio frequency signals which may be needed
during aligning or servicing of all-wave
receivers (from about 100 kc. to 20,000 kc.
or higher).
Alnico-An alloy consisting chiefly of aluminum, nickel and cobalt, used to make
powerful small -size permanent magnets
because it can be strongly magnetized and
will hold its magnetism indefinitely.
alternating current-An electric current
which reverses its direction of flow at
regular intervals many times per second.
alternation-One half of a cycle, consisting
of a complete rise and fall of current in
one direction. Thus, 60-cycle alternating
current has 120 alternations per second.
alternator-A dynamoelectric generator for
generating alternating current voltages.
aluminum-A metal extensively used in
radio for shielding purposes, for making
the foil plates and housings of electrolytic
condensers, for making the plates of gang
tuning condensers, for chassis and panel
construction, etc.
a.m. a -m, A-M, A.M. or AM-Amplitude
amateur-Any person who operates and
experiments with short-wave transmitters
as a hobby rather than for profit. Also
called a ham.
amateur bands-Bands of frequencies assigned exclusively to radio amateurs by
American wire gauge-The wire gauge in
common use in this country for designating wire sizes (diameters) . It has numbers ranging from 0000 as the largest size
to 40 and higher for the smallest sizes.
Formerly called Brown and Sharpe gauge
(B. & S. gauge) .
ammeter-An instrument used for measuring the current flow in a circuit in amperes. An instrument which measures
current flow in milliamperes is a williammeter. An ammeter is always connected
in series in a circuit.
ampere.-The practical unit of electric current flow. The movement of 6,280,000,000,000,000,000 electrons past a given
point in a circuit in one second corresponds to a current of one ampere. A
current of exactly one ampere will flow
when a one -ohm resistance is connected
to a one -volt source.
Ampére, André Marie-French scientist
(1775-1836) after whom the unit of electric current (ampere) was named.
ampere-hour-A current of one ampere flowing for one hour. This unit is used chiefly
to indicate the amount of electrical energy
a storage battery can deliver before it
needs recharging.
ampere -hour meter-An instrument which
indicates or records the number of ampere -hours of energy drawn from a storage
ampere-turn-A unit of magnetomotive
force, which in turn is a measure of the
sound wave being transmitted. Abbreviated as a.m., a-m, AM, etc.
amplitude separator-The clipper or synchronizing separator stage in a television
analyzer-A test instrument used for checking radio parts and circuits. It sometimes includes a special plug-in system
which can be inserted in a tube socket to
extend the socket terminal to the instrument for convenience in making measurements.
angle-Formed when two straight lines
meet at a point. The lines are called the
sides of the angle, and the point is called
the vertex. An acute angle is less than
90°. A right angle is 90°. An obtuse
angle is more than 90°. Two angles whose
sum is 90° are called complementary
angles, and either is said to be the complement of the other.
angle of beam-The angle enclosing the
greater part of the energy transmitted
from a directional antenna.
angle, electrical-A unit used in specifying
a particular instant in an alternating current cycle for comparison purposes. One
cycle is considered as having a total angle
of 360°. Thus, if one voltage reaches a
peak value an eighth of a cycle after another voltage reaches its peak, the angle
between the voltages (the phase difference) is one -eighth of 360° or 45°.
angle of incidence-The angle between a ray
of light falling on a surface and the perpendicular (normal) of the surface at
that point.
angle of lag-The angle that a current or
voltage lags behind another current or
voltage, expressed in degrees (one cycle
strength of the magnetic field produced
by a coil. The number of ampere -turns
is equal to the coil current in amperes
multiplied by the number of turns in the
coil. One ampere-turn is equal to 1.257
ampere-turns-The product of the number
of turns of, and the number of amperes
flowing through the coils of an electromagnet. Thus one ampere-turn would be
one ampere flowing through one turn.
amplification-The process of increasing the
strength (current, voltage or power) of a
signal. Amplification can be provided by
transformers and tuned circuits as well
as vacuum tubes. In general, amplification is the ratio of signal output amplitude to signal input amplitude.
amplification factor-A vacuum tube rating
indicating the theoretical maximum increase in signal strength which can be
provided by a given tube. It is equal to
the ratio of the plate voltage change to the
grid voltage change needed to produce
the same change in plate current when a
tube has no load.
amplifier-A device which produces an am-
plified reproduction of its input signal by
drawing power from a source other than
the input signal. An amplifier usually
consists of one or more vacuum tubes with
associated parts, used to increase the
strength of a signal. Several different
basic types of amplifiers are in use see
class A, AB, B and C amplifiers.
amplify-To increase in strength, as in
amplification of radio signals.
amplitude-The amount of vertical displacement above or below a horizontal reference line on a graph, or the amount of
variation of a quantity from a reference
value, usually zero. Also, the displacement of a phonograph record groove from
its average or unmodulated position.
amplitude distortion-A type of distortion
which occurs when the changes in the current or voltage output of a radio circuit
or device are not exactly proportional, at
every instant of time, to the input current
or voltage changes. Amplitude distortion
definitely results in the production of harmonics which were not present in the
original signal. When the input signal
has a pure sine wave form, a distorted
output wave form is a sign of amplitude
angle of lead-The angle that a current or
voltage leads another current or voltage,
expressed in degrees.
angle of radiation-the angle between the
earth and the strongest portion of the
radiated wave from a transmitting antenna.
angle of refraction-The angle with respect
to the normal which a ray of light takes
when it passes from one medium to another.
angstrom unit-An extremely small unit of
length, used in expressing wavelengths of
light waves. One angstrom unit is equal
to one hundred-millionth of a centimeter.
angular velocity-The speed of a rotating
body when measured by the angle through
which any point of it moves relative to
the axis of rotation. In electrical circuits,
the angular *velocity of a current or voltage is equal to 2n X frequency, or 6.28 X
amplitude modulation-The common system
of radio broadcasting, in which the deviation in frequency above and below the
assigned carrier frequency value is equal
to the frequency of the sound wave being
transmitted, and the amplitude of the
transmitted signal varies in accordance
with the instantaneous amplitude of the
anion-A term sometimes used to describe
current in amperes measured at the point
where power is supplied to the antenna.
anti -capacity switch-A switch designed so
that there will be a minimum of capacity
between the switch contacts or terminals.
antilogarithm-The number corresponding
to a given logarithm. Usually written
antilog. Example : If log 87.9 = 1.9440,
then 87.9 is the antilog of 1.9440.
antinode-Any point, line or surface which
has maximum amplitude in a stationary wave system. The type of antinode is
usually specified, since there can be anti nodes of voltage, current, pressure, ve-
a negative ion which moves toward the
anode. An electro -chemical term.
annealing-A process of softening metals by
first heating and then allowing to cool
announcer-One who introduces performers
and programs at a radio broadcasting station, provides continuity between portions
of a program, and identifies the station.
anode-The radio tube electrode to which
the main electron stream flows. The
anode is more commonly called the plate,
and is usually placed at a high positive
potential with respect to the cathode. It
is usually identified on diagrams by the
locity, etc.
aperiodic-This term is applied to a circuit
which has no definite time period of oscillation. Either its resistance is large
enough to prevent natural oscillations, or
it has no capacity or inductance by which
letter P.
antenna-A metallic structure or an ar-
rangement of conducting wires or rods
used for picking up or radiating radio
waves. Also known as an aerial.
antenna array-A system of antennas
coupled together to obtain directional
antenna coil-That coil in a radio receiver
through which the antenna current flows.
This coil is usually directly connected to
the antenna and ground terminals inside
the set.
antenna coupler.-A device for transferring
r.f. energy from the final plate tank to the
antenna. It may also serve to match the
plate tank impedance to the impedance of
the transmission line.
antenna effect-The error or spurious effect
due to capacity between a loop antenna
and ground. In radio direction -finders,
the antenna effect is cancelled out by the
antenna form factor-The ratio of the effective height of an antenna to its actual
physical height
antenna gain-The effectiveness of an antenna in a particular direction as compared to some standard antenna. Antenna gain is usually considered as the
ratio of the power which must be supplied
to some standard antenna to the power
which must be supplied to the given antenna to produce the same field strength
in a desired direction. Antenna gain in
db is equal to 10 times the log of this
power ratio.
antenna resistance-The total resistance of
the transmitting antenna system at the
operating frequency and at the point at
which the antenna current is measured.
antenna resistance-A transmitting antenna
P where R. is the anrating. R. = P
tenna resistance in ohms, P is the power
in watts supplied to the entire antenna
circuit, and I is the effective antenna
it can be tuned. A circuit which will not
resonate in the tuning range is often called
aperiodic antenna-An antenna which has a
constant impedance over a wide range of
frequencies due to suppression of reflections within the antenna system. Terminated wave antennas and terminated
rhombics are examples.
aperture-An opening in an opaque plate
which limits the cross section of the light
beam passing through it.
A power supply-Any power supply device
which provides power for heating the cathode of a vacuum tube, such as a battery,
power line or generator.
apparent power-In an alternating current
circuit, the apparent power in watts is obtained by multiplying the voltage in volts
by the current in amperes, without considering phase relations. The apparent
power is therefore not the true power if
the circuit contains any reactance.
are-A luminous glow sometimes having the
appearance of an arch or arc of light,
formed by the flow of electric current
through air, gas or vapor. Conduction in
an arc is due mainly to ionization of the
gas or vapor.
arc converter-A type of r.f. oscillator which
utilizes an electric arc for the generation
of a pulsating or alternating current. In
effect, an arc converter changes d.c. to a.c.
argon-A gas used in some rectifier tubes
and electric lamps. It gives off a purple
glow when ionized.
arithmetic-The addition, subtraction, mul-
tiplication and division of ordinary numbers, decimals and fractions.
armature-That part of a motor, generator
or other device which carries the conductors in which a voltage is generated (the
generated e.m.f. if a generator, and the
back e.m.f. if a motor). The armature is
usually the rotating part of a dynamo electric machine. The armature is the
pivoted or spring-mounted iron portion of
a magnetic loudspeaker, buzzer, relay,
magnetic phono pickup or similar magnetic device.
armature reaction-The reaction between
armature flux and field flux which causes
a redistribution of flux lines in a dynamoelectric motor or generator.
arrester-Lightning arrest er.
A.R.R.L.-American Radio Relay League, an
association of amateur radio operators
and other persons interested in amateur
radio activities.
artificial antenna,-A device having all the
essential characteristics of a particular
antenna except that it converts the transmitter output power into heat instead of
radio waves. Used chiefly for testing and
adjusting transmitters. Also called
dummy antenna.
artificial line-A filter circuit having characteristics similar to a transmission line
of given length.
asbestos-A non -inflammable mineral of
fibrous texture, available in flake or
pressed form, and used for heat -insulating
and fire -proofing purposes. The resistance
wire in a Cordohm line cord is wrapped
pheric noise, atmospherics, static or QRM,
and particularly noticeable during thunderstorms.
atmospheric radio wave-A radio wave of
short length reaching its destination after
reflection in the upper layers of the atmosphere.
atom-One of the elemental particles into
which all matter is divided. An atom has
a nucleus consisting of electrons and protons, with additional electrons revolving
around the nucleus. Each of the 93
known elements has a different number
and arrangement of electrons and protons
in its atoms.
atomic weight-The weight of any atom as
compared to the weight of the hydrogen
atom, which is accepted as unity (one).
attenuation-The decrease in the strength
of a radio wave as it travels away from
the transmitter. Also any decrease in the
strength of a signal.
attenuation equalizer-A network of resistors, coils and condensers which changes
the transmission loss of a circuit at certain frequencies in order to make the total
transmission loss essentially constant over
a range of frequencies.
attenuator-A device, usually an arrangement of variable resistances, which permits reducing the strength of a radio
signal a desired amount without appreciably distorting the signal.
audibility-The strength of a sound or
signal as compared to the strength required to produce a sound which can just
barely be heard.
audible-Capable of being heard by the
human ear. The range of human hearing
is usually within the limits of 20 cycles
and 20,000 cycles, but the actual limits
vary greatly for different persons.
audio amplifier-A vacuum tube device
which increases the voltage and power of
an audio frequency signal. It may be a
separate piece of equipment or a section
in a radio receiver.
audio frequency-A frequency corresponding
to an audible sound wave. The extreme
limits of audio frequencies vary with the
individual, and are from about 20 cycles
to about 20,000 cycles per second. Abbreviated a.f., A.F., etc.
audio frequency transformer-An iron -core
transformer used for coupling together
two audio amplifier circuits, and sometimes also for changing the value of an
audio signal.
audio oscillator-An oscillator which generates audio frequency voltages.
audiometer-An audibility meter.
audion-Name used by Dr. Lee DeForest
for the three -electrode vacuum tube which
he invented.
in asbestos.
aspect ratio-The ratio of the width of a
television image to its height.
astatic-Without magnetic polarity. Also
(when capitalized), trade name for crystal
microphones and phono pickups made by
Astatic Microphone Laboratories.
A supply-Filament voltage supply of a
vacuum tube circuit, such as an A battery
or a filament winding on a power transformer.
asynchronous-Not synchronous.
a.t., AT or A.T.-Ampere-turns.
AT cut crystal-A crystal cut at a 35° angle
to the Z axis. It has low temperature
atmosphere-A complex mixture of gases
which surround the earth. The principal
gases are oxygen and nitrogen. Atmosphere is supposed to exist for a distance
of about 100 miles from the earth's surface. Atmospheric pressure at the surface
of the earth is approximately 15 pounds
per square inch ; hence this value is often
used as a unit of pressure called one
atmospheric interference-Crackling and
hissing noises reproduced in the radio
loudspeaker due to electrical disturbances
occurring in the atmosphere surrounding
the earth. These disturbances radiate
electromagnetic waves which are picked
up by antenna systems of receivers. Also
called atmospheric disturbance, atmos7
audio signal-The electrical equivalent of
pickups ; some are arranged to turn each
record over and play both sides.
automatic regulator-An automatic regulator is a device for regulating a system in
such a manner that changes in its functioning are initiated by changed conditions
and carried out without the intervention
of an attendant.
automatic starter-An automatic starter is
a device for starting a system without the
intervention of an attendant.
automatic tuning-An electrical, electromechanical or mechanical system which
tunes a radio receiver automatically to a
predetermined station when a button or
lever is pushed.
audio transformer-Audio frequency transformer.
aural-Pertaining to hearing.
autodyne reception-A system of heterodyne
reception in which one tube acts as both
an oscillator and a detector.
Auto-Expressionator-Trade name for the
volume expander circuit used in some
Crosley receivers.
automatic bass compensation-A special resistor and condenser circuit used in some
radio receivers to make low audio frequency notes sound more natural at low
volume control settings. The circuit automatically compensates for the poor response of the human ear to weak low frequency sounds.
automatic brightness control-A circuit
which automatically keeps the average
brightness of the reproduced image constant in a television receiver.
automatic circuit-breaker-A device which
automatically opens a circuit when the
current becomes excessive.
automatic frequency control-A special
radio circuit which keeps a superheterodyne receiver tuned accurately to a given
station. It is found chiefly on push-button
tuned receivers, where it corrects slight
inaccuracies in the operation of the automatic tuning system.
automatic gain control-Same as automatic
volume control.
automatic grid bias-A circuit arrangement
in which the voltage drop across a resistor
in the cathode lead of a tube serves as
the C bias voltage for the grid of the tube,
eliminating the need for a separate C
bias voltage source.
Courtesy Hnd(nrrart
automatic volume control-A radio circuit
which automatically maintains the output
volume of a radio receiver constant within
limits while the carrier signal picked up
by the antenna is varying in amplitude
over a wide range, or while the receiver is
being tuned to signals which differ in
strength. It is used in practically all
modern receivers, for it minimizes annoying fading of distant stations and prevents blasting when tuning suddenly from
a weak station to a strong station.
automatic volume expansion-A special
audio circuit which increases the volume
range of a radio program or phonograph
record by making the weak passages
weaker and making loud passages louder.
automobile receiver-A receiver designed
for installation in an automobile, usually
underneath the dashboard. Filament
voltages are obtained directly from the
6-volt automobile storage battery, and the
required higher d.c. voltages are usually
obtained from a vibrator power pack in
the receiver. Also called auto radio.
auto radio-An automobile receiver.
auto-transformer-A transformer having
one continuous winding. Usually all of
the winding serves as the secondary, and
automatic record changer-An electric
phonograph which automatically plays a
number of records one after another.
Some types play only one side of each
record ; some play both sides without
turning over the record, by using two
a part of the winding also serves as the
a certain amount without causing motion
of connected gears or parts.
a.v.c., A.V.C. or AVC-Automatic volume
a.v.e.-Automatic volume expansion.
average-The average of a number of quantities is obtained by dividing the sum of
the quantities by the number of quantities
back-shunt signalling-A signalling system
where energy is delivered to the antenna
when a telegraph key is closed and to a
"back shunt" non -radiating circuit when
the key is open.
back-wave-A back -wave is a signal which
is heard from a telegraph transmitter
with the key open. The wave is heard
due to improper neutralization of the
transmitter amplifier.
baffle-A wood, metal or composition horn
or flat surface used with a loud -speaker
to increase the effective length of the air
path from the front to the back of the
loudspeaker diaphragm, thereby reducing
interaction between sound waves produced simultaneously by front and back
surfaces of the diaphragm. A baffle thus
serves to direct the sound produced by
a loudspeaker and improve the fidelity
of reproduction.
Baird, John Logie-A. pioneer of British
Television, who developed a mechanical
television system using the Nipkow scanning dise.
bakelite-A phenolic compound having high
electrical resistance, used as an insulating
material in the construction of radio parts
such as panels, coil forms, tube sockets,
average value-The average of many instantaneous amplitude values taken at
equal intervals during an alternation
(half -cycle) of alternating current. The
average value of a pure sine wave is
0.637 times its maximum or peak amplitude value.
aviation channels-Frequency bands assigned to aviation service for radio communication between aircraft and ground
stations. These bands are both above
and below broadcast band frequencies.
A.W.G.-American wire gauge, formerly
known as the Brown and Sharpe wire
gauge (B. & S. gauge).
B-Notation used to identify the plate cir-
cuit or plate voltage supply of a vacuum
tube. Also used to represent magnetic
flux density.
B- -Notation used to designate the negative plate supply terminal of a vacuum
tube circuit or the negative terminal of
the B battery or other plate voltage
source. Pronounced "B minus."
B+ -Notation used to designate the positive plate supply terminal of a vacuum
tube circuit or the positive terminal of a
B battery or dther plate voltage source.
Pronounced "B plus."
back e.m.f.-Back electromotive force.
back electromotive force -A voltage developed in an inductive circuit by a changing or alternating current, the polarity of
balanced armature unit-An electromagnetic sound-producing device used chiefly
in magnetic loudspeakers. It has a small
moving iron armature which is surrounded by windings carrying audio currents. The armature is pivoted between
the poles of a permanent magnet. Variations in the audio current cause corresponding changes in magnetism, making
the armature rock back and forth. A diaphragm coupled to the armature produces
sound waves.
balanced circuit-A vacuum tube circuit in
which the tube capacity is balanced or
compensated for by an external capacity.
More generally, any circuit which is adjusted so that two factors balance each
balancer-The portion of a radio direction
finder used to balance out the antenna
effect which is due to loop-ground
ballast resistor-A resistor which has the
special characteristic of greatly decreasing
its resistance when current flow tends to
decrease, and increasing its resistance
when current increases, thereby maintaining essentially constant current over a
considerable range of voltage variation.
The resistor is usually in a glass or metal
envelope like a radio tube, and is used in
some radio receivers to compensate for
variations in line voltage.
which is at every instant opposite to that
of the applied voltage. Also called counter
electromotive* force. It can never be
greater than the applied voltage.
background-Music or sound effects produced at low volume level along with a
regular radio program.
background noise-Noise heard along with
a received radio program, due to atmospheric interference or to circuit noises.
background voltage-In a radio direction
finder, any voltage induced in the loop
other than the desired signal voltage.
back-lash-Movement or play in the gears
or parts of a tuning mechanism or other
system, allowing one gear to be moved
ballast tube-A ballast resistor mounted in
an evacuated glass or metal envelope like
that of a radio tube. This construction
improves the automatic voltage regulating
action by reducing radiation of heat from
the resistor element.
ballistic galvanometer-A laboratory instrument for precise measurements. It is
a microammeter having no retarding
spring. The meter movement rotates
through an angle dependent on the
quantity of electricity fed to its coil.
band-In radio, the frequencies which are
within two definite limits are used for a
definite purpose. Thus, the standard
broadcast band extends from 550 kc. to
1600 kc.
band-pass filter-A filter network designed
to pass a certain band of frequencies
while attenuating or rejecting both higher
and lower frequencies.
band selector-A band switch, which permits selecting any one of the bands in
which a receiver or transmitter is designed to operate.
bandspread tuning control-A small variable
condenser connected in parallel with each
main tuning condenser of a short-wave
receiver, to provide more accurate tuning
by spreading a single band over the entire
tuning dial.
band switch-A switch which simultaneously changes all tuning circuits of a
radio receiver or transmitter to a desired
band of frequencies.
band width-The width in cycles covered by
a radio signal ; also a particular group of
station channel assignments (such as an
amateur band width). The frequency
limits of a tuned circuit or a combination
of circuits.
bank winding-A method of winding coils
In which successive turns are placed in
two or more layers so that a multi -layer
coil is completed without going back to
the starting point. This procedure reduces
the distributed capacity of the coil.
bantam jr. tube-An extremely small glass
vacuum tube with a special bantam jr.
base, used chiefly in hearing aid units.
bantam tube-A compactly -designed tube
having a standard octal base but a considerably smaller glass envelope than does
a standard glass tube. Bantam tubes are
used chiefly in compact table model receivers and in battery-operated portable
sets. They are designated by the letters
GT following the tube type number.
bar-A term formerly used to mean a sound
pressure of one dyne per square centimeter. Radio engineers now use the full
term "dynes per square centimeter" to
avoid confusion, because in all fields except acoustics the bar was originally equal
to 1,000,000 dynes per square centimeter.
barium-A chemical element used in photo-
electric cells.
Barkhausen-Kurz oscillator-A micro -wave
oscillator circuit in which the plate is at
cathode potential or even slightly negative, and the grid is positive with respect
to the cathode. The frequency of the
oscillator is determined by the speed of
electrons and the distance between the
grid and plate.
bar magnet-A magnetized straight bar of
steel serving as a permanent magnet.
barometer-An instrument for measuring
the pressure of the atmosphere, used
chiefly for weather forecasting purposes.
base-The number upon which a system of
logarithms is constructed. The base of
the common system of logarithms is 10.
Example login 10,000=4, which means
that 10'=10,000; loglo 351=2.545, which
means that 10.61=351. Log a 453=6.116.
which means that a6118 or 2.718°u8 equals
453. The base is designated to the right
of and below the abbreviation "log" ;
when no base is specified in ordinary problems of computation, the base 10 is always
basket winding-A criss-cross coil winding
in which each turn is so placed that adjacent turns are separated by a considerable space except at the points of crossing,
so as to reduce the distributed capacity of
the coil.
bass-Low audio frequencies.
bass-boost circuit-A circuit designed to em-
phasize low audio frequencies.
bass compensation-Any means for offsetting the natural drop in the response of
the human ear to low audio frequencies
at low volume levels.
bass control-A manually -adjusted control
provided on a radio receiver for the purpose of emphasizing the loudness of the
bass notes in a radio program.
bass response-The ability of a loudspeaker
or amplifier to handle low audio notes,
or the sensitivity of the human ear to
low audio notes.
battery-One or more dry cella or storage
cells connected togethetr to serve as a
d.c. voltage source.
battery receiver-A receiver which uses batteries as a source of power.
bay-One complete vertical section of a
number of amplifiers or other transmitter
units mounted on racks.
bayonet base-A type of tube and lamp base
having two projecting pins on opposite
sides of the smooth cylindrical base.
These pins engage in corresponding slots
in the bayonet -shell socket, thus holding
the tube or lamp in the socket. Electrical
contact is made by means of pins or rings
on the bottom of the base.
beat frequency-The frequency obtained
when signals of two different frequencies
are combined and rectified. The beat frequency is equal in numerical value to the
difference between the original frequen-
battery-A battery having many small
cells connected in series, used for supplying d.c. voltages to the plate and screen
grid electrodes of radio tubes used in
battery-operated equipment.
B.B.C.-British Broadcasting Corporation.
b.c. or BC-Broadcast band.
BCL-Amateur radio abbreviation for
broadcast listener.
beacon course-The equisignal zone or beam
of an aircraft radio beacon, designating a
course through the sky.
beam-In aviation, a constant unidirectional
radio signal transmitted for guidance of
pilots. A plane flying exactly on the
course indicated by a beam is said to be
"flying the beam."
beam angle-The angle enclosing the greater
part of the energy transmitted from a directional antenna.
beam antenna-An antenna so designed that
its radiation is practically confined to a
narrow beam extending in a definite direction.
Beam-a-Scope-Trade name for a built-in
shielded loop antenna used in some General Electric receivers.
beat -frequency oscillator-An audio frequency oscillator whose output is obtained
by combining and rectifying two known
higher -frequency signals which are generated by or obtained from separate circuits.
beat -frequency receiver-Early name for a
superheterodyne receiver.
beating-Combining ' of two different frequencies to produce a new signal having
pulsations in amplitude at the difference
or beat frequency value.
beat note-An audible frequency produced
by the beating of two higher frequencies.
beats-A periodic variation in the amplitude
of the pressure or velocity at a point due
to the interaction of two waves which
differ in frequency. Beats can occur between radio signals as well as between
sound waves or mechanical vibrations.
bel-The unit for logarithmic expression of
ratios of power, voltage or current, named
after Alexander Graham Bell, inventor of
the telephone. The number of bels is the
common logarithm of the power ratio.
In radio work, a smaller unit called the
decibel is used instead of the bel; a decibel is one -tenth of a bel.
B eliminator-An a.c. power pack which
converts a.c. power line voltage to the
pure d.c. voltages required by plate and
screen grid circuits of radio tubes, thereby
eliminating the need for B batteries.
Bell, Alexander Graham-American inventor of the telephone and microphone.
Bellini -Tosi direction finder-An early type
of radio compass.
bell wire-A common term for the cotton covered B. & S. No. 18 copper wire used
for making doorbell and thermostat connections in homes.
beta rays-Rays consisting of negatively charged particles or electrons. Also called
cathode rays.
Beverage antenna-A directional antenna of
low height having a length which is some
multiple of the received wavelength.
b.f.o.-Beat frequency oscillator.
B -H curve-A curve showing the relationship between magnetic flux density (B)
produced in a magnetic path and the magnetic force per unit length (H) in that
bias-The fixed d.c. voltage applied between
the control grid and cathode electrodes of
a radio tube. Also called C bias.
beam, convergent-A beam of light whose
rays begin at different distant points and
meet (converge) at a single point.
beam, divergent-A beam whose rays start
at a single point and spread out.
beam of light-A group or pencil of light
rays having an essentially constant crosssectional area.
beam, parallel-A beam of light whose rays
are exactly parallel to one another.
beam power amplifier tube-A special type
of vacuum tube designed for use in the
o}itput stage of a radio receiver. Deflecting electrodes in the tube concentrate the
electrons into beams to give high power
output along with desirable operating
bearing-A term used in navigation
designate the direction of one point with
respect to another in terms of compass
readings. Thus, a bearing can specify
the angle on which a ship or aircraft lies
from a given point with respect to a
straight line running north and south.
bias cell-A tiny 1 -volt or 114 -volt cell used
singly or in series combinations to provide
a negative C bias voltage for a vacuum
tube amplifier circuit. It will last indefinitely if no current is drawn from it.
bias resistor-The cathode resistor which
provides an automatic C bias voltage for
a tube.
bidirectional-In two directions, one opposite the other, an ordinary loop antenna
is bidirectional, as it picks up energy from
two directions, one exactly opposite the
bilateral-Having two sides.
bilateral antenna-An antenna having the
property of radiating or receiving radio
waves best in directions 180° apart (exactly opposite).
bimorph cell-A cell consisting of two
crystal elements cemented together, used
in crystal headphones, microphones, pickups and loudspeakers.
binaural-Having two ears, or the effect of
hearing with both ears. Also, sound radiated from two sources, creating the
sensation of sound position.
binaural effect-The effect of sound on both
ears. The different sound path lengths
make it possible for a person to determine
the direction from which a sound is com-
black level, used to blank out all video
signals during the transmission of synchronizing signals.
blasting-A distortion of sound caused by
overloading the microphone, loudspeaker
or other part of a transmitting system or
public address amplifier.
bleeder current-A current drawn continuously from a power pack or other voltage
source to improve its voltage regulation
or to increase the voltage drop across
a particular resistor.
bleeder resistor-A resistor which is used
to draw a fixed bleeder current value from
a power pack.
blocked-grid keying-Method of keying a
telegraph transmitter by applying sufficient bias to block tubes when the key is
open. Closing the key removes the bias,
allowing plate current to flow.
blocked resistance-A term used in measuring loudspeaker efficiency. It represents
the resistance due to electrical losses when
the moving elements are blocked so they
cannot move.
blocking-Stopping of operation, as by
applying a high negative bias to the grid
of a tube to cut off plate current.
blocking condenser-Any condenser used in
a radio circuit to block the flow of direct
current while allowing a.c. signal currents
to pass.
blooper-Slang term applied to a regenerative receiver which radiates a signal when
improperly tuned.
blow-out magnet-A permanent magnet or
electromagnet used to extinguish the electric arc formed in an arc transmitter or
when a switch or relay contact carrying
heavy current is opened.
B supply-Plate voltage supply of a vacuum
tube circuit, such as a B battery, an a.c.
or universal power pack, a vibrator power
pack, a d.c. generator, etc.
B. & S.-Brown & Sharpe (wire gauge),
now known as American Wire Gauge
bobbin-A coil of wire wound on a form, or
the form itself. A magnetic coil in a
headphone unit is an example.
body-A definite portion of matter by itself.
body capacity-The capacity existing between the human body and a piece of
radio apparatus.
bombardment-The impact of high-speed
electrons on an electrode or other surface, usually causing secondary emission
of electrons.
bonding-Connecting the metal housings
and shields of radio parts together or to
the chassis with heavy wire so they will
be at the same potential (usually ground
binder-A resinous material which causes
the various materials of a phonograph
record compound to adhere to one another.
Also, the cement -like material used in
carbon resistors to provide mechanical
binding post-A small screw or clamping device for making quick electrical connections.
bipolar-Possessing two poles.
bipolar magnetic driving unit-A headphone
unit having two magnetic poles.
birdie-A high-pitched whistle heard while
tuning a receiver. It actually is a beat
note having a high audio frequency.
blacker -than -black level-In television, the
d.c. voltage value which is greater than
the value representing the color black,
used for control impulses.
black level-In television, the positive d.c.
voltage representing the color black. Usually it is not greater than 80% of the
maximum television signal amplitude.
blanking pulse-In television, the pulse used
to black out the lines that would otherwise be traced on the screen by the electron beam as it returns to the left of the
tube to start another line, and as it returns from the bottom of the screen to the
top to start another frame.
blanking signal-The signal introduced into
the complex video signal at or above the
book condenser-A two -plate condenser
hinged like the pages of a book. Capacity
variation is obtained by changing the
angle between the plates. Usually called
trimmer condenser.
B power supply-Any power supply device
which is connected in the plate circuit of
a vacuum tube, such as a B battery, a.c.
power pack, vibrator power pack or gen-
brilliancy control-Same as brightness control.
broad-A term often used to describe a circuit wh«h will respond to a wide range
of frequencies.
broadcast-A radio transmission intended
for reception by the general public.
broadcast band-The band of frequencies
between 550 kc. and 1600 kc., to which are
assigned all standard broadcast stations
operating in the United States.
broadcasting-A general term applying to
the radiation of radio waves carrying
programs intended for public interest,
education, or entertainment.
broadcast station-A radio station used for
transmitting ptograms to the general pub-
breadboard construction-Layout of all
. radio parts and wiring on one side of a
wood board, so parts may be fastened by
wood screws and easily moved during experimental work.
break-in keying-Method of keying a telegraph transmitter in which the receiver
is inoperative only during the interval the
transmitting key is held down. This
enables the operator to listen continuously broadside directional antenna-An antenna
array whose radiation is substantially at
to other signals on the air. The station
he is working can then stop him for a
right angles to the line along which its
repeat at any time, rather than at the end
elements are arrayed.
of the message.
broad tuning-A condition wherein two or
breakdown voltage-The voltage at which
more stations are picked up at one setting of a receiver tuning dial, due to
the insulation between two conductors
lack of selectivity in the tuning circuits.
will break down and become conductive.
bridge-An arrangement of resistances, bronze-An alloy of copper and tin.
inductances, or capacities, for the com- Brown and Sharpe Gauge-Former name
parison of values of any unit with standthe American Wire Gauge (A.W.G.), comards of the same kind.
monly used in this country for specifying
bridge circuit-A circuit consisting of four
sizes of conductors. It uses a system of
numbers ranging from 0000 for the largest
resistances or impedances connected in
diameter to 40 and beyond for the smallest
series to form a square, with a voltage
source connected between one pair of opdiameters.
posite junctions and an indicating meter brush-A metal or carbon block used
(usually a galvanometer) between the
make contact with a rotating or otherother pair of junctions. One or more rewise moving part in an electrical circuit.
sistors are adjustable. The bridge is said
to be balanced when these are adjusted so brush discharge-Visual ionization occurring on the surfaces of conductors charged
no current flows through the indicating
to high potentials. Also called corona
meter. Example : Wheatstone bridge.
bridge rectifier-A four -element rectifier circuit connected in the characteristic four - brute -force filter-A low-pass filter depending on large values of capacity and incornered arrangement of a bridge circuit.
ductance rather than on resonant effects
A.C. voltage is applied to one pair of opto filter out or block a.c. components while
posite junctions or corners, and d.c. voltpassing direct current.
age is obtained from the opposite pair.
bright level-The zero -voltage line of the b.t.u.-British thermal unit, an English
unit of measure of heat energy. It is compulsating d.c. voltage which constitutes
parable to the calorie in the metric system.
a television video signal. The bright level
represents white, the brightest part of an buck-To oppose.
bucking coil-A coil whose magnetic field
brightness-The amount of light flux per
opposes the magnetic field of another coil,
unit area. Brightness is measured in
such as the hum -bucking coil in an electrolamberts, candle-power per square foot,
dynamic loudspeaker.
or lumens per unit area.
buffer-Any part or circuit used to reduce
brightness control-In a television receiver,
undesirable interaction between radio cirthe control which varies the average ilcuits.
lumination of the reproduced image.
buffer condenser-A condenser connected
brilliance-In radio, good reproduction of
between the anode and cathode of a rectithe higher audio sound frequencies,
fier tube to reduce voltage surges which
making the reproduced program sound
might affect following parts in the appalike the original.
C+ -Notation used to designate the positive grid bias terminal of a vacuum tube
circuit or the positive terminal of a C
battery or other grid voltage source.
cabinet-The ornamental, artistically designed wood, metal or plastic housing In
which a radio receiver chassis and loud.
speaker are mounted.
cable-A general term applied to larger
sizes of wire, either solid or stranded,
buffer stage-An amplifier stage used to prevent feedback of energy from a power
stage to a preceding stage.
bug-A semi -automatic code transmitting
key in which movement of a lever to one
side produces a series of dots, and movement to the other side produces a single
used singly or in combination a cable is
usually heavily insulated, and often is
also lead -covered or shielded with metal
cadmium-A metal sometimes plated on a
steel chassis to improve its appearance
and prevent rusting.
caesium-An alkali metal used in certain
types of photo-cells.
cage antenna-An antenna having conductors which consist of groups of parallel
wires in a cylindrical arrangement.
calibrate-To determine by measurement
or comparison the true values corresponding to each scale reading of a meter or
other instrument. To determine and
record the settings of a control which
correspond to particular values of frequency, voltage, current or some other
call letters-Government-assigned identifying letters for a radio station.
calorie-The unit of heat energy in the
metric system. One calorie is the amount
of heat energy required to raise the temperature of one gram of water one degree Centigrade. There are 252 calories
in a British thermal unit (b.t.u.).
cam-An irregular-shaped rotating or sliding part used to convert rotary motion to
linear motion, or vice versa. Used extensively in mechanical push-button tuning
cambric, varnished-A fine white linen or
cotton fabric, varnish impregnated and
baked, and used as an insulating material
in constructing coils and other radio parts.
When made in the form of tubing, it is
referred to as spaghetti.
camera-The part of a television transmitting apparatus in which the image of the
scene to be televised is formed for a conversion into equivalent electrical impulses.
camera tube-In a television camera, the
cathode ray tube which breaks up pictures
or scenes into elemental areas and converts these into electrical impulses in definite sequence.
candlepower-Unit of measure of light
candohm-Trade name for the particular
type of wire-wound resistor, usually tapped, which is wrapped in heavy fiber in ;
built-in aerial-An aerial which is an integral part of a radio receiver. It may
be a loop aerial, a power line connection
or a sheet of metal mounted in the receiver cabinet.
bus bars-The heavy copper bars used on
switchboards to carry current.
bushing-A tube or washer used for lining
or insulating a hole in a radio chassis or
as a bearing.
buzzer-An electromagnetic device in which
attraction of an armature by an electromagnet interrupts the current flow ; a
spring then pulls the armature back,
closing the circuit again so that the process repeats itself and creates a buzzing
BX cable-Flexible metal conduit used to
protect power line wiring in buildings and
in high -power radio apparatus. Often
called simply BX.
by-pass condenser-A condenser used to provide a low-impedance path for radio or
audio signals around a resistor or between a circuit terminal and ground.
C-Notation used to identify the grid cir-
cuit or grid voltage supply of a vacuum
tube. Abbreviation for capacity, condenser, center tap, and Centigrade.
CC-Degrees Centigrade.
C- -Notation used to designate the negative grid bias terminal of a vacuum tube
circuit or the negative terminal of a C
battery or other grid voltage source.
sulating paper and then encased in metal.
Widely used for bleeder resistors and
voltage divider applications.
capacitor split-phase motor-An induction
motor using a series condenser to produce
the rotating magnetic Held required to
bring an induction motor up to synchronous speed when operated from a singlephase a.c. source.
capacity-The electrical size of a condenser,
determining the amount of electrical
energy which can be stored in a condenser
by a given voltage. The unit of capacity
is the farad; a condenser or circuit has a
capacity of 1 farad when a change of 1
volt per second produces a current of 1
ampere. In radio work, capacity is measured in microfarads (mfd.) and micromicrofarads (mmfd.) ; 1 mfd. is equal
to 1,000,000 mmfd. Capacity exists
wherever two conductors are separated by
an insulating material.
capacity bridge--A wheatstone bridge
formed of capacitive elements, for precise
measurements of unknown capacity. It
must be used with an a.c. source.
capacitive coupling-A type of coupling in
which a condenser provides a direct path
for signal energy between two circuits.
capacitive reactance-The reactance which
a condenser offers to a.c. or pulsating d.c.
It is measured in ohms, and decreases as
frequency and capacity are increased.
carbon-An element used in the construction of radio parts such as resistors, dry
cells, and microphones.
carbon granules-Small particles of carbon
used in microphone buttons.
carbon microphone-A microphone in which
the diaphragm applies a varying pressure
to a container filled with carbon granules,
thereby causing the resistance of the
microphone to vary in accordance with
the varying pressure of sound waves on
the diaphragm.
carbon -pressure recording-That type of
electromechanical facsimile recording in
which a pressure device acts upon carbon
paper to register upon the record sheet.
carbon resistor-A resistor made of carbon
particles and a ceramic binder molded
into a cylindrical shape, with leads attached to opposite ends.
carborundum-A compound of carbon and
silicon which can be used in crystal form
to rectify or detect radio waves, as in a
crystal detector.
cardiold pattern-A heart -shaped pattern
representing the response or radiation
characteristics of an antenna or the response characteristics of a microphone.
carrier-A current or voltage having the
assigned frequency of a radio station, or
the corresponding radio wave which is
capable of traveling out into space from
the transmitting antenna. When no
sounds are being transmitted, such as
during a pause between portions of a
program, only the unmodulated carrier
signal is present in the transmitting and
receiving system.
carrier current-The alternating current
which is associated with a carrier, and
which may be modulated with an intelligence signal. Also, the r.f. carrier current sent over power lines for communication purposes.
carrier frequency-The frequency of the
original unmodulated radio wave produced by a transmitter. In the case of a
broadcast station, the carrier frequency
must be maintained within a few cycles
of the frequency value assigned to that
station by the Federal Communications
carrier level-The strength of a carrier,
expressed as power or voltage, and usually
applying to the level of an unmodulated
carrier suppression-A method of radio
transmission in which the carrier wave is
not transmitted.
carrier wave-The unmodulated component
of a signal wave, usually called simply
the carrier. It carries the sound, picture,
code or facsimile signals from the transmitting station through space to receivers.
carrying capacity-The maximum current
strength that a conductor can safely
transmit without getting too hot and
damaging its insulation.
cartridge fuse-A fuse enclosed in a cartridge having the shape of a rod or cylinder, with contacts at the ends.
cascade-In series, such as tuning circuits
or amplifier stages used one after another.
cascade limiter-An f.m. limiter system
which uses two limiter tubes in series or
cascade to improve operation for both
weak and strong signals and give considerably higher gain than a single-stage
catcher-A part of a Klystron, a tube used
for generating microwaves.
cathode-The electron -emitting electrode
of a radio tube. Thermionic vacuum
tubes employ heated cathodes ; the heat is
either supplied indirectly by a filament
located inside the cathode, or is supplied
by current flowing through the cathode
itself. In this latter case, the cathode is
also the filament.
cathode current-The total current passing
from the cathode through space to the
other electrodes in a vacuum tube.
cathode heating time-The time in seconds
required for the cathode of a tube to
reach normal operating temperature after
normal voltage is applied to the heater.
For convenience and accuracy in measuring this time, the cathode is usually
assumed to be at normal temperature
when the plate current has reached 90%
of its final value.
cathode modulation-A system of amplitude modulation in which the grid bias
and plate voltage are varied simultaneously, thereby varying the cathode
cathode ray-A ray or beam of electrons
emitted from a cathode.
cathode ray escilloscope-A test instrument using a cathode ray tube to make
visible the wave form of a varying current or voltage.
cathode ray television tube-The cathode
ray tube' used in modern television receivers to reproduce the scenes being transmitted.
cathode ray tube-A special type of vacuum
tube in which a beam of electrons is directed at a fluorescent screen by an electron gun, producing a green or white
glow on the screen at the point of impact. The beam passes between electrostatic deflecting plates or electromagnetic deflecting coils which can make it
bend enough to produce any desired pattern or picture on the screen when the
proper varying voltages are applied to the
deflecting system.
cathode ray tuning indicator-A small cathode ray tube used in radio receivers to
indicate when a station is tuned in accurately.
cathode sputtering-A process sometimes
used in the production of the metal master of a phonograph record, wherein the
wax or lacquer original is coated with a
conducting layer by means of an electrical
discharge in a vacuum.
cation-A positive ion.
catwhisker-A small, sharply pointed wire
used in a crystal detector to make contact with a sensitive point on the surface
of the crystal.
C battery-The battery used for supplying
a negative C bias voltage to the control
grid of a vacuum tube.
C bias-An applied voltage used to make
the control grid of a vacuum tube negative with respect to the cathode.
C bias detector-A vacuum tube operated
with almost enough negative bias to cut
off plate current. The tube operates on
the lower bend of the characteristic curve,
and detection takes place in the plate
CBS-Columbia Broadcasting System.
c.c.-Cubic centimeter.
cell-A single unit capable of serving as
a d.c. voltage source. A primary cell, such
as a dry cell, cannot be recharged when
exhausted. A secondary cell, such as the
cell of a storage battery, can be recharged
by passing a current through it in the reverse direction. The term cell is also
used to designate light-sensitive tubes
(photoelectric cells and selenium cells),
probably because these tubes permit increased current flow when illuminated.
cellulose nitrate disc-A phonograph record
made of cellulose nitrate.
celotex-Trade name for a fiber wallboard
often used to form loudspeaker baffles clue
to its sound -absorbing qualities. Also
used in radio and sound picture studios
to control the amount of reverberation.
centering control-In a television receiver,
a control used to shift the entire reproduced image on the screen. The horizontal centering control moves the image
horizontally in either direction, while the
vertical centering control shifts the image
up or down. Centering controls are also
provided on cathode ray oscilloscopes.
center -tap keying-Keying a telegraph
transmitter stage by interrupting the current flowing to the filament center -tap
connection through the plate return lead.
centi-A prefix denoting a hundredth of.
Centigrade-The metric scale of temperature, in which 0 is the freezing point and
100 is the boiling point of water at sea
centimeter-In the metric system of measurements, a unit equal to one -hundredth
of a meter, or approximately .39 inch.
There are 2.54 centimeters in one inch.
Centimeter - gram - second system,
which is the metric system of specifying
length, mass and time.
CH-Choke coil.
chain-In radio, a network of radio stations
connected together by special telephone
lines or special radio relay channels so
that all can broadcast simultaneously a
program originating at a key station.
changeover switch-A special switch arranged to shift the antenna connection
from sending to receiving apparatus and
vice versa.
channel-A narrow band of frequencies including the assigned carrier frequency,
within which a radio station is required
to keep its modulated carrier signal in
order to prevent interference with stations
on adjacent channels. Also, one branch
or path over which signals may travel
thus, a p.a. system may have several input
channels, each with its own sound pickup
device, transmission line and volume control.
characteristic-The first part of a logarithm
(to the left of the decimal point). Example In log 461 = 2.6637, the characteristic
is 2. The characteristic of a number
greater than 1 is positive and is one less
than the number of digits to the left of
the decimal point. The characteristic of
a number less than 1 is negative, and is
one more than the number of zeros immediately to the right of the decimal
characteristic curve-A curve plotted on
graph paper to show the relation of
changing values. For example, a curve
showing how the plate current in a
vacuum tube changes with respect to a
change in grid voltage.
characteristic impedance-The impedance
in ohms as measured between the terminals of a transmission line at the operating frequency. Also called surge impedance and designated by the notation
charge-A quantity of electrical energy held
on an insulated object.
The electrical
energy stored in a condenser. The act of
supplying electrical energy to a metal
object, to a condenser, or to a storage
battery. When an object has more electrons than normal, it has a negative
charge. When an object has less electrons than normal, it has a positive
charger-A device used to convert alternating current into a pulsating direct
current which can be used for charging
an exhausted storage battery.
chassis-The assembled parts on the metal
frame or chassis base of a radio receiver.
not including the housing or cabinet. or
the metal frame itself.
chassis base-The metal framework on
which the parts of a radio receiver or a
section of a transmitter are mounted.
More often called simply the chassis.
chip-The material removed from the phonograph disc by the recording stylus in
cutting the groove during sound recording.
choke coil-A coil used to limit the flow
of alternating current while allowing
direct current to pass. A choke coil
presents a high impedance to the alternating current which it is to block, without appreciably hindering the flow of
direct current. R.F. choke coins have
air or pulverized iron cores, while a.f.
choke coils and filter chokes have iron
Chromatic aberration-A lens defect in
which the different colors of light rays
coming from a single point are not brought
to the same focal point. The cause is
failure of the lens to bend all colors of
light the same amount ; the effect is
colored fringes around the image produced by the lens, and the remedy involves making the lens from suitable
combinations of glass, such as from crown
and flint glass. Television lenses must
be corrected for chromatic aberration in
this way.
cipher-A zero. A secret code.
circuit-A complete path over which electrons can flow from the negative terminal
of a voltage source through connecting
wires and parts to the positive terminal
of the same voltage source.
circuit breaker-An electromagnetic device
which opens or breaks a circuit automatically when the current rises above a
predetermined value.
circuit disturbance test-A professional
radio servicing technique which is widely
used for isolating the defective stage in
a dead receiver. It depends on the fact
that a disturbance introduced in any
receiver stage will reach the loudspeaker
only if all stages between the point of
disturbance and the loudspeaker are good.
The disturbance is introduced in each
stage in turn, working from the loudspeaker toward the antenna ; the first
stage at which no loudspeaker indication
is obtained is then the defective stage.
The disturbance may be introduced by
removing and replacing the tube (not
for universal receivers), touching the
top cap, removing and replacing the top
chopper-A device for continuously breaking up a current or a ray of light.
Christmas tree pattern-The optical pattern
observed when the surface of a phonograph record is illuminated by a beam
of parallel light.
cap clip, or shorting the grid momentarily
to the cathode or the chassis.
circularly polarized wave-A polarized wave
in which the direction of displacement at
a point rotates with constant angular
velocity about an axis in the direction of
propagation, and the magnitude of displacement is independent of its direction.
circular mil-A unit of area used chiefly in
specifying the cross-sectional areas of
round conductors. A circular mil is the
area of a circle whose diameter is one
mil (.001 inch).
circular-mil-foot-A unit conductor having
a cross-sectional area of 1 circular mil
and a length of one foot, sometimes used
for comparing resistance of wires made
from different materials. Thus, the specific resistance of a wire or material is
the resistance in ohms of 1 circular -mil foot of the wire.
clamp-A device for compressing or holding together two or more parts.
class A amplifier-An amplifier in which
plate current flows at all times. Operating values are such that the input signal
voltage swings over a straight portion of
the tube characteristic curve at all times,
but never swings positive and never
swings down to the curved cut-off position.
class AB amplifier-An amplifier in which
plate current flows for appreciably more
than half of each input cycle but not for
the full cycle. The operating point is
essentially the same as for class A, but
the input signal voltage is allowed to
swing a certain amount positive and beyond cut-off so as to improve the efficiency
of operation, and input circuits are specially designed to eliminate the resulting
making a readily removable connection
to a terminal.
clipper-In a television receiver, the circuit which separates the control impulses
from the video signals. Also called synchronizing separator or amplitude sepa-
clockwise-The direction in which the hands
of a clock move.
close coupling-The coupling provided by an
r.f. or i.f. transformer when the primary
and secondary windings are as close together as possible.
coaxial cable-A tube or pipe of conductive
material, usually less than an inch in
diameter, through the middle of which
runs a conductive wire held in position
by insulators. Used to transmit radio or
television signals or to transmit a number of telephone or telegraph messages
simultaneously. Also called coaxial line,
concentric line, pile line, etc.
cobalt-A metallic element often combined
with iron and steel to make special alloys
used in permanent magnets. It is less
magnetic than iron, but retains its magnetism at temperatures as high as 1,100
degrees Centigrade.
class B amplifier-An amplifier in which
the grid bias is approximately equal to
the cut-off value of the tube, so that
plate current is essentially zero when no
signal is applied. Plate current then
flows for approximately half of each
input cycle when a signal is applied. The
code-A system of dot and dash signals used
in the transmission of messages by radio
or wire telegraphy. The International
Morse Code ( also called the Continental
Code) is used everywhere for radio
telegraphy. The American Morse Code is
used commonly for wire telegraphy. Also
a system of sending secret messages.
code recorder-An instrument which makes
a permanent record of code messages
received by radio or otherwise.
coefficient-Any factor of a product can be
called the coefficient of the product of the
remaining factors. Examples In 2xy.
2 is the coefficient of xy ; x is the coefficient of 2y ; y is the coeffiecient of 2x.
Usually, however, only the numerical part
of an expression is called the coefficient.
If there are no numbers in the expression,
the coefficient is assumed to be 1.
coercive force-The amount of opposite magnetomotive force necessary to eliminate
residual magnetism.
grid may be allowed to swing positive on
peaks. Used both in r.f. and a.f. amplifiers. When used as an audio amplifier,
class B operation requires the use of the
push-pull circuit (push -push stage) to
minimize distortion.
class C amplifier-An amplifier in which the
grid bias is greater than the cut-off bias,
so that plate current is zero when no signal is applied, and plate current flows for
appreciably less than half of each input
cycle when a signal is applied. The grid
may swing positive far beyond saturation.
Class C operation is used chiefly for un modulated r.f. stages in transmitters.
clip-A small spring -type clamp having any
of several different designs, used for
coherer-A device used in the early days of
than a channel, to prevent interference
radio communication for detecting the
between stations having adjacent frepresence of electromagnetic waves. It
quency assignments.
usually consisted of a glass tube contain- communication receiver-A receiver deing metallic filings which completed the
signed especially for reception of code or
circuit between two electrodes while
voice messages transmitted by shortallowing current to flow only in one
wave radio communication services.
communication system-A means of excoil-A number of turns of wire wound on
changing intelligence between two or more
an iron core or on a coil form made of
separate locations.
insulating material. A coil offers con- commutating poles-Small poles set between
siderable opposition to the passage of
the main poles of a generator or motor to
alternating current but very little oppoproduce sparkless commutation.
sition to direct current.
commutation-In a d.c. generator, the proccoil form-The tubing or solid object on
ess of changing the generated a.c. voltage
which a coil is wound. It can have any
to a pulsating d.c. voltage by means of a
shape and can be made from any insulatcommutator and brushes. In a high -power
ing material, such as paper, cardboard,
multitube rectifier system, the process of
fiber, bakelite, a plastic or ceramic mashifting the load current from one rectiterial, glass or wood.
fier tube to another.
coincidence counter-A device for counting
pulses which occur in separate circuits at
precisely the same time.
cold cathode-A cathode which does not depend upon heat for electron emission.
The cold cathode of a photoelectric tube
emits electrons when exposed to light,
while in a type BH rectifier tube the
electrons are pulled out of the cold cathode by a sufficiently high voltage applied
to the pointed anode.
collector-In a cathode ray television camera tube, a conductive coating or ring
on the inside of the glass envelope midway between the mosaic and the window
end of the tube, which collects the electrons which leave the light-sensitive mo'ilIvRli l allierafters
saic surface.
collector rings-The rings of an A.C. generator, corresponding to the commutator
of a D.C. generator, from which the commutator-A set of copper segments radially mounted on the armature shaft
brushes collect the electrical energy.
and connected to the armature coils, with
Sometimes called slip rings.
fixed brushes pressing against the comColorama tuning indicator-Trade name
mutator segments at the correct positions
used by General Electric for a system
to give mechanical rectification of the
using colored lights and a saturable -core
a.c. voltage generated in the armature
transformer to indicate when the receiver
is accurately tuned to a station. Green
dial lights glow when tuning is correct, compass-A small permanent magnet
mounted so it can freely rotate. It will
and red lamps glow when the set is tuned
line itself up with the direction of the
off a station.
earth's magnetic lines of force, and point
color code-Any system of colors used to
toward the north and south magnetic
specify the electrical value of a radio part
poles. Used to determine direction in air
or identify terminals and leads.
and sea navigation.
color response-The relative sensitivity of compensator-The portion of a radio direcphotoelectric cells and of the human eye
tion finder which automatically applies
to light of various colors.
part or all of the necessary correction to
the directional indication.
Colpitts oscillator-A tube circuit arranged
so that the cathode is connected to the complementary anFle-One of two angles
junction of two condensers which are in
whose sum is 90 .
series across the coil.
complex number-An expression consisting
communication band-The active band of
of a "real number" plus or minus an
frequencies produced by modulation or
"imaginary" number. Examples R -}- ix ;
keying of a particular transmitter. A
j16. The value following j is the
communication band is always narrower
imaginary component.
compliance-Compliance in a mechanical
system is equivalent to capacity in an
electrical system, and is a measure of the
ability of an object to give or stretch
when a force is applied. Usually used in
referring to the springiness of a loudspeaker moving system.
component-Any part of a whole (current,
force, voltage, etc.) which may be considered by itself. Example : the a.c. component of a pulsating current.
components of a vector-The distances
which determine the position of a vector
with respect to reference lines. The horizontal component is the projection of the
vector upon a horizontal line, and is equal
to the magnitude of the vector multiplied
by the cosine of the angle which the
vector makes with the horizontal. The
vertical component is the projection of the
vector upon a vertical line, and is equal
to the magnitude of the vector multiplied
by the sine of the angle which the vector
makes with the horizontal.
compound-A combination of two or more
compound winding-A two section field
winding for a motor or generator, one
section being in series with the armature
and the other in parallel with the armature.
compression-Squeezing together, as in limiting the audio frequency response of a
device to a certain portion of normal frequency range. Also, a dense region of
air caused by a vibrating body.
concave lens-A lens which is curved inward
on one side and flat on the other side.
concave mirror-A polished reflecting surface curving inward like the inside surface of a sphere or ball.
concavo-convex lens-A lens which is concave on one side and convex on the other
concentric-Having a common center.
concentric cable-Coaxial cable.
concentric line-A shielded transmission
line consisting of coaxial cylinders (a
wire supported by insulators in the center
of a hollow metal tube). Also called
coaxial line, coaxial cable, pile line, etc.
concentric -line oscillator-An oscillator
whose grid and/or plate tank inductances are formed by the elements of a
concentric line. Used in ultra -high frequency work.
condenser-A radio part consisting of two
conducting surfaces separated from each
other by an insulating material such as
air, oil, paper, glass or mica. A condenser is capable of storing electrical
energy. In radio circuits, condensers are
used to block the flow of direct current
while allowing alternating and pulsating
currents to pass. The electrical size or
capacity of a condenser is specified in
microfarads and micro-microfarads.
condenser bank-A number of paper bypass or filter condensers in a single container.
condenser gang-A number of variable condensers operated from the same shaft.
condenser loudspeaker-A loudspeaker in
which the mechanical forces acting in the
diaphragm result from electrostatic interactions of two large, closely spaced
plates when a varying signal voltage is
applied to the plates. Not in common use.
condenser microphone-A microphone consisting essentially of a flexible metal diaphragm and a rigid metal plate arranged
to form a two-plate condenser. Sound
waves set the diaphragm in vibration,
causing the capacity to vary accordingly,
and these capacity variations cause a
varying current flow from the source of
charging voltage.
condenser plates-The half-round metal
plates of a tuning condenser, or the metal
plates of any other condenser.
condenser shaft-The metal rod to which
the rotor plates of a variable tuning
condenser are attached.
condenser, voltage-regulating-A condenser.
usually of the wet electrolytic type, used
in a circuit to maintain a constant voltage
by placing a load on the circuit if the
voltage goes too high.
conductance-The ability of a body to conduct electricity. The unit of conductance
is the mho, which is reciprocal of the ohm.
conduction current-A current formed by
movements of electrons only (not ions) .
conductivity-The ability of a material to
carry electric current.
conductor-A wire or metal structure which
provides a path for electric current between two points. A conductor is thus a
material which offers little opposition to
the continuous flow of electric current.
conduit-A metal pipe through which electrical conductors are run.
cone-The conical -shaped paper or fiber diaphragm of a magnetic or dynamic loudspeaker.
cone of silence-The area directly over the
antenna of a radio beacon transmitting
antenna, in which no signal can be picked
horn-A cone -shaped horn, having
a radius which increases uniformly along
the axis of the horn.
connector-Any device that joins or couples
two or more parts.
console-A large radio receiver cabinet
designed to rest on the floor rather than
on a table.
console receiver-A radio set placed in a
console cabinet.
constant-An unvarying quantity included
as a factor in many formulas, for the purpose of bringing theoretical calculations
into agreement with experience.
constant -amplitude recording-A recording
In which all frequencies of the same intensity are inscribed at the same amplitude. If the entire frequency range is
recorded by the constant amplitude
method, surface noise on the record will
be reduced, due to a better frequency-to noise ratio.
constantan-An alloy of approximately 60%
copper and 40% nickel, used in the construction of precision resistors, rheostats
and measuring instruments.
constant -current generator-A tube circuit
in which the a.c. plate resistance is high
compared to the plate load resistance,
with the result that the current is practically independent of load variations.
A pentode tube acts in this way.
constant -velocity recording-A recording in
which the amplitude of the cut in the
record is inversely proportional to the
frequency in order to hold the vibrational
velocity constant. Since lower frequencies
would require extremely large amplitudes
of cutting, the usual practice is to record at constant amplitude up to about
350 cycles, then change to constant velocity above this point.
contact-A terminal to which a connection
can be made. A joining of bodies to permit the flow of electrical current.
contact microphone-A microphone designed
to pick up mechanical vibrations directly
and convert them into electrical impulses.
It is used chiefly with string, wind and
percussion musical instruments, and is
simply strapped or clamped to the housing of the instrument.
contact potential
voltage difference
which exists between different metals
when in contact with each other.
Continental Code-Same as the International Morse Code. Used universally for
radio telegraphy.
continuity-The property of having a continuous or complete d.c. electrical path,
continuous wave-A radio wave in which
successive cycles are identical (constant
In amplitude) under steady-state conditions. Abbreviated c.w.
contrast control-In a television receiver
the manual control which changes gain.
The most noticeable effect is a variation
or change in the amount of contrast between bright and dark areas of the reproduced image. In effect, it changes the
range of brightness between highlights
and shadows in the image.
control electrode-An electrode to which
a varying voltage is applied for the pur-
pose of varying the current flowing between two or more other electrodes in a
vacuum tube.
control grid-That electrode in a vacuum
tube which has the most effective control
over the plate current passed by the tube.
The control grid is usually the electrode
nearest to the cathode.
control room-A small room in a broadcast
station, partly or completely inclosed in
glass and located next to the main studio,
from which the engineers and production
men control a radio program.
converge-To bring together, as to focus
light rays or radio waves to a single point.
convergent beam-A beam of light whose
rays begin at different distant points and
meet (converge) at a single point.
converter-That section of a superheterodyne radio receiver which changes incoming modulated r.f. signals to a lower frequency known as the i.f. value the converter section includes the oscillator and
the first detector. Also, a device, usually
rotary, for changing electrical energy
from one form to another, as a.c. to d.c.
converter noise-Noise generated in the
oscillator and mixer -first detector sections of a superheterodyne receiver due
to electrons arriving at the plate in spurts
or "shots," so that the plate current
varies from instant to instant.
convex mirror-A polished reflecting surface curving outward like the outside of a
ball or sphere.
convex lens-A lens which is curved outward on one side and flat on the other
coordinate-Any of two or more magnitudes
which determine the position of a point
with respect to reference lines. Ordinary
graphs use rectangular coordinates, in
which the horizontal reference line is
called the X axis or the axis of abscissa,
and the vertical reference line is called
the Y axis or the axis of ordinates. In
polar coordinates, position is determined
with one vector magnitude and the angle
which the vector makes with the horizontal reference line or X axis.
copper-A metallic element widely used in
radio. It is one of the best conductors of
both electricity and heat.
copper-oxide rectifier-A rectifier made up
of discs of copper coated on one side with
cuprous oxide. The discs allow current
to flow in one direction but allow very
little current flow in the reverse direction.
copper -oxide rectifier -type meter-An instrument used to measure a.c. voltages and
currents. The current to be measured is
passed through a full -wave copper -oxide
rectifier, and the resulting direct current
is indicated by a d.c. milliameter.
countersink-To ream, drill or cut a conical
depression around a hole for a flat -head
screw, so that the screw head will be
small flexible wire, usually
stranded, and substantially insulated to
withstand wear.
core-The center of a coil.
core losses-The losses in an iron core coil
or transformer due to eddy currents and
hysteresis in the iron core.
corona-The discharge of electricity which
appears on the surface of a conductor as
a glow of colored light when the potential
gradient (voltage per unit length) exceeds a certain value. It is due to ionization of surrounding air by the high volt-
flush with the surface of the work.
coupled circuits-Separate circuits which
are made to influence one another.
coupler-A device employed to transfer
electric power from one circuit to another.
May be inductive, capacitive or resistive.
coupling-The means by which signals are
transferred from one radio circuit to another. Coupling can be direct through a
conductor, electro -static through a condenser, or inductive through a transformer. Optimum coupling or critical
coupling is that which gives maximum
transfer of signal energy. Tight coupling
is the closest possible coupling under a
given set of conditions. Loose or poor
coupling gives little transfer of signal
energy. Also, a device for connecting two
shafts together end to end.
coupling coefficient-A numerical rating between 0 and 1, specifying the degree of
coupling between two circuits. Perfect
coupling is 1, and no coupling is 0. For
inductive coupling, the coupling coefficient is equal to M
V L L2, where M
is the mutual inductance in henrys,
and L. and L. are the inductance values
in henrys of the individual coils.
coupling condenser-A condenser used to
couple two circuits together.
coupling transformer-A transformer used
to couple two circuits together by means
of mutual induction.
coverage-The portion of a community or
populated region which is effectively
served by a broadcast station from an
corrosion-A chemical action, oxidation or
rusting, which causes a gradual wearing
away of the original metals.
corrugated-Formed with a surface having
the appearance of alternate valleys and
cosecant-The cosecant of an acute angle of
a right triangle (written cac B) is equal
to the hypotenuse divided by the opposite
side. Cosecant is the reciprocal of sine.
See trigonometric function.
cosine-The cosine of an acute angle of a
right triangle (written cos 6) is equal to
the adjacent side divided by the hypotenuse. See trigonometric function.
cosmic rays-Rays originating outside the
earth's atmosphere, having extremely high
frequency and penetrating power. They
can penetrate 18 inches of solid lead or
200 feet of water.
cotangent-The cotangent of an acute
angle of a right triangle (written cot B)
is equal to the adjacent side divided by
the opposite side. Cotangent is the reciprocal of tangent. See trigonometric
Coulomb, Charles Augustin -A French
scientist (1736-1806) noted for his study
of electricity. The unit of quantity of
electricity was named after him.
coulomb-A measure of the quantity of electricity which passes a given point in a
advertising standpoint.
C power supply-Any power supply device
which is connected between the cathode
and grid of a vacuum tube so as to apply
a grid bias, such as a C battery or grid
bias cell.
c.p.s.-Cycles per second.
crater-The cavity formed in the positive
carbon electrode of an electric arc. The
highest light intensity is emitted in the
region of the crater.
crater lamp-A neon lamp having a cup shaped light source, providing a spot
given time. A coulomb is equal to a current of one ampere flowing for one second,
which involves a movement of 6.3 million
million million electrons past a point in
the circuit.
counter-clockwise-In a direction opposite
that in which the hands of a clock rotate.
counter e.m.f.-An electromotive force induced in the armature of a motor, of opposite polarity to the applied voltage. Also
source of light.
critical angle-The angle of incidence beyond which rays of light are no longer
refracted (bent) into a transparent medium, but are totally reflected from its
critical coupling-Coupling which produces
maximum transfer of energy.
c.r.o.-Cathode ray oscilloscope.
cross modulation-A type of station interference (intermodulation) in which the
known as back e.m.f.
counterpoise-A system of wires directly
below an antenna, elevated above and
insulated from the ground, forming a
lower system of conductors for an antenna.
crystal such as silicon or galena in contact with a pointed wire to rectify an
incoming radio signal. Used in crystal
crystal filter-A highly selective tuning
circuit employing a quartz crystal, sometimes used in the i.f. amplifier of a communications receiver to improve selectivity so as to permit reception of a desired
station even when there is strong interference from other stations on nearby
crystal holder-A device to hold a quartz
crystal in a definite position and provide
proper electrical contacts for it. Some
holders have a variable air gap so the
frequency of oscillation may be varied
over a limited range.
loudspeaker in
crystal loudspeaker
which the mechanical forces acting on the
diaphragm result from deformation of a
crystal element. Not in common use.
crystal microphone-A microphone in which
deformation of a piezoelectric crystal by
sound waves or vibrations generates the
output voltage. Widely used in radio.
crystal oscillator-A vacuum tube oscillator
stage whose frequency is determined by
a piezoelectric (quartz) crystal.
crystal oven-A small electrically -heated
oven in which the quartz crystal of a
transmitter is mounted. The oven and
crystal are kept at essentially constant
temperature by automatic temperature
carrier of a desired signal becomes modulated with an undesired signal, so that
the program of the undesired station is
heard in the background of the desired
cross-over frequency-The frequency where
the output from a low-frequency speaker
and a high -frequency speaker are equal.
Below this point, the output is primarily
from the low -frequency speaker, while
above this point the output is from the
high -frequency speaker.
cross -over point-The point at which converging light rays or electron beams cross
and begin to diverge.
cross-section-The total area at right angles
to the length of an object.
cross-talk-Interfering conversation originating at a point other than that of program origin.
cruciform core-A type of transformer core
having the primary and secondary windings on a central core, with four separate
magnetic return paths.
Courtesy General
crystal pickup-A phonograph pickup in
which deformation of a piezoelectric crystal by movements of the phonograph
needle generates the output voltage.
crystal set-A radio receiver which uses a
crystal detector for signal rectification,
and has no vacuum tubes.
C.S.T.-Central Standard Time.
supply-Grid voltage supply.
cube-The third power of a number,
tained by using a number as a factor three
times. Example : 3 x 3 x 3 = 27, which is
the cube or third power of 3.
cube root-A number which, when multiplied by itself three times, equals the
given number. Examples 3 is the cube
root of 27 ; 5 is the cube root of 125. Cube
root is indicated by a radical sign with
3 as the index number. Example x/343.
crystal-A piece
of natural quartz or similar piezoelectric material which has
been ground to a size which will vibrate
naturally at a desired radio frequency
and generate that frequency when set into
vibration. A quartz crystal is used in
radio transmitters to generate with a
high degree of accuracy the tssigned carrier frequency of a station, and is used
in crystal filters of radio receivers to
Improve the selectivity of the i.f. amplifier. The mineral used in a crystal detector is also known as a crystal.
crystal control-Use of a quartz crystal to
maintain operation of a radio station at
cue-A signal, given verbally
by a recog-
nized sound or by sign during a radio
broadcast. Thus, a phrase like "This is
the National Broadcasting Company"
could be a cue signal for radio and telephone operators to switch channels and
lines in preparation for the next network
current-The movement of electrons through
its assigned frequency within the limits
prescribed by law.
crystal detector-A detector utilizing a
Current is measured in
amperes, in milliamperes and in microamperes.
current amplification-The ratio of the signal output current to the signal input
a conductor.
current anti-node-A point along a transmission line or antenna at which current
is a maximum.
current density-The strength of an electric
current per unit cross-sectional area of
a conductor.
current feed-A method of exciting a transmitting antenna by feeding current to it
at a point of maximum current flow.
current loop-A point of maximum current
flow, usually on an antenna. Also called
a current anti-node.
current node-Any point which has zero
current in a transmission line, antenna
or other stationary wave system. Thus,
current nodes exist at the ends of a half wave doublet antenna.
current transformer-A transformer connected into a high current circuit for
measuring purposes. A meter is connected
across the secondary winding, and is calibrated or read in terms of current flowing
in the primary.
curve-The line on a graph which connects
plotted points and shows the relationship
of one variable to another.
curvilinear cone-A curved cone having the
general form of a parabola, used to secure
pure piston action. Often called a para -
cushion socket-A tube socket mounted on
soft rubber or a spring, so that vibration
will not injure or affect the tube.
cut-Removal of spoken or musical material
from a radio program script in order to
fit the prescribed time. Also, a command
telling the studio engineer to disconnect
all microphones, so nothing more can go
out on the air.
cut-off-In a vacuum tube, the grid bias
voltage value at which plate current
ceases to flow. In a selective circuit, the
frequency above or below which an amplifier or circuit fails to respond.
cutout-Any arrangement by which a circuit is automatically opened when the
current flowing through it exceeds or
drops below a certain set value. Usually
an electromagnetic device like a relay.
cutter-The device which transforms electric energy into mechanical motion which
is inscribed into the record by the cutting
stylus during recording.
cutting head-That part of a sound recorder
which cuts or embosses on a disc the irregular grooves corresponding to the wave
form of the sounds being recorded.
cutting stylus-The cutting tool which cuts
the groove into a record during recording.
c.w. or CW-Continuous waves.
cycle-One complete reversal of an alternating current, including a rise to a maximum in one direction, a return to zero, a
rise to a maximum in the other direction,
and another return to zero. The number
of cycles occurring in one second is the
frequency of an alternating current. The
word cycle is commonly interpreted to
mean cycles per second, in which case it
is a measure of frequency. Cycle is
often designated by the symbol
cyclotron-An apparatus which uses electromagnetic and electrostatic means for
imparting tremendously high speeds to
electrified particles. Cyclotrons are used
to bombard the nuclei of atoms so as to
change atomic structure or artificially
produce radioactivity.
cylindrical concave mirror-A curved reflecting surface like the inside of one half
of a cylinder, used to focus light rays to
a line.
cylindrical convex lens-A long lens having
surfaces spherically curved in one direction and straight in the perpendicular to
this direction, used to focus light rays to
a line.
cylindrical wave-A wave whose wave front
is a cylindrical surface.
d.-Distance. Diameter.
damped waves-Radio waves which pro-
gressively decrease in amplitude during
successive cycles.
dampen the studio-To increase the absorption of sound in a studio by bringing
in portable sound -absorbing equipment
such as monk's cloth screens, drapes or
rugs, or by bringing more people into the
damping-Elimination of vibration or oscillation in a meter movement by introducing friction or some other type of loss.
dark spot defect-Dark spots in the reproduced television image caused by electron clouds which form in front of the
mosaic screen in the camera tube at the
D'Arsonval meter movement-The commonest movement employed in precision direct
current measuring instruments. It consists essentially of a small coil of wire
supported on jeweled bearings between
the poles of a permanent magnet, with a
spiral spring holding the coil and the
attached indicating pointer at the zero
position on the meter scale. When the
current to be measured is sent through
this coil, the magnetic fields of the coil
and magnet interact to cause rotation of
the coil and pointer.
db-Decibel ; always written without a
period between the letters.
db meter-A copper-oxide rectifier-type
meter whose scale is calibrated to read
decibel values. Used with audio amplifiers to indicate volume level (particularly in broadcast and p.a. work).
d.c., D.C. or
DC-Direct current
d.c.e.-Double cotton -covered insulation on
d.c. inserter
stage-A television transmitter
stage which introduces a d.c. component
(the pedestal level) into the television
signal. Synchronizing impulses will then
swing the signal in one direction from
the pedestal level, while picture signal
elements swing the signal in the other
direction, with the swing away from the
pedestal level increasing with brightness
in the latter case.
d.c. plate resistance-The average or d.c.
plate voltage divided by the average or
d.c. plate current in a vacuum tube.
d.c. receiver-A receiver designed to operate
from a d.c. power line, such as from the
110 -volt d.c. lines still being used in older
sections of some cities.
d.c. transmission-In television, the transmission of a television signal with the
direct current component represented in
the picture signal.
d.c.voltage-A voltage which sends a direct
current through a circuit, and hence forces
electrons around a circuit in the same
direction all the time.
deadbeat-A descriptive term applied to instruments whose pointers move -to a position without undue oscillation and come
to a "dead" stop. A highly damped meter
dead -center position-The position in which
a brush would be placed on the commutator of a d.c. motor or generator if there
were no distortion of field flux by armature reaction.
dead end-The part of a radio studio which
has the greatest sound absorption.
dead end-The portion of a tapped coil
through which no current is flowing.
dead receiver-A receiver which will not
dead spot-A region in which signals from
certain radio stations are received poorly
or not at all, such as under a steel railroad bridge.
decade box-A system of resistors or other
units whose values are arranged in multiples of 10 so that any desired value of
the unit may be obtained.
deci-A prefix indicating one -tenth of a unit.
decibel-A unit used for expressing a change
in signal level in an a.f. circuit or a
change in sound level. The power level
change in decibels is equal to 10 times the
common logarithm of the power ratio. One
decibel (db) is the amount by which the
pressure of a pure sine wave sound must
be changed in order for the change to be
just barely noticeable by the average
human ear. A decibel can express an
actual level only when some definite reference level is assumed to be zero db.
With sound, the threshold of audibility
is generally assumed to be zero db, while
in a.f. work a power of 0.006 watt is most
generally used as the reference level of
zero db.
decimal point-A period separating a decimal fraction from a whole number.
decoupling-Means taken to prevent coupling between stages or sections of a stage.
definition-Clarity or degree of perfection
of transmission and reception. The characteristic which enables radio listeners
to distinguish between actors in a drama
or to identify various musical units in an
orchestra, and enables television viewers
to distinguish fine detail in the reproduced image.
deflecting coil-A coil of wire used to control by electromagnetic means the movement of the electron beam in a cathode
ray tube in an oscilloscope, television
camera or television receiver. Also called
a deflecting yoke.
deflecting electrode-An electrode in a cathode ray tube to which a potential is applied for the purpose of moving the beam
in a horizontal or vertical direction.
deflection-A movement of an object away
from its resting (normal) position, such
as deflection of a meter pointer, an electron beam in a cathode ray tube or the
vane in a shadow -type tuning indicator.
deflection sensitivity-The beam deflection
in a cathode ray tube caused by a given
change in the field intensity. For electrostatic deflection this is usually given
as volts per inch of deflection.
De Forest, Lee-An American, inventor of
the three -element (triode) vacuum tube.
degaussing-Neutralizing the magnetic field
of a ship so that if it passes over a magnetic mine, the magnetic striker on the
mine will not act and the mine will not
degeneration-Negative feedback, which decreases the amplification. Also called inverse feedback or stabilizing feedback.
deionization time-The time required for the
grid of a gas tube to regain control after
plate current has been interrupted.
delayed a.v.c.-An automatic volume control
circuit which does not begin to act until
signals reach a certain strength. It permits reception of weak signals even
though they are fading at times, whereas
normal a.v.c. tends to make weak signals
delta circuit-A network of three resistors
or impedances connected so they appear
to be arranged in the form of a triangle
like the Greek letter delta (A).
demodulation-The process of rectifying or
detecting a modulated radio signal in
order to remove the carrier and obtain
the desired audio or picture signal.
denominator-The part of a common fraction which is written below the line. Example
the denominator
is 16 ; in
denominator is R.
densitometer-An instrument used to meas-
ure the density or opacity of a material.
The electronic version employs a light
beam, a photoelectric cell and an indicating meter.
density-A measure of the light -reflecting
or transmitting properties of an area. A
measure of the concentration of matter in
a material, in which case density is equal
to weight divided by volume. Current
density is the total current divided by the
cross-sectional area of the conductor.
depolarizes-The chemical used in a primary
cell to prevent polarization due to excess
hydrogen formation at the carbon electrode.
DET.Detector tube or stage.
detector-That stage in a receiver at which
demodulation takes place. In the detector
stage of a t.r.f. receiver, the desired audio
signal is separated from the r.f. carrier.
In the second detector of a superheterodyne receiver, the desired audio signal is
separated from the i.f. carrier.
detune-To change slightly either the capacity, the inductance or both in a tuned
circuit, so that it no longer is in exact
resonance at the applied frequency.
d.f. station-A radio direction -finding station.
diagram-A plan or layout for a receiver,
transmitter or other apparatus. In a
schematic circuit diagram, schematic symbols represent radio parts. In a pictorial
circuit diagram, actual sketches of radio
parts are used. In a block diagram, entire circuits, stages or sections are represented by labelled blocks. In all diagrams, lines are used to represent circuit
dial-Any means for indicating the value
to which a control knob has been adjusted.
Tuning dials of broadcast band receivers
indicate the frequency to which the receiver is tuned, either in kilocycles directly or in kilocycle values having one
zero removed sometimes the wave -length
in meters will also be indicated. Tuning
dials of all -wave receivers may indicate
frequencies in kilocycles and megacycles
as well as in meters.
dial cable-The braided cord or flexible wire
cable used to make a tuning knob control
the position of the pointer or dial which
indicates the frequency to which a radio
receiver is tuned.
dial light-The pilot lamp which illuminates
the tuning dial of a radio receiver.
diameter-A line passing through the center
of a circle and ending at opposite points
on the circle. The distance across, or
width of the circle.
diaphragm-A thin, flexible sheet which can
produce sound vibrations (as in a loudspeaker) or can be moved by sound waves
(as in a microphone). In photography
and in television cameras, an adjustable
device used to reduce the effective area of
a lens so as to increase the depth of focus.
diathermy-Therapeutic use of a high -frequency current to generate heat within
some part of a person. Diathermy machines are actually short-wave transmitters, and often cause serious radio interference.
dielectric-The insulating material between
the plates of a condenser.
dielectric constant-The ratio of the capacity of a condenser using a given substance
for a dielectric to the capacity of the
same condenser with air for a dielecfric.
Air has a dielectric constant of 1, glass
a dielectric constant of 4 to 8, etc.
dielectric strength-The voltage a dielectric
of unit thickness can withstand without
breaking down.
diffraction-The bending of a radio wave or
light ray around an obstacle.
diffusion-Scattering of light.
dimmer-An adjustable resistance by means
of which lights may be gradually dimmed
or brightened.
diode-A vacuum tube having two electrodes, one being the cathode and the
other the plate or anode. A diode allows
electrons to pass in only one direction
from the cathode to the anode.
diode-pentode-A vacuum tube having a
diode and a pentode in the same envelope.
diopter-A unit equal to the reciprocal
of focal length in meters.
dipole antenna-To the radio physicist, an
elemental (very small) length of radiating antenna, having opposite charges at
the ends and having uniform current distribution. The term is used to describe
any short antenna, not necessarily resonant at the transmitting frequency.
Also, sometimes loosely used to describe a
doublet antenna.
direct coupling-The use of a conductor to
connect two circuits together and provide
a direct path for signal currents.
direct current-An electric current which disc-A phonograph record or blank. Also
flows in only one direction. It is not nec
the rotating element of a mechanical teleessarily constant in value.
vision scanning system.
direct -current amplifier-An amplifier whic h discharge-A release of energy which has
is capable of amplifying small variation s
been stored up, as in the case of a disin direct current.
charge from a condenser.
direct inductive coupling-A method o f discriminator-That stage of an f.m. recoupling in which one circuit is connecte d
ceiver which converts f.m. signals directly
directly to a tap on the inductance ele
into audio signals. Also, a similar stage
ment of another circuit.
in an a.f.c. system.
directional antenna-An antenna which dissector tube-Trade name for the cathradiates or receives radio waves better in
ode ray television camera tube developed
some directions than others.
and used by Farnsworth.
directional pattern of an antenna-A special distortion-Improper reproduction of a
graph (polar characteristic) which indisound or television radio program due
cates the intensity of the radiation field
to changes occurring in the wave form
of a transmitting antenna at a fixed disof the intelligence signal somewhere in
tance in different directions in space. In
the path it takes through the transmitting
the case of a receiving antenna, it indiand receiving system or through an amcates the response of the antenna from
plifier system.
different directions to a signal having distributed capacity-Capacity distributed
unit field intensity.
between conducting elements such as
direction finder-A radio receiving device
wires, as distinguished from capacity
which can be used to determine the line
concentrated in a condenser. Usually
of travel of radio waves. It usually employs a highly directional loop antenna.
direction -finder deviation-The difference
between the observed radio bearing and
the true (corrected) radio bearing of a
direction finder.
direction of polarization-The direction of
the displacement vector in a linearly polarized wave. In an electromagnetic
wave, however, the direction of polarization is the direction of the electric displacement. Thus, a vertically polarized
wave is one having the electric Held component in a vertical (up and down) plane
with respect to the earth's surface.
director-In a directional antenna system.
the director is the front portion which is
not connected to the transmitter or reused to specify the small capacity existceiver. The purpose of the director is to
ing between. the turns of wire in a coil.
increase the effectiveness of the antenna
in the forward direction.
distributed constants-Constants which exist along the entire length or area of a
directly proportional-Varying uniformly as
circuit, such as distributed capacity besome other value varies.
tween each pair of adjacent turns in a
direct resistance -coupled amplifier-An amcoil, or the distributed inductance which
plifier stage coupled to a following stage
exists in each elemental length of a conby directly connecting the plate element
of the first stage to the control grid element of the second stage. The plate load distributed inductance The inductance
which exists along the entire length of a
for the first stage is a resistor which is
conductor, as distinguished from selfcommon to both stages.
inductance concentrated in coils.
direct scanning-A method of scanning in
which the entire subject is simultaneously distribution control-The control which
varies the amount of correction applied
illuminated, and a device is used to view
to the saw -tooth wave in a television
a limited area of the scene at a time.
receiver so as to give the desired linear
direct wave-A wave that is propagated
scanning of lines.
directly through space, without being reflected.
divergent-Spreading out from a point
of origin, as of light rays or radio waves.
directivity The antenna characteristic
which causes it to radiate or receive divergent beam-A beam of light whose
more power in certain directions than
rays start at a single point and spread
in others.
dividend-A number or quantity that is
to be divided. Example : In the expres-
sion 1400=70=20, the dividend is 1400.
(The divisor here is 70, and the quotient
is 20.)
division-The process of finding how many
times one number is contained in another. The standard sign which indicates
division is =. In algebra, a horizontal
line (or sometimes a fraction bar) is
used instead of the conventional division
and E/R all
sign. Example : E±R,
mean that
dividing positive and negative numbers,
the quotient is positive if both numbers
have like signs, and the quotient is negative if the numbers have unlike signs.
divisor-The number by which a number
or quantity is to be divided. Example : In
1400 _ 70 =220, the divisor is 70. (The
dividend here is 1400, and the quotient is
E is to be divided by R.
dog house-The structure at the base of a
transmitting antenna tower which houses
the antenna tuning equipment and
Doherty amplifier-An amplifier circuit in
which one tube supplfes unmodulated carrier power and a second tube, feeding the
same load as the first, is biased so no
plate current flows until the r.f. grid
voltage (modulated carrier signal) exceeds the bias on the tube. When this
happens, power is fed to the load, and
the effective impedance of the load is
lowered. This results in an increase in
power from the first tube.
double -button carbon microphone-A carbon microphone employing two buttons or
containers for carbon granules, one on
each side of the diaphragm, so as to
secure a push-pull action which gives
increased signal ouput.
double -concave lens-A lens with both sides
curved inward, so the center is the thinnest section. It causes light rays to
double -convex lens-A lens with both sides
curved outward, so that the center of
the lens is the thickest portion.
double modulation-The process of modulation in which a carrier wave of one
frequency is first modulated by the signal wave, and is then made to modulate a
second carrier wave of higher frequency.
double -pole switch-A switch which simultaneously changes connections in two
separate circuits or in both sides of the
same circuit.
double superheterodyne-A superhet using
two first detector stages. The local oscillator signal combines with the desired
signal in the first tube to produce a preliminary i.f. value, and this combines in
the second tube with the same local oscillator signal to produce the final i.f. value.
Used in some f.m. sets to get more gain
and to stabilize operation at high frequencies.
double -throw switch-A switch which connects one circuit terminal to either of two
other circuit terminals.
doublet antenna-A Hertzian antenna system, independent of the earth, usually a
half wavelength long or some multiple of
this length. The term is also used to
describe a shorter antenna which should
be called a dipole antenna.
down lead-The wire connecting the antenna
proper with the receiver. More often
called a lead-in.
Dow oscillator-An electron -coupled oscillator circuit originated by Dow.
d.p.d.t.-Double-pole, double -throw. A type
of switch.
d.p.s.t.-Double-pole, single -throw.
drain-A term used to indicate that current is being taken from a voltage source.
drive pin-A pin similar to the center pin
on a phonograph turntable, but located to
one side of center, sometimes used to prevent the record from slipping on the turntable during recording.
driver stage-The amplifier stage preceding
the high -power audio output stage in a
transmitter. It is called a driver stage
because it delivers power as well as voltage for excitation of the output stage.
drop-The voltage drop developed across a
resistor due to current flow through the
drop -out current-That value to which the
current through a relay coil must be
reduced before the armature will be released (will drop away from the core).
drum speed-The number of scanning lines
per minute in a facsimile system.
drum switch-A series of contacts on a
rotating drum which make contact with
fingers fastened to an insulated support.
Used for complex circuit changes.
dry battery-A group of dry cells connected in various series, parallel or series parallel arrangements to get desired voltage and current values.
dry cell-A type of primary cell in which
the electrolyte is in the form of a paste
rather than a liquid. Dry cells are used
extensively in radio batteries.
dry electrolytic condenser-An electrolytic
condenser in which the electrolyte is a
paste rather than a liquid, to permit using
the condenser in any position without
danger of the electrolyte leaking out.
d.s.c.-Double silk -covered insulation on a
d.t.-Double-throw. A type of switch.
dual modulation-The process of modulating a common carrier wave or sub-carrier
by two different types of modulation, such
as both amplitude and frequency modulation, each conveying separate information.
dummy antenna-A resistor or other device
which duplicates the electrical characteristics of a transmitting antenna without
radiating radio waves. Used for testing
and adjusting transmitters.
duodiode-A vacuum tube having two diodes in the same envelope. Also called
double diode.
duodiode-pentode-A vacuum tube having
two diodes and a pentode in the same
Also called double -diodepentode.
duodiode-triode--A vacuum tube having two
diodes and a triode in the same envelope.
Also called duplex diode-triode.
duotriode-A vacuum tube having two triodes in the same envelope. Also called
double triode.
duplex operation-Simultaneous transmission and reception of radio signals between two stations.
duralumin-An alloy of aluminum which
is comparable in strength and hardness
to soft steel. It contains 95.5 parts aluminum, 3 parts copper, 1 part manganese
and .5 part magnesium.
dynamic microphone-A microphone operating on the same moving coil principle
as a dynamic loudspeaker. Sound waves
move the diaphragm, causing the attached
voice coil to move in and out of a fixed
magnetic field produced by a permanent
magnet. The a.f. output voltage is thus
induced in the moving coil.
dynamic pickup-A phonograph pickup in
which the electrical output is due to motion of a conductor or coil in a magnetic
dynamo-A term sometimes used to describe an electric. motor or generator.
dynamotor-A rotating device acting both
as motor and generator, used to change
a d.c. voltage to an a.c. voltage or to a
higher d.c. voltage. It is used chiefly for
portable and mobile operation of radio
transmitters and p.a. amplifiers from
storage batteries.
dynatron-A tube circuit arranged so that
secondary emission from the plate causes
plate current to decrease as plate voltage
is increased. The resulting negative resistance characteristic makes a dynatron
useful in radio for oscillator circuits.
dynatron oscillation-Oscillation produced
by negative resistance due to secondary
emission from the plate of a vacuum tube.
dyne-The c.g.s. unit of physical force. A
dyne is equal to 1/980th gram.
dyne per square centimeter-The unit of
sound pressure. The term bar was formerly used to mean a sound pressure of
one dyne per square centimeter, but the
term is being dropped in acoustics. A bar
was originally a pressure of 1,000,000
dynes per square centimeter in all fields
except acoustics, hence the confusion.
dynode-One of the "plate" elements in a
multiplier type tube.
DX-A slang expression for distance, used
E-Voltage (d.c. value or effective a.c.
distant radio stations.
dynamic characteristic-A graph plotted for
operating conditions of a tube, with a.c.
e-Instantaneous value of voltage.
E or e-Notation commonly used for elec-
value) .
chiefly in connection with reception of
tromotive force or voltage.
eccentric circle-A blank endless groove
whose center is other than that of the
record, provided on some records to actuate the tripping mechanism of an automatic record changer after the record has
been played.
eccentric spiral-The blank spiral groove
leading from the end of a record to the
eccentric circle.
echo-A radio wave which has been reflected at one or more points in the transmission medium, so that it is received
applied to the grid.
dynamic loudspeaker-A loudspeaker in
which the diaphragm or cone is attached
to a small coil mounted so it can move
within a constant magnetic field. Audio
frequency currents flowing through this
coil (called the voice coil) make it move
in and out, thereby causing the diaphragm
to reproduce sound waves. The magnetic
field is produced by a permanent magnet
in p.m. dynamic loudspeakers, and by an
electromagnet (field coil) in electrodynamic loudspeakers.
separately from the main transmission.
Also, a sound wave heard after reflection
from one or more surfaces.
echo chamber-A reverberant room used to
add hollow effects and actual eclioes to
radio programs. These effects may also
be produced electrically.
eddy currents-Circulating currents induced
in conducting materials by varying magnetic fields. They are undesirable because they represent loss of energy and
cause heating. Eddy currents are kept
at a minimum by employing laminated
construction for the iron cores of transformers, a.f. choke coils, and other magnetic devices.
Edison base-The standard screw base used
for ordinary electric light bulbs in this
Edison cell-A type of storage battery employing an alkali electrolyte. Not used
much in radio.
effective antenna length-The length which,
when multiplied by the current at the
point of maximum current, will give the
same product as the length and uniform
current of an elementary dipole antenna
at the same location, and give the same
radio field intensity in the direction of
maximum radiation.
effective current-That value of alternating
current which will cause the same heating effect as a given value of direct current. For sine wave alternating currents,
the effective value is approximately seven tenths of the peak value. Also called the
r.m.s. value.
effective height-An antenna rating. It is
equal to the height of a perfect antenna
giving the same field strength.
effective value-The alternating current
value which will produce as much heat
as the corresponding direct current value.
Thus, an alternating current with an
effective value of 1 ampere will produce
the same heat as a direct current of 1
ampere. The effective value is also
called the root -mean -square (r.m.s.)
value, because it is equal to the square root
of the average (mean) of the squared
instantaneous values equally spaced in an
alternation or half -cycle. All a.c. meters,
unless definitely marked otherwise, read
effective values of voltage and current.
efficiency-The ratio of energy output to
energy input, usually expressed as a percentage. A perfect electrical device
would have an efficiency of 100%.
Er-Grid voltage of a tube.
elasticity-The ability of a substance to return to shape after being stretched or
otherwise deformed.
E layer-An ionized layer in the atmosphere, capable of reflecting or bending
radio waves back to earth. The E region
extends between about 55 and 85 miles
above the earth's surface.
electralloy-A soft iron alloy used for radio
chassis construction.
electrical bandspread-The use of a small
variable condenser in parallel with each
main tuning condenser in a short-wave
receiver, to provide more accurate tuning
by spreading the stations in a single
band over the entire tuning dial.
electrical interference-Interference caused
by the operation of electrical apparatus
other than radio stations.
electrical transcription-A 16 -inch diameter
recording of sound or music, designed for
playing at a speed of 33-1/3 revolutions
per minute, having high fidelity and made
especially for broadcast purposes. Transscriptions permit broadcasting of a program at any desired time by any number
of stations.
electric eye-Popular expression for a cathode ray tuning indicator tube used in
modern radio receiving sets. It consists
of a fluorescent screen with a dark sector
which varies in direct proportion to the
strength of the incoming signal. Also, a
popular name for a photoelectric cell.
electric field-A region in space surrounding a charged object. Lines drawn to represent the direction in which the electric
field will act on other charged objects are
called electric lines of force. A moving
electric field, such as that associated with
electrons in motion or with a radio wave,
is always accompanied by a moving magnetic field.
electricity-A general term used when referring to the energy associated with
electrons at rest or in motion.
electric organ-A musical instrument which
employs electrical circuits and electrical
devices instead of wind to produce tones
similar to those of a pipe organ.
electrochemical recording-Recording by
means of a chemical reaction brought
about by the passage of signal -controlled
current through the sensitized portion of
the record sheet of a facsimile receiver.
electrode-An essential part inside a vacuum
tube, such as the cathode, the various
grids and the plate. Also, the plates of a
primary cell, secondary cell or electrolytic
condenser, or the carbons of an arc.
electrode current-The current passing to
or from an electrode through the space
inside a vacuum tube.
electrode dissipation-Power dissipated as
heat by a vacuum tube electrode as a
result of electron and/or ion bombardment.
electrode voltage-The voltage applied between an electrode and the cathode in a
vacuum tube.
ductor which constitutes an electric
electron coupling-A method of coupling in
which an electron stream transfers energy
from the anode grid of the oscillator to
the plate in the load circuit. Electron
coupling is used principally with multi grid tubes. It was first introduced by
Dow, and is sometimes called a Dow
electron drift-The actual movement of
electrons when a current flows.
electron emission-The ejection of electrons
from the surface of a material into surrounding space due to heat, light, high
voltage or other causes. In a thermionic
vacuum tube, electron emission from the
cathode Is produced by heat from the
electron gun-That part of a cathode ray
tube which includes the electron-emitting
cathode and the associated parts which
concentrate, control and focus the stream
electrodynamic loudspeaker-A dynamic
loudspeaker in which the magnetic field
is produced by an electromagnet. The
coil of this electromagnet is known as the
field coil.
electrolysis-To the radio man, electrolysis
is the action which occurs whenever electric currents cause corrosion by flowing
in and out of the surface of a conductor,
due to resistance developing in a joint
or conductivity in adjoining insulation.
The resulting corrosion causes characteristic green spots to develop on copper
wire and will eventually break the circuit. To the chemist, electrolysis is the
decomposing of a compound into its elements by electricity.
electrolyte-The liquid or chemical paste
which is used between the electrodes of
a dry cell, storage battery or electrolytic
electrolytic condenser-A fixed condenser in
which the dielectric is a thin film formed
on the surface of one aluminum electrode by a liquid or paste electrolyte. Also
see dry electrolytic condenser.
electrolytic rectifier-An electrolytic cell
which allows current to pass in only one
direction. Little used today.
electromagnet --A coil of wire, usually
wound on an iron core, which produces a
strong magnetic field when current is
sent through the coil.
electromagnetic field-The electric and
magnetic fields produced by the flow of
electrons through a wire or coil.
electromagnetic induction-The action which
causes a voltage to be induced in a
closed loop when the number of magnetic
lines of force passing through the loop
is changed in any way.
electromagnetic unit-A unit of measurement of magnetic force, derived from
basic c.g.s. units.
electromagnetic wave-A wave in which
there are both electric and magnetic fields,
at right angles to each other. Electromagnetic waves are known as radio
waves, heat rays, light, X rays, etc.,
depending on the frequency.
electromechanical-A combination of mechanical and electrical forces.
electromechanical recording-Facsimile recording by means of a signal -actuated
mechanical device.
electromotive force-The force that causes
motion of electrons. More often called
voltage or potential.
electron-The elementary particle of negaSome electrons are
tive electricity.
closely associated with atoms of matter,
while others, called free electrons, move
readily between atoms under the influence
of electric or magnetic fields. It is the
movement of electrons through a con-
of electrons to a spot of the desired size
on the fluorescent screen at the end of
the tube.
electronic control-The control of a machine
or device by apparatus employing electron tubes.
electronic lens-An arrangement of electrodes and/or magnetic deflecting and
focusing coils which is used to control
the direction and size of a beam of electrons, much as a glass lens controls light
electronics-That branch of science which
relates to the conduction of electricity
through gases or in a vacuum. Electronics
is thus a broad field of electricity which
deals with all types of applications for
electron tubes, including radio, television,
photoelectric applications, facsimile, diathermy, industrial control, etc.
electronic optics-That branch of electronics
dealing with the control of the movements of electrons by the application of
electrostatic and electromagnetic forces.
electronic scanning-Scanning by means of
a cathode ray tube, as opposed to mechanical scanning by means of a disc or
electronic television-A television systèm in
which the scene to be transmitted is
scanned and reconstructed by electron
beams in cathode ray tubes. The process
is entirely electrical, with no mechanical
moving parts.
electron microscope-A device which directs
a beam of electrons on the object being
examined, magnifies the resulting shadow,
and makes this shadow visible on a fluorescent screen or records it on photographic film. Magnification as high as
30,000 diameters has been obtained, far
greater than can be obtained with the
best optical microscopes.
electron -multiplier tube---A vacuum tube so
designed that the initial electron current
produced by a thermionic or light-sensitive cathode causes secondary emission
from a number of anodes to take place
and contribute to the total electron current. Each time an anode is struck by
an electron stream, the secondary electrons combine with the electron stream
to form a larger electron stream, which
in turn produces more secondary emission from the next anode in line. The
final electron current arriving at the collector anode is the sum of the individual
secondary emission currents and the
initial cathode current.
electron tube-Any partly -evacuated, completely -evacuated or gas -filled tube used
to control the flow of electrons in a
circuit. Vacuum tubes, phototubes, mercury vapor rectifier tubes and cathode
ray tubes are all electron tubes.
electroplating-A process for applying a
thin coating of metal to a metallic surface by means of an electric current.
electroscope-An instrument for detecting
static charges of electricity.
electrostatic-Pertaining to static electricity.
electrostatic coupling-The coupling of two
circuits by a capacity, so that one circuit
influences the other through condenser
charges and discharges.
electrostatic field-The influence (often
called electric lines of force) which exists
in space near an electrically charged
body and is capable of acting on another
charged body.
electrostatic focusing-Focusing of an electron beam in a cathode ray tube by the
action of an electric field.
electrostatic shield-A grounded piece of
metal used to prevent the interaction of
electric fields. It is used between primary and secondary windings of some
electrostatic voltmeter-A voltmeter which
operates on the principle that two like
charged bodies will repel each other.
Such a voltmeter has two plates opposite
each other, one free to move. As the
voltage applied to the plates is increased,
the movement increases and a pointer
connected to the movable plate indicates
the degree of voltage applied.
electrothermal recording-That type of
electrochemical facsimile recording in
which the chemical change is produced
principally by heat.
element-One of the ninety-two known
basic forms of matter which make up
the universe. The term is also used to
refer to the important parts of a device
thus, the cathode, grid and plate would
be called the elements of a triode vacuum
elemental area-In television and facsimile,
any segment of a scanning line, the dimension of which along the line is exactly
equal to the nominal line width.
elliptically polarized wave-A wave in
which the direction of displacement at a
point rotates about a point in a plane
and the magnitude of displacement varies
as the radius of an ellipse.
e.m.f.-Electromotive force.
emission characteristic-A relation, usually
in the form of a graph, between the
emission of a vacuum tube electrode and
the cause of the electron emission (such
as the temperature, voltage or current of
the filament or heater).
emitron-Term applied to one British version of a television camera tube.
empirical--Based on experience or observation.
e.m.u.-Electromagnetic unit.
enameled wire-Wire coated with an insulating layer of baked enamel.
energy-Ability to do work. Thus, the
electrical energy stored in a dry cell has
the ability to heat a radio tube filament,
operate a buzzer, etc.
envelope-A curve which is drawn to pass
through the peaks of a graph showing
the wave form of a modulated r.f. carrier
signal. Also, the glass or metal housing
of a radio tube.
Er-Plate voltage of a tube, measured with
respect to the cathode.
equalizer-A coil or condenser used alone,
in combination with each other or with
resistors, inserted in a radio circuit for
the purpose of producing a flat electrical or acoustical frequency response
over a desired frequency range, or for
changing the response to satisfy particular requirements.
equation-A mathematical statement that
two numbers, quantities or expressions are
equal. The equality sign (=) is used
to separate the two equal quantities.
Examples P= EI; 7'= 49; (a + b)'_
a2 -i- 2ab -}- b'. A formula is an equation
because it involves equality, but an equa :
tion is a formula only when it expresses
a scientific fact, law or principle.
equipotential line-An imaginary line in
space along which no potential difference
exists between any two points of the line.
This same definition applies to equipotential surface and equipotential space.
equisignal radio range beacon-A radio
beacon station which transmits two distinctive signals, these being received with
equal intensity only in certain directions
which constitute the route in air for
equisignal sector-The on -course region in
which the two different signals from an
equisignal radio range beacon are received
with equal intensity.
equivalent circuit-An arrangement of resistors, coils and condensers to simulate
or electrically replace a more complicated circuit, to permit easier analysis.
equivalent loudness level-The intensity
level in decibels of a 1000 -cycle pure tone
which seems equivalent in loudness to the
sound under consideration. The threshold
of hearing for a 1000 -cycle pure tone is
usually used as the reference level.
equivalent resistance-A lumped or concentrated resistance which would cause the
same loss as smaller resistance values
distributed throughout an entire part or
circuit. Used chiefly for convenience in
computations or for determining circuit
E region-The region of the ionosphere between about 55 and 85 miles above the
earth's surface.
erg-The basic unit of work in the c.g.s.
system. The work done by a force of
one dyne acting through a distance of
one centimeter.
Esg Sreen grid voltage, measured from
screen grid to cathode.
escutcheon-The ornamental wood, metal
or plastic framework for a radio dial,
tuning indicator or other panel -mounted
part in a radio receiver or amplifier.
a reflector, the exciter is the portion
which is directly connected to the source
of power (to the transmitter) . In a transmitter, the exciter is the crystal oscillator or self-excited oscillator which generates the carrier frequency. Also, the
small auxiliary generator used to provide field excitation for some large generators.
exciting current-The current which flows
through the primary winding of a power
transformer when there is no load connected to any secondary winding.
exponent-A number written at the right of
and slightly above another number to in dictate how many times the number is to
be multiplied by itself. The result is
the power of the number. Examples :
5' means 5X5X5X5, and is pronounced
"5 fourth power." The result, 625, is the
fourth power of 5. 12 means 1X1, and
is pronounced "1 square" or "1 second
power." A negative exponent means to
find the reciprocal of the number with a
positive exponent. Example :
fractional exponent indicates the root
of a quantity. Example :
xi means \/x; xi means fix; xt means v,xb
exponential horn-A loudspeaker horn
whose cross-sectional area varies exponentially with its length.
extinction potential-The lowest value to
which the plate voltage of a gaseous
triode can be reduced, with a certain
grid bias (if used), without stopping the
flow of plate current.
extraordinary wave-One of two components into which a radio wave is split
in the ionosphere by the earth's magnetic
field. This wave is sometimes called
the X wave. The other component is the
ordinary wave.
E.S.T.-Eastern Standard Time.
e.s.u.-Electrostatic unit, used in the
system for specifying the strength of an
electric field.
ether-The medium which is supposed to
°F-Degrees Fahrenheit, the English scale
heat and light waves are supposed to
traveL Its existence has not yet been
facsimile-The process of transmitting and
fill all space, and through which radio,
of temperature.
reproducing photographs, drawings, handwriting, sketches and printed matter of
any kind for permanent record reception
by means of a radio or wire communication system. "Type A facsimile" is a
system of facsimile communication in
which images are built up of lines or dots
of constant intensity. "Type B facsimile"
(telephotography, photoradio, etc.) is a
system of facsimile communication in
definitely proved.
excitation-Application of a signal to the
input of an amplifier stage. Application
of signal power to a transmitting antenna.
Application of voltage to the field coils
of a motor or generator, or to the field
coil of an electrodynamic loudspeaker.
exciter-In a directional transmitting antenna system of the type which includes
The farad is too large a unit for practical radio work, hence smaller units are
usually employed. The microfarad, equal
to one millionth of a farad, is widely
used. An even smaller unit, the micromicrofarad, is also used in radio ; it is
equal to one millionth of a microfarad.
Faraday, Michael-English scientist (17911867) who discovered electromagnetic induction.
Faraday shield-A network of parallel
wires all interconnected at the same end
like a comb to provide electrostatic shielding. The end which connects to all conductors is grounded, and the entire assembly placed between two coils to eliminate
stray capacity, or is placed around a 1009
aerial to eliminate electrostatic pickup of
signals. Also called a Faraday screen.
FCC-Federal Communications Commission.
Federal Communications Commission- A
board of commissioners appointed by the
President under the Communications Act
of 1934, having the power to regulate all
U. S. communication systems, including
radio, television, telegraph, cable and
feed-To transmit a program over telephone
lines to stations or groups of stations or
to any listening point.
feedback-The returning of a fraction of the
output of a stage to the input either electrically or acoustically. When the fed back signal is in phase with the input signal, positive feedback or regeneration
exists and increases the amplification.
This may produce squealing or howling.
When the fed -back signal is out of phase
with the input signal, negative feedback
or degeneration exists and decreases the'
feedback cutter-In sound recording, a cutter in which a voltage generated by
movement of the cutting stylus is fed
back into the amplifier system, usually
for the purpose of reducing distortion or
stabilizing frequency characteristics.
feeder-A main wire or set of wires supplying energy from a source to a useful load.
fiber-A hard, tough material made of
paper and cellulose, compressed into
sheets, rods or tubes and used in radio
for insulating and supporting purposes.
fidelity-The faithfulness with which part
or all of an electrical system delivers an
exact reproduction of the input signal
wave form.
field-In television, the area covered during
one vertical sweep of the scene. In normal scanning, the field is the entire scene.
In double interlaced scanning the field is
one-half the area of the scene. Also, a
general term describing the effect produced in surrounding space by an electrically 'harged object, by electrons in
which images are built up of lines or dots
of varying intensity.
facsimile receiver-The apparatus employed to translate the signal from the
facsimile communication channel into a
facsimile record of the subject copy.
facsimile recorder-The part of a facsimile
receiver in which the picture signal in
its final form is systematically registered upon a paper record sheet.
facsimile transmission-The transmission
of signal waves produced by scanning
fixed graphic material, including pictures,
for permanent reproduction on paper or
facsimile transmitter-The apparatus used
to translate pictures and other subject
copy into signals which can be transmitted by radio.
factor-If two or more numbers are multiplied together, each of them or the
product of any combination of them is a
factor of the product. Example 2, x, y,
2x, 2y and xy are all factors of 2xy.
fade-To change gradually in loudness. A
program is faded in by making it gradually louder, and is faded out by diminishing its volume gradually to zero.
fadeout-Intentional, gradual disappearance of a movie or television scene prior
to viewing a different scene. Also, the
failure of radio waves to arrive at a
location due to magnetic storms or atmospheric disturbances.
fader-A device for electrically diminishing
or increasing volume in an audio amplifier
system. Also, a type of volume control
which gradually reduces the volume of
one audio signal while gradually increasing the volume of another signal.
fading-A variation in the intensity of
received radio signals to changes in atmospheric conditions along the path taken
by radio waves between the transmitter
and receiver.
Fahnestock clip-A spring -type terminal to
which a temporary connection can readily be made.
The temperature -measuring
system generally used in the United
States, in which 32 degrees is the freezing point and 212 degrees is the boiling
point of water at sea level.
farad-The basic unit of capacity. A condenser is said to have a capacity of 1
farad when a change of 1 volt per second
across it produces a current of 1 ampere.
operated apparatus for use as a filament
voltage source.
filter-A selective circuit network designed
to pass currents within a certain range of
frequencies or to pass direct current, while
reducing considerably the amplitudes of
currents at undesired frequencies. A lowpass filter passes all frequencies below its
cut-off value. A high-pass filter passes all
frequencies above its cut-off value. A
band-pass filter passes all frequencies between its two cut-off values. A band elimination filter passes frequencies outside
its two cut-off values, eliminating frequencies between. A filter usually consists of a resistor, coil, condenser or any
combinations of these parts, sometimes
also with a crystal. Thus, the filter in a
radio power pack is a coil, condenser and
resistor combination which receives a pulsating direct current having many a.c.
components, but delivers an essentially
pure and constant direct current. A filter
may be used in an aI. circuit to change or
correct tone characteristics by attenuating
certain audio frequencies. The term filter
also applies to a pane of glass which absorbs or blocks certain colors of light
while allowing others to pass.
filter choke-An iron -core coil used in a
filter system to pass low frequency currents or direct current while limiting
or blocking the flow of higher -frequency
alternating or pulsating currents.
filter condenser-A condenser used in a filter
system to permit passage of higher-frequency currents while limiting or blocking the flow of lower -frequency currents
and direct current. Thus, a power pack
filter condenser passes hum ripple currents while blocking direct current.
final radio stage-The stage which supplies
power to the transmitting antenna.
first audio stage-The first stage in the
audio amplifier of a radio receiver. Audio
signals are fed into this stage by the
detector of a t.r.f. receiver, and by the
second detector of a superheterodyne receiver.
first detector-That stage in a superheterodyne receiver in which the incoming modulated r.f. signal and the r.f. signal from
the local oscillator are combined to produce the i.f. signal.
fishbone antenna-A directional antenna
consisting of a number of doublets arranged on both sides of a transmission
line, with all doublets making the same
angle with the line as in the skeleton of a
fish or a so-called herringbone pattern.
fishpaper-A specially-treated fiber paper
used to insulate transformer windings
from the transformer core. Also used for
other applications where an insulating
paper with high mechanical strength is
motion or by a magnet. See eléctric field
and magnetic field.
field coil-In an electrodynamic loudspeaker,
electric motor or generator, the coil or
coils which produce the constant -strength
magnetic field.
field frequency-In television systems employing interlaced scanning, this term
refers to the number of times per second
the frame area is fractionally scanned
by a downward sweep of the electron
field intensity-In radio, this is the effective (r.m.s.) value of the electric or
magnetic field produced at a point by
radio waves from a particular station. It
is usually expressed as electric field intensity in microvolts per meter or millivolts per meter. Unless otherwise specified, it is assumed that the measurement
is made in the direction of max_mum field
intensity. Also, the amount 01 magnetic
flux produced by an electromagnet or permanent magnet.
field poles-The projecting iron ends of the
field coils of a motor or generator.
field rheostat-A variable resistance used
to regulate the current flowing through
the field coils of a motor or generator.
field strength-Same as field intensity.
figure-A written or printed character representing a number. A numeral. A
digit. Examples : 1, 5, 6, etc.
filament-The resistance wire through
which filament current is sent in a vacuum
tube to produce the heat required for
electron emission. When electron emission
is from the surface of the filament wire
itself, the filament also serves as the
cathode. In a heater -type or :ndirectlyheated tube, the filament supplies heat
to a separate cathode electrode.
filament circuit The compietn circuit
through which filament currant flows
from the filament voltage source to the
filaments of radio tubes.
filament current-The current sapplied to
the filament of a vacuum tube f er heating
filament emission-The process by which
electrons are given off from a heated
filament in a vacuum tube.
filament rheostat-A variable resistance
used to limit the flow of current through
the filaments of older types of vacuum
filament voltage-The voltage value which
must be applied to the filament terminals
of a vacuum tube in order to send the
rated value of filament curren through
the filament.
filament winding-A separate secondary
winding provided on the power transformer of a radio receiver or other a.c.-
fixed condenser-A condenser having a definite capacity value which cannot be adjusted.
fixed resistor-A resistor having a definite
ohmic value which cannot be adjusted. A
fixed resistor with intermediate connections or taps is known as a tapped
flare factor-The outward curvature of a
loudspeaker horn, expressed as a number.
flat top-The horizontal portion of an antenna.
flat -top response-A broad frequency response such as that obtained by tuning
primary and secondary trimmers of an
i.f. transformer to slightly different fre-
F layer-An ionized layer in the F region
of the atmosphere, existing chiefly
number-A number obtained
by dividing
the focal length of a lens by the effective
diameter of the lens. A lens having a
focal length of 8 inches and a useful
diameter of Y2 inch would have an f
number of 16, written as f16, f/16, f :16,
f.16, F/16, F 16, etc. The lower the f
number, the brighter the image and hence
the shorter the exposure required by an
ordinary camera, movie camera or television camera.
focal length-The distance between the
optical center of a lens and its principal
focus at which light rays coming from
an infinite distance would meet.
focusing coil An electromagnetic coil
placed around a cathode ray tube or television camera tube for the purpose of
controlling the cross-sectional area of the
beam at the fluorescent screen.
focusing control-In a cathode ray oscilloscope or television system, the control
which adjusts the size of the visible spot
produced at the screen by the electron
gun in a cathode ray tube.
focusing electrode-An electrode in a cathode ray tube to which a potential is
applied for the purpose of controlling
the cross-sectional area of the beam at
the fluorescent screen.
focusing, electromagnetic-Control of the
cross-sectional area of the electron beam
in a cathode ray tube by means of a
magnetic field produced by a focusing
night. In bright daylight, two layers
exist, the F1 layer and the F2 layer.
F1 layer-The lower of the two ionized
layers normally existing in the F region
in bright daylight.
F. layer-The higher of the two ionized
layers normally existing in the F region
in broad daylight.
flicker-The erratic movement of an entire
televised image or projected motion pictures.
floating charge-Continuous charging of a
storage battery, usually at a low current,
for the purpose of keeping the battery
fully charged, particularly when it must
stand idle for periods of time. Also called
trickle charging.
floating grid-A vacuum tube grid which
is not connected to any circuit.
flood projection-In facsimile systems, the
optical method in which the subject copy
is illuminated and the scanning spot is
created by an aperture between the subject copy and the light-sensitive device.
fluorescence-Light emitted as a result of
electron bombardment or as a result of
absorption of radiation from some other
fluorescent screen-A coating of chemical
material which glows when bombarded
by electrons. In a cathode ray tube, the
coating is on the inside surface of the
evacuated glass envelope of the tube.
flux-Magnetic lines of force.
flux density-The total number of magnetic
lines of force per unit of area.
flux-meter-An instrument used to measure
the number of magnetic lines of force
passing through a given area.
flying spot-The spot of light which moves
across or scans the picture or object
being televised by a mechanical television
system using a scanning disc.
f.m., f -m, FM or F.M.-Frequency modulation.
focusing, electrostatic-Control of the crosssectional area of the electron beam in a
cathode ray tube by means of a high d.c.
voltage applied to a focusing electrode.
foil-Very thin, pliable metal sheets of
aluminum, lead, tin or other metals, used
extensively in radio for plates of fixed
condensers and sometimes for shielding.
foot-candle-The intensity of illumination on
a surface one foot from a standard candle.
foot-pound-A unit of energy equal to the
work done in raising a mass of one
pound a distance of one foot.
force-Any physical cause which can produce motion or change the motion of a
forming-The process of preparing the thin
film on the surface of the positive electrode of an electrolytic condenser, so
as to give it the characteristics of a condenser. Also, the processing of lead
plates for use in storage batteries.
formula-A scientific fact, law or prin-
ciple which is expressed as an equation
by means of letters, symbols and conR2 + X2;
stant terms. Examples Z2
IR. A formula is an equation beE
cause it involves equality, but an equation is not always a formula.
frame-In television,
nating current. Thus, the oscillator and
mixer-first detector stages make up the
frequency converter of a superheterodyne
frequency deviation-In frequency modulation, the amount by which the instantaneous carrier frequency of the signal differs
from the resting frequency.
frequency deviation meter-A meter (usually a complex circuit of which the indicating meter is only a small part) which
measures the number of cycles drift from
a specified reference frequency. It is required by the FCC for all broadcast
frequency distortion-A type of distortion
which occurs when a circuit or device
amplifies or transmits unequally the different frequencies it is handling.
frequency doubler-A class C amplifier adjusted so the plate circuit will have strong
harmonics of the input signal. The plate
tank circuit is tuned to the second harmonic, hence the output frequency of the
circuit is twice the input frequency.
frequency drift-A slow change in the frequency of an oscillator or transmitter,
usually due to temperature changes in
oscillator circuit parts.
frequency meter-An instrument for measuring frequency. Sometimes called a
frequency modulation-A relatively new
system of radio broadcasting perfected
by Major E. H. Armstrong, in which
the AMOUNT OF DEVIATION IN FREQUENCY above and below the resting
frequency is at each instant proportional
to the AMPLITUDE of the sound wave
being transmitted, and THE NUMBER
SECOND above and below the resting
frequency is equal to the FREQUENCY
of the sound wave being transmitted.
Advantages of this system include almost
complete freedom from atmospheric and
man-made interference, as well as little
or no interference between stations, thereby permitting the transmission of a much
greater volume range and a wider audio
frequency range than is possible with
amplitude modulation. One disadvantage
is the necessity of employing ultra -high
carrier frequencies at which the range
of a station is limited to approximately
one complete scanning of every part of the field of view
being transmitted. In facsimile, a rectangular area, the width of which is the
available line and the length of which is
determined by the nature of the facsimile
frame frequency-In television, the number
of times per second the frame area is
completely scanned. In double interlaced
scanning, the frame frequency is one-half
the field frequency, since it takes two
downward sweeps to scan every element
of the frame.
framer-A device for adjusting facsimile
equipment so that the recorded elemental area bears the same relation to the
record sheet as the corresponding trans-
mitted elemental area bears to the subject
copy in the direction of line progression.
framing control-In television, a general
term applying to any of the control knobs
used for adjusting the centering, width
and height of the reproduced image. In
facsimile, the control which shifts the
picture sideways.
free electrons-Those electrons which are
free to move between the atoms of a
material when acted upon by electric or
magnetic forces.
free -point tester-A type of test instrument
for radio servicing which permits transferring any tube in a receiver to a socket
on a test panel. The test panel is connected to the receiver socket by means
of a cord and plug. Voltage and current
measurements for each tube electrode are
then made quickly by plugging a meter
into appropriate jacks on the test panel.
free-space radiation pattern-The radiation
pattern an antenna would have if out in
free space where there is nothing to reflect, refract or absorb the radiated
freezing point-The temperature at which
any particular liquid freezes and changes
from the liquid to the solid state.
F region-The region of the ionosphere between about 85 and 250 miles above the
earth's surface.
frequency-The number of complete cycles
per second which an alternating electric
current, a sound wave or a vibrating object undergoes. A cycle consists of a
current rise from zero to maximum, a
return to zero, a rise to a maximum in
the opposite direction, and a return to
zero again. When speaking of an electric
current or radio wave, the frequency in
cycles is approximately equal to 300,000,000 divided by the wavelength in
frequency converter-A circuit or device
which changes the frequency of an alter-
100 miles.
frequency multiplier-A radio stage or section used to multiply the frequency value
of a signal a whole number of times.
frequency record-A phonograph record
upon which various fret uencies throughout the desired audio frequency spectrum
have been recorded.
frequency response-A rating or graph
which expresses the manner in which a
circuit or device handles the different
frequencies falling within its operating
range. Thus, the frequency response of a
loudspeaker may be specified as being
essentially flat or uniform between 100
and 6000 cycles.
frequency response curve-A graph showing the frequency response of a radio
part, circuit or system.
frequency separator-The television receiver circuit which separates the horizontal synchronizing impulses from the
vertical synchronizing impulses.
frequency shift-A change in the frequency
of an oscillator or transmitter.
frequency stability-The ability of a radio
transmitter to maintain a given carrier
frequency. It is usually expressed as a
percentage deviation within which the
carrier frequency is maintained.
frequency standard-A highly stable low frequency oscillator, usually operated at
50 kc. or 100 kc. The harmonics of the
fundamental frequency are used to provide reference points every 50 or 100 kc.
throughout the radio spectrum.
frequency tolerance-The maximum permissible amount of variation in either direction from the assigned carrier frequency.
frictional loss-Energy expended in overcoming friction between moving parts.
front-to -back ratio-In a multi-element
directional antenna, the ratio between
the signal radiated in the desired front
direction and the signal radiated in the
opposite or rear direction. Also called
front -to -rear ratio.
a tube.
gage-Alternate spelling of gauge, and
equally correct.
gain-In an amplifier stage or system, the
ratio of output voltage, current or power
to input voltage, current or power,
usually expressed in decibels. Increasing
the gain means increasing the volume of
sound which is produced by an audio
gain of an antenna-A rating expressing
how much better one transmitting or
receiving antenna is than another. For
constant transmitted power level, the
measured gain is the ratio of the signal
powers produced at the input terminals
of a receiver by the two antennas under
galena-Lead sulphide, a shiny bluish gray
mineral often used as the crystal in a
crystal detector.
galvanometer-A fundamental current -indicating meter. Usually having a scale indicating relative deflection or degrees of
deflection, from which the amount of current can be calculated. When the meter
has a current scale indicating milliamperes or amperes directly, it is called a
millianuneter or ammeter.
gamma ray-An electromagnetic radiation,
similar to X-rays but of shorter wavelength.
gang switch-Two or more rotary switches
mounted on the same shaft and operated
by a single controL
gang tuning condenser-Two or more variable tuning condensers mounted on the
same shaft and operated by a single
gas current-A current consisting of positive ions produced by gas ionization in a
tube, flowing to an electrode.
gaseous conduction-The conduction of electricity through a gas due to ionization of
the gas by collision of electrons with
gas molecules, when a suitably high voltage is applied between electrodes.
gaseous tube-An electronic tube into
which a small amount of gas or vapor is
admitted after the tube has been evacuated. Ionization of the gas molecules
during operation of the tube gives greatly
increased current flow.
gas focusing-Focusing of the electron beam
in a cathode ray tube by the action of
ionized gas.
gasket-A ring or washer used for packing or insulating.
gas magnification-A term sometimes used
to describe the increased electron flow
full -wave rectifier-A radio tube or other
device which rectifies an alternating current in such a way that both halves of
each input a.c. cycle appear in the pulsating rectified output. A full -wave rectifier tube contains two separate diode
sections, one passing current during one
alternation, and the other passing current
during the opposite half -cycle.
fundamental frequency-The lowest frequency in a complex signal having harmonics. The lowest or natural resonant
frequency of a part or circuit, such as an
fundamental wavelength-The wavelength
corresponding to the fundamental frequency.
fuse-A protective device consisting of
G-Grid of
short piece of wire which melts and
breaks when the current through it exceeds the rated value of the fuse. Fuses
are inserted in radio circuits to open the
circuits autour tically in case of serious
overload, thereby preventing damage to
parts in the circuit.
fuse link-The metal portion inside a fuse,
which melts at the rated current value.
in a gas -filled photocell due to ionization
of gas.
gasoline -driven generator-An electric generator, either a.c. or d.c., which is driven
by a small gasoline engine.
gas tube-A tube in which a small amount
of gas has been admitted after evacuation,
to give to the tube special electrical
gauge-A standard of measurement or a
device for measuring by comparing with
a standard.
gauss-The unit of flux density equal to one
magnetic line of force per square centimeter.
Gauss, Karl Friedrick-The German mathematician (1777-1855) after whom the unit
of flux density was named.
G-E-General Electric Co.
Geissler tube-A long gaseous tube which
gives off colored light when a suitable
voltage is applied to the electrodes which
are at opposite ends of the tube. A
Geissler tube is the early laboratory version of modern neon tubing used in signs.
genemotor-A small motor-gen rator set,
generally employed for plate voltage supply purposes in mobile radio installations.
general number-A letter or symbol used
for representing quantities. Thus, R is a
general number (sometimes called a literal number) when used to represent a
number of ohms of resistance.
generator-A machine which converts mechanical energy into electrical energy.
It consists essentially of a large number
of conductors mounted on ar armature
which is rotated in a magneti: field produced by field coils. A aerie& generator
has the armature, field and load all in
series. A shunt generator has the armature, field and load all in parallel. A
compound generator has two fields, one in
series with the armature and the other
in parallel with the armature. Also, a
radio device or circuit which develops
an a.c. voltage at a desired frequency
when energized with d.c. or low -frequency
a.c. power.
geometric mean-The square root of the
product of two quantities.
geometry-That branch of mathematics
which deals with the relations and measurements of solids, surfaces, lines and
angles in space.
german silver-An alloy of brass and nickel.
getter-An alkali metal introduced into a
vacuum tube during manufacture and
vaporized after the tube has been evacuated, to absorb any gases which may
have been left by the vacuum pump. The
silvery deposit on the inside of the glass
envelope of a tube, usually near the tube
base, is the result of getter vaporization.
ghost image-In television, an undesired
duplicate image appearing a fraction of
an inch to one side of the desired image,
due to reception of a reflected signal
along with the signal coming directly
from the television station. The remedy
involves using a directional receiving
antenna adjusted so it will receive signals
coming over only one path.
gilbert-The unit of magnetomotive force.
One gilbert is equal to .796 ampere -turn.
gimmick-A simple capacitor formed by
twisting two wires together. Also, a few
turns of insulated wire wound around the
secondary of an antenna transformer.
One end is connected to the antenna
terminal, and the other is left unconnected. It is used chiefly in universal
a.c.-d.c. receivers, where it serves to make
the gain more uniform over the entire
tuning range.
glass -type tube-A vacuum tube or gaseous
tube having a glass envelope or housing.
glow -discharge voltage regulator-A special
gas tube whose resistance varies between
about 5000 and 30,000 ohms, depending
on the amount of applied voltage: It is
used to maintain a constant voltage supply
to oscillator tubes in short wave u.h.f.
and f.m. receivers and in transmitter
exciter units.
glow lamp-A gaseous tube having a glass
envelope through which can be seen a
glow due to ionization of the molecules
of gas. Neon gas gives a red glow, mercury vapor gives blue, and argon gas
gives a light purple glow. Also called
glow tube.
G.-Mutual conductance of a tube.
G.M.T.-Greenwich Mean Time.
GND., gnd.-Ground.
gold-A metallic element used in some deli-
cate electrical instruments, and used for
electroplating the housings of radio parts
which must withstand severe corrosive
conditions, as in the tropics.
goniometer-A special type of r.f. transformer used with a radio compass or
direction finder. It has two primaries at
right angles, connected to the two loop
aerials, and a rotary secondary connected to the receiving or sending circuit.
gram-The unit of weight in the metric
system. One pound is equal to 453 grams.
phonograph (English
graph-A pictorial presentation of the relation existing between two or more quantities.
graphite-A soft form of carbon, used as a
grid-An electrode mounted between the
cathode and the anode of a radio or
electronic tube to control the flow of
electrons from cathode to anode. The grid
electrode is usually either a cylindrical shaped wire screen or a spiral of wire
through which electrons can readily move.
grid bias-Another term for C bias, which
is the voltage used to make the control
grid of a radio tube negative with respect to the cathode.
grid bias cell-A bias cell used in the grid
circuit of a vacuum tube.
grid characteristic-The graph plotted with
grid voltage values as abscissas and grid
current values as ordinates.
grid circuit-The circuit connected between
the grid and cathode of a tube. It forms
the input circuit of the tube.
grid clip-A spring clip used to make an
easily removable connection to the cap
terminal located at the top of some
radio tubes.
grid condenser-A small fixed condenser
inserted in the grid circuit of a vacuum
pact of electrons going from cathode to
plate in the vacuum tube.
grid -glow tube-A gaseous triode used in
electronic control applications for controlling relatively large currents by means
of very small grid currents.
grid leak-A resistor of high ohmic value,
used to connect the control grid to the
cathode in a grid leak-condenser detector circuit.
grid -leak condenser detector-A type of detection in which a.f. potentials developed
across a grid resistor by the flow of grid
current through that resistor result in
plate current changes at the desired
audio frequencies. This type of detector
is identified by the presence of a grid leak
and grid condenser in the grid circuit.
grid modulation-Modulation produced by
introduction of the modulating wave into
any of the grid circuits of any tube in
which the carrier frequency wave is
grid return-The lead or connection which
provides a path for electrons from the
grid circuit or C bias battery to the
grid suppressor-The resistance connected
between the control grid and the tuned
portion of the grid circuit of a radio
frequency amplifier to prevent oscillation.
grid swing-The total variation of grid
voltage, from positive peak to negative
peak of the applied signal.
grille-An arrangement of wood or metal
bars placed across the front of the loudspeaker in a radio receiver for protective
purposes and to enhance the design of
the cabinet.
grille cloth-A loosely woven cloth stretched
behind the loudspeaker grille of a radio
receiver to keep dust and other foreign
matter out of the loudspeaker, as well
as to conceal the loudspeaker diaphragm.
Sound waves travel unimpeded through
this cloth.
grommet-A special washer, made of rubber or other insulating material, used to
prevent a wire from touching the sides
of a chassis hole through which the wire
is run.
groove-The track cut in a phonograph
record by the stylus during recording, or
the track in which a phonograph needle
rides during playback.
ground-The earth, to which a connection
is made by means of a buried conductor
grid conductance-The ratio of the change
in grid current to the change in grid
voltage producing it, under the condition
of constant plate voltage.
grid -controlled rectifier-A triode mercury
vapor tube in which the grid determines
when plate current starts to flow but
not how much current will flow.
grid current-The current passing to or
from a grid through the space inside a
vacuum tube.
grid detection-Detection taking place in
the grid circuit of a vacuum tube. Also
called grid leak detection or grid current
grid dip oscillator-An oscillator with a
sensitive current meter connected in its
grid circuit. When the oscillator is connected to a resonant circuit, resonance
between the circuit and the oscillator is
indicated by a sharp change in the meter
reading, indicating that power is being
drawn from the oscillator and the two are
in resonance.
grid emission-Emission of electrons or
ions from a grid, usually due to the im40
for radio purposes. Also, the chassis of
a receiver when it is connected to ground
and serves as the return path for signal
circuits. The ground is considered to be
at zero r.f. potential.
ground absorption-The loss of power in
transmission of radio waves due to dissipation in the ground.
ground clamp-A metal strap or clamp used
for making a good electrical connection
to a ground rod or grounded pipe. The
clamp has a screw terminal or soldering
lug to which the ground wire of a radio
receiver can readily be attached.
guy wire-A wire used to brace the mast
or tower of a transmitting or receiving
antenna system.
H-Heater or' filament
of a tube. Magnetic
intensity or magnetomotive force per cm.
half -wave rectifier-A radio tube or other
device which converts alternating current into pulsating direct current by
allowing current to pass only during onehalf of each alternating current cycle.
ham-An amateur radio transmitter operator.
harmonic-A multiple of any particular
frequency. Thus, the second harmonic'
of a fundamental frequency would be
equal to two times that fundamental
harmonic distortion-Another name for
wave form distortion.
harmonic generator-A vacuum tube or
other generator used to generate a signal
having many strong harmonics.
Hartley oscillator-A vacuum tube oscillator circuit identified by a tuned circuit
which employs a tapped winding connected between the grid and plate of the
vacuum tube, with the tap going to the
ground potential-When a terminal is at a
potential difference of zero with respect
to the ground, it is at ground potential.
All grounded terminals are at ground
potential. Terminals negative with respect to ground are below ground potential terminals positive with respect to
ground are above ground potential.
ground-reflected wave-The component of
the ground wave that is reflected from
the ground.
ground resistance-The resistance of the
ground or earth portion of an antenna
ground system-That portion of an antenna
system which is closely associated with
the ground, including the earth itself
and any wires buried in it.
ground waves-Radio waves which travel
along the surface of the earth instead of
going up into the sky, and are affected
by the presence of the earth (lose strength
rapidly due to dissipation of energy in
the earth).
ground wire-A wire used to make a connection from radio apparatus to a ground
clamp or other grounded object. Outward radiating buried ground wire is commonly used with large transmitting antennas to improve the contact with the
guard band-A .25-megacycle wide frequency band provided at the high -frequency end of each television channel to
prevent interference between adjacent
television channels.
guided wave-A wave whose propagation is
concentrated in certain directions.
hash-Characteristic electrical noise produced by vibrators which have excessive
sparking at the contact points.
Hazeltine licensed-Radio apparatus which
uses Hazeltine patents under a licensing
agreement with the Hazeltine Corporation.
headphone-A small telephone receiver,
held against an ear by a clamp passing
over the head, used for private reception
of radio programs or for reception of
signals which are too weak to provide
loudspeaker volume. Headphones are
usually used in pairs, one for each ear,
with the clamping strap holding them
both in position.
heater-A filament used in vacuum tube
only for the purpose of supplying heat
to an indirectly heated cathode.
heater current-The current supplied to a
vacuum tube filament which is used only
for heating purposes.
heater voltage-The voltage applied between the terminals of a vacuum tube
filament used only for heating purposes.
Heaviside layer-A layer of ionized gas
which scientists believe exists in the region between 50 and 400 miles above the
surface of the earth, and which reflects
radio waves back to earth under certain conditions. Also called the Kennelly -
heterodyne reception-A process of changing the carrier frequency of an incoming
radio signal by combining it with a
locally-generated signal. Usually called
superheterodyne reception.
hexode-A vacuum tube having six electrodes-a plate, a cathode, a control grid,
and three other electrodes which are usually grids.
high-fidelity receiver-A receiver capable of
reproducing audio frequencies in a range
from 50 to about 8000 cycles or wider
without serious distortion. A receiver
which approaches the goal wherein the
reproduced program cannot be distinguished from the original studio program.
high -frequency resistance-The total effective resistance of a circuit due to all
effects, including eddy current, hysteresis,
dielectric, corona and ohmic losses.
high -frequency trimmer-In a superheterodyne receiver, the trimmer condenser
which controls the calibration of a tuning
circuit at the high-frequency end of a
tuning range.
high-level modulation-Modulation at a
point in a transmitter where the power
level is approximately the same as at the
output of the transmitter, such as in the
final radio stage.
high -mu tube-A tube having a high amplification factor.
high-pass filter-A filter network designed to
pass all frequencies above a cut-off frequency value while attenuating or rejecting lower frequencies.
high Q-High ratio of reactance to a.c.
resistance for any resonant circuit or
Heaviside layer.
height control-The control in a television
receiver which adjusts the picture size
in a vertical direction.
Heising modulation-A modulation. system
in which the plates of both the r.f. oscillator and the modulator tube are fed
through a single common choke having
high impedance at both audio and radio
frequencies. This choke prevents any
change in the total plate current drawn
by the two tubes together. Therefore,
the a.f. plate current variation in the
modulator tube produces a similar but
opposite a.f. variation in the plate current of the r.f. oscillator tube. This is
also called constant current modulation.
helix-A coil wound in spiral form. The
shape of a machine screw thread.
henry-The unit of inductance. A device
has an inductance of 1 henry when an
electromotive force of 1 volt is induced
in it by a current changing at the rate
of 1 ampere per second. Plural: henrys.
Henry, Joseph-An American, noted for
his work with electromagnets and electromagnetic actions. The unit of inductance
is named after him.
heptode-A vacuum tube having seven electrodes-a plate, a cathode, a control grid
and four other electrodes which are usually grids.
hermetically sealed-Sealed so as to be airtight.
Hertz antenna-An antenna which is electrically independent of the ground.
heterodyne frequency-Same as beat frequency, which is the difference frequency
of two signals.
heterodyne frequency meter-A completely
shielded, accurately calibrated oscillator
used for frequency measurement purposes
by comparison of the unknown signal
with the accurately known signal frequency of the meter.
heterodyne interference-Interference between two stations transmitting on nearly
the same frequencies so their waves produce a beat note which causes an audible
tone in receivers.
.high-resistance voltmeter-A voltmeter having a very high resistance, so that very
little current is drawn by the meter,
from the circuit in which a measurement
is made.
high-tension-A term applied to circuits
where voltages of the order of thousands
of volts exist.
high -vacuum tube-A vacuum tube which
has been evacuated so thoroughly that
gaseous ionization cannot occur during
normal operation.
hill and dale recording-Another name for
vertical recording.
hissing-A noise encountered in sensitive
radio receivers due to feedback or to
circuit and tube shot effects.
hold controls-In a television receiver, the
two manually -adjusted controls which
adjust the natural oscillating frequencies
of the oscillators employed in the horizontal and vertical sweep circuits.
honeycomb coil-A coil wound in a crisscross manner to reduce distributed capacity. Also called lattice -wound coil.
heat produced in it by the passage of
the current to be measured.
howl-An undesirable audio frequency oscillation occurring in a radio or amplifier
system, due either to electrical or acoustic
hookup-A diagram giving circuit con-
nections for a radio receiver, amplifier
or transmitter.
hop-An excursion of a radio wave from
the earth to the ionosphere and back to
earth, in traveling from one point to another. It is usually used in expressions
such as single -hop, double -hop, and multi hop. The number of hops is called the
order of reflection.
horizon-In radio wave propagation over
the earth, the line which bounds that part
of the earth's surface reachad by the
direct wave. On a spherical surface, the
horizon is a circle. The distance to the
horizon is affected by atmospheric refraction.
horizontal-Level. From side to side, not
horizontal deflecting electrode-One of the
cathode ray tube electrodes to which
voltage is applied to move the electron
beam horizontally from side :o side on
the screen.
horizontal flyback-In a television system,
the right-to -left return motion of the electron beam from the end of one line to the
beginning of the next. Also called horizontal retrace or line flyback.
horizontal hold control-The hold control
used to adjust the free-runnirg time of
the horizontal sweep oscillator.
horizontal polarization-A method of transmitting radio waves in which the plane
of polarization is parallel to the surface
of the earth.
horizontal retrace-Same as horizontal flyback.
horizontal sweep-The left -to -right scanning motion across a picture or scene
being televised.
horizontal synchronizing impulse-The impulse sent at end of each line for receiver controlling purposes. Same as line synchronizing pulse.
horn-A loudspeaker having a tapering tube
(of varying cross-sectional area) in place
of a baffle. The smaller end of the horn
is the throat, and the larger end is the
horsepower-A unit of power, which is the
rate of doing work. One horsepower is
mechanically equivalent to 33,000 ft. lb.
per minute or 550 ft. lb. per second, and
is electrically equivalent to 746 watts.
horseshoe magnet-A magnetized steel bar
bent into the shape of a horseshoe.
hot -cathode tube-A vacuum or gaseous
tube in which the cathode is heated to
provide electron emission.
hot-wire ammeter-An ammeter which depends for its action on the exransion of
a tine wire under the influence of the
H pad-An attenuation network having its
elements arranged in the manner of the
letter H. It has a constant input and
output impedance.
h.p.f.-High-pass filter.
low and constant audio frequency,
usually either 60 or 120 cycles, heard in
the background of a received radio program. A defective filter condenser in an
a.c. power pack is a common cause of
hum in a radio receiver.
hum -bucking coil-An extra coil placed on
the center pole of an electrodynamic
loudspeaker to cancel hum currents which
might be induced in the voice coil by the
field coil.
hum modulation-Hum which is audible
only when a station is tuned in, originating in an r.f. stage. This hum modulates an incoming signal due to some
non -linearity in the stage.
hunting-Speed variation or oscillation
about the average or synchronous speed
of rotation of a motor.
hydrometer-A device used to measure the
specific gravity of a liquid, such as the
electrolyte in a storage battery. The
resulting readings are an indication of
the state of charge of the battery.
hypotenuse-The side of a right triangle
opposite the right angle.
hysteresis-Failure of the magnetic flux to
increase or decrease in accordance with
changes in the magnetizing force acting
on a magnetic material. This non -linearity in the magnetization causes heat
losses in iron -core transformers which
are known as hysteresis losses.
hysteresis loop-A graph showing the relation between magnetizing force and flux
density over a complete cycle of magnetization and demagnetization.
i-Instantaneous value of current.
I-The letter
commonly used to designate
iconoscope-A cathode ray television pickup
tube developed by the Radio Corporation
of America for use in electronic television
cameras. It converts each picture element of the scene being televised into a
corresponding electrical impulse. Scanning of the image is accomplished by
making an electron beam sweep back and
which is below the oscillator frequency of
the i.f. value, and the other being an
undesired station which is above the oscillator frequency by the i.f. value.
image interference ratio-A superheterodyne radio receiver rating indicating how
effectively the r.f. tuned circuits ahead
of the first detector can reject signals at
the image frequency.
image reconstructor-The cathode ray tube
or other device used in a television receiver to convert the received picture signals into an image of the scene originally
imaginary number-Term used to designate
the square root of a negative number.
impedance-The total opposition which a
radio part or circuit offers to the flow of
alternating or pulsating direct current at
a particular frequency. Impedance is a
combination of resistance and reactance
and is measured in ohms.
impedance coupling Coupling between
stages by means of an impedance.
impulse-A momentary increase in the current or voltage in a circuit.
impulse generator-A device which generates electric impulses for synchronizing
purposes in a television system.
impulse separator-The television receiver
circuit which separates the horizontal impulses from the vertical impulses.
Courtesy RCA
forth across the mosaic many times per
i.c.w. or
idler pulley-A pulley used to change the
direction of a belt or cord. Its shaft
does not rotate any other part.
i.f. or I.F.-Intermediate frequency.
ignitron-A half -wave mercury-vapor rectifier tube in which the arc (electron
stream) is started at the beginning of
each active cycle by a special igniter
electrode immersed in the mercury -pool
cathode and energized by an auxiliary
incident light-Direct light falling on a sur-
illuminosity meter-A device for measuring
light flux or amount of illumination. It
generally uses a photoelectric cell as the
means of converting light energy into an
electric current which can be measured.
image-A reproduction of a person, object
or scene, such as that produced by a
television receiver.
image antenna-An imaginary antenna
which can be considered the source of
reflected waves.
image dissector-A cathode ray television
pickup tube developed by Philo T. Farnsworth for use in electronic television
cameras. Its construction and operating
principles are different from those of
the iconoscope, but it serves essentially
the same purpose of converting a scene
into corresponding electrical impulses.
image frequency-In a standard superheterodyne receiver in which the oscillator
operates above the incoming signal frequency, the image frequency is the frequency equal to the sum of oscillator frequency and the i.f. value. The image
frequency is therefore above the desired
signal frequency by twice the i.f. value.
image interference-A type of interference
in which two stations are heard at the
same time, one being the desired station
incident wave-An oncoming wave.
index-The small number in the angle of a
radical sign, indicating the particular
root to be extracted. Examples: In
64, the index
x, the index is 4 ; in
is 3.
index of refraction-A number indicating
the amount a ray of light will be bent out
of its normal path when passing through a
particular material. It is equal to the
speed of light in air divided by the speed
of light in the particular material being
indirectly heated cathode-A cathode which
is heated by a separate filament in a thermionic vacuum tube.
indirect scanning-A method of scanning in
which a beam of light is moved across
a scene or picture, and the light reflected
from the illuminated scene is picked up by
a photocell or group of photocells.
indirect wave-Sky wave.
indoor antenna-A receiving antenna system located entirely inside a building
either under a rug, around the walls of
a room, between the walls, or in the attic.
induced voltage-A voltage produced in a
circuit by changes in the number of mag44
inertia-The property of matter which
netic lines of force which are linking or
cutting through the conductors of the
inductance-That property of a circuit or
coil which causes an electromotive force
(voltage) to be set up due to a change
in current in the circuit or coil, or which
determines how much electromotive force
will be induced in one of two neighboring
coils or circuits by a change in either of
them. Inductance is effective only when
a varying or alternating current exists,
and has no effect on direct current. The
basic unit of inductance is the henry.
A circuit has an inductance of 1 henry
when a change of current of 1 ampere
per second induces an electromotive force
tends to prevent motion, or resists a
change of motion.
infinite-Larger than imaginable. Without
infinite -impedance detector-Another name
for a C bias detector. Usually applied to
a detector with the plate load in the cathode circuit.
infinity-A number greater than any known
number. The sign used to designate infinity is oo.
infra -red rays-Rays of longer wavelength
than visible light rays, hence invisible
to the human eye, used for photoelectric
burglar alarm systems and other special
injection grid-A special grid element placed
in a vacuum tube in such a way that it
has reasonable control over the electron
stream without causing interaction between itself and the control grid. It is
used as the oscillator input in the first
detector stage of some superheterodyne
ink -vapor recording-That type of electromechanical facsimile recording in which
vaporized ink particles are directly deposited upon the record sheet.
in phase-Descriptive of two alternating
quantities which have the same frequency
and which pass through their zero and
maximum values at the same instant of
time, exactly in step with each other.
Input capacity-The sum of all interelectrode capacities existing between the control grid and cathode of a vacuum tube.
input impedance-The impedance between
the input terminals, equal to the ratio of
the a.c. voltage applied to the input terminals of a circuit or device to the alternating current thereby produced.
input transformer-A transformer used to
deliver energy to the input of a device
or amplifier.
instantaneous recording-A recording which
may be used without further processing.
instantaneous value-The value of an alternating current, voltage or power at any
one point in its cycle.
insulation-Any material which has a sufficiently high electrical resistance to permit its uee for separating one electrical
circuit, part or wire from others. Cotton,
silk, baked enamel, mica, porcelain, rubber
and bakelite are a few of the common insulating materials used in radio.
insulator-An object which offers a great
deal of opposition to the movements of
electrons, used for supporting or separating bare conductors.
integer-Any whole number (without fractions or decimals).
integral sign-The sign 5, used in higher
inductance bridge-A form of Wheatstone
bridge circuit used to determine inductance values. It must be supplied with
an a.c. source of power.
inductance -tube modulation-Frequency
modulation by means of an oscillator control tube which acts as a variable inductance in parallel with the tank circuit of an r.f. oscillator, causing the oscillator frequency to vary in proportion
to the a.f. voltage applied to the grid
of the oscillator control tube.
induction-An action whereby the variable
flow of current through one coil produces
a voltage in a nearby coil even though
there is no electrical connection between
the coils. The coupling is produced by
magnetic lines of force.
induction field-That portion of the electromagnetic field produced by a transmitting
antenna which acts as if it were permanently associated with the antenna. The
radiation field, on the other hand, breaks
away from the antenna to form radio
induction motor-An electric motor which
operates on the principle that a pivoted
closed loop of wire will rotate essentially
in step with a rotating magnetic field.
inductive coupling-A form of coupling in
which energy is transferred from a coil in
one circuit to a coil in another circuit by
induction. Magnetic lines of force produced by the flow of current through one
coil cause an a.c. voltage to be induced
in the other coil.
inductive feedback-Feedback of energy
from the plate circuit to the grid circuit
of a tube by inductive coupling.
inductive reactance-Reactance due to the
inductance of a coil or other part in an
alternating current circuit. Inductive
reactance is measured in ohms, and is
equal to the inductance in henrys multiplied by the frequency in cycles, times the
number 6.28. Inductive reactance therefore increases with frequency.
inductor-Inductance. Coil.
mathematics to indicate that the operation of integration (finding the sum of
small elements or differentials) is to be
intelligence signal-The electrical signal
that corresponds to the information or intelligence (sound waves, television scenes,
code, etc.) being handled ; also known as
the low -frequency signal.
intensity-Strength or value of current.
intercarrier noise suppression-A means for
suppressing the noise otherwise heard
in a high -gain receiver when it is tuned
between station carriers. The audio input
of the receiver is blocked automatically
when no signals exist at the second detector. Also called interstation noise
the next downward travel of the scanning
interlock-A system which makes it im-
possible to open or close certain switches
or relays until certain actions have taken
place. For example, interlocking relays
and switches may make it impossible to
apply plate voltage to mercury vapor
rectifier tubes until their filaments have
reached operating temperature. Also,
similar switches used on doors of transmitters which automatically break the
high voltage supply circuits when doors
are opened, to protect the operator.
intermediate frequency-In a superheterodyne receiver, the frequency to which all
incoming carrier signals are converted
before being fed into the intermediate
frequency amplifier.
intermediate frequency amplifier-That section of a superheterodyne receiver which
is designed to amplify signals with high
efficiency at a predetermined frequency
called the intermediate frequency of the
intermediate frequency transformer
transformer used at the input and output
of each i.f. amplifier stage in a superheterodyne receiver for coupling purposes
and for providing selectivity.
intercommunication system-An amplifier
system which provides two-way communication between two or more rooms in a
building. Each station in the system contains a microphone and loudspeaker,
usually combined as a single dynamic
unit. A headphone or telephone receiver
is sometimes provided also for private
reception of messages. The stations may
be connected to each other by wire cables,
or may receive and transmit messages
through the electric wiring system in the
interelectrode capacity-The capacity which
exists between two electrodes in a vacuum
tube. Although this is usually a very low
value, it becomes extremely important
when tubes are operated in ultra -high
frequency circuits.
interference-Noises or undesired radio programs which interfere with reception of a
desired radio program.
interference filter-A device used between
a source of interference and a radio receiver to attenuate or eliminate noise.
It generally consists of coils and condensers arranged so as to oppose or bypass noise impulses and keep them out
of receiver circuits.
interference guard bands-Bands of frequencies in which no signals are transmitted, existing on either side of the
communication band in a radio channel,
providing separation between signals of
stations having adjacent frequency assignments so as to prevent station interference.
interference pattern-A pattern showing the
distribution of pressure or some other
quantity at a given location due to stationary waves. Also, any interfering
patterns seen on a television receiver,
caused by noise, hum, etc.
interlaced scanning-In television, a type
of scanning in which every other line of
the image is scanned during one downward travel of the scanning beam, and
the remaining lines are scanned during
intermittent reception-A type of radio receiver trouble in which the receiver performs normally for a time, then becomes
dead or otherwise defective, with the
process repeating itself at regular or irregular intervals.
intermodulation-A process wherein two
or more different signal frequencies combine in a non-linear circuit to produce
new frequencies corresponding to sums
and differences of the fundamental frequencies and their harmonics.
Intermodulation interference-A type of station interference which occurs when two
undesired signals whose frequencies differ
by exactly the i.f. value of a superheterodyne receiver force their way through
the preseleetor to the first detector, and
there produce an i.f. beat signal without
the aid of the local oscillator. The
trouble is characterized by garbled speech
and squeals when a desired station is
tuned in.
International Morse Code-The dot and
dash code used universally for radiotelegraphy, and also used for wire telegraphy
in some European countries. It is also
known as the Continental Code.
interrupted continuous wave-A continuous
wave which is interrupted at an audio frequency at the transmitter. Abbreviated
i.c.w. The audio tone modulation mikes
reception of i.c.w. code signals possible
with ordinary receivers (without beat oscillators) .
interrupter-Apparatus for breaking up a
continuous current into successive pulses.
interstage-Between stages.
interval timer-An electronic tube device
used to measure time intervals. It may
consist of a blocked oscillator, where the
rate of unblocking is controlled by a
resistor and condenser. When the condenser discharge reaches a predetermined
value, the oscillator is unblocked and produces a pulse. The condenser is then
charged and the oscillator again blocks.
The time constant of the resistor and
condenser determines the time interval
between oscillator pulses.
inverse feedback-Negative feedback, also
called degeneration or stabilized feedback.
A fraction of the output signal of an
amplifier stage is intentionally fed back
to the input so it is out of phase and
decreases the amplification, thereby reducing distortion and noise and permitting greater undistorted power output.
inversely proportional-Related in such a
way that when one value increases, the
other decreases a proportionate amount,
and vice versa.
inverse peak voltage-The maximum a.c.
voltage that can be applied to a rectifier
tube without arcing or flashover when the
filament is positive and the plate negative.
inverted amplifier-An ri. amplifier circuit
in which power from a preceding stage
Is fed into the cathode circuit and the
grid is operated at ground potential.
This eliminates the necessity for neutralization.
inverted L antenna-The conventional antenna used for broadcast reception, having a long horizontal portion suspended
between insulators, with the single -wire
lead-in connected to one end of the horizontal portion.
inverter-A device which changes d.c. to
a.c. It may be electromechanical, as a
vibrator, or entirely electronic as in the
thyratron inverter.
ion-An electrified particle, such as an atom
or molecule, having either fewer or more
electrons than normal. A positive ion is
a particle which has lost electrons, and
a negative ion is one which has acquired
more electrons than normal.
ionization-An action whereby atoms or
molecules of gas in an electronic tube
are converted into electrically charged
ions which are attracted by charged electrodes. Ionization makes a gaseous tube
more conductive than an equivalent vacuum tube.
ionosphere-A portion of our atmosphere
which contains the Heaviside layer ( E
region) the F region and other ionized
layers. These layers reflect radio waves.
ionospheric storm-A period of disturbance
in the ionosphere, during which radio
waves are reflected in abnormal ways.
ionospheric wave-A radio wave that is reflected from the ionosphere. Often called
a sky wave.
Ip-Plate current of a tube.
IR drop-Voltage drop produced across a
resistor (R) by the flow of current (I)
through it.
I2R loss-Power loss due to current flow
through resistance.
I.R.E.-Institute of Radio Engineers.
iron -core coil-A coil having iron inside its
windings. The iron is usually in the
form of laminations, but it may also be
pulverized iron mixed with a binding
iron -core transformer-A transformer in
which iron makes up part or all of the
path for magnetic lines of force traveling
through the transformer windings.
Isolantite-A high -quality insulating material used in the construction and mounting of radio parts, particularly those employed in ultra -high frequency circuits.
so-called imaginary number, equal to
jack-A plug-in type spring terminal widely
used in radio apparatus for temporary
connections. A connection is made to a
jack simply by plugging into it a probe or
plug attached to a flexible insulated wire
or cable. Some jacks have extra contacts
which are opened or closed when the
probe is inserted, thereby giving automatic switching action.
jamming-Intentional transmitting of radio
waves in such a way as to interfere with
reception of signals from another station.
jewel bearing-A small piece of natural or
synthetic jewel, usually sapphire, carefully ground to form a bearing for the
pivot of a meter movement.
jitters-Distortion in the received facsimile
picture caused by momentary errors in
synchronism between scanner and recorder in a facsimile system.
of a cathode ray television camera tube
is placed at an angle with the principal
axis of the tube.
kick-The sudden movement of the pointer
of an ohmmeter when it is connected to
a condenser of fairly large capacity.
joule-The unit of electrical work or energy.
One joule equals one watt -second.
jumper-Any wire used to connect two
points together or short out a part tem-
junction-A joint or connection. Also point
kilo-Metric prefix meaning
of contact between two dissimilar metals
or materials, as in a thermocouple or a
copper -oxide rectifier.
kilocycle-One thousand cycles.
kilogauss-A unit of flux density equal to
1000 gausses or 1000 lines of flux per
square centimeter.
kilovolt-amperes-A unit of apparent power,
equal to 1000 volt-amperes.
K-Letter used
to designate the cathode
of a tube. Also used in formulas to represent a constant or numerical value
which does not change its value during
any one discussion.
kc.-Kilocycles per second.
keeper-The piece of iron used to close the
magnetic circuit of a permanent magnet
to prevent loss in magnetic strength.
Kennelly -Heaviside layer-A layer of ionized gas supposed to exist in the region
between 50 and 400 miles above the surface of the earth. It reflects radio waves
back to earth under certain conditions,
making possible long-distance radio reception.
Kenotron-A high -vacuum rectifier tube.
Kerr cell-A device used in some mechanical
television systems to modulate a light
beam with television signals. The cell
rotates a beam of plane polarized light
in proportion to the voltage applied between the two plates of the cell.
key-A lever-type switch designed for rapid
opening and closing of a circuit during
transmission of code signals. Also, a
special type of lever switch used on
telephone -type switchboards to control
speech circuits of a transmitter.
kilowatt-A unit of electrical power equal
to 1000 watts.
kilowatt-hour-A unit of electrical energy,
equal to 1000 watt-hours. (Watts X
kinescope-A cathode ray tube developed
by RCA and used in television receivers
for the purpose of reproducing on a screen
the scene originally televised.
Courtesy RCA
kinetic energy-The energy (ability to
work) which a moving object possesses
by virtue of its motion.
Kirchhoff's Current Law-A fundamental
electrical law which states that the sum
of all the currents flowing to a point in
a circuit must be equal to the sum of all
the currents flowing away from that
Kirchhoff's Voltage Law-A fundamental
electrical law which states that the sum
of all the voltage sources acting in a complete circuit must be equal to the sum of
all the voltage drops in that same circuit.
klystron oscillator-A type of microwave
oscillator which uses a velocity -modulated
electron stream inside a metal resonator
to get considerable r.f. power at frequencies above 300 megacycles.
knife switch-A switch in which one or
more flat metal blades, each pivoted at
one end, serve as the moving parts. The
blades are usually of copper; when the
switch is closed, they make contact with
flat gripping spring clips and complete the
key -click filter-A filter which attenuates
the surge produced when the keying circuit of a transmitter is opened.
key clicks-Those components of a code
signal which are created by the opening
of the sending key but are not essential
for communication.
keying chirps-Peculiar sounds accompanying code signals when the transmitter is
unstable and shifts in frequency each
time the sending key is closed.
keystone-shaped-A reproduced image which
is wider at the top than at the bottom
(or vice versa).
keystoning-The keystone -shaped scanning
pattern secured when the electron gun
knob-A radio part, usually round but
sometimes having a pointer or other position -indicating means, which is attached
to the end of a control shaft to make it
easier to rotate the shaft with the fingers.
kwh.-Kilowatt hours.
in which the groove modulation is cut so
the phonograph needle moves from side
to side during playback.
latitude-Distance north or south of the
geographical equator, measured in degrees, minutes and seconds, ranging from
0° at the equator to 90° at either pole.
lattice -wound coils-Coils in which the
windings are criss-crossed.
law of electric charges-Like charges repel
each other; unlike charges attract each
commonly used to designate a
coil or an inductance value in henrys.
laboratory-A place (building or room)
where scientific experiments and investigations are carried out, or where radio
equipment is developed.
lacquer discs-Phonograph records usually
of metal, glass or paper, which are coated
with a lacquer compound (often containing cellulose nitrate) and used either
for "instantaneous" recordings or lacquer
lag-When two alternating quantities have
the same frequency but do not pass
through corresponding zero and maximum values at the same instants, the one
which reaches a particular point in a
cycle last is said to lag the other.
lagging current-An alternating current
which is being retarded by the self-inductance of the circuit, so that its changes
occur after the voltage changes have occurred. When there is only pure inductance in the circuit, the current lags 90
degrees behind the voltage.
lambert-The unit of brightness, equal to
one lumen per square centimeter.
laminated-A type of construction widely
used for the cores of iron -core transformers, choke coils, electromagnets, motors
and generators. It involves building up
the desired shape of core with thin strips
of a magnetic material such as soft iron
or silicon steel, in order to keep core
losses at a minimum.
lamination-A thin sheet of magnetic iron
or steel, used to build up the core of a
transformer or other device designed to
operate at low audio frequencies or
power frequencies.
land-The surface between two grooves
on a phonograph record.
lapel microphone-A small microphone
which can be attached to a lapel or pocket
by means of a clip.
lap winding-A method of winding an armature in which each coil terminates at the
next adjacent commutator segment.
lateral force-Force exerted from the side.
lateral recording-A lateral recording is one
law of magnetism-Like poles repel, unlike
poles attract.
law of position-The relationship which exists between the focal length and the distances of object and image from an optical
- _-
, where P = distance
from lens to object, Q = distance from
lens to image, and f = focal length of lens.
layout-A diagram indicating the placement of parts on a panel or chassis.
LC-Inductance times capacity.
LC ratio-Ratio of L to C (L
C) .
lead (pronounced leed)-Any connecting
wire, such as a battery lead, a test lead.
etc. Also, the opposite of lag. When
two alternating quantities have the same
frequency but do not pass through corresponding zero and maximum values at
the same instants, the one which reaches
a particular point in a cycle first is said
to lead the other.
lead (pronounced led)-A soft gray metal
used in storage batteries, solder and for
shielding cables. It is one of the few
metals that will shield against the radiations of radium and other radioactive
lead cell-The common storage battery cell,
which uses lead compound plates for both
positive and negative electrodes.
lead-in-That portion of an antenna system
which connects the main portion of an
antenna to the input of a receiver or to
the disconnecting switches or instruments
of a transmitter or its tuning house.
lead-in insulator-A porcelain tube inserted
in a hole drilled through an outer wall or
window frame of a house. The lead-in
wire of the antenna is run through this
lead-in spiral-A blank spiral g >ve at the
beginning of a record, used to lead the
phonograph needle into the recorded
lead screw (pronounced leed screw)-The
threaded rod which leads the cutter or reproducer across the surface of the disc
during recording.
leakage-Undesirable flow of
through or over the surface of an insulating material. This term is also used
to describe magnetic flux which takes a
short-cut path so that it does no useful
leakage current-A current flowing between
two or more electrodes of a tube by any
path other than that through space.
leakage flux-That portion of the total
magnetic flux which does not link all of
the turns of wire in a coil or transformer
and is consequently wasted.
leakage resistance-The resistance of a path
taken by leakage currents. Thus, the
leakage resistance of a condenser is the
normally high resistance which it offers
to the flow of direct current.
leaky-A term used to describe a part whose
resistance has dropped so much that excessive current flows or leaks through
the normally high-resistance path.
leaving here o.k.An engineering phrase
indicating proper transmission at a certain point. Used in checking technical
difficulties in broadcasting.
lecher wires-Parallel wires coupled to a
transmitter or receiver for the purpose
of measuring wavelength. The parallel
wires form a transmission line along
which standing waves appear. The wavelength is equal to twice the distance between any two consecutive current nodes.
left-handed elliptically polarized wave-An
elliptically polarized wave in which the
rotation of the direction of displacement
is counterclockwise for an observer looking in the direction the wave is traveling.
left-hand taper-A volume or tone control
having more resistance in the right half
of the control than the left half, when
held with the shaft pointing toward you
and the terminal lugs pointing downward.
leg-A branch of a radio network.
lens-A transparent object, usually glass,
having one or more curved surfaces designed to change the direction of rays
of light.
lens disc-A form of television scanning
disc in which each opening is fitted with
a condenser lens for the purpose of se-
curing greater brilliancy or light concentration.
lens speed-A measure of the amount of
light a lens will pass, equal to focal length
divided by diameter.
Lenz's law-An induced current always
opposes the current which produced it.
level-A value or amount, as of voltage or
light-Visible electromagnetic waves.
lightning arrester-A protective device used
to sidetrack directly to ground a discharge
of lightning which strikes a radio receiving or transmitting antenna.
light ray-A beam of light having a small
light-sensitive cell-Any device which
changes its electrical characteristics when
the amount of light (illumination) falling
on it is changed. Photocells, photovoltaic
cells and photoconductive cells are examples.
light velocity-All electromagnetic radiations, including those of light, travel in
space (in a vacuum) with the same velocity of approximately 186,000 miles per
second or 300,000,000 meters per second.
limiter-In an f.m. receiver, the section
which removes amplitude variations from
the f.m. signal at the output of the i.f.
amplifier, thereby limiting interfering
a straight-line character -
linear control-A volume or tone control
having uniform distribution of resistance
along each unit length of the resistance
linear detection-A type of detection in
which the audio frequency output is directly proportional to the radio frequency
input for all normal signals.
linearity control-A control for adjusting
scanning wave shapes in television systems. There may be top, bottom, right
and left linearity controls all in one
unit of a television system.
linearly polarized wave-A transverse wave
in which the displacement has a constant
direction at a point in space.
linear rectification-A process of rectification in which the rectified current or
voltage is proportional to the amplitude of
the input wave over a wide range of
input amplitudes.
line cord-A two-wire cable terminating in
a two -prong plug, used to connect a radio
receiver to an a.c. or d.c. wall outlet.
line cord resistor-An asbestos -wrapped resistance element incorporated in a line
cord for the purpose of dropping the line
voltage to the proper value for application
to the series -connected tube filaments of
a universal a.c.-d.c. receiver. Sometimes
known by the trade name Cordohm.
line filter-A device inserted between the
line cord plug of a radio receiver and the
power line to block noise signals which
might otherwise enter the receiver from
the power line. It contains one or more
choke coils and condensers.
line flyback-In a television system, the
right -to -left return motion from the end
of one line to the beginning of the next.
Also called horizontal flyback or horizon-
ing material from the studio, pushing back
curtains to expose window and wall surfaces, and setting up sound -reflecting
load-That part or combination of parts
into which power is fed to accomplish a
desired result. Also used to indicate the
amount of power taken from a circuit.
loading coil-A coil inserted in a circuit
to increase its inductance but not to provide coupling with any other circuit.
load line-A line drawn on a graph of
Ep-Ip curves to show what operating conditions will be for a particular load in
the tube plate circuit.
local oscillator-The oscillator section of a
superheterodyne receiver. It may have
a separate tube or use a part of the
mixer -first detector tube.
local program-A program released only
through one station.
locked groove-A blank, endless groove at
the end of modulated grooves on a record.
to prevent further travel of the phonograph needle. This groove is off -center
on most modern phonograph records, to
provide an in -and -out motion for actuating the tripping mechanism of an automatic record changer.
loctal-Same as loktal.
log-Logarithm. A list of radio stations.
A record of stations with which a radio
transmitter has been in communication ;
tal retrace.
lines of force-Imaginary lines used for
convenience in designating directions in
which electric or magnetic forces act in
line -stabilized oscillator-An oscillator in
which a section of transmission line is
used as a sharply-selective frequency controlling element.
line synchronizing impulse-In television,
the impulse which is sent at the end of
each line for controlling purposes.
line voltage-The voltage existing at a wall
outlet or other terminals of a power line
system. In the United States, the line
voltage is usually between 110 and 120
volts, but may vary at times above and
below these limits.
linkage-Coupling together by lines of force
which pass through both parts.
link coupling-The coupling of two separated inductances by a closed loop. A
few turns of wire are placed about each
inductance and are then connected together by a pair of wires or a low -impedance concentric line.
Lissajou patterns-The patterns obtained
when alternating voltages of various
amplitude ratios, frequency ratios and
phase differences are applied to both
pairs of deflecting plates in a cathode
ray tube.
literal number-A letter or symbol used for
representing quantities. Thus, R is a
literal number (sometimes called a general number) when used to represent a
number of ohms of resistance.
litz wire-A special stranded wire in which
each strand is on the surface for a certain
distance. Used to reduce skin effect.
live-A term used to describe a wire or
circuit which is energized and therefore
has a voltage.
live end-The part of a radio studio which
gives the greatest reflection of sound.
liven the studio-Removal of sound -absorb-
radio operators are required by law to
keep this log. A detailed record describing 'the program being broadcast each
minute of the operating day by a broadcast station. A record of the meter readings which are required by law to be
taken at regular intervals in a broadcast
transmitter and in certain other types of
log-1-Antilogarithm. To be read "A number whose log is."
login-Logarithm of a number to the base
10, which is the common logarithm of a
logs-Logarithm of a number to the
base e, which is 2.718 in the natural system of logarithms.
logarithm-The common logarithm of a
quantity is the exponent of the power to
which the number 10 (the base of the
common system of logarithms) must be
raised in order to equal the quantity.
Thus, 4 is the logarithm of 10,000 (log
4) because 10` is equal to 10,000.
In the natural system of logarithms, the
base is 2.718, which is designated by the
Greek letter e.
logging-Making a record of the exact dial
setting at which a radio station is received, or making a written record of
any other essential data in connection
with radio equipment.
usually used as the reference level for
loudness levels in db. The loudness level
is sometimes called equivalent loudness
or equivalent loudness level.
loudspeaker-A device for converting electrical energy into acoustic energy which
is radiated into a room or open air. A
loudspeaker is often called a speaker
when no confusion will result therefrom,
as in compound terms like speaker field,
speaker cone, etc.
louver-A type of loudspeaker grille construction in which sloping slats or equivalent parts of a molded plastic cabinet
hide the loudspeaker yet allow sound
waves to emerge unhindered.
loktal tube-A small -size glass radio tube
having a special base construction which
locks the tube firmly in the corresponding special 8-prong loctal socket. The
tube prongs are sealed directly into the
glass envelope. Loktal tubes are used
chiefly in midget a.c.-d.c. receivers and
in auto radios.
longitude-The distance east or west of a
meridian passing through Greenwich,
England, measured in degrees, minutes,
and seconds.
long waves-Wavelengths longer than the
longest broadcast band wavelength of 545
meters. Long waves correspond to frequencies between about 15 kilocycles and
550 kilocycles.
loop antenna-An antenna consisting of one
or more complete turns of wire. It may
be built into a radio receiver cabinet or
separately mounted, and is usually tuned
to resonance by a variable condenser.
Loop antennas are used extensively in
radio direction -finding apparatus.
spelled louvre.
low -frequency padder-In a superheterodyne receiver, a semi -adjustable condenser which is placed in series with the
oscillator tuning circuit to adjust the calibration of the circuit at the low -frequency
end of the tuning. range.
low-level modulation-Modulation at a
point in a transmitter where the power
level is low compared to that at the out-
put of the transmitter.
low -loss construction-A type of radio part
construction involving the use of insulating materials which maintain their in-
sulating characteristics at high radio frequencies.
low-pass filter-A filter network designed to
pass all frequencies below a cut-off frequency value, while attenuating or rejecting higher frequencies.
low-tension-Low voltage.
L pad-An attenuation network having its
elements arranged in the manner of the
letter L.
lug-A small strip
of metal placed on a
terminal screw or riveted to an insulating
material to provide a convenient means
for making a soldered wire connection.
lumen-A unit of light flux. One candle
Courtesy Continental Radio d Teievteion
or 12.56 lumens of light.
luminescence-Radiation of light by an object which has previously been exposed
to strong light.
lumped constant-A single constant which
is equivalent electrically to all the distributed constants of that type which
exist in a coil or circuit.
loops-Antinodes. The points of greatest
amplitude in a standing wave.
loose coupling-Very little coupling between
two coils, so that only a small part of the
magnetic flux of one coil links the other
loss-Energy which is dissipated before it
accomplishes useful work.
loudness-That quality of a sound which determines how much sensation it produces
in human ears.
loudness level-The intensity level in decibels of a 1000 -cycle pure tone which
seems equivalent in loudness to the sound
under consideration. The threshold of
hearing for a 1000 -cycle pure tone is
m.-Meters (metric unit of length).
M-Mutual inductance. Also, a letter sometimes used to indicate that a particular
resistance value is to be multiplied by
Thus, 50M would mean 50,000
MQ or Mw-Thousand ohms.
is 50,000 ohms.
Thus, 50M52
eye-Popular name for a cathode ray
tuning indicator tube.
magnet-A piece of iron or steel which has
the property of attracting other pieces of
magnetic material such as iron, and has
the property of attracting or repelling
other magnets. A permanent magnet pos-
sesses this property permanently while an
electromagnet possesses magnetic properties only when current is flowing
magnetic shield-An iron housing used with
a radio part to prevent external magnetic fields from affecting the part and
to prevent magnetic fields produced by
the part from affecting other circuits and
magnetic storm-A rapid and violent fluctuation in the intensity of the earth's
magnetic field, disrupting radio and telegraphic communication.
magnetic vane meter-An a.c. meter containing a metal vane pivoted inside a
coil in such a way that magnetic forces
rotate the vane and attached pointer and
thereby indicate the strength of the alternating current flowing through the meter.
magnetism-A property characterized by
ability to attract iron objects and to influence moving electrons.
magnetization curve-A curve showing the
relation between the magnetizing force
H (ampere -turns or gilberts per cm.) and
the flux density B (lines per sq. centimeter) . Also called B -H curve.
magnetizing force-Magnetomotive force,
which produces magnetic flux.
magnetomotive force-The force which produces magnetic flux in a magnetic circuit.
That which sets up and maintains a
magnetic field. It corresponds to electromotive force in an electric circuit.
magnetostriction-The very slight change in
the size of material like nickel when it
is magnetized.
magnetostriction oscillator-An oscillator in
which the grid and plate circuits are
coupled through a special rod of magnetic material. The alternate expansion
and contraction of the rod with changes
in plate current governs the fundamental
frequency of the oscillator.
magnetostrictive-Changing in size (dimensions) when placed in a magnetic field.
magnetron-A specially constructed radio
tube in which the electron flow is controlled by an external magnetic field.
magnet wire-Insulated copper wire in sizes
commonly used for winding coils used in
electromagnetic devices such as transformers, choke coils and relays.
magnitude-The amount or value of a
through its coil.
magnetic circuit-A complete path for magnetic lines of force. It always includes
the permanent magnet or electromagnet
which is producing the magnetic lines of
magnetic contactor-A magnetically actuated device for opening or closing an
electric power circuit.
magnetic damping-Damping cue to eddy
currents which develop a retarding force.
magnetic density-The number of magnetic
lines of force per unit cross-sectional area.
magnetic field-The space around a permanent magnet or a current -carrying conductor or coil where magnetic flux exists.
magnetic flux-Magnetic lines of force.
magnetic focusing-Focusing of an electron
beam in a cathode ray tube b; the action
of a magnetic field.
magnetic lines of force-Imaginary lines
used for convenience to designate the
directions in which magnetic forces are
acting throughout the magne is field associated with a permanent magnet, electromagnet or current -carrying conductor.
magnetic loudspeaker-A loudspeaker consisting essentially of a permanent magnet,
a pivoted armature which is mechanically
connected to the diaphragm ar cone, and
a coil which is connected to the output
stage of a radio receiver oc other apparatus. Interaction between the permanent magnetic field and that developed
in the armature by the coil results in
movement of the armature and production
of sound waves by the diaphragm.
magnetic microphone-A general term for
any microphone in which the output voltage depends upon variations in the reluctance of a magnetic circuit Dynamic
and velocity microphones are examples.
power lines.
magnetic pickup-A phonograph pickup consisting of a permanent magnet, one or two manganin-A metal alloy commonly used for
coils, an iron armature and a core strucits resistance properties in rheostats and
ture so arranged that movement of the
resistors, because it is not appreciably
phonograph needle in the record groove
affected by changes in temperature. It
varies the amount of magnetic flux passis composed of about 84% copper, 12%
ing through the coils, thereb, inducing
manganese, and 4% nickel.
audio frequency voltages in the coils.
man-made static-High-frequency noise sigmagnetic saturation-A condition of an iron
nals which are produced by sparking in
core whereby further increases in magelectrical apparatus or power lines and
netizing force produce little increase in
picked up by radio receivers, with the
magnetic flux.
result that buzzing and crashing sounds
are heard along with a desired radio
mantissa-The second part of a logarithm
(to the right of the decimal point). It
is always a decimal, is always positive, and is found by referring to a
table of logarithms. Example : In log
461 = 2.6637, the mantissa is .6637.
manual tuning-Tuning a radio receiver to
a desired station by rotating the tuning
control knob by hand.
Marconi antenna-An antenna which is disrectly connected to ground or is close
enough to ground so that the ground
plays an essential part in the radiation
marking wave-In telegraphic communication, the active portions of the code characters being transmitted. The inactive
portions, in between the code characters,
are called the spacing wave.
masking disc-A device to restrict the cone
of electrons to a small size to prevent
spherical aberration in an electronic lens.
mass-That property of a body which determines the acceleration it will have
when acted upon by a given force, such
as by gravity.
mast-A vertical pole or structure supporting one end of an antenna.
master-The commanding officer on board
a ship. Also the negative die made from
the original wax recording which is used
to produce other dies, from which are
made the stamping dies used to produce
phonograph records.
master control board-The panel on which
all the main operating controls of a broadcast studio or transmitter are located.
master oscillator-The oscillator which establishes the carrier frequency of a transmitter.
matched impedance-Circuits balanced or
matched so that their total impedances
at the point of coupling together are
matching-Connecting two circuits or parts
together with a coupling device in such
a way that the impedance of either circuit will be equal to the impedance existing between the coupling terminals to
which that circuit is connected.
matrix-A negative from which duplicate
phonograph records are molded.
matter-Any physical entity which has
maximum-Greatest quantity or amount of
maximum undistorted output-The maximum audio power output which a radio
receiver or audio amplifier will deliver
without having more than 10% total harmonic distortion. Tests have shown that
this amount of distortion is not ordinarily
noticeable or objectionable.
maximum usable frequency-The highest
frequency that can be used for reliable
radio transmission at a specified time between two points on the earth by reflection from the regular ionized layers of
the ionosphere.
maxwell-The unit of magnetic flux, equal
to one magnetic line of force.
MAYDAY-The international distress call
for radiotelephone communication. It is
derived from the French pronunciation
of "M'aidez," meaning "Help me."
MBS-Mutual Broadcasting System.
m.c.w. or MCW-Modulated continuous
mechanical bandspread-The use of a vernier tuning dial to make the gang tuning
condenser rotate more slowly than the
tuning control knob, so as to make station tuning easier in crowded short-wave
mechanical damping-The mechanical resistance which is generally associated
with the moving parts of a cutter or a
mechanical television-Any television system in which the scene to be transmitted
is broken up into picture elements, and
reconstructed at the receiving end by a
moving mechanical mechanism such as a
rotating scanning disc.
megacycle-One million cycles per second.
megger-A high -range ohmmeter used for
measuring leakage resistances and insulation resistances. The necessary high voltage is generated by a self-contained, hand operated generator.
megohm-One million ohms.
mercury-A heavy, silvery -colored metal
which is liquid at ordinary room temperatures. When heated, it gives off a vapor
which is highly conductive when ionized.
mercury-vapor rectifier tube-A rectifier
tube containing a small amount of mercury. When the filament or heater -type
cathode is heated, mercury vapor is produced, and the resulting ionization of the
mercury-vapor molecules gives a much
higher plate current than would be obtained in an equivalent vacuum -type rectifier tube.
Mershon condenser-A commercial wet electrolytic condenser.
mesotron-A particle having a unit negative charge like an electron but a mass
in between that of electrons and protons.
Also called heavy electron, barytron, dynatron, penetron, X particle, etc. Mesotrons
make up a large part of cosmic rays.
metallized resistor-A resistor made by de 54
positing a thin film of high -resistance
metal on the surface of a tube or rod
made of glass or other insulating material.
Leads are attached to opposite ends of
the unit.
metal tube-A vacuum tube having a metal
envelope instead of a glass envelope.
Electrode connections are made through
glass beads fused into the top and bottom
of the metal envelope. The octal bakelite
base is designed to take eight equally
spaced terminal prongs, but some of the
prongs are omitted on tubes having less
than eight terminals.
meter-The unit of length in the metric
system. One meter is equal to 3.28 feet.
Also an instrument used for making electrical measurements. A voltmeter measures voltage ; an ammeter or milliammeter
measures currents ; a wattmeter measures
power ; an ohmmeter measures resistance.
metric system-A decimal system of measures and weights, using the meter and the
gram as basic units. The system of units
based on meters for length, grams for
of flexible diaphragm which moves in accordance with sound wave variations.
This movement, in turn, generates a voltage which is fed to the input of an amplifier.
microphone button-A button-shaped container filled with carbon particles. When
attached to the diaphragm of a microphone, the resistance between the terminals of the button varies in accordance
with movements of the diaphragm.
microphone cable-The specially made group
of wires connecting a microphone to an
amplifier or mixer.
microphone preamplifier-An audio amplifier which amplifies the output of a microphone sufficiently so that the audio signal
may be sent over a transmission line to
the main amplifier. Sometimes, particularly with condenser microphones, this
microphone amplifier is mounted right on
the microphone stand or in the microphone housing itself.
mho-The unit of conductance. It is the
reciprocal of resistance.
mica-A transparent flaky mineral which
splits readily into thin sheets and has
excellent insulating and heat -resisting
qualities. It is used extensively to separate the plates of condensers, to insulate
electrode elements of vacuum tubes, and
for many other insulating purposes in
radio apparatus.
mica condenser-A condenser which employs
sheets of mica as the dielectric material
which insulates adjacent plates from each
micro-Prefix meaning one millionth of.
microammeter-A meter designed to measure extremely small currents.
microampere-One millionth of an ampere.
microfarad-A unit of capacity equal to
one millionth of a farad. The microfarad
is the capacity unit most commonly used
in radio work. It is abbreviated as mfd.
Modern Dynamic Microphones
microphone stand-A table or floor -type
stand used to support a microphone in a
desired position.
microphone transformer-The iron -core a.f.
transformer which couples the microphone
to a microphone amplifier, to a transmission line, or to the input circuit of the
main audio amplifier.
microphonic-A condition in which mechanical movement of some radio part other
than a microphone causes corresponding
variations in circuit current. A radio
tube is microphonic if a pinging sound is
heard in the loudspeaker when the side
of the tube is tapped with a finger; the
tapping is then setting the internal elements into vibration. If sound waves
from the loudspeaker are producing this
vibration of tube elements, the sound will
be 'sustained as a howl.
microvolt-One millionth of a volt. Abbreviated µv.
microvolts per meter-A measure of the
radio field intensity, equal to the signal
strength at the antenna in microvolts divided by the effective height of the antenna in meters.
microwave-A very short electromagnetic
wave, usually having a wavelength less
or µf.
microhenry-One millionth of a henry.
breviated as µb.
micromho-A unit of conductance equal to
the one-millionth part of a mho.
micromicrofarad-A unit of capacity equal
to one millionth of a microfarad, and abbreviated as mmfd. or µµf.
micron-A unit used to express wavelengths of light. One micron is equal to
10,000 angstrom units or .0001 cm.
microphone-A device which converts sound
waves into corresponding audio frequency
electrical energy. It contains some form
than one meter (higher than 300 megacycles).
microwave oscillator-An oscillator which
generates a frequency higher than 300
megacycles (less than one meter)
mil-A unit of measurement equal to one
thousandth of an inch (.001 inch), used
chiefly in specifying the diameters of
round conductors.
mil-foot-A wire one foot long having a
diameter of 1 mil.
milli-Prefix meaning one thousandth of.
milliammeter-A meter which measures current flow in milliamperes.
milliampere-A unit of current equal to one
thousandth of an ampere. Abbreviated ma.
millihenry-A unit of inductance equal to
one thousandth of a henry. Abbreviated
millimeter-A metric unit of length equal
to one thousandth of a meter. One millimeter is approximately equal to one
twenty-fifth of an inch. Abbreviated mm.
millivolt-A unit of voltage equal to one
thousandth of a volt. Abbreviated mv.
milliwatt-A unit of power equal to one
thousandth of a watt. Abbreviated mw.
min.-Minutes. Minimum.
minimum-Lowest, least or smallest quantity of anything.
minus sign-A sign (-) used in mathematics to indicate subtraction or a negative value. Used in radio to indicate the
negative terminal of a voltage source or
to indicate negative polarity.
minute-One-sixtieth part of a degree. One
complete revolution of an angle -generating line is 360°, which is 360 X 60 minutes
or 360 X 60 X 60 seconds.
mixer-A control which permits combining
the output signals of two or more microphones or other a.f. signal sources in any
desired proportion before these signals
are fed to the input of the main a.f. amplifier. Also, the stage in a superheterodyne
receiver in which the incoming modulated
r.f. signals are mixed with the local oscillator signals to produce the i.f. signal.
mixer -first detector-The stage in a superheterodyne receiver in which the desired
signal is combined with the signal of a
local oscillator to create the intermediate
M.O.-Master oscillator.
mobile receiver-A receiver designed to be
operated while in motion. Usually refers
to commercial communication equipment.
mobile station-A radio station operated in
a movable location such as on an auto-
mobile, rire truck, railway train, ship or
mobile transmitter-A transmitter designed
to be operated while in motion and normally so operated.
modulated amplifier-The r.f. stage in a
transmitter at which the intelligence signal is made to modulate the r.f. carrier
modulated stage-The radio frequency stage
to which the modulator is coupled and
in which the continuous wave (carrier
wave) is modulated in accordance with
the system of modulation and the characteristics of the modulating wave.
modulated wave-A radio wave which varies
either in frequency (frequency modulation) or in amplitude (amplitude modulation) in accordance with the wave form
of the intelligence signal being trans-
modulating electrode-An electrode used in
a cathode ray tube to control the beam
modulating wave-The a.f. signal, picture
signal, facsimile signal, code signal, etc.,
which is made to modulate the carrier
wave of a transmitter.
modulation-The process of producing a
wave, some characteristic of which varies
as a function of the instantaneous value
of another wave which is called the modulating wave.
modulation capability-The maximum percentage modulation which can be used
without objectionable distortion.
modulation distortion-Distortion of wave
form due to a greater plate current
change on positive half cycles than on
negative half cycles. Prevalent in screen
grid tubes.
modulation envelope-A curve which is
drawn to pass through the peaks of a
graph showing the wave form of a modulated r.f. carrier signal.
modulation factor-The ratio of the maximum amplitude of the modulation envelope to the amplitude of the unmodulated carrier. Multiplying this factor by
100 gives percentage modulation.
modulation percentage-The ratio of signal
voltage to carrier voltage, expressed in
per cent.
modulator-The final audio stage in a radio
transmitter. It feeds the intelligence
signal into the modulated amplifier stage,
where the signal is made to modulate
the r.f. carrier signal.
molded condenser-A condenser molded in
bakelite or other suitable insulating material for the purpose of keeping out dust
and moisture.
rotates in a magnetic field produced by
molecular theory of magnetism-The theory
which treats each molecule oß matter as
a complete permanent magnet. When a
piece of material is magnetized, all the
molecular magnets line up will like poles
pointing in the same direction.
molecule-The group of atoms which constitutes the smallest particle in which a
compound or material can exist separately.
monitor-A person who checks the quality
of a radio or television program at the
studio or transmitter. Some times called
monitor operator. Also, a receiver or
loudspeaker used at broadcast studio,
transmitter or other location for the purpose of checking or monitoring the programs of a radio station or public address
monitoring-The act of listening to a program picked up by a microp:one, either
during rehearsals or actual broadcasts,
to check quality and determine proper
levels for sound effects.
monitor panel-A group of controls used
to govern the level of sound signals from
a studio, or of television vide) signals as
picked up by the scanning mechansim or
television camera tubes at a television
field coils.
motorboating-Regeneration occurring at
audio frequencies in a radio receiver or
audio amplifier, resulting in put -put -put
sounds resembling those made by a motorboat.
motor-generator-An electric motor directly
connected to one or more generators for
the purpose of converting a power line
voltage to other desired voltages or frequencies.
mouth of a horn-The large end of the horn
of a horn loudspeaker.
moving -coil loudspeaker-Another name for
a dynamic loudspeaker, in which the mechanical forces acting on the diaphragm
are produced by interaction between the
magnetic field of the moving conductors
(voice coil) and the steady applied magnetic field produced by a field coil or
permanent magnet.
moving -coil microphone-A moving -conductor microphone in which the moving conductor is in the form of a coil located in a
strong magnetic field produced by a permanent magnet. Usually called a dynamic
moving -conductor microphone-A general
term applying to all microphones in which
the output voltage depends upon motion
of a conductor in a magnetic field.
M.S.T.-Mountain Standard Time.
multi -band antenna-An antenna which can
be used with satisfactory results on a
number of frequency bands.
multielectrode tube-A vacuum tube having
more than three electrodes associated
with a single electron stream.
multimeter-A test instrument having provisions for measuring voltages and currents, as well as resistance.
monkey chatter-Garbled speech or music
heard along with a desired program.
This type of interference occurs when
the side frequencies of an ad.acent-channel station beat with the desired station
monoscope-A special type of cathode ray
tube which produces television picture signals corresponding to the design or picture which has been printed on its screen.
This tube is used in television picture
signal generators to providie a satisfactory signal source for te-evision receiver test purposes during those times
when no television station is on the air.
M.O.P.A.-Master oscillator power ampli-
multipath transmission-Signals reaching
the radio receiving antenna by two or
more paths. The resulting differences in
amplitude and phase give an echo effect.
multiple-tuned antenna-An antenna which
is connected to ground through tuning
coils or condensers at more than one point,
so that the total of the reactance in parallel will make the antenna resonant at the
Morse Code-A system of dot aid dash signals used in the transmission .f messages
by radio or wire telegraphy. The International Morse Code (also called the Continental Code) is used universally for
radiotelegraphy, while the American
Morse Code is used only for wire telegraphy.
mosaic-In television, the light-sensitive
surface of an iconoscope, consisting of
millions of tiny silver globules on a sheet
of ruby mica, each globule treated with
caesium vapor to make it photosensitive.
mother-A positive recording produced directly from the metal master or negative.
motor-A machine which converts electrical
energy into mechanical energy. It consists essentially of a large number of conductors mounted on an arma:ure which
desired frequency.
multiple -unit tube-A vacuum tube having
two or more groups of electrodes, each
with its own electron stream, In a single
envelope. See duodiode, duotriode, diode pentode, duodiode-triode, duodiode-pentode and triode pentode.
multiplex radio transmission-The transmission of two or more carrier waves,
using a common carrier wire circuit.
multiplication-The process of determining
by a briefer computation the result of
adding any given number or quantity a
certain number of times. Thus, 3 X 4
is 4 added together 3 times, or 4 -I- 4 + 4.
Multiplication is indicated by the sign X.
In algebra, the multiplication sign is
usually omitted between general numbers (numbers expressed by letters) or the
symbol is used to denote multiplication.
Examples : I X R, IR and IR all mean
that I is to be multiplied by R 2nfL
means 2 times n times f times L. In algebra, the product of two numbers having
like signs is positive. The product of two
numbers having unlike signs is negative.
multiplier-A resistor used in series with a
voltmeter to increase the range of the
multiplier tube-A tube in which emitted
electrons are pulled along by increasingly
higher potentials and are made to strike
a number of plates (called dynodes) suc-
cessively. At each plate, secondary emission occurs, resulting in a high current
from the last plate. This gives the effect
of high gain.
multiplying factor-The number by which a
meter reading is multiplied to get the
true value.
multivibrator-A type of relaxation oscillator which consists of two triode tubes
connected so that energy from the plate
circuits is fed to the opposite grid circuit
at the proper time and in the proper
phase to produce a square -wave output.
muting switch-Device used in automatic
tuning systems to silence the audio system while stations are being selected or
tuned in.
mutual conductance-The ratio of the
change in plate current to the change in
grid potential producing it, under the
condition of constant plate voltage.
mutual inductance-The common property
of two associated coils or electric circuits
which determines how much electromotive force will be induced in one by a
change of current in the other. Mutual
inductance is measured in henrys, and is
designated by the letter M.
mutual induction-The generation of a voltage in one circuit by the varying current
in another circuit when inductive coupling
mv./m.-Millivolts per meter. (Sometimes
used for microvolts per meter.)
N-Number of turns on a coil.
National Electric Code-A set of rules
erning construction and installation of
electrical apparatus, as approved by the
National Board of Fire Underwriters.
natural frequency-The fundamental
(lowest) resonant frequency of a coil condenser circuit, not a harmonic frequency.
natural frequency of an antenna-The fundamental resonant frequency of an antenna alone (without added inductance or
natural wavelength-The wavelength corresponding to the natural frequency of a
NBC-National Broadcasting Company.
needle-That part of a phonograph pickup
which converts the variations in the
record grooves into mechanical movements which are in turn converted into
audio frequency signals by the pickup element. The needle must be carefully
shaped to follow faithfully the high -frequency variations in the grooves without
causing excessive record wear.
needle pressure-Effective weight of the
stylus or needle on the phonograph record.
negative-A term used to describe a terminal which has more electrons than normal.
Electrons flow out of the negative terminal of a voltage source.
negative bias-The use of a voltage which
makes the control grid of a radio tube
negative with respect to the cathode.
negative charge-A body is negatively
charged when it has more than the normal
number of electrons. The number of excess electrons is a measure of the amount
of charge.
negative feedback-Degeneration, which decreases the amplification. Also called inverse feedback or stabilized feedback.
negative modulation-In an a.m. facsimile
system, that form of modulation in which
the maximum transmitted power corresponds to the maximum density of the
subject copy. In an f.m. system, it is
that form of modulation in which the
highest transmitter frequency corresponds
to the maximum density of the subject
copy. In television, a method of transmission in which a decrease in scene
illumination causes an increase in the
radiated power of the transmitter.
negative picture'phase-A condition wherein
increases in brilliancy make the television picture signal voltage swing in a
negative direction, below the zero level.
negative resistance-A characteristic of an
electric arc or some vacuum tubes wherein
the voltage drop across a circuit decreases when the current increases.
negative terminal-A terminal having more
than the normal number of electrons.
N.E.M.A.-National Electric Manufacturers
neon-A pure gas sometimes used in electronic tubes. It produces a characteristic
red glow when ionized.
neon glow lamp-A neon -filled gaseous tube
having a glass envelope through which
can be seen the characteristic red glow
of neon when ionization occurs during
operation of the tube.
neon oscillator-A neon lamp with a condenser and resistor incorporated in a circuit in which the time constant may be
varied over a wide range by adjustment
of the capacity or resistance value,
thereby changing the frequency of oscillation.
neper-Obsolete unit of power gain or loss,
replaced by the decibel and volume unit.
network-Any complex electrical circuit.
Also, a group of broadcasting stations
connected together by radio or wire telephone lines so that all stations can broadcast a program originating at one of the
neutral-An object which has its normal
number of electrons and therefore is uncharged electrically.
neutralization-A term used in radio to
describe any process which balances out
or prevents an undesirable effect such as
neutralizing condenser-A variable condenser used in transmitting and receiving
circuits to feed a portion of the a.c. plate
voltage back to the grid circuit. This
voltage is 180° out of phase with the grid
voltage and reduces the tendency of the
stage to go into oscillation.
neutralizing tool-See aligning tool.
neutral wire-The middle wire of a three wire two-phase power line, usually
neutrodyne circuit-A circuit in which a
portion of the r.f. plate voltage is fed back
into the grid circuit 180° out of phase to
reduce the tendency toward oscillation.
neutron-An electrically neutral particle
having about the same mass as a proton.
nichrome-An alloy of nickel, iron and
chromium which has a high resistance per
unit volume and is capable of withstanding high temperatures. It is used
extensively in the construction of wirewound resistors, as well as in the heating
elements of soldering irons and other electrical heating appliances.
Nicol prism-Two prisms of Iceland Spar
crystal cemented together with Canada
balsam. The combination is used to polarize light beams.
night errors-Errors introduced by variations in terrain, time of day, season of
year, different transmission characteristics, etc., which affect bearings taken
with loop antennas of radio direction
nodal point keying-A method of keying an
arc transmitter in which the transmitting
key connects to a point in the antenna
circuit which is essentially at ground
potential at all times.
node-Any point, line or surface which has
zero amplitude in a stationary-wave sys=
tern. The type of node is usually specified,
since there can be voltage nodes, current
nodes, pressure nodes, velocity nodes, etc.
noise-In radio, a term used chiefly in connection with interfering disturbing sounds
heard along with desired programs.
noise filter-A device which is inserted between a wall outlet and the power cord
plug of a radio receiver to block noise
interference which otherwise might enter
the receiver. Noise filters are also placed
between the power line and the device
producing noise, to prevent escape of the
noise signals into the power line.
noise level-The strength of noise signals
in a tube circuit, amplifier, program line,
etc., or the level of acoustic noise in a
particular location.
noise limiter-A special radio circuit which
limits the effects of interfering noises by
cutting off all noise peaks which are
stronger than the highest signal peak
being received.
noise-reducing antenna system-An antenna
system in which the only part capable of
picking up signals is the antenna proper,
this being erected high enough to be out
of the noise -interference zone. The lead-in
is a special shielded cable or twisted twowire line which can pass through the interference zone without picking up noise
Courtesy RCA
noise silencer-A special vacuum tube circuit which can be introduced into superheterodyne receivers to reduce the effects
of static and man-made interference
noises. Its chief value is in short-wave
communication receivers.
nomogram-Alignment chart or graph used
to speed up calculation of inductance or
other properties. Also called nomograph.
combinations of electrons and protons.
The plural is nuclei.
very high opposition to the flow of electricity. An insulating material.
non-homing tuning system-A motor -driven null indicator-Any device which will indiautomatic tuning system in which the
cate when a Wheatstone bridge circuit is
direction of motor rotation is reversed at
in balance (will indicate when current
the ends of the tuning range. When a
is zero).
station -selecting button is pressed, the number-One or more written or printed
motor will rotate in the direction in
characters used to express an amount of
which it was last rotating. Should the,
units. Examples : 1, 7, 45, 10,000, etc.
dial setting for the desired station be in numeral-One or more written or printed
the other direction, the motor will rotate
characters used to express a number.
the tuning mechanism to the end of the
Example : Arabic numerals 1, 2, 3, etc.
scale and will then reverse and proceed
Roman numerals I, V, X, etc.
to tune the receiver to the desired station
numerator-The part of a common fraction.
which is written above the line. Example
non -inductive circuit-A circuit having pracwL
tically no inductance.
In A/1ß, the numerator is 9 ; in
non -inductive condenser-A
having practically
numerator is wL.
layers of foil and paper are staggered
in winding so that one
trudes at one end, while the other layer
protrudes at the other end.
non-inductive resistor-A wire -wound re- obsolescence-free-Not liable to become out
sistor so constructed that the wire coil
of date because of new developments or
has practically no inductance. Used at
new inventions. A term applied particuhigh frequencies.
larly to tube testers and other test instruments.
non-inductive winding-A method of winding a coil so that the magnetic field about obtuse angle-An angle that is greater than
a turn cancels the field produced about
a right angle (greater than 90°).
the next adjacent turn. Used in making octal base-A type of tube socket base
non -inductive resistors.
having eight equally-spaced prongs and
non-linear-Not directly proportional.
a central aligning key. When some of
non-magnetic-Descriptive of materials such
the prongs are not needed, they are
as glass, wood, copper, brass and paper
omitted without changing the positions
which are not affected by magnetic field
of the remaining prongs.
and which cannot be magnetized.
octal glass-type tube-A glass tube having
non-resonant line-A transmission line
an octal base.
having a physical length much shorter octave-The interval between two frequenwavelength
operatthan a quarter
cies having a ratio of two to one. The
ing frequency so that the distributed voltreference frequency used in the United
age and
States for music is 440 cycles ; with this
termiAlso, a line of any
the frequencies between 440 and 880 cycles
nating devices
would be one octave, and 220 to 440 cycles
(standance so that there are
would be the next lower octave.
ing) waves.
octode-A vacuum tube having eight elecnon -storage camera tube-A type of televitrodes-a plate, a cathode, a control grid
sion camera tube which produces a picture
and five other electrodes.
signal which is proportional at any in- oersted-Unit of magnetic reluctance equal
stant to the intensity of the illumination
to magnetomotive force in gilberts divided
on the corresponding elemental area of
by flux in maxwells.
the scene at that instant.
ohm-The unit of electrical resistance. The
non -synchronous vibrator-A vibrator which
resistance of a device is one ohm when
only interrupts a direct current, without
a d.c. voltage of one volt will send a currectifying the resulting stepped -up a.c.
rent of one ampere through that device.
The Greek letter omega (w or SI) is commonly used to represent ohm.
normal-The perpendicular to the point
of contact. Also, the expected or regular ohmic value-The resistance in ohms which
a part or circuit offers to the flow of
direct current.
north pole-The pole of a magnet at which
the magnetic lines of force leave the ohmmeter-A test instrument which measmagnet.
ures and indicates directly the resistance
of a part or the resistance between any
nucleus-The central portion of an atom
two points in a circuit. It consists essen consisting of a proton alone or various
non-conductor-Any material which offers
tially of a milliammeter in series with a
suitable d.c. voltage and suitable series or
shunt resistors.
Ohm's Law-A fundamental electrical law
which expresses the relationship between
voltage, current and resistance in a direct current circuit, or the relationship
between voltage, current and impedance
in an a.c. circuit. The three forms of
the law in each case are given below, in
which E is the pressure in volts, I is
current in amperes, R is resistance in
ohms and Z is impedance in ohms.
sensitivity rating for
meters. It is obtained by dividing the
resistance (of the meter and multiplier
resistors) by the full-scale voltage value.
The higher the ohms -per -volt rating, the
more sensitive is the meter.
opaque-Preventing the passage of light
open circuit-A circuit which is not electrically continuous and in which current cannot flow.
operating angle-In an amplifier, the angular portion of a cycle during which plate
current flows. For class C amplifiers it
is less than 180° ; for class B amplifiers
it is about 180° ; for class A amplifiers it
is 360°.
operating point-The point on a grid -voltage plate -current characteristic curve of
a tube which corresponds to the d.c. grid
bias value and d.c. plate current value
for operating conditions.
operating power-The power that is actually supplied to the radio station antenna.
"Maximum rated carrier power" is the
maximum power at which the transmitter
can be operated satisfactorily, and is
determined by the design of the transmitter and the type and number of vacuum
tubes used in the last radio stage. "Plate
input power" means the product of the
direct plate voltage applied to the tubes
in the last radio stage and the total direct current flowing to the plates of these
tubes, measured without modulation.
"Antenna input power" or "antenna
power"means the product of the square
of the antenna current and the antenna
resistance at the point where the current
is measured.
operating voltage-The d.c. voltages applied
to the filament, plate, screen grid and
control grid elements of a tube to establish its operating characteristics.
operator-A person whose duties include
the adjustment, maintenance and operation of radio transmitting equipment.
optical pattern-The pattern which is ob-
served when the surface of a phonograph
record is illuminated by a beam of parallel light.
optics-The science which treats of the
phenomena of light.
optimum-Best possible.
optimum coupling-That amount of cou-
pling between two circuits which gives
maximum transfer of signal energy.
ordinary wave-One of two components into
which a radio wave is split in the ionosphere by the earth's magnetic field. This
wave is sometimes called the O wave.
See extraordinary wave.
ordinate-The coordinate value which specifies distance in a vertical direction on
an ordinary graph.
orient-To turn or adjust in a definite direction with respect to some reference.
oscillation-A condition whereby high-frequency currents are generated in a circuit.
oscillator-The stage in a radio receiver,
transmitter or other apparatus in which
a vacuum tube and associated parts generate alternating current energy when fed
with direct current energy. Thus, the
oscillator stage in a superheterodyne receiver generates an r.f. signal of the correct frequency to produce the i.f. carrier
signal when mixed with an incoming
station signal. In a transmitter the
oscillator stage generates the carrier frequency of the station or a frequency equal
to some definite fraction of the assigned
frequency. Also, a signal generator used
by servicemen.
oscillator coil-The r.f. coil used in the
oscillator circuit of a superheterodyne
receiver or other radio apparatus to pro-
duce oscillation.
oscillator harmonic interference-The result of interaction between incoming signals and harmonics of the local oscillator
(usually the second harmonic) in a superheterodyne receiver.
oscillator-mixer-first detector-A single
stage, usually employing a pentagrid converter tube, which combines the functions
of the local oscillator and the mixer -first
detector in a superheterodyne receiver.
oscillator padder-An adjustable condenser
in series with the oscillator tank circuit
of a superheterodyne receiver used to
make possible better tracking between
oscillator and preselector at the low -frequency end of the tuning dial.
oscillatory circuit-A circuit containing inductance and capacity having values such
that a voltage impulse will produce an
oscillatory (alternating) current.
oscillograph-A test instrument which records photographically the wave form of
a varying current or voltage.
oxide-A combination of an element with
oscilloscope-A test instrument which shows
visually on a screen the wave form of a
varying current or voltage.
outdoor antenna-An elevated wire erected
oxygen. Rust is an oxide of iron.
oxide -coated filament-A filament coated
with a metallic oxide to increase the
electron emission. -Oxides of barium and
strontium are most often used. These
oxides are also applied to cathodes of
heater type tubes.
outside a building for the purpose of receiving radio waves.
outlet-A set of terminals from which electric power may be obtained. Thus, power
at the a.c. line voltage may be obtained
from a wall outlet in a building connected
to an a.c. power system.
output-The useful electrical energy delivered by a radio receiver, a.f. amplifier,
electrical generator, or any other signal
or power source.
output capacity-The sum of all inter -electrode capacities existing between the
plate and cathode of a vacuum tube.
output impedance-The impedance as measured between the output terminals of a
radio device, receiver or amplifier at a
definite frequency or at a predominant
frequency in the audio range which the
device is to handle. For maximum efficiency, the load impedance should match
or be equal to this output impedance.
output indicator-A meter, tuning eye or
other device used to show changes in output during receiver alignment.
output meter-A meter connected to the output of a receiver or amplifier for the purpose of measuring variations in output
signal strength.
output stage-The final stage in a receiver
or a.f. amplifier. In a radio receiver,
the output stage feeds the loudspeaker
directly. In an a.f. amplifier, the output
stage may feed into one or more loudspeakers, a transmission line, or a cutting
head in the case of a sound recording
output transformer-An iron-core a.f. transformer used to provide efficient coupling
between the output stage of a radio receiver or a.f. amplifier and its load. It
is often mounted on the loudspeaker.
output tube-See power output tube.
overcutting-Excessively high level in recording.
overlap-The amount by which the effective
height of the scanning spot exceeds the
nominal width of the scanning line in a
facsimile system.
overload-A load greater than an electrical
device is designed to carry.
overload relay-A relay which opens a circuit automatically when current becomes
of a tube. Power in watts. Primary winding of a transformer.
p.a. or P.A.-Public address. Power amplifier.
pad-A network of resistors, sometimes
variable, inserted in a circuit to introduce
a loss. Used where input and output impedances must be matched or maintained
padder-In a superheterodyne receiver, the
trimmer condenser placed in series with
the oscillator tuning circuit to control the
receiver calibration at the low -frequency
end of a tuning range.
panel-A sheet of metallic or non-metallic
material on which the operating controls
of a radio device such as a receiver, transmitter or p.a. amplifier are mounted.
paper condenser-A fixed condenser employing foil plates separated by paraffined or
oiled paper. It is usually constructed in
tubular form.
parabolic reflector-A reflector which brings
parallel light rays from a distant source
to a sharp focus at a single point.
parallel connection-A connection in which
current divides between two or more
parts, as contrasted to a series connection in which the same current flows
through all parts. Thus, batteries are
connected in parallel by connecting the
positive terminals together, then connecting the negative terminals together.
parallel resonant circuit-A tuning circuit
consisting of a coil and condenser connected in parallel. At resonance, it offers
a high impedance, so that a large value
of signal voltage is developed across it
at the frequency to which it is tuned.
parallel -rod oscillator-A microwave oscillator whose grid and plate tank circuits
are formed of parallel rods, wires or pipes
of required length and dimensions.
parasitic element-An antenna element
which receives its excitation by induction
or direct radiation from the driven element, and which reradiates the energy
in the proper phase relationship to get the
desired results.
over-modulation-Modulation greater than
100%, resulting in distortion due to complete stoppage of radio frequency oscillations during portions of each cycle.
overtone-A harmonic of a fundamental
parasitic oscillations-Unintended self-sustaining oscillations in a circuit.
parasitic suppressor-A combination of in -
sound frequency.
ductance and resistance inserted in the
grid circuit of an r.f. amplifier stage to
suppress high -frequency parasitic oscillations by damping the circuit in which they
patchboard-A board or panel containing a
series of single or double jacks at which
various circuits are terminated. The cir-
cuits are interconnected by short cables
called patchcords. Used in telephone and
broadcast practice.
patchcord-A short two- or three -conductor
cable with male plugs at each end, used
to interconnect various circuits which
are terminated at a control panel, or
peak-The maximum instantaneous value
of a varying voltage or current
peak forward anode voltage-The maximum
instantaneous plate -cathode voltage in
the direction in which a vacuum tube is
designed to pass current.
peak inverse anode voltage-The maximum
instantaneous plate-cathode voltage in the
direction opposite to that in which a tube
is designed to pass current.
peak response-Maximum response.
peaks-Momentary high volume levels produced during a radio program as a natural result of changes in pitch, accent or
speech emphasis, causing the volume indicator to swing upward.
pedestal-The constant voltage value existing just before and after the synchronizing impulses occur in a television signal.
penetration frequency-The highest frequency at which a radio wave traveling
vertically upward will still be reflected
regularly by a particular ionized layer
of the ionosphere. Also called the critical
pentagrid tube-A tube having five grids.
Often called a pentagrid converter tube
because of its frequent use as a converter
(oscillator -mixer -first detector) in superheterodyné receivers.
pentode-A vacuum tube having five electrodes. Ordinarily these will be the
cathode, control grid, screen grid, suppressor grid and anode.
percentage modulation-With respect to an
amplitude-modulated wave, this means
the ratio of half the difference between
the maximum and minimum amplitudes
of the modulated wave to the average
amplitude, expressed in percentage. In
other words, it is the value obtained when
the modulation factor is multiplied by 100
to express it as a percentage. With respect to a frequency -modulated radio
wave, percentage modulation is the ratio
of the actual frequency deviation to
the frequency deviation required for 100%
modulation, expressed in percentage.
percentage modulation meter-An instru-
ment used to measure the percentage of
modulation of a transmitter. It may be
a meter or a cathode-ray oscilloscope.
percent ripple-The ratio of the r.m.s. ripple voltage value to the average d.c. voltage value at the output of a rectifier or
d.c. generator, expressed in per cent.
Peridynamic loudspeaker bailie Trade
name for a special box -type loudspeaker
baffie which reduces standing waves and
gives good bass response.
period-In alternating current, the time
quired for one cycle or one complete
change to take place.
periodic antenna-An antenna which varies
in impedance when the frequency changes,
because of reflections or standing waves
in the antenna system. Open-end wires
and resonant antennas of all kinds are
permalloy-An alloy of nickel and iron used
as core material for high -quality audio
frequency transformers.
permanent magnet-A piece of hardened
steel or other magnetic material which
has been artificially magnetized and retains its magnetism.
permanent magnet dynamic speaker-A
moving coil speaker with its field supplied
by a permanent magnet.
permeability-A measure of how much better a particular material is than air as a
path for magnetic lines of force. The
permeability of air is assumed as 1.
Permeability values for good magnetic
materials can be as high as 5000 or more.
permeability tuning-A method of varying
the inductance of an iron -core r.f. coil by
moving a pulverized iron core in or out
of the coil.
permeance-The reciprocal of reluctance.
p.f.-Power factor.
phantom circuit-A circuit superimposed
on two other circuits. Used in telephone
and broadcast work to make two pairs of
wires provide three complete circuits.
phase-A particular instant of time in an
alternating current cycle. When two alternating current values pass through corresponding zero values at the same instants of time, they are said to be in
phase angle-The amount, expressed in degrees, by which a voltage or current lags
behind or leads another voltage or current. One cycle =
phase distortion-A type of distortion occurring when a radio circuit or part
changes the phase relationship between
different frequencies in the incoming signal. Phase distortion is not particularly
important in radio, but is highly important in television.
phase inverter-A single vacuum tube used
to change the phase of a signal voltage
180°, so a push-pull stage can be properly driven without the use of a coupling
phase modulation-A system of radio communication in which the phase of the
r.f. carrier is varied in proportion to
variations in the audio signal.
phase shift-A change in the phase difference between two varying quantities.
phasing-The adjustment of the picture
position along the scanning line in a
facsimile system.
phasing line-That portion of the length
of a scanning line set aside for the
phasing signal in a facsimile system.
phenomenon-Any observable action, change
or occurrence having scientific interest.
Phillips screw-A screw having an indented
cross in its head in place of the conventional slot.
couverts these mechanical movements
into the audio signals.
phonograph record-A 10- or 12 -inch diameter shellac-composition disc recording
manufactured chiefly for home use, and
designed for playing at 78 revolutions per
minute. It does not have as high fidelity
as an electrical transcription.
phonotron-A hot -cathode gas discharge
tube in which there is no means for controlling the magnitude of the unidirectional current flow.
phosphor bronze-A hard, springy, nonmetallic alloy of copper, tin and phosphorus, widely used in radio for contact
phosphorescence-The ability to give off
light without being heated to incandescence.
photocell-A popular name for a photo emissive cell or phototube.
photoconductive cell-A type of light-sensitive cell whose ohmic resistance varies
with changes in light falling on the cell.
sensitive to
changes in light.
photoelectric cell-A light-sensitive cell,
which can be any one of three basic types
-photoemissive, photoconductive or photovoltaic. It converts variations in light
into corresponding variations in voltage
or current.
photoemissive cell-A type of light-sensitive
cell in which a treated cathode, mounted
in a glass envelope, emits electrons under
the action of light, these electrons being
collected by the anode. There are two
kinds, vacuum and gas -filled. Also called
photocell and phototube.
photographic recording-Facsimile recording by exposure of a photosensitive surface to a signal -controlled light beam or
spot of a facsimile receiver.
photo -island grid-A thin sheet of metal
having many very fine perforations (about
400 holes per inch), used as the photosensitive surface in the storage-type
Farnsworth television dissector tube.
phon-A term sometimes used in place of
decibel to specify equivalent loudness
phone-A headphone.
Also an
early machine using a spring motor, reproducing the recording by mechanical
phonograph-See record player.
phonograph connection-A set of two terminals sometimes provided at the back of a
radio receiver for making connections to
a phonograph pickup. The terminals
connect to the input of the a.f. amplifier.
This connection permits use of the entire
audio amplifier and loudspeaker to reproduce phonograph records.
phonograph oscillator-An r.f. oscillator arranged for modulation by the output of
a phonograph pickup, so that the resulting modulated r.f. signal can be fed to
the antenna and ground terminals of a
radio receiver. This permits using the
entire receiver (rather than just the a.f.
amplifier) for amplifying and reproducing phonograph records.
phonograph pickup-A device which converts variations in the grooves of a phonograph record into corresponding audio
signals. It consists essentially of a needle
which converts record groove variations.
into mechanical movements, and a cfystal,
dynamic or photoelectric system which
photometer-An instrument for measuring
the brightness of various sources of light.
photometry-A branch of the science of
optics dealing with the measurement of
photosensitive-Responsive to changes in
light intensity.
phototube-A vacuum tube in which the
cathode is irradiated with visible or invisible light for electron-emitting purposes. A high -vacuum phototube is one
which is evacuated to such a degree that
its characteristics are unaffected by gas
ionization. A gas phototube is one containing a quantity of gas to give increased
piped program-A program which has been
transmitted over wires.
pipe line-A shielded transmission line con-
photovoltaic cell-A type of light-sensitive
cell which generates a voltage when illuminated, this voltage varying with the
amount of light falling on the cell. Also
called a self -generating cell.
Photronic cell-A trade name applied to one
make of photovoltaic cell.
pickup-See phonograph pickup. Also, any
device which converts original intelligence
into an equivalent electrical signal, such
as a television camera or a microphone.
picture element-In a television system, the
smallest portion of a picture or scene
which is individually converted into an
electrical signal and transmitted.
picture frequency-In television, the number of complete pictures which are
scanned and transmitted in one second.
picture signal-The electrical impulses resulting from scanning of successive elements of a visual scene by a scanning
sisting of coaxial cylinders (a wire inside
a pipe). Also called coaxial line, coaxial
cable, concentric line, etc.
pitch-The frequency of a tone.
plane-A flat surface.
plane of polarization-In a radio wave, this
picture synchronizing impulse-The impulse
which controls the time at which the television reproducing device returns from
the lower right corner to the upper left
pie-One layer or section
of a multisection
Pierce oscillator-A form of crystal oscillator circuit in which the frequency -controlling crystal element is connected between grid and plate of the oscillator
tube. It needs no tuned plate circuit, and
may therefore drive a final amplifier or
buffer stage with but one tuning control.
Used primarily by amateur radio operators.
piezoelectric-Possessing the ability to produce a voltage when mechanical force is
applied, or produce a force when a voltage
is applied, as in a piezoelectric crystal.
pigtail-A flexible connection between a
stationary terminal and a part or terminal
which has a limited range of motion.
pilot lamp-A small lamp mounted on the
panel of a radio receiver to illuminate the
tuning dial, or mounted on the panel of
other radio apparatus to indicate when
the apparatus is turned on.
pin jack-A small receptacle into which is
pushed a pin -like member to complete a
circuit connected to the two parts.
is a plane which is perpendicular to the
wave front and parallel to the electric
vector component of the wave. In a vertically polarized wave, this plane is vertical (perpendicular to the earth). In a
horizontally polarized wave, this plane is
horizontal (parallel to the earth).
plane -polarized wave-A transverse wave in
which the direction of the displacement at
all points in a certain space is parallel to
a fixed plane parallel to the direction of
plano-concave-A lens having one flat and
one inward -curved surface.
piano-convex-A lens having one flat and
one outward -curved surface.
plastic-A general term used in connection
with any of the black or colored materials
used for molding radio receiver cabinets,
control knobs, tube bases, sockets and the
insulating portions of many other radio
parts. It is an excellent insulating material and has a naturally smooth, glossy
surface which requires no finishing or
polishing operations after molding.
plate-The common name for the principal
anode in a vacuum tube. It is usually at
a high positive potential with respect to
the cathode, and therefore attracts the
electrons emitted by the cathode.
plate circuit-A circuit including the plate
voltage source and all other parts connected between the cathode and plate
terminals of a radio tube.
plate current-The current flowing through
the plate circuit of a radio tube and between the plate and cathode inside the
tube. The electrons which make up the
plate current always flow in the direction
from the cathode to the plate.
plate dissipation-The power in watts which
is used up as heat in the plates or anodes
of tubes. It is equal to the product of
the plate voltage and the plate current
plate impedance-The ratio of the change
in plate voltage to the change in plate
current, all other conditions being fixed.
plate keying-Keying a telegraph transmitter stage by interrupting the plate circuit supply of a transmitter.
plate load impedance-The impedance of
the path between plate and cathode in a
plate modulation-Modulation produced by
introduction of the modulating wave into
the plate circuit of any tube in which the
carrier frequency wave is present.
plate resistance-The resistance in ohms of
the plate -cathode path in a tube.
plate supply-The voltage source used in a
vacuum tube circuit to place the plate at
a high positive potential with respect to
the cathode. The plate supply voltage is
always higher than the actual plate voltage, because of the voltage drops across
resistances in the plate circuit.
plate voltage-The d.c. voltage existing between the plate and cathode terminals of
a radio tube.
playback-An expression used to denote the
immediate reproduction of a recording.
pliotron-A high-vacuum thermionic tube
having one or more grid electrodes to control the magnitude of the unidirectional
current flow. Radio amplifier tubes are
thus pliotrons.
plug-A connecting device at the end of a
flexible cord, used for making an instantly -removable connection to a corresponding terminal jack or outlet. Also,
a bit of advertising material inserted into
a radio program.
plug-in coil-A coil having as its terminals
a number of prongs arranged to fit Into
a socket mounted on the radio chassis.
With this arrangement, the tuning range
of a receiver or transmitter can be
changed simply by pulling out one coil
and inserting another in the socket.
major discrepancy indicates a defect between the two points.
polarity-In a radio part or circuit, the quality of having one of two possible charges,
negative or positive. In a magnetic circuit or part, the quality of having one of
two possible poles, north or south.
polarization-The particular property of an
antenna system which determines its radiation characteristics, such as vertical or
horizontal polarization.
polarization errors-Errors in the bearing
or course indicated by a radio direction
finder or radio beacon, introduced by horizontally polarized components of the electric field under certain atmospheric conditions which usually occur at night. Sometimes called night effects.
polarized cell-A cell that has become inoperative due to the formation of hydrogen about its positive pole.
polarized light-Light vibrating in only one
direction, produced by passing the light
through a piece of quartz, a Nicol prism,
a Kerr cell or a special type of glass called
polarizing current-The d.c. current flowing
through an iron -core choke coil or transformer which determines the permeability
of the core and, thus the value of inductance.
Polaroid-Trade name for a certain type of
light -polarizing material made by depositing on a transparent celluloid or glass
sheet a chemical solution having light polarizing properties.
polar radiation pattern-A graph showing
how much sound is radiated from the cone
of a loudspeaker in various directions, or
how radio waves are radiated from an
pole-One end of a magnet. One electrode
of a battery.
police calls-Broadcasts or calls made by
police radio stations.
more than one phase.
porcelain-A material used for insulators,
made by baking a molded mixture of
plug-in resistor-A filament voltage -dropsilica, clay, feldspars and water. It has
ping resistor mounted in a metal or glass
a dielectric constant of from 4 to 6.
enclosure and provided with a plug-in portable receiver-A completely self-conbase.
tained radio receiver having the loudplus sign-A sign ( ) used in mathematics
speaker, all necessary batteries, and a loop
to indicate addition or a positive
antenna built into a compact carrying
Used in radio to indicate the positive
case. Terminals are sometimes provided
terminal of a voltage source or to indifor external antenna and ground conneccate positive polarity.
p.m. dynamic-Permanent magnet dynamic. position-The point of intersection of two
or more radiocompass bearings taken
pointer-That part of a meter or tuning dial
from widely separated radio beacons.
which moves over the scale ; an indicator.
term used to describe a terminal
point-to-point resistance-A method of testhaving fewer electrons than another, so
ing wherein the resistance between given
that it attracts electrons from the other
points in a set is measured and checked
terminal in seeking to return to its nor against expected normal values. Any
mal state. Thus, electrons flow into the
positive terminal of a voltage source.
positive charge-The charge on an object
having less electrons than normal.
positive feedback-Regeneration, causing an
increase in signal strength.
positive ion sheath-Collection of positive
ions on the control grid of a gas -filled
triode tube. If a high negative bias is
applied to the grid, the positive sheath
will get so thick as to stop plate current
positive modulation-In television, a method
of transmission in which an increase in
scene illumination causes an increase in
the radiated power of the transmitter.
In an a.m. facsimile system, that form of
modulation in which the maximum transmitted power corresponds to the minimum
density of the subject copy. In an f.m.
system, that form of modulation in which
the highest transmitter frequency corresponds to the minimum density of the
subject copy.
positive picture phase-A condition wherein
increases in brilliancy make the television
picture signal voltage swing in a positive direction, above zero level.
Cour tea,
resistance element, and the output circuit is connected between the movable
contact and one end terminal. Rotating
the movable contact thus varies the proportion of the total voltage which is transferred to the output circuit. The volume
control of a receiver or p.a. amplifier is
generally a potentiometer.
power-The rate at which electrical energy
is delivered and consumed. Electrical
power is measured in watts. Also, the result obtained when a number or quantity
is multiplied by itself a particular number of times. The exponent of the number
indicates the number of times this selfmultiplication is to be performed. Ex-
amples : 36 is the second power, of 6 ; 2T
is the third power of 3.
power amplification-The ratio of signal
output power to signal input power.
power amplifier stage-An audio amplifier
stage which is capable of handling a relatively large amount of audio power without distortion. An r.f. amplifier stage in
a transmitter which serves primarily to
increase the power of the r.f. carrier
power cord-The cord which carries power
from a standard wall outlet to a radio
receiver. A line cord.
power detector-A detector which may be
operated at fairly high values of input
voltage without objectionable distortion_
power factor-A percentage rating obtained
by dividing the resistance of a part or circuit by its impedance at the operating frequency, then multiplying the result by
100. A resistor has a power factor of
100%; high -quality condensers and coils
have very nearly zero per cent power
power factor meter-Meter used to indicate
per cent lag or lead produced by a load.
Used to monitor loads when a power company exacts a penalty for low power factor (caused by too high an inductive
load) .
power level-The amount of electrical power
passing through a given point in a circuit_
Power level can be expressed in watts, in
decibels or in volume units.
power level indicator-An a.c. voltmeter
which is calibrated to read in terms of
audio power level.
power line-A pair of wires carrying electric power from one location to another_
power of ten-A number obtained by multiplying 10 by itself one or more times_
Thus, 100 is the second power of 10.
power output tube-A radio tube especially
designed for use in the a.f. output stage
of a radio system. It is capable of handling much greater current than the ordinary amplifier tube, and hence delivers
high output power.
positron-A natural elemental quantity of
positive electricity having much smaller
mass than a proton. Often called a positive electron, because its mass appears to
be about the same as that of an electron.
potential-The voltage existing between one
point in a circuit and another point, or
between one point and ground.
potential difference-The difference in voltage between two points as a result of cur-
rent flow.
potentiometer-A resistance unit having a
rotating contact arm which can be set at
any desired point on the resistance element. The total available voltage is applied to the fixed end terminals of the
primary colors-This refers to light, not
paint. The primary light colors are red,
green and blue. All other colors may be
power pack-The power supply unit of a
radio receiver, amplifier, transmitter or
other radio apparatus. Its function is
to convert the available power line or
storage battery voltage to the values required by filament, grid and plate circuits.
power ratio-The ratio between power input
and power output, used in calculating db
loss and gain.
power relay-The final relay which controls
a power circuit or magnetic contactor.
Often called auxiliary relay.
power switch-Sometimes known as ONOFF switch. The device which applies
power to a device so it can operate.
power transformer-An iron -core transformer having a primary winding which
is connected across the a.c. power line,
a high -voltage secondary winding for the
power pack rectifier tube, and one or. more
low -voltage secondary windings which
supply the required a.c. voltages to the
tube filaments.
power tube-See power output tube. Also
the tube used in the last r.f. stage of a
transmitter, capable of handling more current and power than an ordinary amplifier
preamble-That part of a radio message
which contains the prefix, message number, office of origin, word check, time filed,
date and other data.
preamplifier-An amplifier used ahead of
the main amplifier or at the input of a
transmission line.
pre-emphasis-A method whereby the relative recorded level of some frequencies is
increased with respect to other frequencies during recording or during f.m. transmission.
preselector-The section ahead of the fre'
quency converter in a superheterodyne receiver. It may include one or more tuned
or untuned r.f. stages or may simply consist of one or more tuned circuits connected between the antenna and the input
of the first detector.
pressing-A record produced from a matrix
or stamper in a record-molding machine.
pressure microphone-A general term for
any microphone in which the electrical
output is caused by variations in the pressure exerted by a sound wave. Examples are carbon, condenser, crystal and
dynamic microphones.
PRI. or P-Primary winding of a transformer.
primary-First in order of time, placement,
development' or importance.
primary cell-A type of cell in which the
generated voltage is due to permanent
chemical changes in the cell material. A
primary cell cannot be recharged. This
is the earliest known type of cell.
formed by mixing various combinations
of these three.
primary relay-The relay which responds
to the initial change in a sequence of
primary skip zone-The area around a radio
transmitter beyond the ground -wave
range but within the skip distance. Radio
reception is possible in the primary skip
zone only by sporadic, scattered and zigzag reflections.
primary standard-An exact quantity, size,
frequency or interval deriving its characteristics from an absolute standard
fixed by general agreement.
primary winding-The input winding of a
transformer. It can be identified by the
fact that the. r.f., a.f. or power line alternating current or pulsating d.c. is sent
through this winding.
prime number-A number which has no factor other than itself and unity. Examples 5, 13, 17.
prism-A piece of transparent material with
a uniform triangular cross-section.
product-The result obtained by multiplying together two or more numbers. Example 48 is the product of 12 X 4.
propagation-Transfer of energy by wave
property-Whatever belongs or pertains to
a certain object, as a distinguishing quality or characteristic.
proton-The natural, elementary quantity
of positive electricity. The mass of the
proton is 1847 times that of the electron.
A proton has the same quantity of positive electricity as an electron has of negative electricity, hence one proton balances
one electron.
protractor-An instrument for measuring or
constructing angles.
P.B.T.-Pacific Standard Time.
public address amplifier-An audio ampli-
fier capable of supplying sufficient audio
power to loudspeakers for adequate sound
coverage of public gatherings.
public address system-A complete system
for reproducing voice and speech with
adequate volume for large public gatherings. It includes one or more microphones, a powerful audio amplifier with
suitable power supply, and a sufficient
number of loudspeakers to give coverage
of the auditorium, stadium or other large
space. Most installations also include a
phonograph, which may or may not be of
the automatic record changer type.
pull-up current-The minimum current
which will cause the armature of a relay
to be pulled up against the relay core.
pulsating current-A current which changes
in value but not in direction. It can be
considered as a direct current combined
with a smaller value of alternating current.
pulse-A momentary sharp change in a current or voltage.
push -back hook-up wire-Tinned copper
hook-up wire covered with a loosely
braided cotton insulation which can be
pushed back from the end of a wire length
with the fingers to expose sufficient bare
wire for a connection. Radio men use
this type of wire almost exclusively for
experimental and repair work.,
push button-A switch which opens or
closes a circuit by means of pressure upon
a button.
push-button tuner-A tuning unit which
automatically tunes a radio receiver to
a station when the button assigned to
that station is pressed. In electrical automatic push-button tuning, the button
actuates switches which connect a set of
preadjusted trimmer condensers into the
receiver tuning circuits. In electromechanical automatic push-button tuning,
the button controls the starting and stopping circuits of a small motor which rotates the regular gang tuning condenser
of the receiver. In mechanical automatic
push-button tuning, pressure on the but-
ton is transferred by a lever or cam system into a force which rotates the gang
tuning condenser to the correct position
for the desired station.
push-pull circuit-A two-tube audio output
circuit so arranged that both tubes operate simultaneously and their individual
a.f. plate currents add in the common
load. This circuit arrangement has the
added advantage that it balances out all
even harmonics which would otherwise
cause distortion.
push-pull transformer-An iron -core a.f.
transformer designed for use in a pushpull amplifier circuit. If it is the input
transformer, it will have a center -tapped
secondary winding. If it is the output
transformer, it will have a center -tapped
primary winding.
push -push circuit-A two -tube audio output
circuit so arranged that the tubes operate
alternately into a common load.
pyrometer-An instrument for measuring
has an extremely high Q, this term is
usually limited to coils.
Q factor-A rating used to express certain
characteristics of coils, condensers and
resonant circuits. In a circuit, it is obtained by dividing the reactance of one
of the components (usually the inductance) by the a.c. resistance of the circuit.
Q signal-One of the three -letter abbreviations starting with Q in the International
List of Abbreviations, used to represent
complete sentences in radiotelegraphy.
When the question form of the sentence
is intended, the code signal for an interrogation mark is sent after the abbreviation. Thus, QRM means "I am being interfered with," and QRM? means "Are
you being interfered with?" Other common Q signals used in a similar manner
are : QRN, Atmospheric interference.
QRR, Amateur distress call-equivalent
to SOS. QRT, Stop sending, used to
clear bands in emergency. QRR, Wait.
QSY, Shift frequency. QSO, Conversation ; a contact, a series of transmissions.
QSL card-A card sent by a radio amateur
to verify communication with another
quadratic equation-An equation which contains the square of the unknown quantity
and no higher degree.
Examples :
I2R ; 9x2
+ 7x
quantitative-Capable of measurement.
quarter-wavelength transformer-A section
of transmission line one -quarter wavelength long, used as an impedance -matching transformer.
quartz-A natural crystalline material
high temperatures.
widely used in radio.
quartz crystal-A thin slab about the size
of a half -dollar, cut from a natural crystal
of the mineral quartz and carefully
ground to a thickness which will make it
vibrate at the desired natural frequency
when supplied with energy. It is used
as the master carrier frequency source in
the crystal oscillator stage of a radio
Q-The merit (degree of perfection)
of a
coil or condenser, equal to the reactance
of the part divided by the a.c. resistance
of the part. Since the average condenser
free space (radiation) is implied by the
term- radio, while wired radio is used to
describe radio waves which are guided intentionally by conductors. Also, a receiving set capable of picking up radio waves
and reproducing the intelligence they convey. This intelligence may consist of
speech, music, code signals, or other
quenching signal-A signal introduced into
a regenerative detector stage to prevent
oscillation on strong signals.
quotient-The result obtained by division.
Example : In 1400 ± 70 = 20, the quotient
is 20. (The dividend here is 1400, and the
divisor is 70.)
of radiant
energy by an element or material, either
spontaneously or under the influence of a
cyclotron or other activating device.
radio beacon-A radio transmitting station
which is fixed in location and transmits a
characteristic signal which can be used
by mobile (ship or aircraft) stations to
determine bearings, locations or courses.
radio bearing-The angle between the direction of travel of a radio wave and due
radio broadcasting-A one-way transmission of voice and music to anyone within
receiving range of the radio station.
radio channel-A band of frequencies sufficiently wide for a single radio circuit between two points. The width of a channel depends upon the type of transmission ; a broadcast band channel is 10 kc.
wide, and a television channel is 6 mc.
radio circuit-A system for carrying out
radio communication between two points.
Also, any individual circuit in a radio
radio communication-The transmission
and reception of any form of intelligence,
such as writing, signs, signals, pictures,
and sounds of all kinds.
radio compass-A radio direction finder
used chiefly in marine and aircraft radio
stations for navigational purposes.
radio control-The control of moving objects such as airplanes, automobiles, ships,
torpedoes, etc., by means of signals transmitted over radio waves from the transmitter location to special radio receiving
equipment in the object being controlled.
radio direction finder-A radio receiving
device which can be used to determine the
line of travel of radio waves.
radio fadeout-Partial or complete blocking
of radio waves through the parts of the
ionosphere affected by a sudden ionospheric disturbance.
radio field intensity-The effective (r.m.$)
value of the electric or magnetic field
produced at a point by radio waves from
a particular station. It is usually expressed as electric field intensity in microvolts per meter or millivolts per meter.
Unless otherwise specified, it is assumed
that the measurement is made in the direction of maximum field intensity.
radio frequency-A frequency at which
radioactivity-The emission
R.-Resistor ; resistance in ohms.
radial-Extending from the center in the
form of rays.
radian-An angle which, when placed with
its vertex at the center of a circle, inter-
cepts an arc equal in length to the radius
of the circle. A complete circle contains
2n radians, hence 1 radian is 57.2959°,
and 1° is 0.01745 radian.
radiate-To emit electromagnetic waves
into space.
radiation-The process wherein the transmitting antenna system of a radio station
converts the modulated r.f. output of the
transmitter into radio waves which travel
away from the station through space.
radiation efficiency-A transmitting antenna
rating, equal to the ratio of the power
radiated to the total power supplied to
the antenna at a given frequency.
radiation field-The electro -magnetic field
which breaks away from the transmitting
antenna and goes out into space. Also
called radio wave or electro -magnetic
radiation pattern-A diagram showing how
well an antenna system radiates or picks
up radio waves in various directions.
radiation resistance-A transmitting anI', where Ra
tenna rating. Rs = P
is the radiation resistance in ohms, P is
the power in watts radiated by the antenna, and I is the current in amperes
measured at the point where power is supplied to the antenna.
radical sign-The sign V, which is placed
before a number to indicate that its square
root is to be extracted. Always combined
with a vinculum to form the symbol Nr.
When some other root is to be extracted,
the index number of that root is placed in
the angle of the radical sign. Examples
V 49 means square root of 49, which is 7 ;
s 64
means cube root of 64, which is 4 ;
fourth root of 81, which is 3.
radicand-The number or quantity under a
radical sign. Examples : In 'MT, the
64, the radicand is
radicand is x ; in
81 means
radio-The art of communication by means
elecof radio waves. Radio is a branch of
tronics. Travel of radio waves through
electromagnetic radiation of energy is
useful for communication purposes. The
present useful limits of radio frequencies
are about 10 kilocycles to 10,000 megacycles.
ground observers in terms of the pressure,
temperature and humidity at regular intervals during the ascent of the balloon
into the stratosphere. When the balloon
bursts, the instrument is lowered to earth
by a parachute. Also called radiosonde.
radio prospecting-Use of radio equipment
to locate mineral or oil deposits.
radio range beacon-A radio beacon station
which transmits waves in definite directions, in such a way that departures from
a given course can be observed by aircraft
or ships.
radio receiver-An instrument which amplifies radio frequency signals, separates the
r.f. carrier from the intelligence signal,
amplifies the intelligence signal additionally in most cases, then converts the
intelligence signal into sound waves.
radiosonde-A radio meteorograph.
radio spectrum-All the wavelengths or frequencies which may be used for the transmission of energy, communications or
signals by radio. At the present development of the art, the useful radio spectrum is considered to extend from 10 kilocycles to 30,000 megacycles, or 3000 meters
to 0.01 meter. These frequencies are
classified into bands with designations
and abbreviations as given in the table
on this page.
radio station-A station equipped to engage
in radio communication or radio transmission of energy. A station includes all apparatus used at a particular location for
one class of service and operated under a
single instrument of authorization. Radio
stations are classified according to the
nature of the service they furnish.
radio station interference-Selective interference caused by radio waves from one
or more undesired stations.
radiotelegraphy-Radio communication by
means of the International Morse Code.
radiotelephone transmitter-A transmitter
capable of sending voice and music, as
contrasted to a radio -telegraph transmitter which can send only code.
radio frequency amplifier-A vacuum tube
amplifier stage to provide amplification
at radio frequencies. In a t.r.f. receiver,
all stages ahead of the detector are r.f.
amplifier stages. In a superheterodyne
receiver, the amplifier stage sometimes
used ahead of the first detector (in the
preselector) is an r.f. amplifier stage.
radio frequency choke-A choke coil designed to have high impedance at radio
frequencies, so that it limits or blocks
the flow of r.f. currents.
radio frequency transformer-An air -core
or pulverized iron -core transformer used
in r.f. circuits.
radio landing beam-A radio beam, usually
curved, which serves for vertical guidance of aircraft when landing during unfavorable weather conditions.
radio link-The carrying of a program
(sound or television) from point of pickup
to- main studio by means of radio (usually at u.h.f.) instead of telephone lines.
radio marker beacon-A radio beacon station used for marking the location of a
point, a boundary or a small area, such
as for aircraft blind landing systems.
radio metal locator-A radio instrument
which indicates the presence of metal
within its operating range by a change in
meter reading or a change in a tone signal heard in headphones. Used for determining positions of buried pipe lines,
buried metal objects, metal objects concealed in the clothes of prisoners, metal
objects imbedded in logs about to be
sawed, deposits of metallic minerals, etc.
radio meteorograph-A combination meteorograph and radio transmitter carried
aloft by an unmanned gas-filled rubber
balloon and so designed that it will transmit back to earth ultra -high frequency
radio signals which can be interpreted by
10 kc to
30 kc to
300 kc to
3 mc
30 kc inclusive
300 kc
3 mc
30 mc to
300 mc
300 mc to
3,000 mc
3000 mc to 30,000 mc
Very Low
Very High
Ultra High
Super High
r-radiotelephony-Two-way voice communication between two or more stations by
means of radio waves.
radio transmission-The transmission of
signals through space at radio frequencies
by means of electro -magnetic waves.
radio transmitter-A device for producing
r.f. power for purposes of radio transmission.
Radiotrician-A graduate of National Radio
Institute, thoroughly trained as a radio
serviceman or radio operator.
radio wave-A combination of electric and
magnetic fields varying at a radio frequency, and capable of traveling through
space at the speed of light. It is produced
by feeding the output of a radio transmitter to the transmitting antenna, and may
carry modulation.
radio wave propagation-The transfer of
energy by electromagnetic radiation at
radio frequencies.
radius-The distance from the center of a
circle or arc to any point on that circle
or are.
random winding-A winding made with no
regard for the position of the turns or
layers in reference to each other.
ratio-The value obtained by dividing one
number by another. Thus the ratio of 15
to 3 is 5. The ratio of 3 to 15 is 1/5.
ray-The path along which electrons or light
waves travel in space.
R-C-Resistor-condenser coupling.
RC.-Time constant (product of resistance
in megohms and capacity in mfd.)
RCA-Radio Corporation of America.
RCA licensed-Manufactured under a licensing agreement which permits use of
patents controlled by the Radio Corporation of America.
reactance-Opposition offered to the flow
of alternating current by the inductance
or capacity of a part. Reactance is
measured in ohms, and depends upon the
frequency of the alternating current as
well as upon the electrical value of inductance or capacity. A condenser has capacitive reactance, and a coil has inductive
reactance. The letter X is used to designate reactance.
real image-An image formed by an actual
concentration of light.
receiver-A device for receiving radio
and voice are recorded on discs or other
materials by a sound recorder. Pictures
and printed matter transmitted by radio
are reproduced on paper by a facsimile
recording-A phonograph record. Also, the
process of making records or of registering the received signal upon the record
sheet of a facsimile receiver or measuring
record player-A motor -driven turntable
and an electrical pickup used for converting the variations on a phonograph record
into electrical signals. These signals
must be fed into the audio section of a
radio receiver or into a separate audio
amplifier for additional amplification before they can be reproduced as sound
waves by a loudspeaker.
rectangular coordinates-The two values
which specify the position of a point with
respect to two reference lines at right
angles to each other. The horizontal
reference line is called the X axis or the
axis of abscissas, and the vertical reference line is called the Y axis or the axis
of ordinates.
rectification-The process of changing alternating current into a current which
flows in only one direction (usually a
pulsating direct current).
rectifier-A device which changes an alternating current into a pulsating direct current. It may be a vacuum tube, gaseous
tube, crystal, vibrator or copper-oxide device and may provide either half -wave
or full-wave rectification.
rectilinear scanning-The process of scanning an area in a predetermined sequence
of narrow straight parallel strips.
reference recording-Recording of a radio
program or other material, made for
the purpose of checking same.
reflected impedance-The effective impedance which appears across the primary of
a transformer when a reactive load is connected to the secondary.
reflected resistance-The effective resistance which appears across the primary
of a transformer when a resistive load
is connected across the secondary.
reflected wave-The wave caused by the reflection of part of an incident or oncoming
reflection loss-The power lost in a transformer or transmission line due to a
difference in the impedance of the source
and load.
reflector-In a directional antenna system,
the reflector is the rear portion which is
not connected to the transmitter or receiver. The purpose of the reflector is to
increase the effectiveness of the antenna
in the forward direction.
reciprocal-The reciprocal of a number is 1
divided by that number. Éxample :
is the reciprocal of R.
recorder-An instrument which makes
permanent record of a varying electrical
signal. Thus, code messages are recorded
on paper tape by a code recorder. Music
Courtesy Genera/ Electric
reflex circuit-A circuit through which a
radio signal passes both before and after
a change in its frequency.
refracted wave-The wave caused by the
refraction (change in direction) of the
part of an incident or oncoming wave
which travels into a new medium.
regeneration-A method of securing increased output from an amplifier by feeding a part of the amplifier output back to
the amplifier input in such a way that
reinforcement of the input signal is obtained. With this arrangement, a signal
may pass through the same amplifier over
and over ,again, with an increase in
strength each time. Also called positive
regeneration control-A rheostat, potentiometer, or variable condenser which is
used in a regenerative receiver to control
the amount of signal which is fed back
from output to input in the regenerative
detector stage.
regenerative detector-A vacuum tube detector in which intentional feedback of
r.f. energy from the plate circuit to the
control grid circuit produces regeneration, greatly increasing the useful amplification.
regenerative receiver-A radio receiver
which employs controlled regeneration to
increase the amplification provided by a
vacuum tube stage (usually the detector
regulation-Ability to maintain constant
output despite variations in load.
relaxation oscillator-A type of oscillator
circuit in which alternate charging and
sistor. Either a saw -tooth or square output wave can be obtained.
relay-An electromagnetic device which permits control of current in one circuit by
a much smaller current flowing in another
relay transmitter-A transmitter which rebroadcasts television or sound programs
to increase the service area. Often called
repeater stations.
reluctance-Magnetic equivalent of electrical
resistance. Opposition offered to magnetic flux.
reluctivity-The reciprocal of permeability.
remote control-Controlling from the regular studio a program which is produced
outside and relayed to the studio by wire
or short-wave channels. Control of any
device from a distance.
remote pickup-A radio program picked up
from a remote location and sent to the
studio by wire or ultra -shortwave facilities. Any program not originating in the
repeater-An amplifying station used to
boost the volume on long telephone lines.
repeat point-Double-spot tuning in a superheterodyne receiver.
reproduction speed-The area of copy recorded per unit time in a facsimile system.
re-recording-A recording made from the
reproduction of a recording.
residual magnetism-Magnetism which remains in the core of an electromagnet
after the electrical circuit has been
resistance-The opposition which
a device
or material offers to the flow of direct
or alternating current. The opposition
which results in productioi of heat in the
material carrying the curre qt. Resistance
is measured in ohms, and is usually designated by the letter R.
resistance -capacitance coupling-The coupling together of two vacuum tube stages
or circuits by means of a resistor and
resistance coupling-Another name for resistance-capacitance coupling.
resistance loss-IZR loss.
resistivity-A measure of the ability of a
material to oppose the flow of electricity.
The resistance in ohms which a unit cube
of a material offers to the flow of electric
resistor-A radio part which offers resistance to the flow of electric current. Its
electrical size is specified in ohms or
megohms (one megohm equals 1,000,000
A resistor also has a power handling rating in watts, indicating the
amount of power which can safely be dissipated as heat by the resistor.
discharging of a condenser through a resistance determines the number of pulses,
so the frequency is determined by the
time constant of the condenser and re-
resonance-In a series resonant circuit,
the current is a maximum at resonance.
In a high Q parallel resonant circuit, the
voltage across the coil or condenser is a
maximum at resonance, and the external
current is a minimum. In a circuit containing both inductance and capacity, a
condition in which the inductive reactance
is equal to and cancels out the capacitive
reactance at a particular frequency.
resonance curve-A frequency response
curve which shows in graphical form the
manner in which a tuned r.f. amplifier
(or any other apparatus containing at
least one resonant circuit) handles or
amplifies the various frequencies in its
operating range.
resonant circuit-A circuit containing inductance and capacity values such as to
produce resonance at an operating frequency. Also called a tuned circuit.
resonant current step-up-The ability of a
parallel resonant circuit to circulate a
current many times greater than the current fed into it.
resonant frequency-The frequency at
which resonance occurs in a coil and condenser circuit.
resonant line-A transmission line whose
inductance, capacity and length make it
resonant at the transmitted frequency.
resonant -line oscillator
ultra -high-frequency oscillator using parallel rods to form the grid and plate
resonant resistance-The resistance of a
parallel resonant circuit at resonance.
resonant voltage step-up-The ability of a
series resonant circuit to deliver a voltage
several times as great as that fed into it.
resonator-A hollow chamber forming the
tuned circuit of a micro -wave oscillator.
resonator, cavity-A hollow tube or box of
such dimensions to make it resonant at
certain ultra -high frequencies. An extreme form of concentric -line oscillator
tuned circuit.
response characteristic-A curve showing
the response of a radio device, circuit or
system over a range of frequencies. It
is usually made with response values as
ordinates and frequency values as abscissas. A logarithmic frequency scale is
beam from the end of one line or field to
the start of the next line or field.
return wire-The ground or common lead.
The negative wire in a d.c. circuit.
reverberation-The continuation of sound
by successive reflection.
reverberation time-The time in seconds required for a sound of a given frequency
to decrease, after the sound source is
stopped, to one millionth of its initial
r.f. or R.F.-Radio frequency.
rheostat-The general name for a device
which hits the resistance element partly
exposèd to enable the amount of resistance in use to be easily adjusted by the
simple movement of a control knob. A
rheostat enables frequent and immediate
change in resistance while the circuit
is electrically alive.
rhombic antenna-A directional antenna
consisting of four long wires arranged to
form a rhombus (a parallelogram with all
four sides equal, like a diamond).
ribbon microphone-A moving -conductor microphone in which the moving conductor
is a single corrugated metal ribbon
mounted between the poles of permanent
magnets. Often called a velocity microphone.
ride gain-To control the volume range of
a program electrically in order to transmit it over lines and equipment within
proper limits. The monitor engineer does
this while watching the volume indicator.
Rider's manuals-A series of reference
books which contain servicing information and circuit diagrams of radio receivers manufactured from 1919 on.
These manuals are used chiefly by radio
right angle-The angle formed by two
straight lines which meet at an angle of
right-handed elliptically polarized waveAn elliptically polarized wave in which
the rotation of the direction of displacement is clockwise for an observer looking
in the direction the wave is traveling.
right-hand taper-A volume or tone control
potentiometer having more resistance in
the left half of the control than the right
half, when held with the shaft pointing
toward you and the terminal lugs pointing downward.
right triangle-A triangle in which one of
the angles is a right angle (900).
rim-drive-A method of driving a phonograph or sound recorder turntable with a
rubber -covered wheel which is in contact
with the rim of the turntable. The wheel
is powered by an electric motor.
ripple-An alternating current component
which is present in the output of a d.c.
resting frequency-The assigned carrier frequency of a: radio station which employs
the frequency modulation system of broadcasting. The resting frequency is radiated only during intervals when no sound
waves are being transmitted.
magretentivity-The property of retaining
netism after the magnetizing force has
been removed.
retrace-The path traveled
by an electron
voltage supply such as a power pack or
d.c. generator.
ripple Biter-A low-pass filter (which passes
only frequencies below a critical cut-off
frequency) used to reduce the ripple current of a rectifier or d.c. generator while
allowing direct current to pass freely.
ripple voltage-The a.c. component in the
output of a rectifier or d.e. generator.
R.M.A.-Radio Manufacturers Association,
an organization of leading manufacturers
in the radio industry. Its work involves
standardizing sizes and designs of radio
parts, standardizing of color markings on
parts (such as the R.M.A. color code for
resistors and condensers) and standardizing of radio terms and definitions.
R.M.A. color code-A standard method of
designating part values and part leads by
colored markings.
r.m.s.-Root mean square value, which is
the effective value of an alternating current. It corresponds to the equivalent
direct current value which will produce
the same heating effect. Unless otherwise specified, alternating current values
are always r.m.s. values. Equal to about
.7 of the peak value.
rocking-A term applied to the back and
forth rotation of the main tuning gang
as the oscillator padder in a superheterodyne receiver is adjusted at the low frequency end of the dial.
root-A number which, when multiplied by
itself a number of times, equals the given
number. The radical sign -/
is used
to indicate square root, and the radical
sign with an index number in its angle
is used to indicate any other root. Example
3125 = 5, which means that
the fifth root of 3125 is 5.
rosin -core solder-Solder which has as its
core the correct amount of rosin flux for
effective radio soldering work. The rosin
is released automatically as the solder is
applied to the heated joint.
rotary beam antenna-A highly directional
short wave receiving or transmitting
antenna system mounted on a high pole or
mast in such a way that it can be rotated
to any desired position either manually
or by an electric motor drive.
rotary converter-A dynamo having a single
armature equipped with both slip rings
and a commutator, so that both a.c. and
d.c. can be obtained from it simultaneously if used in conjunction with a motor
or engine. If a.c. is fed into the slip
rings, the dynamo will act as both a motor
and a generator, and deliver a d.c. output.
rotary switch-Any switch which is operated by rotating its control knob.
rotor-The rotating part, such as the rotating armature of an electric motor or
rotor plates-The movable plates of a variable condenser. They are usually connected electrically to the metal frame of
the condenser.
Rn-Plate resistance of a tube.
r.p.m.-Revolutions per minute.
rumble-Low-frequency vibration mechanically transmitted to the recording or reproducing turntable and superimposed on
the reproduction.
S-A letter
sometimes used to designate the
secondary winding of a transformer.
sal ammoniac-Ammonium chloride. A
chemical used in primary cells.
sapphire-A gem used in the tips of highgrade phonograph needles and in cutting
needles used with sound recorders.
saturation-In a magnetic circuit, the condition wherein increases in magnetomotive force produces negligible additional
saw-tooth a.c. voltage-An a.c. voltage whose
wave form looks like the teeth of a saw.
scalar quantity-A quantity which has only
scale-A series of marks printed on a fiat
surface over which a pointer moves. The
value of the mark directly behind the
pointer corresponds to the reading.
scale divisions-Lines which divide a meter
scale into many parts. A scale division
is the region between one line and the
next adjacent line.
scaling circuit-A circuit which actuates a
counting device on receiving a predetermined number of pulses. If it acts on
every other pulse, it is a scale -of -two circuit.
sean-In mechanical scanning, the scanning
lines are produced by a beam of light controlled by a scanning disc or other moving
mechanical part. In electrical or electronic scanning, the scanning lines are
produced by a beam of electrons sweeping
over the surface.
scanner-That part of a facsimile transmitter which systematically translates
the densities of the elemental areas of
the subject copy into signal -wave form.
scanning-The process of analyzing successively the amount of light present in each
of the picture elements which make up
the total area of a picture .or scene being
converted into electrical signals for television or facsimile transmission.
scanning disc-A rotating disc having a
spiral row of holes or lenses near the
edge, used to break up a picture or scene
into elemental areas, or to reconstruct
from an electrode when it is hit or bombarded by high-speed electrons.
secondary winding-Any of the output windings in a transformer.
second detector-That stage of a superheterodyne receiver which separates the
audio modulation from the intermediate
frequency carrier signal.
selective fading-Fading which is not the
same at all frequencies.
selective interference-Radio interference
whose energy is concentrated in a narrow
band of frequencies. Some examples are
other radio stations on the same or adjacent frequencies, harmonics of other
radio stations, and unshielded diathermy
selectivity-The degree to which a radio
receiver is capable of reproducing signals
of one station while rejecting signals
from all other stations on adjacent chan-
televised scenes. Used in some mechanical television systems.
scanning line-A single continuous narrow
strip which is determined by the process
of scanning in television or facsimile.
scanning spot-The area viewed simultaneously by the pickup system of the scanner in a facsimile system.
scattered reflections-Reflections from a
region of the ionosphere, which interfere
and cause rapid fading. They are variable in respect to time of occurrence,
geographical distribution, intensity and
frequency range.
s.c.c.-Single cotton -covered insulation on a
s.c.e.-Single cotton covering over an enamel
insulating layer on a wire.
schematic diagram-A diagram which shows
electrical connections 'of a radio device
by means of symbols which are used to
represent the radio parts.
scratch filter-A filter circuit used in connection with a phonograph pickup to
block those frequencies at the higher end
of the audio range at which needle scratch
is most prominent.
screen-A shield.
screen grid-An electrode mounted between
the control grid and plate of a vacuum
tube for the purpose of reducing the capacity between these two electrodes.
screen grid tube-A vacuum tube having a
screen grid. It may be a tetrode (four element tube) or a pentode (five -element
selenium cell-A photoconductive cell using
some form of selenium as the light-sensitive material. The resistance of the cell
varies with the amount of light falling
on the cell.
self-bias-Referring to a vacuum tube stage
which produces its own grid bias voltage.
Plate current flowing through a resistor
in series with the cathode lead produces
across this resistor the voltage drop used
for grid bias purposes. Also called automatic C bias.
self-excited oscillator-An oscillator which
starts itself, being connected so any
change in plate current will induce a voltage in a tank circuit, which changes the
grid voltage so that oscillations will be
developed and maintained.
self-inductance-The property which determines how muck electromotive force
will be induced in a coil or circuit by a
change of current in that same coil or
Self-inductance, often called
simply inductance, is measured in henrys
and is designated by the letter L.
Selsyn motor-A synchronous motor which
accurately follows the phase of the voltage fed to it. Usually, a pair of these
motors are connected together and used
for remote control purposes. One then
acts as a generator, so that any speed,
position or direction of rotation of its
rotor is accompanied by a similar speed,
position or direction of rotation in the
sense finder-The portion of a radio direction finder which determines which of
two opposite directions (180° apart) a
radio wave is coming from.
sensitive relay-A relay requiring very
small amounts of current for operation.
sensitivity-A measure of the ability of a
screen grid voltage-The d.c. voltage which
is applied between the screen grid and the
cathode of a vacuum tube to make the
screen grid positive with respect to the
sealing compound-Wax employed in condenser blocks and transformer housings
to prevent air and moisture from reaching
the parts.
SEC.-Secondary winding of a transformer.
secant-The secant of an acute angle of a
right triangle (written sec 91 is equal to
the hypotenuse divided by the adjacent
side. Secant is the reciprocal of cosine.
See trigonometric function.
secondary cell-A d.c. voltage source which
is capable of storing electrical energy.
When exhausted, it can be recharged by
sending direct current through it in the
reverse direction. Each cell of an ordinary storage battery is a secondary cell.
secondary electrons Electrons emitted
from a body due to the impact or bombardment of other electrons.
secondary emission-Emission of electrons
radio receiver to reproduce weak signals
electron beam is in a dark -spot area.
with satisfactory volume. The smaller the shadow tuning indicator-A
tuning meter
input necessary to give a stated output,
having a small square metal vane mounted
the higher the sensitivity.
on a shaft, which in turn is connected to
series connection-A connection in which
a meter movement. A pilot lamp is
the same current must flow through all of
mounted behind the vane so that,a shadow
the series-connected parts. When dry
is thrown upon a glass screen. The meter
cells or batteries are connected in series
is so constructed and connected into a
so that their voltages add, the minus termradio receiver circuit that the shadow
inal of one cell must be connected to the
will be narrowest when the receiver is acplus terminal of the next cell.
curately tuned to a station.
series feed-Application of d.c. operating sharp-A term usually used to describe the
voltage through a circuit carrying a sigselectivity of a circuit which will respond
nal current.
to a very limited range of frequencies or
to a single frequency only.
series resonant circuit-A circuit in which
a coil and condenser are connected in SHF-Super high frequencies.
series with the source of voltage, or where shield-A metal can or housing placed
the exciting voltage is induced into the
around a radio part to prevent its electric
coil, and where the inductive reactance of
and magnetic fields from affecting nearby
the coil will be equal to the capacitive
parts or to prevent other fields from afreactance of the condenser at the desired
fecting it.
resonant frequency. At resonance, the
current through a series resonant circuit shielded line-A transmission line having
an external conducting surface (a sheath
is a maximum.
or shield) which confines the radio sigserrated pulse-In television, a vertical
nals to the space within the shield (presynchronizing pulse divided into a numvents radiation of radio waves by the
ber of small pulses which act for only half
line) or prevents pick-up of undesired
a line.
signals by the line.
serrated rotor plate-A variable condenser shielded pair-A two-wire transmission line
rotor plate having slots cut radially
surrounded by a metal sheath.
around its axis to divide the plate into
sections which may be bent in or out to shielded wire- Insulated wire having
around it a shield of tinned braided copchange capacity during alignment.
per wire.
service area-The region around a broadexcitation-Production of oscillations
cast station in which its signal strength shock
in an oscillatory circuit by a sudden elecis strong enough to insure satisfactory
trical discharge or pulse.
reception at all times.
circuit-An undesirable connection,
service band-A band of frequencies allooccurring accidentally or because of a.
cated to a given class of radio communipart breakdown, which exists between
cation service, such as the broadcast
the two sides of a circuit or between any
band, a specific police band, etc.
two circuit terminals ; it often results in
serviceman-A radio repairman or radio
excessive current flow and damage to
some parts.
service oscillator-A test instrument used short-wave converter-A radio device which
to generate radio frequency oscillations
can be connected between a broadcast refor alignment and test purposes.
ceiver and its antenna system to permit
reception of higher-frequency stations
SG-Letters used to designate the screen
which the receiver could not otherwise
grid electrode of a vacuum tube.
receive. It consists essentially of an
s.g.-Signal generator.
oscillator -mixer-first detector arrangeshaded -pole induction motor-An induction
nient like that used in a superheterodyne
motor utilizing field displacement caused
receiver, and serves to convert the high by a small coil (may be a single shorted
frequency signals to a broadcast band
turn) wound around a part of one field
frequency which can be handled by the
pole for purposes of initiating rotation.
regular receiver.
shading ring-A large copper ring placed short waves-Wavelengths shorter than
around the central pole piece of a loudthose included in the broadcast band.
speaker field magnet to act as a shorted
hence waves shorter than 200 meters.
turn and buck out hum voltages. Also
Short waves correspond to frequencies
called shading coil, and used on part of
higher than the highest broadcast band
one pole of small a.c. motors to produce
frequency of 1600 kilocycles.
a rotating magnetic field.
shot effect-The uneven or non-uniform imshading signal-A signal which raises the
pact of electrons on the plate of a vacuum
gain of the amplifier of a television camtube, which shows up as noise in a very
era for those intervals of time when the
sensitive audio amplifier.
shunt-A resistor placed across the termi-
nals of an ammeter to allow a definite
part of the circuit current to go around
the meter. Also, any parallel -connected
part, or the act of placing one part in
parallel with another.
shunt feed-Same as parallel feed. The
application of d.c. operating voltage
through a circuit parallel to and separated
from the signal circuit.
shunt-wound-A motor or generator wound
so the armature and field are in parallel.
shutter-A device for cutting off light
reaching a lens, as in a television camera.
side band-A band of frequencies on either
side of the carrier frequency of a modulated radio wave.
side frequency-A frequency, on either side
of the carrier frequency, produced in
amplitude modulation.
sign-A symbol used to indicate a particular
operation in arithmetic, algebra, or
mathematics in general.
Examples :
-I- Addition sign (plus).
Subtraction sign (minus)
X Multiplication sign ( times)
Division sign (divided by)
V Radical sign (square root of)
J Integral sign (integral of)
= Equality sign (equals) .
signal-A radio wave or alternating current which carries intelligence of any
form. More generally, any alternating
current having other than an a.c. power
line frequency, which varies in some manner with time for the purpose of conveying information, a message or an effect in
signal generator-A test instrument used by
radio servicemen to produce a modulated
or unmodulated r.f. carrier signal having
a known radio frequency value, sometimes
of one type of cathode ray television
camera tube. A capacity exists between
each globule and this plate. As each
globule loses electrons, the effect is relayed electrically to the signal plate
through the mica dielectric.
signal-shifter-Trade name of a variablefrequency r.f. exciter or oscillator intended chiefly for amateur communication transmitters.
signal-to-noise ratio-The ratio of the intensity of a desired signal at any point
to the intensity of noise signals at that
same point. The higher the signal -.o noise ratio, the less noise there is to interfere with reception.
signal tracing-A radio receiver sei vicing
technique which involves tracing the progress of a radio signal through an entire
receiver, stage by stage, while the receiver
is in operation. Measurements which are
made during this procedure by a special
signal -tracing test instrument indicate
when the defective part or stage has been
signal -tracing instrument-A test instrument designed to indicate the presence
of signals at any point in a radio receiver
at a particular frequency.
signal wave-A wave which conveys a
signal. It frequently consists of a carrier
and side bands.
sine-The sine of an acute angle of
is equal to the opposite side divided by the hypotenuse. See
triangle (written sin
trigonometric function.
also at a known voltage. It is used as a
signal source during alignment of a radio
receiver and when hunting for the defective part in an improperly operating
receiver. An all -wave signal generator
has several ranges, and hence can be set
to any carrier frequency which an all wave receiver can receive.
signal plate-The metal plate on the back
of the mica sheet supporting the mosaic
sine wave-The wave form of a pure alternating current such as that produced by
a.c. power systems. It reaches a peak
or maximum in one direction, drops to
zero, reverses its direction and reaches a
peak in the opposite direction, then returns to zero again during one complete
single -button carbon microphone-A micro78
phone having a carbon -filled button on
only one side of its diaphragm.
single -dial control-Tuning in a station by
means of a single control which is mechanically linked to all tuning condensers
in the set.
single -ended tube-A metal tube with all
grid connections on the base (no top
cap). Its type number contains the
letter S after the first numerals, as 6SK7
or 12SQ7.
slide rule dial-A type of tuning dial used
on radio receivers, in which a vertical
marker moves horizontally over long
straight scales resembling the scales of a
slide rule.
slip-The difference between synchronous
and actual speed in an induction motor.
slip rings-The collector rings of an a.c.
S meter-A meter used in communication type receivers to indicate the strength of
the received signal in arbitrary units.
socket-A mounting device for tubes, plug-in
coils, plug-in condensers, plug-in resistors
and crystals, having holes with spring
clips arranged to fit and grip the terminal
prongs of the part being plugged in. Also,
a bayonet or screw -type socket for pilot
single -pole switch-A toggle or knife switch
having only one movable contact arm or
single -side-band transmission-A method of
broadcasting in which one side band is
transmitted but the other side band is
suppressed. The carrier wave may be
either transmitted or suppressed. Used
in television.
single -throw switch-A toggle or knife
switch of the ON-OFF type, capable of
closing or opening only one circuit for
each blade of the switch.
sink-Term sometimes used by telephone
engineers to designate a load or power consuming device.
sinusoidal-Having a sine wave form.
skew-Distortion produced by a facsimile
recorder due to lack of synchronism between scanner and recorder.
skin effect-The tendency of a high -frequency current to flow near the surface
of a conductor.
skip distance-The distance between the
farthest point reached by the ground wave
of a radio station and the nearest point
at which the reflected sky wave comes
back to earth. This skip effect usually
occurs only during high -frequency transmission (short-wave transmissions).
sky waves-Radio waves which travel up
into the sky from the transmitting antenna and are reflected back to earth by
the Kennelly-Heaviside ionized layer.
slide rule-A device consisting of sliding
ruler -like scales and a movable indicator,
arranged to give a convenient mechanical
equivalent of a table of logarithms. It is
used chiefly for performing the operations
of multiplication, division, squaring,
cubing, extracting square root and determining trigonometric functions.
soft tube-A vacuum tube in which a small
amount of gas was allowed to remain
when the bulb was evacuated. Soft tubes
were formerly used as detectors. They
are sensitive but noisy. Also, a tube
which has become gassy.
solder-An alloy of lead and tin which
melts at a fairly low temperature and
is used in radio for making permanent
electrical connections between parts and
soldering iron-A device used to apply heat
to a joint which is to be made permanent
by soldering.
solderless connections-Wiring connections
made by the use of small screw clamps
which firmly hold the wires to be joined.
solenoid-An electromagnet having a movable iron core.
sound-A general term used to specify a
sound wave (a travelling vibration in
air or some other elastic medium) or a
sound sensation. (the effect of this sound
wave on human ears) . Sound is sometimes defined as a vibration of a body or
material at a rate which can be heard by
human ears. The extreme limits of human
hearing are 20 cycles and 20,000 cycles,
but animals can hear still higher frequencies. Thus, bats can hear sound
waves as high as 50,000 cycles. Sound
can travel through any medium which
possesses the ability to vibrate; the resulting travelling vibrations are called
sound waves.
sound effects-Various devices or record-
which utilizes the oscillatory discharge of
a condenser through a coil and a spark
gap as 'the source of its r.f. power.
s.p.d.t. switch-Single-pole, double-throw
speaker-A loudspeaker. This short term
is frequently used when no confusion will
result therefrom, as in compound terms
like speaker field, speaker cone, etc. Also
may mean a lecturer performing before
a microphone.
specific gravity-The weight of a substance
as compared to the weight of an equal
volume of water.
specific inductive capacity-Another name
for dielectric constant, which is the ratio
of condenser capacity with a given dielectric to the capacity of a similar condenser with air as the dielectric.
specific resistance-The resistance of a unit
conductor having a cross-sectional area of
1 circular mil and a length of 1 foot (a
circular -mil -foot). Also called resistivity,
and designated by the Greek letter p
ings used to produce life -like sound imitations.
sound gate-The mechanism through which
sound motion picture film passes for the
purpose of converting the sound track on
the film into audio signals. An exciter
lamp, lens assembly and photocell are
associated with the sound gate. Television film pickup devices use a sound
gate to provide the sound accompaniment
for the televised movie.
sound level meter-An instrument for measuring sound intensities electrically, having an output indicator calibrated in db
or directly in units of sound intensity.
sound panel-Movable panels of rock wool
for sound absorption, or hard surfaces for
sound sensation-The sensation produced in
the human ear and brain by a sound wave.
sound track-A graphic record of sound
produced on film or on sensitized paper
for reproduction.
sound wave-A travelling wave produced by
vibration of an elastic medium (air,
metal, wood, etc.) at a rate which can
be heard.
source-A term sometimes used to describe
the part which is supplying electrical
energy or radio signals to a circuit.
south pole-The pole of a magnet at which
the magnetic lines of force enter the
space charge-The electrons accumulated
in the space between the cathode and
plate of a vacuum tube, usually close to
the cathode. Being negative, the apace
charge tends to limit the number of electrons which can reach the plate, and
hence limits the plate current.
space -charge effect-The repulsion exerted
on electrons emitted from the cathode of
a vacuum tube by electrons accumulated
in space near the cathode, resulting in a
reduction of plate current.
space -charge grid-A grid located next to
the cathode and made positive with respect to the cathode, for the purpose of
reducing the limiting effect of the space
charge on plate current.
spacing wave-In telegraphic communication, the emission which takes place in
between the code characters or when no
code characters are being transmitted.
spaghetti-Heavily varnished cloth tubing
sometimes used to provide additional insulation for radio circuit wiring.
spark gap-An arrangement of electrodes
across which a spark will jump at a
predetermined voltage. Among the types
of spark gaps formerly used in transmitters are plain gap, rotary gap, synchronous gap and quenched gap.
spectrum-All frequencies used for a particular purpose. Thus, the ratio spectrum
extends from about 10 kc. up to over
10,000 megacycles.
speech amplifier-An audio amplifier.
spherical-Having the form of a ball or
spherical aberration-A lens defect in which
the light rays coming from a single point
are brought to different focal points by
the edges of the lens than by the center
of the lens, causing a blurred image. In
manufacturing high-quality lenses, it is
avoided by grinding the lens slightly
different from spherical form.
spherical wave-A wave whose wave front
is a spherical surface.
spider-A highly flexible fiber ring which
serves to center the voice coil of a dynamic
loudspeaker between the pole pieces and
at the same time provide a restoring
spark transmitter-A radio transmitter
force, causing the voice coil to return to
the same starting point after each movement. Also, a small metal cap used to
couple the driving pin to the apex of the
cone in magnetic speakers.
spider -web antenna--A special type of all wave antenna.
splice-A joint between two wires which
possesses mechanical strength as well as
good electrical conductivity.
split rotor plate-See serrated rotor plate.
sponsor-A person or business firm who
pays a broadcast station and the performers for a radio program in which a
certain amount of the time alloted is devoted to advertising a commercial prod -
sporadic E layer-A portion of the normal
E layer of the atmosphere which sometimes breaks away and exhibits special
sporadic reflections-Sharply defined reflections of substantial intensity from an
ionized layer of the ionosphere at frequencies greater than the critical frequency of the layer. They are extremely
variable in respect to time of occurrence,
geographic distribution, and frequency
spot projection-The optical method in
which the scanning (or recording) spot
is created by an aperture between the
light source and the subject copy or
record sheet.
spot speed-The product of the length of
scanning line by the number of scanning
lines per second in a facsimile system.
spottiness-The effect in a television picture resulting from variations in the instantaneous light value of the reproduced
image due to electrical disturbances between the scanning and reproducing de-
square mil-The area of a square whose
sides are .001 inch (one mil).
square root-A number which, when multiplied by itself, equals the given number.
Examples : 2 is the square root of 4 ; 13
is the square root of 169. The radical
sign -V, without an index number in the
angle of the sign, indicates that the square
root of the number is to be extracted
(determined) .
squealing-A condition in which a highpitched note is heard along with the desired radio program. It can be due to
interference between stations or to a
number of other causes.
s.s.c.-Single silk-covered wire.
stability-Freedom from oscillation in tuned
or other circuits of a receiver.
stabilized feedback-Another term for negative feedback, degeneration or inverse
feedback, used because this type of feedback can stabilize the gain of an amplifier
stage or reduce distortion or noise arising
in the stage.
stage-A single vacuum tube circuit containing either a single vacuum tube or
two or more tubes connected in push-pull,
push -push, or parallel.
stage-by -stage
elimination method
method of servicing receivers similar to
the circuit disturbance method except
that the test signal is introduced by
means of a test oscillator.
standing wave-The distribution of voltage
or current along a single or multiple conductor, after the circuit has reached a
steady state. An instantaneous picture
of the distribution has a wave shape along
the conductor, hence the name.
spreader-The insulating cross -arm used to
space aerial wires when more than one
wire is used.
s.p.§.t. switch- Single -pole, single -throw
spurious radiation-Any emission from a
radio transmitter at frequencies outside
of its assigned communication band.
spurious response-A condition wherein a
receiver is resonant at one or more frequencies other than that to which it is
sq. ft.-Square feet.
sq. in.-Square inches.
square-The product obtained by multiplying a number by itself. Example : 49 is
the square of 7, because 7 X 7
square -law detector-A detector whose output current is proportional to the square
of the r.f. input voltage.
stand-off insulator-An insulator used to
support a wire at a desired distance away
from the building or other support on
which the insulator is mounted.
static-Interfering noises heard in a radio
receiver due to radio waves created -by
atmospheric electrical disturbances such
as discharges of lightning.
static characteristic-The characteristic of
a tube when supplied only with d.c.
operating voltages (no signal voltages) .
station-An assembly of radio transmitting
equipment and its transmitting antenna.
stationary wave-A wave produced by combining two or more waves having the
same frequency, often called a standing
wave. The standing wave in a half -wave
doublet antenna, for example, is produced
by combining of an original wave with its
reflections from the ends of the antenna.
stator-The fixed set of plates in a variable
condenser. The non -rotating part of an
electric motor or generator.
step-down transformer-A, transformer in
which the secondary winding has fewer
turns than the primary, so that the
secondary delivers a lower voltage than
is applied to the primary.
step-up transformer-A transformer in
which the secondary winding has more
turns than the primary, so that the
secondary delivers a higher voltage than
is applied to the primary.
storage battery-One or more secondary or
storage cells connected together, usually
in series.
storage cell-A secondary cell. More specifically, one of the cells in the ordinary
automotive storage battery, delivering a
voltage slightly higher than two volts
and capable of being recharged.
storage -type camera tube-A type of
cathode ray television camera tube in
which the elemental areas on the photosensitive plates build up their charges
gradually, developing a picture signal
which is proportional to the time of charging of the plates by light from the scene.
The iconoscope is- an example.
straight line characteristic-Any action
which can be represented by a straight
line on a graph. When this condition
exists, one quantity varies in direct proportion to another.
strain-The change of shape, size, or form
caused by applied force.
strand-One of the small wires in a group
of wires twisted or braided together.
stranded wire-A number of small wires
twisted or braided together and used as
a single conductor.
stray capacity-Capacity which exists between parts, between wires and between
a chassis and various parts and wires.
stress-The force which causes a displacement or distortion in the shape of a substance.
striking potential-The grid potential of a
gas -filled triode at which plate current
begins flowing.
;stroboscope-An instrument used to permit
visual inspection of moving objects by
illuminating them at the same definite
points in their rotation or recurring
strobotron-A special glow lamp which has
the ability to produce accurately timed
flashes of light which permit visual in-
spection of high-speed moving parts. Used
in a stroboscope.
studio-A room in which radio programs
stylus-A specially shaped needle used to
cut grooves and record sound waves in
wax or prepared record blanks.
stylus drag-The effect of the friction between the record surface and the reproducing stylus.
stylus force-Effective weight of reproducer
or force in vertical direction on stylus
when same is in operating position.
subcarrier-An intermediate wave modulated by the facsimile signals and in turn
used to modulate the main carrier, either
alone or in conjunction with subcarriers
on other channels.
subharmonic-A frequency which is a fraction of the fundamental frequency. Thus,
the second subharmonic is % the fundamental frequency ; the third subharmonic
is %, etc.
subject copy-The material in graphic form
which is to be transmitted by a facsimile
transmitter for facsimile reproduction by
the recorder.
subscript-A small number or letter written
at the right of and below another letter,
for distinguishing purposes. Example:
In XL and Xc, the subscripts L and C
serve to distinguish inductive reactance
(XL) from capacitive reactance (Xc) ;
in R = R1 + RI + R, + R,, numeral subscripts serve to distinguish different resistor values. XL is pronounced "X sub
L" ; R3 is pronounced "R sub three" or
"R three."
subtraction-The process of finding the numerical difference between two quantities
or numbers.
SUP-Suppressor grid of a tube.
superheterodyne receiver-A type of radio
receiver in which the incoming modulated
r.f. signals are amplified a small amount
in the preselector, then fed into the frequency converter section (consisting of
the oscillator, and mixer-first detector )
for conversion into a fixed, lower carrier frequency called the i.f. value of
the receiver. The modulated i.f. signals
are given very high amplification in the
i.f. amplifier stages, then fed into the
second detector for demodulation. The
resulting audio signals are amplified in
the conventional manner by the audio
amplifier, then reproduced as sound waves
by the loudspeaker.
super high frequency-A frequency in the
band between 3000 mc. and 30,000 me.
superimposed-Added on to.
super-regenerative detector-A form of regenerative detector in which the feedback
is periodically reduced by a quenching
frequency to prevent oscillation and still
maintain high sensitivity. This quenching frequency may be generated by a
separate tube or by the same tube. Used
principally in ultra -high frequency circuits.
super-sensitive relay-A relay which operates on a current value less than about
250 microamperes (1Y.ß ma.) .
a rectifier filter system so as to improve
switch-A mechanical device for opening
and closing an electrical circuit, or for
changing the connections between parts
or circuits.
SWL-Short-wave listener.
symbol-A simple design used to represent
a radio part on a schematic diagram.
Also, a letter used in formulas to represent a particular quantity.
symmetrical-Balanced. Equal to each side
of a normal or center line.
synchronization-The process of keeping
the image-reconstructing part of a television or facsimile receiver in step with
the corresponding device at the transmitter.
synchronized-In step with.
synchronizing-In facsimile, the maintenance of predetermined speed relations
between the scanner and the recorder
within each scanning line.
synchronizing separator-The circuit which
separates the control impulses from the
video signals.
synchronizing signals-Electrical impulses
used to keep the television receiving system in step with the transmitting system,
so that the picture or scene will be reconstructed properly.
synchronous-Simultaneous in action and
in time (in phase) .
synchronous condenser-A synchronous motor which is over -excited so that it produces a leading current, used to correct
power factor where inductive loads are
across the power line.
synchronous vibrator-A vibrator which
serves the dual function of converting a
low d.c. voltage to a low a.c. voltage and
at the same time rectifying a high a.c.
voltage. When used in an auto radio
power pack, it eliminates the need for
a rectifier tube.
supersonic frequency-A frequency just
above the audible range.
supersonic vibrations-Vibrations which
cannot be heard by the unaided human
ear because they are above the audible
frequency range.
supply-Another name for voltage source.
suppressor-A resistor inserted in series
with the spark plug lead or the distributor
lead of an automobile engine to suppress
spark interference which might otherwise interfere with reception of radio
programs in the auto radio set. Also, a
resistor or choke coil used in a radio circuit to suppress oscillations.
suppressor grid-A grid placed between the
screen grid and the plate of a vacuum
tube and maintained at or near cathode
potential, in order to force secondary electrons back to the plate.
surface defects-Defects which are readily
visible on top the radio chassis or in the
connections to a radio, such as: tube top
cap off ; disconnected antenna lead-in, a
dead tube, etc.
surface leakage-A leakage of current over
the surface of insulation.
surface noise-The noise reproduced in
playing a record due to rough particles
in the record material and/or irregularities in the walls of the groove left by the
cutting stylus.
surge impedance-The impedance in ohms
as measured between the terminals of a
transmission line at the operating frequency. Also called characteristic impedance, and designated by the notation Zo.
surges-Sudden increases of current in a
table model receiver-A radio receiver havpower line or circuit.
ing a cabinet of suitable shape and size
susceptance-The reciprocal of reactance.
to permit placing on a table.
SW-Short-wave. Switch.
talk -listen switch-A switch used in intercommunication systems to enable the
sweep circuit-A special oscillator circuit
which generates a voltage having a saw operator to use the receiving loudspeaker
as a microphone. It connects the loudtooth wave form suitable for making the
speaker to the input of the amplifier and
electron beam of a cathode ray tube sweep
connects the line to the output of the
back and forth across the fluorescent
amplifier when in the "talk" position.
swinging choke-A special iron -core choke. tan-Tangent.
operated with an almost saturated core, tangent-The tangent of an acute angle of
in order to make the inductance vary
a right triangle (written tan 9) is equal
or swing as the average current changes.
to the opposite side divided by the adjaIt is sometimes used as the input choke of
cent side. See trigonometric function.
tank circuit-A resonant circuit used in an
directly proportional to temperature. The
formula for determining the resistance
at any given temperature is: Rt = Ro
(1 + at) where R, = total resistance at
a temperature of t degrees Centigrade,
R°=total resistance at 0°C. and a=temperature coefficient of resistance at 0°C.
This value is 0.00427 for copper.
temperature -compensating condenser-A
condenser used to compensate for reactance changes in oscillator circuits due to
changes in temperature, being designed
to change in capacity in the opposite
manner so the reactance change will be
temperature saturation-Also known as
filament saturation. The condition whereby no more electrons will be emitted
from the cathode even though the cathode
temperature is further increased.
tension-Potential difference or voltage.
term-A portion of an algebraic expression
which is separated from other parts by a
plus or minus sign. Example In the
3a + 2b2, the terms
expression 17a2
are 17a2, 3a and 2b2. Like terms have the
same literal parts ( the same letter combinations.) Thus, the expression 17a2x +
2a2x contains all like terms,
and they can be combined by direct addition and subtraction to give 21.7a2x. Unlike terms contain different letter combinations, and cannot be combined directly
by addition and subtraction. Example
17ab +8I2 + 3x.
terminal-A point to which electrical connections are made.
test lead-A flexible insulated lead used
chiefly for connecting meters and test instruments to a circuit under test.
test prod-A sharp Metal point provided
with an insulated handle and means for
connecting the point to a test lead. It is
used for making a touch connection to a
circuit terminal.
tetrodo-A four -electrode vacuum tube. Ordinarily, these electrodes will be the cathode, control grid, screen grid and anode.
thermal agitation-The effect produced by
the random movement of free electrons
in a conductor, due to heat. They produce
tiny pulses of electron current which, if
taking place in a resonant circuit such
as a tuning coil and condenser, will be
amplified along with the signal currents.
thermionic-Relating to electron emission
under the influence of heat. Practically
all modern vacuum tubes are thermionic
thermionic emission-emission of electrons
from an electrode under the influence of
thermionic tube-A vacuum tube in which
the cathode is heated for electron-emitting
oscillator to store energy.
T antenna-A flat -top antenna, the lead-in
of which is taken from about the center
of the horizontal portion.
tap-A connection made somewhere along
an inductance or resistance, other than
the ends.
taper-Distribution of resistance over the
range of rotation of a volume or tone
tapped control-Volume or tone control potentiometer having a fixed tap somewhere
along the resistance winding for the purpose of providing fixed bias or automatic
bass compensation.
tapped resistor-A fixed resistor of the wire wound type, with extra terminals along
the winding to provide various voltage
values needed in voltage divider applications.
tap switch-A multipoint switch.
target-the electrode which collects electrons in a Farnsworth television dissector
telecine projector-A device used to televise motion picture film.
telegraph-modulated wave-A continuous
wave which is varied in amplitude or frequency by means of telegraphic keying.
telephony-A method of reproducing sounds,
especially those of the voice, at a distance.
telephotography-Radio or wire transmission of still pictures or photographs.
telephoto lens-A lens used to photograph
or televise distant objects.
Teletrician-A graduate of National Radio
Institute, thoroughly trained in television theory and service.
television-The transmission and reception
of a rapid succession of images of fixed
or moving objects by means of radio
waves travelling through space or over
television channel width-The range of
frequencies necessary to broadcast a tele-
vision signal.
television connection-Terminals which permit the use of an ordinary radio receiver
in amplifying and reproducing the audio
signals associated with a television program. These terminals simply connect
to the input of the audio amplifier in the
receiver, just as do the phonograph connection terminals.
temperature coefficient-The -change in characteristics of a substance for each degree
Centigrade change in temperature.
temperature coefficient of resistance-The
amount which each ohm of resistance is
increased for each degree rise in temperature. For all pure metals, over ordinary
temperatures, the increase in resistance is
applied voltage the time constant is equal
to the circuit's inductance in henrys divided by its resistance in ohms.
time delay relay-A relay whose contacts
open or close a specified length of time
after the controlling impulse has been
thermocouple-A pair of dissimilar con-
ductors so joined as to produce a voltage
when the junction is heated.
thermocouple ammeter-An ammeter dependent for its indications on the voltage
produced in a thermocouple when heated
by the current to be measured.
thermometer-An instrument for measuring
thermostat-A device used to open or close
circuits with changes in temperature.
thoriated filament-A vacuum tube filament
made by compounding thorium and
three-band receiver-A radio receiver having three different tuning ranges.
threshold-Just at the verge of being observed by our senses or by an indicator
of some sort.
threshold of audibility-The loudness level
at which sound is just barely heard.
threshold of feeling-The loudness level at
which sound is felt rather than heard.
Often causes painful sensations.
throat of horn-The smaller end of the horn
of a horn loudspeaker.
throw -out spiral-A blank spiral groove
cut in an eccentric manner at the end of
a recording; provided to actuate the
mechanism of an automatic record
thyratron-A grid -controlled mercury vapor
time signals-Naval Observatory time signals which are broadcast regularly each
day by government radio station NAA in
Arlington, Virginia on a number of different frequencies. These signals are used
by Army and Navy stations, ships at sea,
jewelers and other persons throughout
the entire country for setting timepieces.
NAA signals are rebroadcast by some
broadcasting networks at certain hours.
tip jack-A small receptacle into which a
metal tip can be plugged to complete a
tip plug-A small plug which fits into a tip
toggle switch-A small switch operated by
means of a lever.
tolerance-The permissible variation from a
rated or assigned value.
tone-The general character of a reproduced radio program as it affects the
human ear ; the quality of the program.
tickler-A coil connected in series with the
plate circuit for the purpose of feeding a
portion of the amplified signal current
back into the grid circuit by induction for
repeated amplification. The tickler is
used chiefly in regenerative detector circuits.
tie -down point-A frequency at which a
receiver is aligned. Usually 600 kc. and
1400 ke. for the standard broadcast band.
Alignment may also be checked at 1000
kc., thereby making three tie -down points.
tier array-An array (arrangement) of
antennas one above the other, used chiefly
in ultra -high -frequency work.
tight-coupling-The closest possible coupling
between two circuits under given conditions.
tijting-A vertical sweep (up or down movement) of a television camera.
time constant-In a capacitive -resistive circuit, the number of seconds required for
the capacity to receive 63% of its full
charge after the e.m.f. is applied. With
steady applied voltage the time constant
is equal to the product of the circuit's
capacity in farads and its resistance in
ohms. In an inductive -resistive circuit,
the number of seconds required for the
current to reach 63% of its final value
after the e.m.f. is applied. With steadily
Also used to describe a single frequency
audio sound.
tone control-A circuit control sometimes
provided on a radio receiver to permit
strengthening the response either at low
or at high audio frequencies at will, so as
to make the reproduced radio program
more pleasing to a particular audience.
tone -modulated wave-An interrupted continuous wave, which is a continuous wave
modulated at an audio frequency.
tone modulation-Modulation of a carrier
with fixed audio frequency tone.
top cap-A metal cap sometimes placed on
the top of a vacuum tube and connected
to one of the electrodes, usually the control grid.
torque-The force which produces rotation.
T. P. T. G.-Tuned-plate-tuned grid.
tracking-A term used to indicate that all
of the tuned circuits in a receiver follow
the frequency indicated by the tuning dial
pointer as the receiver is tuned over its
entire tuning range.
transceiver-A radio circuit used both for
transmitting and receiving, by employ 86
generating and amplifying an r.f. carrier
signal modulating this carrier with intelligence, and radiating the modulated
r.f. carrier into space after it is amplified
additionally and fed to the transmitting
transparent-Permitting the passage of
light rays.
transpose-To interchange position.
transverse wave-A wave in which the displacement is transverse (crosswise) to
the direction of propagation.
treble-A term sometimes used to designate high audio frequencies.
t.r.f.-Tuned radio frequency.
triangulation-A method of fixing the position of an aircraft or surface vessel by
taking bearings with a radiocompass on
at least two (and sometimes more) shore
or fixed land stations.
trickle charger-A device, usually a rectifier
operating from an a.c. power line, which
is designed to charge a battery continuously at a low rate.
trigger-action-Any circuit in which a weak
controlling impulse initiates the main current flow.
trigonometric function-Any of the ratios
which exist between the sides and angles
of a right triangle.
trigonometry-A branch of mathematics
which deals with the relations existing
among the angles and sides of triangles.
trimmer condenser-A small semi -adjustable condenser, usually adjusted with a
screwdriver, and used in the tuning circuits of radio receivers and other radio
apparatus to permit accurate alignment
of these circuits.
triode-A three -electrode vacuum tube. usually having a cathode, control grid and
ment of suitable switching arrangements.
transconductance-Same as mutual conductance. The amplification factor divided by
the a.c. plate resistance. The a.c. plate
current divided by the a.c. grid voltage
with no load in the plate circuit. It is
measured in mhos.
transcribe-To broadcast a program by
means of electrical transcription.
transcription-An electrical transcription,
in which part or all of a radio program
is recorded for future use.
transducer-A device which transfers
energy from one system to another. The
energy may be any form-electrical, mechanical, acoustical, etc.-and it may or
may not be changed from one form to
another by the transducer. Examples :
A loudspeaker is a transducer which
changes electrical energy into acoustical
energy. A phonograph pick-up is a transducer which changes mechanical energy
into electrical energy.
transfer relay-A relay controlled by and
controlling other relays.
transformer-Two or more coils mounted
on a common support in such a way that
the magnetic lines of force produced by
the flow of alternating or pulsating direct
current through one coil will pass through
the other coil and induce in it a corresponding a.c. voltage.
transients-Erratic changes in voltage or
current. A momentary voltage or current surge.
transient time-The time necessary for an
electrical circuit to reach a steady-state
transition frequency-The frequency at
which the changeover from constant amplitude recording to constant -velocity
recording takes place.
transitron oscillator-An oscillator in which
the inner tube grid is used as an anode,
the outer grid as a control element and
the plate merely as a collector anode. The
outer grid has a negative transconductance to the anode grid. Used to produce
stable sine wave oscillations at both high
and low frequencies.
translation loss-The loss in high -frequency
reproduction which occurs as the groove
velocity decreases in a recording.
transmission line-Any set of conductors
used to carry r.f. or a.f. signals or energy
from one location to another.
transmission loss-The loss of power suffered by a transmitted wave in passing
along a transmission path or through a
circuit or other device. Usually measured
triode-pentode-A vacuum tube having a
triode and a pentode in the same envelope.
tri-tet oscillator-An oscillator circuit popular with amateur radio operators because
it has strong harmonics which make it
ideal for multiband operation. Also has
the feature of buffering or isolating the
crystal circuit and the output, since the
screen grid acts as the oscillator anode.
troposphere-That part of the earth's atmosphere extending outward from the
earth for about six miles, in which temperature generally decreases with alti-
tude. clouds form, and convection is active.
tropospheric wave-A radio wave that is
reflected by some location in the troposphere.
T.U.-Transmission unit (replaced by db1.
tube-A vacuum tube, gaseous tube or
photoelectric cell mounted in a somewhat
tube -shaped glass or metal envelope.
tube heating time-The time required for
in decibels.
transmission unit-A decibel.
transmitter-A comprehensive term applying to all of the equipment used for
the coolest portion of a mercury-vapor
tube to reach normal operating temperature.
tube tester-A test instrument used to test
the condition of radio tubes.
tube voltage drop-In a gas or vapor -filled
tube, this is the plate -cathode voltage
during the conducting period.
tubular condenser-A paper or electrolytic
condenser having as its plates long strips
of foil which have been rolled into a compact tubular shape.
tuned antenna-An antenna which is made
to resonate at the desired operating frequency.
tuned circuit-A resonant circuit, consisting of a coil and condenser which are
preset or can be adjusted to give resonance at a desired frequency.
tuned filter-A parallel resonant circuit
used to attenuate signals at the resonant
tuned -grid, tuned -plate oscillator-A vacuum
tube oscillator having a parallel resonant
circuit in series with the plate circuit
and another parallel resonant circuit in
series with the grid circuit. The grid
resonant circuit is tuned to the operating
frequency and the plate resonant circuit
is .tuned slightly above the operating frequency, so as to act like an inductance.
Oscillation is maintained by capacity
feedback' through the internal capacity of
the tube.
tuned radio frequency amplifier-An r.f.
voltage amplifier circuit using tuned circuits in the coupling system.
tuned radio frequency receiver-A receiver
in which r.f. amplification is provided by
a number of vacuum tube amplifier
stages, each of which has one or more circuits which are tuned to resonance at the
incoming signal frequency by a section of
the gang tuning condenser. The amplified r.f. signals are fed directly into the
detector for demodulation.
tuned radio frequency transformer-A
transformer having one or both windings
tuned ; used for coupling two r.f. amplifier
tungar rectifier tube-A gaseous diode rectifier tube employed in battery chargers.
tungsten-A pure metal used in radio chiefly
for the filaments and other elements of
radio tubes.
tuning-The process of varying the inductance or capacity in a coil -condenser circuit to provide resonance at a desired frequency. Also, the process of setting all
of the tuning circuits in a radio receiver
simultaneously to a desired frequency by
rotating the tuning dial or pressing a but-
ton of a push-button tuner.
tuning circuit-Usually a circuit containing
inductance and capacity, either of which
may be adjusted so the circuit will be responsive to a particular frequency.
tuning control-The receiver control by
which the operator varies the tuned circuits of the receiver to bring in the desired sound or television program.
tuning eye-A cathode ray tuning indicator
tuning indicator-A device which indicates
when a radio receiver is tuned accurately
to a radio station.
tuning, meter-An ordinary meter connected
into a radio receiver circuit for use as a
tuning indicator.
tuning wand-A flexible rubber or fiber rod
having a brass plug in one end and a
powdered iron core at the other end, used
for checking receiver alignment.
turn-In a coil, one complete loop of wire
around the coil form.
turns-per-volt-The number of turns needed
on the secondary winding of a transformer to give 1 volt of output voltage
when the primary voltage is normal.
turns ratio-The ratio of the number of
turns in a secondary winding of a transformer to the number of turns in the
primary winding.
turnstile antenna-A series of crossed horizontal doublet antennas arranged vertically on a mast and fed 90° out of phase.
Used in television and other u.h.f. systems
where circular radiation patterns are desired.
a record player or electric
phonograph, the motor -driven disc on
which the phonograph record is placed.
In a sound recorder, the motor -driven
disc on which is placed the disc to be cut.
tweeter-A loudspeaker designed to handle
only the high audio frequencies (about
6000 to 15,000 cycles).
twin-triode-Two triode type tubes in a
single envelope.
twisted pair-Two small insulated conductors twisted together, without a common covering.
two -band receiver-A radio receiver having
two reception ranges. One will generally
vacuum tube keying-A keying system in
which a vacuum tube is placed in series
with the center -tap lead of the final stage,
its grid being connected to filament
through the transmitting key. When the
key is open, the tube blocks and no plate
current (cathode current of final stage)
flows. Grounding the grid (closing the
key) unblocks the tube, current flows, and
a pulse is sent out.
vacuum tube transmitter-A radio transmitter in which vacuum tubes are utilized
to convert the applied electric power into
radio frequency power.
vacuum tube voltmeter-A test instrument
which utilizes a vacuum tube circuit for
measuring voltages without greatly affecting the circuit to which the instrument is connected.
valve-The term used in Great Britain to
designate a radio tube.
variable condenser-A condenser whose capacity may be changed either by varying
the space between plates (as in a trimmer condenser) or by varying the amount
of meshing between the two sets of plates
(as in a tuning condenser).
variable mu tube-A screen grid tube having
a grid so designed that the mutual conductance varies with the C bias. When
used as an amplifier, the amplification
váries with the C bias.
variable resistance-A resistance which can
be changed in value while in use.
variocoupler-A variable r.f. transformer
consisting of two independent windings,
one stationary and the other adjustable
with relation to the fixed element so as
to change the mutual inductance.
variometer-A variable inductance having
a movable coil mounted inside a stationary
one. The two coils are connected in
series. The total inductance of the unit
can be varied continuously through a wide
range of values by rotating the innen coil
cover from 535 kc. to 1720 kc., which includes the broadcast band and some
police calls, and the other will generally
be between 5.65 mc. and 18.1 me.
u.h.f. or UHF-Ultra-high frequency.
ultra-audion oscillator-A variation of the
Colpitts oscillator circuit.
ultra -high frequency-A term commonly
used to indicate a frequency higher than
about 30 megacycles. Now limited by a
definition of the F.C.C. to the band of
frequencies between 300 mc. and 3000 mc.
See radio spectrum.
uncharged Without electrical charge.
Having a normal number of electrons.
undamped wave-A continuous wave.
underlap-The amount by which the effective height of the scanning spot falls short
of the nominal width of the scanning line
in a facsimile system.
unidirectional-Flowing in one direction
only, as direct current.
unidirectional loop-A loop which will pick
up energy from one direction only.
unilateral bearing-A bearing obtained with
a radio direction finder having a unidirectional response.
unit-A reference quantity for measuring
purposes. Common radio units are the
volt, ampere, ohm, watt, henry, farad, etc.
unity coupling-The condition wherein all
the magnetic flux of the primary passes
through the entire secondary.
universal output transformer-An iron -core
a.f. output transformer having a number
of taps on its windings to permit its use
in practically any average radio receiver.
universal receiver-A receiver capable of
operating from either a.c. or d.c. power.
unmodulated-Without modulation. The
r.f. carrier signal alone, as it exists during
pauses between station programs.
Varley loop-A variation of tjie Wheatstone resistance bridge, used to determine
distance from the bridge to the point at
which a line may be grounded. Used
mostly in telephone and telegraph work.
vector-A straight line whose length is proportional to the magnitude or amount of
a quantity, and whose arrow head points
in the direction of that quantity.
vector diagram-An arrangement of vectors
showing the relations between alternating
vector quantity-A quantity which has both
magnitude and direction.
vee antenna-A long single -wire antenna
arranged in the form of a "V", used by
itself or as an element of a directional
y or
V-Volts. Voltage. Voltmeter. Vac-
uum tube.
vacuum-A space from which practically
all air has been removed.
vacuum tube-A device consisting of a number of electrodes mounted in an envelope
or housing from which practically all air
has first been removed. Also called an
electron tube or radio tube. Conduction
of electricity between two or more of the
electrodes may take place through the
intervening space inside the tube.
velocity microphone-A microphone made
up of a thin, light -weight corrugated ribbon mounted between the poles of powerful permanent magnets. Sound waves
move this conducting ribbon back and
forth in the magnetic field, with the result
that an a.f. voltage is induced in the ribbon. The ribbon responds to the velocity
of the air particles rather than to air
vernier condenser-A small variable tuning
condenser which is placed in parallel with
a larger tuning condenser for the purpose
of providing a finer adjustment after
the large condenser has been set roughly
to the desired position.
vernier dial-A type of tuning dial in which
a complete rotation of the control knob
makes the tuning condenser shaft rotate
only a small fraction of a revolution,
thereby permitting fine and accurate
vertical antenna-A single vertical metal
rod, suspended wire or metal tower used
as an antenna.
vertical deflecting electrodes-The electrodes of a cathode ray tube to which
voltage is applied to move the electron
beam up and down (from top to bottom)
on the screen.
vertical hold-The control in a television receiver which adjusts the free -running
period of the vertical sweep oscillator.
vertically polarized wave-A linearly polarized wave whose direction of polarization
is vertical.
vertical polarization-A method of transmitting radio waves in which the plane
of polarization is perpendicular to the
surface of the earth.
vertical recording-A recording in which the
groove modulation is up and down. Also
called hill and dale recording.
vertical sweep-The downward movement,
line-by-line, from the top to the bottom
of a picture or scene being televised.
veryy high frequency-Any frequency between 30 mc. and 300 mc.
V.I.-Volume indicator.
vibrate-To move back and forth.
Vibrating reed frequency meter-A series
of metal reeds whose natural periods of
vibration are adjusted to different values.
When the meter is placed in contact with
a vibrating object or an a.c. current is
passed through a series of coils close to
the reeds, the reed which is timed to the
frequency of the vibration or current
vibrates violently. The reed ends are
usually painted so that looking at the
ends will show which one is vibrating.
vibrator-An electromagnetic device which
converts a d.c. voltage to pulsating d.c.
or a.c. It is used in the power packs of
auto radios and some public address amplifiers to convert the 6-volt auto storage
battery voltage to a low a.c. voltage.
This a.c. voltage is then stepped up by a
power transformer, and converted into a
high d.c. voltage either by a conventional
rectifier tube circuit or by an extra set
of contacts on the vibrator itself.
video-A Latin word meaning "I see," applied to television parts and circuits
which handle picture signals, and applied
also to signals associated with the picture
being transmitted.
video frequency-One of the frequencies
present in the output of a television
camera as a result of scanning the image
being transmitted. It may be any value
from almost zero to well over 4,000,000
video frequency amplifier-The amplifier
stages which build up video signal
strength after the video demodulator
video signal-The picture signal by itself
in a television system.
viewing screen-In a cathode ray oscilloscope, the screen which converts the useful energy of the electron beam into a
visible pattern.
vinculum-A straight horizontal line serving
as a sign of grouping, used chiefly with
radical signs and fractions. Examples :
When used with
VR' + X,
fractions, the vinculum indicates that
the entire group above the line is to be
divided by the entire group below the line.
virtual cathode-The space charge or electron cloud in front of the cathode in a
vacuum tube.
virtual height-The height of an ionized
layer of the ionosphere at which reflection
from a definite boundary surface would
cause the same time of travel as the actual
reflection for a wave transmitted from the
ground to the ionosphere and reflected
virtual image-An image which appears to
be where it isn't, such as behind a mirror.
voder-A device consisting of vacuum tube
circuits and highly selective electrical
filters controllable through a keyboard in
such a way that speech sounds can be
artificially produced. The name is an abbreviation of Voice Operation Demon-
coil-The moving coil which is attached to the diaphragm of a dynamic
loudspeaker. The coil which has audio
voltages applied to it.
volt-The practical unit of voltage or electromotive force. One volt will send a
current of one ampere through a resistance of one ohm.
voltage amplification-Amplification which
increases the voltage of a signal rather
than its power. Also, a rating obtained
by dividing the a.c. output voltage of an
amplifier stage by the a:c. input voltage.
voltage amplifier-An amplifier designed
primarily to build up voltage without supplying any appreciable amount of power.
voltage divider-A resistor having one or
more fixed or adjustable contacts along
the length of its resistance element, in
addition to the customary two end terminals. The total available voltage is applied between the two end terminals, and
desired portions of this voltage are obtained from any two terminals on the
voltage divider.
voltage doubler-A rectifier circuit which
doubles the output voltage by charging a
condenser on one-half cycle and discharging it in series with the applied voltage
during the next half -cycle.
voltage drop-The voltage developed across
the terminals of a radio part by the flow
of current through the part.
voltage feed-A method of exciting a transmitting antenna by applying voltage at a
voltage loop or antinode.
voltage node-Any point which has zero
voltage in a stationary -wave system. Thus
a voltage node exists at the center of a
half -wave doublet antenna.
voltage rating of a condenser-The maximum sustained voltage which can safely
he applied across the terminals of a condenser without causing breakdown of the
insulation between condenser plates.
voltage regulating transformer-A type of
power transformer used to deliver a constant output voltage value in spite of considerable variation in input voltage.
voltage regulation-The ability of a generator or other voltage source to maintain
nearly constant terminal voltage for all
load values from zero to the maximum
rated capacity.
voltage regulator tube-A two -element gaseous tube used in a.c. radio receivers to
keep the input a.c. voltage to the receiver
power pack essentially constant despite
wide variations in the line voltage. Also
used to maintain a constant d.c. potential
across a circuit.
voltage rise-A generated or source voltage.
voltage saturation-The plate voltage at
which all electrons emitted from the
cathode are being collected by the plate
so that further increases in plate voltage
have no effect on plate current.
voltaic cell-Any cell which produces voltage.
volt-ampere-The unit of apparent power in
an a.c. circuit containing reactance. It
is equal to the voltage in volts multiplied
by the current in amperes, without regard
for phase. True power is always less
than apparent power.
voltmeter-A meter used to measure electrical pressure or voltage in volts.
volt-ohm-milliammeter-See multimeter.
volume-The intensity or loudness of the
sound produced by a radio loudspeaker.
volume compression-Limitation of volume
range so over-modulation will not take
volume control-A device which varies the
a.f. output of a receiver or p.a. amplifier,
thereby changing the volume of the sound
produced by the loudspeaker.
volume expander-A special manually -adjusted audio circuit which can be set to
increase the volume range of a radio program or phonograph record by making
the loud portions of the program louder,
thereby counteracting volume compression
at the transmitter. Volume expanders
are also made as self-contained, self powered units which can be inserted between a phono pick-up and the input
terminals of an audio amplifier.
volume indicator-A meter which indicates
the volume level of sound, enabling the
monitor engineer to determine whether
the level is too high or too low.
volume unit-A unit used to specify the
number of db above a reference level of 1
milliwatt (.001 watt). When a level is
given in volume units (vu), there is no
need to specify the reference level since it
is implied in the definition of vu. A vu
is equal to a db when changes in power
are involved.
volume -unit indicator-An instrument calibrated to read a.f. power level in vu when
connected across a 600 -ohm line.
VT-Vacuum tube.
v.t.v.m.-Vacuum tube voltmeter.
vu-Volume unit.
W-Power in watts.
wafer socket--A type of socket in which the
clips for gripping the tube prongs are
w or
mounted between two wafers or sheets of
insulating material.
walkie-talkie-A small pack transmitter receiver which can be carried by one man,
used for portable communication work.
water-cooled tube-A transmitting tube
whose plate element is cooled by circulating water.
watt-The practical unit of electrical power.
In a d.c. circuit, the power in watts consumed by a device is equal to the applied
voltage multiplied by the current in
amperes. In an a.c. circuit, however, the
power value obtained in this manner must
also be multiplied by the power factor
of the part. The power factor is always
Courtesy General Electric
essentially 1 for a resistor.
THESE ARE TELEVIwattage rating-A rating expressing the WATER-COOLED TUBES.
maximum power which a device can
safely absorb or handle. To determine
how high a wattage rating is required for
arbitrarily chosen wave -lengths, includa particular resistor, multiply the value
ing waves of all lengths between the lowin ohms of the resistor by the square of
est and highest chosen.
the current which is to flow through the
resistor (resistance X current X current), wave band switch-A switch used in a
and choose a resistor having a wattage
transmitter or receiver to change from
rating approximately twice the computed
one wave band to another.
value so as to give ample margin of
wave duct-A tubular conductor capable of
safety in operation.
concentrating the propagation of radio
watt-hour-Unit of electrical energy. One
waves within its boundaries.
watt expended for 1 hour equals 1 wattwave form-The shape of a wave as shown
pictorially or graphically, usually with
wattmeter-A meter used to measure the
reference to changes in voltage or curpower in watts or kilowatts which is
being consumed by a device, chiefly in
front-A surface composed, at any
a.c. circuits.
instant, of all points just reached by a
wave-A vibration in an elastic medium,
travelling radio wave.
such as sound waves in air or radio waves
guide-A tubular conductor through
in space.
which ultra -high -frequency electromagnetic waves will pass without the use of
a return conductor. More generally, any
system of material boundaries which is
capable of guiding radio waves.
wavelength-The distance travelled in a
time of one cycle by an alternating curWAFER SOCKET
rent, sound wave or radio wave. This is
the same as the distance between successive peaks having the same 'polarity in
wave angle-The angle at which a radio
the wave. For wave motion in ether, the
«-ave leaves a transmitting antenna or
wavelength in meters is equal to the numarrives at a receiving antenna. The two
ber 299,820,000 divided by the frequency
angles needed to specify the direction of
in cycles per second.
a radio wave are the azimuth angle (corresponding to a direction above the sur- wavemeter-A device arranged and calibrated to measure or indicate the length
face of the earth) and the deviation angle
of a radiated wave directly in meters.
with respect to the surface of the earth.
(Also known as frequency meter.)
wave antenna-An antenna approximately
one wavelength long at the operating fre- wave trap-A device sometimes connected
to the aerial system of a radio receiver
quency. It has definite directional charto reduce the strength of signals at a paracteristics.
ticular frequency, such as at the frewave band-A band of frequencies, such as
quency of a strong local station which is
that assigned to a particular type of cominterfering with reception of other stamunication service. Waves between two
weak coupling-Loose coupling.
wet electrolytic condenser-An electrolytic
condenser which uses a liquid electrolyte.
Wheatstone bridge-An instrument invented
by Sir Charles Wheatstone, English physi-
cist, and used for accurate resistance, inductance or capacity measurements. It
is called a bridge because the balance between the known and unknown values
is indicated by the absence of current in
a wire. which forms a bridge or path between opposite junctions of the circuit.
wide-angle lens-A lens having a short focal
length, so as to give a wide field of view.
wind charger-A generator driven by a propeller mounted on or geared to its shaft.
The unit must be mounted in a location
where wind velocity is sufficient to rotate
the propeller ; this means it should be on
a mast or tower extending well above
surrounding trees and buildings. The
generator is usually of the d.c. type, and
is used for charging a radio storage battery or the batteries of a 32 -volt farm
lighting plant.
winding-One or more turns of wire which
make up a continuous coil. Used chiefly
in coils, transformers and electromagnetic devices.
wire-A metallic conductor having essentially uniform thickness, used in radio
chiefly to provide a path for electric currents between two points. It may be
bare or covered with an insulating material such as enamel, cotton, linen, or silk.
wired radio-Communication by means of a
radio carrier signal travelling through
wires instead of through space.
wire gauge-A system of numbers used to
designate wire sizes (diameters) . The
American Wire Gauge or A.W.G. (formerly Brown and Sharpe or B. & S. Gauge)
is in common use in this country, and has
numbers ranging from 0000 as the largest
size to 40 and beyond for the smallest
player-A motor-driven
wire -wound resistor-A resistor which is
constructed by winding a high-resistance
wire on an insulating form. The resulting element may or may not be
covered with a ceramic insulating layer.
wobbulator-A device used with a signal
generator to vary the frequency between
two values periodically.
woof-A word -sound used by engineers to
check "peaks."
woofer-A loudspeaker designed particularly for the reproduction of low audio
frequencies at fairly high power levels.
work-The product of the force acting on a
body and the distance through which the
body is moved. Thus, lifting a 5 -lb.
loudspeaker a distance of 3 feet is equivalent to 15 ft. -lb. of work.
working voltage-The highest voltage which
can be applied continuously to a condenser
without causing a break-down of the
wow-A flutter of low frequency, perceptible
to the ear as a change in pitch during
reproduction of a recording.
X-A letter
used in formulas to designate
reactance or to designate an unknown
X axis-A reference axis in a quartz crystal.
Also the horizontal axis of a graph.
Xc-Capacitive reactance in ohms.
x-cut-A piezoelectric crystal or quartz
plate cut in such a manner that the X axis
is perpendicular to its faces. Sometimes
called a Curie cut.
Xr.-Inductive reactance in ohms.
x-rays-Rays which have frequencies between the higher ultra-violet frequencies
and the lower gamma rays. They are
produced by the striking of cathode rays
on a solid and are capable of penetrating
opaque objects.
xtal-Abbreviation for quartz crystal.
turntable and phono pickup mounted in
the same cabinet with an r.f. oscillator.
The phono pickup converts a recording
into a.f. signals which modulate the r.f.
carrier of the oscillator. The resulting
signal is radiated through space, as a
miniature broadcast signal, and can be
picked up by any radio receiver in the
same house merely by tuning that receiver
to the broadcast band frequency on which
the wireless record player is operating.
wirephoto-A process of transmitting facsimiles of pictures over telephone wires
by converting into and reconverting from
electrical signals.
y-Symbol used for the admittance in mhos.
y-axis-In a quartz crystal, a line perpendicular to the two diametrically opposite
parallel faces. It lies in a plane which
is at right angles to the x-axis. Also, the
vertical axis of a graph.
Y circuit-A network of three resistors or
impedances arranged in the form of a Y
or star.
y-cut-A piezoelectric crystal cut in such
a manner that the y-axis is perpendicular
to its faces. Also sometimes called a faceparallel cut or 30° cut.
yoke-A coil placed around the neck of a
tube which produces magnetic deflection
of the electron beam in an iconoscope or
kinescope when energized by currents of
the proper voltage, phase and wave form.
e-Greek letter epsilon, used to represent
2.718, the base of the natural system of
6-Greek letter theta, frequently used to
Z-A letter
used in formulas to designate
impedance in ohms.
Z axis-The optical axis of a crystal. Perpendicular to the x and y axis.
Zeppelin antenna-An antenna which is onehalf wavelength long or a multiple
thereof, fed at one end by one lead of a
transmission line, at a voltage loop. The
total length of the two leads of the transmission line is a half wavelength long or
a multiple thereof.
zero-beat-A condition where two frequencies are exactly the same.
zero bias-Zero voltage between the control
grid and cathode of a vacuum tube, so
that these two electrodes are at the same
zero level-The reference level used when
specifying a level in decibels. Zero level
is 6 milliwatts in most radio work.
zone of silence-An area in which radio
signals cannot be received or sent.
represent phase angle.
X-Greek letter lambda, used to designate
wavelengths in meters.
µ--Greek letter mu, meaning micro, which
is "one millionth of."
µv/m-Microvolts per meter.
a-Greek letter pi, used to designate 3.1416,
which is the ratio of the circumference of
a circle to its diameter.
p-Greek letter rho, used to indicate specific
w-Greek letter omega, used to designate
2xf, which is 6.28 times the frequency in
w-Greek letter omega, used to designate
Sä-Greek letter omega (capital letter),
used to designate ohms or sometimes
(When No-ConnecCross Overs are
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