Hammarlund_SP-600-JX-21_user_TO31R2-4-101

Hammarlund_SP-600-JX-21_user_TO31R2-4-101
...---------------*---------------;;r
1.0. 31R2-4-10l-1
HANDBOOK
OPERATION INSTRUCTIONS
RADIO RECEIVER
MODEl SP·600·JX·21
(HAMMARLUND)
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PUBLISHED UNDER AUTHORITY OF THE SECRETARY OF THE AIR FORCE
_________________ *
---31
15 DECEMBER 1955(
Air Force OC, 15 Jul 65-500-Reprinr
CHANGED 1 AUGUST 1956-
T.O. 31R2-4-101-1
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1 August 1956
1 August 1956
1 August 1956
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A
Revised 1 August 1956
T.O. 31R2-4-101-1
Table of Contents
TABLE OF CONTENTS
Section
Page
I
1
II
III
IV
DESCRIPTION
1-1.
General
1
1-3.
Purpose of Equipment
1
1-11.
Description of Equipment
1
1-26.
Operational Theory
1-31.
Capabilities and Limitations.
5
1-36.
Equipment Required for Phone or Slow-speed Telegraph
Reception .
6
.
4
PREPARATION FOR USE
7
2-1.
Uncrating
2-3.
Inspection
2-5.
Replacement of Defective Parts
7
2-8.
Setting Up the Receiver
7
2-12.
Installation
10
2-19.
Testing
13
..
7
..
7
14
OPERATION
14
3-1.
General
3-3.
Description of Controls
3-22.
Presentations and Readings
3-25.
Operating Procedures .
17
3-54.
De-energizing the Equipment
21
3-57.
Precautions To Be Observed
21
EMERGENCY OPERATION
14
..
.
16
..................
22
....
22
4-1.
General
4-3.
Antenna System
22
4-5.
Emergency Tube Replacement
22
Revised 1 August 1956
Section
T.O. 31R2-4-101-1
Figure J- 1. Radio Receiver, Model SP-600-JX-2 J
ii
T.O. 31R2-4-101-1
Section I
Paragraphs 1-1 to 1-15
SECTION I
DESCRIPTION
1-1. GENERAL.
1-2. This handbook contains operation instructions for
Radio Receiver, Mod!'.! SP-600-JX-21, (figure 1-1)
manufactured by the HRmmarlund Manufacturing Co.,
Ine., New York 1, N. Y.
1-3. PURPOSE OF EQUIPMENT.
1-4. The radio receiver is designed for enclosedstation, fixed or mobile use. It is adaptable to shipboard,
airborne, or field applications, and may be used in a
two-way operational activity. The radio receiver provides
for the reception of keyed, amplitude-modulated, and
frequency-shift carrier signals. The carrier signal intelligence may be slow-speed (manual) or high-speed
(automatic) telegraph, phone, teletype, facsimile, ete.
For Morse code and teletype operation, use is made of
cow and single-tone carrier signals. For teletype operation, two-tone and frequency-shift carrier signals may
also be used.
1-5. To render the signal intelligence audible and/or
recordable, auxiliary components are required. When the
receiver is to be used for the reception of phone or
slow-speed telegraph signals, a headset and/or loudspeaker are used; in other modes of operation, these
components are used to monitor the signal. To receive
high-speed telegraph signals, a recorder driving unit and
lor a tape ink recorder are required. For frequencyshift teletype reception, use is made of suitable frequencyshift converter equipment associated with a teletypewriter.
1-6. The output of the receiver, for signals other than
phone, may be developed in the form of doc output to
denote a dot (mark) and no doc output to denote a dash
(space), the signal intelligence being contained in the
succession of dots and dashes. Alternately, it may be
developed in the form of a-c output wherein, for the interval of each dot (mark), or for the interval of each
dot (mark) and each dash (space), keyed-tone signals
result. The signal in the form of doc output is suitable
to operate applicable recording equipment such as a tape
ink recorder, a line relay, or a tone generator. The signal
in the form of a-c output provides the audible output of
the system; or it is used to operate a recorder driving
unit associated with the tape ink recorder, or to provide
input to a suitable frequency-shift converter associated
with a teletypewriter.
1-7. The tone generator keyed output may be used
to provide the signal to the headset and/or loudspeaker
monitor. It may also be fed to a transmission line to provide the signal at the remote end of the line. The keyedtone used is in the voice frequency range, each signal
requiring a frequency band of 170 cycles, and the line
may be used for several such tone signals, as well as for
phone signals.
1-8. The radio receiver provides for continuously variable reception within the frequency range of 0.54 mc to
54.0 mc, and for crystal-controlled fixed-frequency reception within the frequency range of 0.75 mc to 54.0
me. The receiver uses single heterodyne conversion for
its three lower frequency bands and double heterodyne
conversion for its three higher bands (above 7.4 mc).
The receiver signal-to-noise ratio and sensitivity characteristics provide for the reception of extremely weak
signals and the receiver is well suited for the reception
of short-wave signals which are inherently subject to
nonselective and selective fading.
1-9. The radio receiver has an internal beat-frequency
oscillator used in heterodyne detection of keyed-carrier
signals to provide audio signal intelligence to the headset and/or loudspeaker monitor.
1-10. The radio receiver has a self-contained power supply designed to operate from a 50-cps to 60-cps, singlephase a-c source within the voltage range of 90 to 270
volts. The receiver power consumption is 130 watts.
The power transformer primary and secondary are separately fused. The 1.6-ampere slow-blow primary fuse,
and the o/g-ampere high-voltage secondary fuse are contained in cartridge-type fuseholders located on the rear
apron of the receiver.
1-11. DESCRIPTION OF EQUIPMENT.
1-12. GENERAL. The radio receiver is a 20-tube radiocommunications type designed for direct mounting in
a standard 19-inch relay rack. It comprises a chassis and
light grey front-panel assembly to which are mounted a
top cover and a bottom plate.
1-13. RECEIVER CONNECTOR USES. With the exception of the headset "PHONES" jack (20, figure 3-1),
located on the front panel, and the "ANT" input connector (8, figure 2-1), all receiver connectors and terminals are located on the rear apron. The a-c power cable
of the receiver is also located on the rear apron.
1-14. The re-::eiver input circuit is designed to accommodate a balanced doublet or straight-wire antenna. The
input impedance of the receiver is designed to match
a 95-ohm transmission line. Other suitable antenna installations specifically designed for the desired operating
frequency may also be used. The antenna is connected to
the receiver "ANT" input connector (8, figure 2-1)
with type RG-22/U cable.
1-15. The "IF OUTPUT" connector (6, figure 2-2)
provides a received signal (usually frequency-shift) at
the receiver i-f output for frequency-shift converter use,
usually as part of a space-diversity receiving system. The
i-f output circuit in the receiver is isolated from the
b-f-o circuits, therefore b-f-o injection voltage is not
available at the "IF OUTPUT" connector.
1
Section I
Paragraphs 1-16 to 1-23
T.O. 31R2-4-101-1
1-16. The reveiver "AUDIO OUTPUT" terminals (8,
figure 2-2) are suited for a 600-ohm loudspeaker or
transmission line. The receiver a-c signal output (phone,
single-tone telegraph or teletype, or two-tone teletype)
is available at the "AUDIO OUTPUT" terminals. To
render high-speed telegraph and single-tone or twotone signals intelligible, the tape ink recorder used for
high-speed telegraph and the teletypewriter used for
teletype reception are associated with demodulator equipment connected to the receiver by suitable transmission
line. When a local teletypewriter is used to operate
another teletypewriter remotely or locally connected to
the transmission line, the send teletypewriter relay is
connected to the jumpered "AUDIO OUTPUT" terminals so that the line current on "mark" balances out
between the balanced split output transformer windings
of the receiver, for which the jumpered connection provides a mid-point tap. This use of the line may be
simultaneous to its other uses.
1-17. The receiver "DIODE OUTPUT" terminals
(2, figure 2-2) and the "AVC" terminals (3)
are used to interconnect two receivers in a spacediversity receiving system. The "AVC" terminal designated "G" is grounded for each receiver to a common
ground while that designated "-" is interconnected
between receivers. This is done to provide common avc
between receivers for space-diversity reception of an
amplitude-modulated or frequency-shift signal. With
this arrangement, the avc due to the stronger signal received on one receiver decreases the weaker signal and
the noise output of the other. To provide for spacediversity reception of phone, the audio output from only
one receiver is used. To do this, the jumpered "DIODE
OUTPUT" terminals are opened on one receiver and
the "-" terminal connected to the other receiver, which
provides the output. To provide for space-diversity reception of cw to a tone keyer (generator) or tape ink
recorder, the receiver interconnections are as outlined
for phone, but no avc and no bfo are used. This is the
case when the doc output from the three interconnected
"DIODE OUTPUT" terminals is used. When the a-c
output is used, the diversity demodulator, associated
with the tape ink recorder, is provided with the a-c
output from the "AUDIO OUTPUT" terminals (8) of
each receiver. To provide for the space-diversity reception of frequency-shift carrier signals, the i-f output
or the audio output from each receiver may be used to
provide input to suitable frequency-shift converter equipment.
1-18. The "AC" power receptacle (12, figure 2-2) on
the rear apron of the receiver may be used for operating
an accessory, such as an electric clock or lamp. Power is
available at the receptacle whenever the receiver is connected to a power source, regardless of the settings of the
receiver controls.
1-19. RECEIVER OPERATION. All operational activities require that the receiver switches and controls be
set properly for the mode of operation contemplated.
These controls are all located on the front panel of the
2
receiver, with the exception of the "METER AD] RF"
control (5, figure 2-2) and the "METER AD] AF"
control (7) used to calibrate the tuning meter (1, figure
3-1) on the front panel, and the "BFO IN]" adjustment
control (4, figure 2-2), all three of which are located
on the rear apron of the receiver. These controls are
factory adjusted, and are not to be moved from their
adjustment positions.
"
1-20. The radio receiver is adaptable to a two-way operational activity through use of the "SEND/REC" switch
(21, figure 3-1). With the receiver "RF GAIN" control
(11) turned clockwise from its "OFF" position, when
the a-c source is connected to the receiver, a-c power is
applied for either position of the "SEND/REC" switch.
When the switch is in its "SEND" position, the receiver
is disabled for protection in the presence of a strong local
carrier such as that produced by local tranmission during
a two-way communication activity. When the switch is
in its "REC" position, the receiver provides for instant
reception.
1-21. When the radio receiver "FREQ CONTROL"
; 8, figure 3-1) is set to the "VFO" positlOn, the "TUNING" control (15) provides continuously
variable tuning of any desired carrier within the frequency band selected by the "BAND CHANGE" switch
(17). When the "FREQ CONTROL" selector switch is
s~t to one of the "XTALS" positions, the receiver provides for fixed-frequency crystal-controlled reception of
any signal within the frequency range of 0.75 mc to 54.0
mc, provided that the proper crystal has been inserted
into the numbered crystal socket corresponding to the
selected switch position. The "BAND CHANGE" switch
functions as before, and the "TUNING" control is
used to adjust the r-f amplifier circuits to the operating
frequency. Exact tuning of the crystal-controlled first
heterodyne oscillator is provided by the "6. FREQ"
control (7). The "TUNING LOCK" (14), when turned
clockwise, provides optional locking means for the vernier dial (6), the main tuning dial (4), and the tuning
mechanism, to prevent accidental detuning of the receiver due to vibration or accidental shift of the controls. The "TUNING" control itself remains free to
turn even when the "TUNING LOCK" is locked.
1-22. The receiver "SELECTIVITY" switch (22, figure 3-1) provides a choice of six degrees of bandwidth
or selectivity. The switch position chosen is that which
provides optimum receiver performance for the existing
quality of the received signal. When the switch is in one
of its "XTAL" positions, the "XTAL PHASING" control (23) is used to highly attenuate any interfering
signal, even when it is closely adjacent to the desired
signal. The receiver "LIMITER/OFF" switch (19) in its
"LIMITER" position provides for effectively reducing
ignition noise and other pulse-type noise from the receiver audio output.
1-23. The receiver "MOD/CW" switch (13, figure
3-1) in its "CW" position renders the bfo operative. The
"BEAT OSC." control (10) provides the means of adjusting the tone output within a frequency range of ±3
s~lector switch
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figure i -2. Radio Receiver, Simplified Block Diagram
~
Section I
T.O. 31R2-4-101-1
Paragraphs 1-24 to 1-29
kc. The "BEAT OSc." control may be turned in either
direction on scale to provide the 3-kc range for the received cow signal. When the "MOD/CW" switch is in
the "MOD" position, the receiver provides for the reception of amplitude-modulated signals. When the receiver
is to be used for the reception of a frequency-shift signal, the "MOD/CW" switch position is dependent upon
whether the receiver i-f output or the receiver a-f output
is to be furnished to the associated frequency-shift converter equipment. When the receiver i-f output is used,
the use of the bfo provides optional receiver output for
monitoring purposes. When the receiver a-f output is
used, the bfo must be in operation. When the receiver
is to provide suppressed-carrier (single or double sideband) reception, the bfo is used to reinsert the carrier
at the receiver. For this application, the "BEAT OSc."
control is set to a position providing a bfo frequency of
455 ke.
1-24. The receiver "RF GAIN" control (11, figure
3-1) is adjustable to compensate for wide variations
encountered in the level of any carrier received. To
maintain the receiver a-f output constant within narrow
limits for the "RF GAIN" control setting chosen, the
receiver incorporates automatic volume control. The receiver "AYC/MAN" switch (12), when set to the
"AYC" position, provides this action. Provisions are included in the receiver for a-v-c operation even during
the reception of slow-speed telegraph signals. The
"RF GAIN" control is effective in either position of
the "AYC/MAN" switch.
1-25. The receiver tuning meter (1, figure 3-1) provides a tuning indication for the desired signal, when
the "AYC/MAN" switch (12) is set to the "AYC"
position. When the "RF GAIN" control (11) is set
to its maximum clockwise setting, the meter top scale
indication is the ratio of the received signal level to a
signal of one microvolt, expressed in db. When the
"METER" switch (18) is held in its depressed "AF"
position, the meter bottom scale indication is the ratio
of the receiver audio output to the standard reference
output of six milliwatts, expressed in db.
1-26. OPERATiONAL THEORY.
1-27. GENERAL. An analysis of the operation of the
radio receiver is best evolved by considering the signal
path through the receiver r-f, i-f, and a-f sections, into
which the receiver may be considered theoretically subdivided. The self-contained power supply of the receiver
is considered separately. The simplified block diagram
(figure 1-2) indicates in block form the relationship
between the various sections of the receiver.
1-28. R-F SECTION. The r-f section of the receiver provides selective circuitry for any selected signal within the
receiver frequency range of 0.54 to 54.0 me. It does this
through the use of six sets of r-f tuner subassemblies
housed in a rotary turret assembly. Each set is used for
one frequency band of the receiver and comprises an antenna r-f tuner, two identical interstage r-f tuners, and an
oscillator r-f tuner. The "BAND CHANGE" switch (17,
figure 3-1) provides for indenting the rotary turret as4
sembly so that the r-f tuner subassemblies for a particular
frequency band become part of the r-f section of the receiver. The antenna and two-stage r-f gain provided to
the signal assures that the signal-plus-noise to noise ratio
developed in the r-f section· is high enough so that even
very weak signals provide useful receiver output. The
r-f section preselection assures that the gain available to
the signal is greatly in excess of that provided any undesired signal. Since the receiver utilizes the principles of
superheterodyne reception, a signal removed from the desired signal by twice the 455-kc intermediate frequency
also provides an i-f signal acceptable to the i-f section of
the receiver. This image frequency, like any other undesired signal, is greatly attenuated. However, for signals
tuned in on the three higher frequency bands of the receiver, the image frequency for an intermediate frequency of 455 kc would be too close to the desired
signal. To maintain high image-rejection ratios, the receiver provides for double superheterodyne reception on
these bands. On the three lower frequency bands (below
7.4 me), the signal tuned in is heterodyned to a 455-kc
i-f signal. On the three higher frequency bands, it is
first heterodyned to a 3955-kc i-f signal, which is then
heterodyned to a 455-kc i-f signal. With the receiver
"FREQ CONTROL" selector switch (8) in its "YFO"
position, the receiver provides for continuously variable
tuning. When the switch is in one of its "XTALS" positions, the receiver first heterodyne variable oscillator is
replaced by a fixed-frequency crystal-controlled heterodyne oscillator. Doing this results in receiver frequency
stability superior to that attainable for variablefrequency tuning. Its use pre-establishes the communication channel, even when receiving conditions are poor,
without necessitating a time-consuming search by the
operator.
1-29. I-F SECTION. The i-f section of the receiver incorporates the 455-kc i-f amplifier wherein practically
all of the overall gain and selectivity of the receiver is
developed. Also, it incorporates the single-double conversion switch, which assumes its single or double conversion position dependent on whether the rotary turret
is indented respectively for one of its three lower or
three higher frequency bands. For signals tuned in on
one of the three lower frequency bands, the signal has
access to the 455-kc i-f amplifier through a 455-kc i-f
gate. For this condition the switch renders the doubleconversion i-f channel inoperative. For signals tuned in
on one of the three higher frequency bands, the signal
reaches the 455-kc i-f amplifier through the 3955-kc i-f
double-conversion channel. For this cOJ;ldition the switch
renders the 455-kc i-f gate inoperative. The six choices
of receiver selectivity provided by the "SELECTIYITY"
switch (22, figure 3-1) are developed in the 455-kc i-f
channel of the receiver. At the input to the 455-kc i-f
amplifier is the 455-kc i-f crystal-filter circuit incorporated in the receiver. The use of the crystal filter enables
the receiver to attain the three degrees of sharp "XTAL"
selectivity. The precise antibacklash gear-train tuning
mechanism provides for completely accurate resetability
and calibration accuracy of the receiver so that maximum
T.O. 31R2-4-101-1
benefit can be derived from the sharp, crystal passbands
of the 455-kc i-f crystal filter. The "XTAL PHASING"
control (23) is part of the crystal filter. The 455 -+- 3-kc
bfo and associated "BEAT OSc." control (10) and the
"IF OUTPUT" connector (6, figure 2-2) are associated with the 455-kc i-f channel of the receiver.
1-30. A-F SECTION AND POWER SUPPLY. The a-f
section of the receiver incorporates an a-f amplifier to
develop the a-f power output of the receiver. The
"AUDIO GAIN" control (16, figure 3-1) is used to
control the receiver output to the "AUDIO OUTPUT"
terminals (8, figure 2-2) and that to the "PHONES"
jack (20, figure 3-1). The self-contained power supply
develops all the a-c and the doc supply voltages used by
rhe receiver. The critical doc supply voltages are regulated to maintain constant the sensitivity and frequency
stability. The "RF GAIN" control (11) is part of the
power-supply bias rectifier. Its chosen setting, in conjunction with the a-v-c system of the receiver, when
used, determines the gain developed in the r-f and i-f
sections of the receiver.
1-31. CAPABILITIES AND LIMITATIONS.
1-32. GENERAL. The radio receiver provides optimum
receiver performance when properly installed and operated. The antenna input connector provides for connection to a balanced doublet or single-wire antenna system. The 95-ohm cable used provides flexibility as to the
relative locations of the receiver and the antenna system.
In use, the receiver may be subjected to temperatures
within the range of O°C (32°F) to 60°C (140°F), at
relative humidities as high as 95 percent. After a 15minute warmup period, the frequency stability ranges
from 0.001 percent to 0.01 percent of the signal frequency. The receiver incorporates advanced design and
shielding to reduce radiation characteristics to a minimum. This enables the receiver to maintain performance
in multi-receiver installations and to comply with shipboard regulations. The receiver embodies the necessary
chassis rigidity to withstand severe vibration and shock.
It is adequately treated with fungicidal varnish to condition it for tropical use.
1-33. PRESELECTION. The image frequency of any
signal tuned in on the receiver is attenuated to the extent that if the desired signal strength were one microvolt, the strength of the image frequency signal would
have to be at least 4000 microvolts (at 7.4 mc) to develop the same receiver output. At other signal frequencies the strength of the image frequency signal
would have to be greater. Also, if the receiver is tuned
to 600 kc, a 455-kc signal input to the receiver will have
to be 2700 microvolts to produce the same effect as a onemicrovolt signal at 600 kc. For frequencies other than
600 kc, this 455-kc i-f rejection ratio of the receiver is
better. Likewise, the 3955-kc i-f rejection ratio of the
receiver is 'it least 50,000 for any signal frequency on
bands 4, 5, or 6, the frequency bands for which the 3955kc i-f channel of the receiver is operative.
1-34. -SENSITIVITY. The receiver threshold sensitivity
(minimum signal input to develop its rated a-f output) is
Section I
Paragraphs 1-30 to 1-35
two microvolts for an A-M signal, and 0.75 microvolt for
a cow signal, or better. The undistorted power output of
the receiver at threshold sensitivity is two watts or better.
This a-f output is provided at a signal-plus-noise to
noise power ratio of ten to one. This provides for
optimum receiver performance in the presence of a weak
signal tuned in, since the background noise caused by
the first electron tube and the antenna r-f tuner does
not interfere with reception. The receiver sensitivity may
be reduced in the presence of a strong signal by turning
the "RF GAIN" control (11, figure 3-1) counterclockwise from its maximum clockwise position. This is done
to prevenr overloading of the r-f and i-f sections of the
receiver. The receiver a-f output may be decreased by
turning the "AUDIO GAIN" control (16) counterclockwise. This is done to prevent overloading of the a-f
section of the receiver and to provide for comfortable
reception at the desired a-f output level. When the receiver a-v-c system is operative and the "RF GAIN"
control is set to its maximum clockwise setting, the receiver output remains constant within a one-to-four voltage ratio when the input is increased from 2 to 200,000
microvolts. The use of ave precludes excessive audio out·
put when tuning through a carrier signal relatively
strong compared to the setting of the "AUDIO GAIN"
control, and compensates for the possible fading characteristics of the signal over long or short intervals of
time.
1-35. SELECTIVITY. The bandwidth, or selectivity,
of the receiver is adjustable to provide for the reception
of a signal under varying conditions of propagation.
Since noise, regardless of its origin, is of the pulse type
and comprises all frequencies, the noise level in the
audio output of the receiver depends upon the overall
selectivity of the receiver. The "BROAD" settings of the
"SELECTIVITY" switch (22, figure 3-1) produce more
noise output than the "SHARP" settings. In the presence
of noise, it is advantageous to restrict the overall receiver bandwidth to the narrowest possible, consistent
with intelligible reception. However, the bandwidth requirements vary with the type of signal being received.
For phone reception, the i-f channel bandpass requirements are 455 kc ± 2500 cps. This is also the requirement for single-tone telegraph reception. For keyed c-w
operation such as slow-speed telegraph, teletype (60
words per minute), and high-speed telegraph (400 words
per minute), the requirements are 455 kc -1- 50 cps, 455
kc ± 75 cps, and 455 kc -+- 600 cps, respectively. When
two tones, one for "mark" and another for "space", or
two channels are used, the bandwidth requirements are
doubled. The bandwidth requirements also depend upon
the frequency stability of the received signal and the
frequency stability of the receiver itself. For reception
of a cow signal, a narrow bandwidth can be used. To
provide for reception of phone signals, the bandwidth
may be reduced to reduce noise output; however, the
use of a narrower bandwidth results in loss of the
higher-frequency audio components in the received signal and may impair the intelligibility of reception. To
provide for reception of telegraph or teletype signals,
5
T.O. 31R2-4-101-1
Section I
Paragraphs 1-36 to 1-37
full advantage should be taken of the "SELECTIVITY"
switch positions to reduce interfering noise. The "SELECTIVITY" switch provides a choice of six degrees of
overall bandwidth. The sharp, crystal-derived bandwidths are 0.2 kc, 0.5 kc, and 1.3 kc. The broad, noncrystal bandwidths are 3.0 kc, 8.0 kc, and 13.0 kc.
1-36. EQUIPMENT REQUIRED FOR PHONE OR
SLOW-SPEED TELEGRAPH RECEPTION.
1-37. The tabulation of the complete equipment required for reception of phone or slow-speed telegraph
signals is subdivided into two tables. The equipment
supplied and covered by this publication is listed in
table I. The components and auxiliary equipment of the
receiving system, required but not supplied, are listed
in table II.
TABLE I. EQUIPMENT SUPPLIED
Quantity
6
Name
TABLE II. COMPONENTS AND AUXILIARY
EQUIPMENT REQUIRED BUT NOT SUPPLIED
Quantity
*AR
Radio Receiver, Model
SP-600-JX-21
1
Plug, antenna connector
UG-102/U
1
Adapter, angle plug
UG-104/U
1
Plug, i-f output connector
PL-259
Government
Designation
Crystal, Specification
MIL-C-3098
CR-18/U
1
Headset
Navy Type
-49507
1
Cord, headset
Navy Type
-49534
1
Loudspeaker
LS-3
AR
Cable, lead-in
RG-22/U
1
Antenna system, balanced doublet or
single wire
1
Source, a-c, singlephase, 90 to 270V,
50 to 60 cps, 130
watts
Government
Designation
1
Name
*One crystal required for each operational signal frequency.
Section II
T.O. 31R2-4-101-1
Paragraphs 2-1 to 2-9
SECTION II
PREPARATION FOR USE
2-1. UNCRATING.
2-2. Carefully remove "the receiver from its shipping
container, using the following procedure:
a. Remove the two steel straps from the wooden case.
b. Remove the cover nailed to the case.
c. Remove the excelsior from around the cartoned receIver.
d. Remove the cartoned receiver from the case.
e. Remove the waterproof tape from the folds of the
waterproof paper wrapped around the cartoned receiver,
and remove the waterproof paper wrapper.
f. Open the carton and remove the inner carton containing the receiver.
g. Remove the vapor-proof bag from around the inner
carton.
h. Unflatten the corners of the inner carton, open it,
and remove the silica gel.
i. Remove the wood frame from the carton, and the
corrugated interiors comprising two side pieces, one
front, one back, and one top, each accordion folded.
j. Remove the receiver and set it out of the way in a
convenient place near its final location.
k. Put all packing material in the wooden case and
store.
b. To remove electron tube V4, loosen the knurled
screw holding the tube shield. Then turn the tube shield
counterclockwise, while exerting inward pressure, and
remove the tube shield. The tube is of the pin type and
is removed preferably with a suitable tube remover.
c. To remove any electron tube other than V4 V17
or V19, first remove the tube shield by twisting c~unter~
clockwise while exerting inward pressure. All tubes except V17 and V19 are of the pin type, and are preferably
removed with an appropriate tube remover.
2-7. FUSES. To remove either the 1.6-ampere fuse or
the o/s-ampere fuse, located respectively in the "LINE"
fuseholder (11, figure 2-2) and the "-B" fuseholder
( 1) on the rear apron of the receiver, press in the top
of the fuseholder while turning it approximately 45 degrees in a counterclockwise direction. Removing the
pressure in this position will release the fuse which is
spring-clamped to the top of the fuseholder. The fuse
and the top of the fuseholder may now be pulled apart.
To replace either fuse, follow the reverse procedure.
Be certain to use fuses having the ratings specified above. Use of any other fuses may result
in damage to the receiver.
2-3. INSPECTION.
2-4. When the receiver has been removed from its
shipping container, carefully inspect it for any signs of
damage that may have occurred in shipment. Inspect the
front panel controls, the tuning dial windows, and the
meter for any defects. Inspect the tubes to make sure
that they are firmly seated in their sockets and that
none are broken. Inspect the fuses in the fuseholders on
the rear apron of the receiver to make certain that fuses
of the proper ratings are inserted in the fuseholders.
2-5. REPLACEMENT OF DEFECTIVE PARTS.
2-6. ELECTRON TUBES. If defective electron tubes are
discovered during inspection, replacement must be made
before operation is attempted. To replace defective electron tubes use the following procedure. (See figure
2-1.)
a. To remove electron tubes V17 and V19, the tophat-type tube clamp must first be removed. To remove
the clamp, press inward on the spring, while lifting the
clamp off the tube. Remove the tube by drawing it out
from its tube socket. Replace the top-hat clamp by seating it on the top of the tube so that the vertical bolt
ad jacent to it can be threaded through the hole in the
spring, with pressure providing a ratchet motion until
the clamp is firmly seated in place.
2-8. SETTING UP THE RECEIVER.
2-9. POWER TRANSFORMER CONNECTIONS.
When shipped, the power transformer primary tap of
the receiver is connected to operate from a 50- to 60-cps,
117-volt, a-c source. If the receiver is to be operated
from other than a 117-volt source, change the primary
tap. connection. Table III shows the a-c source voltage
ratIng of each of the primary tap terminals, which are
TABLE III. POWER TRANSFORMER
TAP VOLTAGE RATINGS
Tap No.
2
3
4
5
6
7
8
9
Voltage Rating
95
105
117
130
190
210
234
260
7
T.O.
Section II
3
31R~-4·101-1
7
5
4
8
27--26
10
25
II
24
23 ------or....
15
22
1.
2.
3.
4.
5.
6.
7.
8.
9.
Electron tube V 12
Electron tube V16
Electron tube V 15
Electron tube V17
Electron tube V19
Electron tube V20
"GND" terminal
"ANT" input connector
Electron tube V 1
21
20
10.
11.
12.
13.
14.
15.
16.
17.
18.
19
18
Electron tube V3
Electron tube V2
Knurled thumbscrew
Retainer spring assembly
Crystal sockets
Electron tube V5
Electron tube V13
Pilot lamp
Metal buttons
17
16
19.
20.
21.
22.
23.
24.
25.
26.
27.
Figure 2-1. Radio Receiver, Top View of Chassis
8
Electron
Electron
Electron
Electron
Electron
Electron
Electron
Electron
Electron
tube
tube
tube
tube
tube
tube
tube
tube
tube
V4
V8
V7
V6
V9
VIO
V18
V14
Vll
T.O. 31R2-4-101-1
identified by numerical designation on the bottom of
the power transformer (13, figure 2-2).
Section II
Paragraphs 2-10 to 2-11
to the
12.045
can be
quency
signal frequency; for signal frequencies above
mc, on bands 4, 5, and 6, the crystal frequency
calculated by adding 3955 kc to the signal freand dividing the sum by three.
2-11. To mount the crystal units in the crystal sockets,
proceed as follows:
Choose the power transformer primary tap
whose voltage rating is closest to the available
a-c source voltage.
2-10. CRYSTAL SELECTION AND MOUNTING.
When fixed-frequency, crystal-controlled operation is to
be utilized, the proper type CR-18/U crystal(s)' must be
obtained and inserted into the crystal socket(s) (14, figure 2-1). When ordering a crystal, the crystal frequency
and the signal frequency should be specified. For bands
1, 2, and 3, the crystal frequency can be calculated by
adding 455 kc to the signal frequency; for band 4, in
the signal-frequency range of 7.4 mc to 12.045 mc, the
crystal frequency can be calculated by adding 3955 kc
a. Loosen the knurled thumbscrew (12) on top of the
frequency-control unit, and push the retainer spring assembly (13) to the rear.
b. Insert the crystals into the crystal sockets (14),
numbered 1 through 6, on the frequency-control unit.
e. Bripg the retainer spring assembly forward until
the springs are over the tops of the crystals in the
sockets, and tighten the knurled thumbscrew.
d. Using a pen or pencil, mark on the plastic chart
(9, figure 3-1) the signal frequencies for which the
crystals are intended.
2
3
13
4
~
12
II
L
2.
3.
4.
5.
6.
10
9
~'-
7
8
"-B" fuse
"DIODE OUTPUT" terminals
"AVC" terminals
"BFO IN}" control
"METER AD] RF" control
"IF OUTPUT" connector
7.
8.
9.
10.
1L
12.
e
'"
5
6
"METER AD] AF" control
"AUDIO OUTPUT" terminals
Power cord
"SPARE FUSES" cover
"LINE" fuse
"AC" power receptacle
13. Power transformer
Figure 2-2. Radio Receiver, Rear View
9
Section II
T.O. 31R2-4-101-1
Paragraphs 2-12 to 2-18
2-12. INSTALLATION.
2-13. MOUNTING. The receiver is designed for rack
mounting in a standard 19-inch rack. The receiver front
panel is 101/ 2 inches high. Mount the receiver in a position which permits the free access of air.
2-14. POWER. Make sure that the primary-tap lead
at the bottom of the power transformer is connected to
the tap which most nearly agrees with the 50-cps to 60cps power source voltage; refer to paragraph 2-9. Plug
the receiver into the power source using the receiver
power plug.
2-15. ANTENNA AND GROUND CONNECTIONS.
The antenna input circuit of the receiver is designed to
accommodate a balanced doublet or single-wire antenna
installation; however, other suitable antenna systems
specifically designed for the desired operating frequency
may be used. The input impedance of the receiver is
designed to match a 95-ohm transmission line. Connect the antenna to the "ANT" input connector (8, figure 2-1) using type RG-22/U cable, a type UG-104/U
angle plug adapter, and a type UG-102/TJ connector
plug. Figure 2-3 illustrates the antenna-cable fabrication procedure. If a single-wire antenna installation is
to be used, connect the antenna lead-in wire to one
terminal of the connector plug and a ground lead from
the other terminal of the connector plug to the receiver
"GND" terminal (7). In all installations, bond the receiver "GND" terminal to the installation ground, using a suitable bonding strap.
COUPLING RING
2-16. HEADSET. For monitoring purposes, plug a
headset into the "PHONES" jack (20, figure 3-1).
Either a high-impedance or a low-impedance headset may
be used; however, the high-impedance (8000-ohm) type
is recommended.
2-17. LOUDSPEAKER. Connect a permanent-magnet,
dynamic-type, loudspeaker w~.th a suitable 600-ohm
matching 'transformer across the "AUDIO OUTPUT"
terminals (8, figure 2-2). For applications requiring
the insertion of d-c control or indicating voltages, remove the jumper connecting the two balanced sections
of the 600-ohm output at the "AUDIO OUTPUT" terminals, and connect the insertion circuit in its place.
When the 600-ohm output is not used, connect
a 600-ohm, 2-watt resistor across the "AUDIO
OUTPUT" terminals to avoid component damage from high transient peak voltages.
2-18. RECEIVER INTERCONNECTIONS FOR
DIVER~ITY RECEPTION.
a. Receiver interconnections for space-diversity reception of phone signals are shown in figure 2-4. Connect
the "AVC" terminals (3, figure 2-2) designated "G"
on each receiver to a common ground and interconnec.t
the "AVC" terminals designated "-" on the two receivers. Open the jumpered "DIODE OUTPUT" terminals (2) on one of the receivers, and connect the
BACK SHELL
FRONT SHELL
Cut end of cable even.
Remove vinyl jacket 1-1/8 in.
Bare 5/8 in. of conductors.
Tin exposed conductors and braid.
Slide coupling ring on cable. Screw back shell on cable. Solder hole should align with conductors as shown.
Assemble front shell to back shell. Solder holes in both front
and back shells should align. Solder braid to shells through
solder holes. Solder conductors to contacts. Do not use excessive heat.
For final assembly; screw coupling ring on back shell.
Figure 2-3. Fabrication of Antenna Cable
10
Section II
T.O. 31R2-4-101-1
/" JUMPER
REMOVED
DIODE/OUTP~T
-
AVC
1-
+
G
AUDIO OUTPUT
o.------1:l
0
0
SP-600-JX-21
~
AVC
DIODE OUTPUT
v
-
-
+
G
AUDIO OUTPUT
a.---------o
SP-600-JX-21
TO LOUDSPEA KER
Figure 2-4. Receiver Interconnections for Phone Space-diversity Receiving System
jV JUMPER REMOVED
AVe
DIODE/OUT:UT
-
+
0
0
-
G
AUDIO OUTPUT
0
a...-----u
0
SP-600-JX-21
Ave
DIODE OUTPUT
---r.
-
SP-600-JX -21
II
0
-
+
AUDIO OUTPUT
a..-----o
AA/\
0
G
II
600 OHMS
2WATIS
-l-
TAPE INK
RECORDER
Figure 2-5. Receiver Interconnections for Space-diversity D-C Output Receiving System
11
Section 11
T.O. 31R2-4-101-1
AVC
DIODE OUTPUT
a---u
-
+
1-
G
AUDIO OUTPUT
0-
1·.
SP-600-JX-21
:~I
"""'"0
I •
•
I •• • • • • .t\I\I'v- • • •• :
,
I
I
600 OHMS
2 WATTS
I
IF
OUTPUT
[~} .....
•• FREQUENCY - SHIFT
CONVERTER
• 10·
I
I
I
I
I
I
I
r----------------~
I
~
r------------------------~
•
I
I
I
I
I
DIODE OUTPUT
I
0-
I
I
-
I
I
~.
I
I
I
-
G
0.------0
.~
I•
SP-600-JX-21
I
I
I
I
I
I
+
AUDIO OUTPUT
I
I
I
I
I
I
AVC
.."
I
• I
eo • • • • "/\/\/\,,. • • • •
600 OHMS
2 WATTS
I
I
I
I
I
I
I
I
I
I
IL
I
I
I
[~]
••
I
I
r------ J
0-
IF
OUTPUT
I
I
I
I
I
I
r--------------~
I
- - - - INDICATES CONNECTIONS FOR
I
A-F SIGNAL OUTPUT
I
........
I
I
I
I
IL
___
_____
------------L-- _ _ _ _ _ _ _ _ _ _ _ _ _ _
INDICATES CONNECTIONS COMMON
TO BOTH SYSTEMS
~
~
I NDICATES CONNECTIONS FOR
I-F SIGNAL OUTPUT
RADIO TELETYPE
TERMINAL
EQUIPMENT
-0
-0
Figure 2-6. Receiver Interconnections for Frequency-shift Space-diversity Receiving System
"DIODE OUTPUT" terminals designated "-" to the
like terminal of the second receiver. Connect the loudspeaker across the "AUDIO OUTPUT" terminals (8)
of the second receiver.
b. For space-diversity reception of cow signals, interconnect the two receivers as shown in figure 2-5. Open
the jumpered "DIODE OUTPUT" terminals of one of
12
the receivers, and connect the "DIODE OUTPUT" terminal designated "-" to the like terminal of the second
receiver. Connect the three interconnected "DIODE
OUTPUT" terminals to the associated recording equipment.
c. The interconnections required for space-diversity
reception of frequency-shift carrier signals are shown
in figure 2-6. Interconnect the "AVC" terminals of the
Section II
Paragraphs 2-19 to 2-20
T.O. 31R2-4-101-1
COUPLING RING
PLUG SUB-ASSEMBLY
Cut end of cable even.
Remove vinyl jacket 1-1/8 in.
Bare 5/8 in. of center conductor. Trim braided shield. Slide
coupling ring on cable. Tin exposed center conductor and
braid.
Screw the plug sub-assembly on cable. Solder assembly to
braid through solder holes. Use enough heat to create bond
of braid to shell. Solder center conductor to contact.
.
,--
-
- --
.,.
.
For final assembly, screw coupling ring on plug sub-assembly.
.-,
figure 2-7. fabrication of I-f Output Cable
two receivers as per step "a" of this paragraph. Keep
the jumpers across the "DIODE OUTPUT" terminals of
the receivers. Connect the frequency-shift converter
equipment to the "AUDIO OUTPUT" terminals of each
receiver if an audio signal is to be applied to the associated terminal equipment, or if a 45S-kc signal is to be
used, connect the "IF OUTPUT" connector (6, figure
2-2) of each receiver to the associated frequency-shift
converter equipment, using RG-ll/U cable and PL-259
plugs. For fabrication instructions applicable to the i-f
output cable, refer to figure 2-7.
2-19. TESTING.
2-20. When the equipment has been installed, check
the complete installation for proper operation. Turn the
receiver on by rotating the "RF GAIN" control (11, figure 3-1) in a clockwise direction from its "OFF" position and set the "SEND/REC" switch (21) to its "REC"
position. Allow the receiver to warm up for 15 minutes.
Then check the operation of the receiver in the various
possible modes of operation on each of the six bands,
following the operating procedures outlined under paragraph 3-25 as applicable.
13
Section III
Paragraphs 3-1 to 3-13
T.O. 31R2-4-101-1
SECTION III
OPERATION
3-1. GENERAL.
3-2. For optimum receiver performance, proper operating procedures must be observed. The complexity of the
operating procedures depends primarily upon the type
of signal to be received, and also upon the quality of the
communications link between transmitter and receiver.
The receiver is adjusted for its various modes of operation by means of the appropriate operating controls.
3-3. DESCRIPTION OF CONTROLS.
3-4. The contrpls used in normal receiver operation
are all located on the front panel and are shown 10
figure 3-1. All references to the controls conform to
the front panel designations.
3-5. POWER. A-c power is applied to the receiver circuits by rotating the "RF GAIN" control (11), clockwise from its "OFF" position. The power switch is an
integral part of the "RF GAIN" control assembly and
its actuation is indicated by an audible click and by the
illumination of the main tuning dial (4) and the vernier
dial (6).
CAUTION
Once power has been applied to the receiver,
do not switch it off momentarily and then back
on. The high initial filter-capacitor charging
current may cause the o/g-ampere fuse to fail.'
3-6. "SEND/REC". The "SEND/REC" switch (21) disables the r-f section of the receiver when actuated to the
"SEND" position. This position is used during transmission intervals in a two-way communication system to
prevent possible damage to the receiver from the strong
local transmission. When the switch is returned to its
"REC" position, normal receiver operation is restored.
3-7. "BAND CHANGE". The "BAND CHANGE"
switch (17) is used to select the frequency band which
includes the desired signal frequency. The selected band
is indicated at the "MEGACYCLES" window (5) and
the top of the main-dial movable pointer (2) is automatically positioned to indicate the main-tuning-dial
frequency band being used.
3-8. "TUNING". For variable-frequency operation,
the "TUNING" control (15) is used to tune the r-f
amplifier section of the receiver and the variablefrequency first heterodyne oscillator to provide for reception of the desired signal. In the fixed-frequency,
crystal-controlled mode of operation, a separate fixedfrequency, crystal-controlled first heterodyne oscillator
is used, and the "TUNING" control is used to tune
only the r-f circuits for acceptance of the desired signal.
The "TUNING" control drives the vernier dial (6),
14
visible through the window at the right side of the front
panel, and the main tuning dial (4) to indicate the frequency selected.
3-9. "TUNING LOCK". The "TUNING LOCK" (14),
when turned in a clockwise direction, clamps the vernier
dial (6), [he main tuning dial (4), and the tuning mechanism at the desired setting. The "TUNING" control
(15) remains free to turn. The "TUNING LOCK" prevents accidental detuning of the receiver due to severe
vibration or accidental shifting of the "TUNING" control.
3-10. "FREQ CONTROL". The "FREQ CONTROL"
selector switch (8) establishes the mode of operation of
the first heterodyne oscillator section of the receiver
and also, when set to its various "XTALS" positions,
establishes the oscillator frequency. When the "FREQ
CONTROL" selector switch is set to the "VFO" position, the variable-frequency first heterodyne oscillator is
selected, and its frequency is determined by the setting
of the "TUNING" control (15). When the "FREQ
CONTROL" selector switch is set to any of its six
"XTALS" positions, a separate fixed-frequency, crystalcontrolled first heterodyne oscillator is selected. The
frequency of the oscillator is determined by the frequency of the crystal inserted into the numbered crystal
socket corresponding to the selected switch position.
3-11. "6 FREQ". The "6 FREQ" control (7) is used
to tune the crystal selected by the "FREQ CONTROL"
selector switch (8) precisely to the proper frequency.
The calibration of the "/::,. FREQ" control is arbitrary;
however, advancing the control from the "HIGH" setting to the "LOW" setting decreases the frequency of
oscillation. The crystals employed have a frequency tolerance of 0.005 percent, and the "f:." FREQ" control
has adequate range to compensate for deviations in
crystal frequency within these limits.
3-12. "RF GAIN". The "RF GAIN" control (11),
when turned from its "OFF" position, is used to control
the gain of the r-f and i-f sections of the receiver. When
the control is turned to the "OFF" position, the a-c
power switch associated with the control removes power
from the receiver as described in paragraph 3-5. The
"RF GAIN" control functions in either position of the
"AVC/MAN" switch (12).
3-13. "AVC/MAN". The "AVC/MAN" switch (12)
establishes the type of gain control used in the r-f and i-f
sections of the receiver. When the switch is actuated to
the "MAN" position, the gain of the r-f and i-f sections
is established by the "RF GAIN" control (11) alone.
In the "AVC" position of the switch, a delayed a-v-c
system of control is selected. For any fixed setting of
the "AUDIO GAIN" control (16), the receiver output
T.O. 31R2-4-101-1
is maintained reasonably constant at a level predetermined by the "RF GAIN" control setting, provided
that the input signal level is sufficient to overcome the
delay voltage in the a-v-c system. A minimum carrier
level of two microvolts at the receiver antenna input
connector is required for normal a-v-c operatiqn.
3-14. "AUDIO GAIN". The "AUDIO GAIN" control
(16) is used to provide comfortable headset and/or
loudspeaker reception or to provide the means for adjusting the audio output to a level suitable for operating auxiliary equipment associated with the receiver.
3-15. "SELECTIVITY". The "SELECTIVITY" switch
(22) has six positions which establish receiver bandwidths of 0.2 kc, 0.5 kc, or 1.3 kc eXTAL"), or 3 kc,
8 kc, or 13 kc ("NON-XTAL"). A crystal filter incorporated in the i-f section of the receiver is utilized in the
three "XTAL" positions of the "SELECTIVITY" switch.
In the three "NON-XTAL" positions, the crystal filter
is shorted out. The three "XTAL" positions provide
2
3
narrow bandwidths useful in the rejection of adjacentchannel interference and are used under conditions of
extreme interference where quality or fidelity of the receiver output is secondary to continuity of service.
3-16. "XTAL PHASING". The "XTAL PHASING"
control (23) is part of the crystal filter referred to in
paragraph 3-15, and functions only when the "SELECTIVITY" switch (22) is set to one of its three
"XTAL" positions. When adjacent-channel interference
is encountered, the "XTAL PHASING" control is adjusted in conjunction with the "SELECTIVITY" switch
to provide attenuation of the interfering carrier.
3-17. "LIMITER/OFF". The "LIMITER/OFF" switch
(19) is used under conditions of ignition or similar
pulse-type noise interference. When the switch is set to
the "LIMITER" positions, the limiter circuit in the receiver is operational, and noise (and desired audio) is
removed from the receiver outpt·t for the. interval of
each noise pulse. The internal limiter circuit is disabled
by actuating the switch to its "OFF" position.
6
5
4
Section III
Paragraphs 3-14 to 3-17
8
7
C
9
\..iJ
•
23---.:--...;
10
(.;<
II
22-------;
21
20
19
Tuning meter
Movable pointer
Fixed pointer
Main tuning dial
"MEGACYCLES" window
o. Vernier dial
7. "I'::, FREQ" motrol
8. "FREQ CONTROL" selector switch
I.
2.
3.
4.
5.
18
17
9.
1o.
11.
12.
13.
14.
15.
16
Plastic chart
"BEAT OSc." control
"RF GAIN" control
"AVC/MAN" switch
"MOD/CW" switch
"TUNING LOCK"
"TUNING" control
16.
17.
18.
19.
20.
21.
22.
23.
"AUDIO GAIN" control
"BAND CHANGE" switch
"METER" switch
"LIMITER/OFF" switch
"PHONES" jack
"SEND/REC" switch
"SELECTIVITY" switch
"XTAL PHASING" control
Figure 3-1. Radio Receiver, Front Panel Controls and Indicators
15
Section III
T.O. 31R2-4-101-1
Paragraphs 3-18 to 3-24
3-18. "MOD/CW". The "MOD/CW" switch (13) is
used to control operation of the internal bfo of the receiver. For reception of amplitude-modulated signals,
the "MOD/CW" switch is set to its "MOD" position
and the bfo is disabled. When the switch is operated to
the "CW" position, plate voltage is applied to the bfo
through the switch, and b-f-o operation is restored to
provide for the reception of unmodulated signals. Additionally, a separate capacitor is switched into the a-v-c
circuit to increase the circuit time constant and permit
a-v-c operation during cow reception.
3-19. "BEAT OSc.". The "BEAT OSc." control (10)
is used to adjust the nominal 455-kc frequency of the
receiver bfo within the range of ± 3 kc, thus providing
a variable tone output during cow reception. The setting
of the control is optional, and is normally set to provide
the most intelligible reception. When set exactly to 455
kc, the control is useful for locating and tuning in weak
signals of any kind, as well as for carrier reinsertion at
the receiver when suppressed-carrier, single- or doublesideband signals are being received. For the reception
of frequency-shift radio teletype signals, the "BEAT
OSc." control is adjusted to provide the proper "mark"
and "space" frequencies for the associated teletype
equipment. The bfo is operative only when the
"MOD/CW" switch (13) is in the "CW" position.
.1-20. "METER". The "METER" switch (18) is used in
conjunction with the tuning meter (1) to obtain an indication of the r-f signal input to the receiver and the
a-f output to a connected load. With the "METER"
switch in the normal "RF" position, the "A VC/MAN"
switch (12) set to the "AVC" position, and the "RF
GAIN" control (11) set at maximum, the tuning meter
indication as read on the upper scale is the ratio of
the input signal level to a signal of one microvolt,
expressed in decibels. The meter "RF" indication also
provides a means for accurately tuning in an input signal. When the "METER" switch is held in its depressed
"AF" position, the lower scale of the tuning meter indicates in decibels the ratio of the receiver audio output to a standard reference of six milliwatts.
Always turn the "AUDIO GAIN" control
(16) fully counterclockwise and make certain
that the proper load is connected to the receiver before actuating the "METER" switch to
the "AF" position. Then, with the switch depressed, slowly advance the "AUDIO GAIN"
control to its proper setting. Failure to observe
this precaution may result in damage to the
tuning meter.
3-21. "PHONES". The "PHONES" jack (20) provides
the means for connecting a headset to the audio output
section of the receiver. Either high-impedance or lowimpedance head phones may be plug-connected to the
receiver. The high-impedance type is recommended.
16
3-22. PRESENTATIONS AND READINGS.
3-23. TUNING PRESENTATION. The main tuning
dial (4, figure 3-1) and the vernier dial (6) are used to
accurately set the receiver to a desired signal frequency.
The main tuning dial has six frequency scales calibrated
in megacycles, and an arbitrary outer scale. The movable
pointer (2) is used to read the scale corresponding to
the frequency band chosen and the fixed pointer
(3) is used to read the arbitrary outer scale. The vernier
pointer is used to read the vernier dial (6), which has
an arbitrary 0-to-l00 scale. The numeral under the fixed
pointer of the main tuning dial indicates the number of
revolutions that have been made by the vernier dial at
any setting. EXAMPLE: When the fixed pointer of the
main tuning dial indicates 4 and the vernier dial indicates 87.6, the reading to log for this setting is 487.6.
The precise mechanical vernier system divides the rotation of the main tuning dial over each frequency band
into approximately 600 vernier divisions, with one-halfdivision calibration points. Since one-tenth divisions on
the vernier dial may be estimated accurately, each frequency band is divided into approximately 6000 readable settings. Tnis permits extreme accuracy in the logging of stations.
3-24. METER READINGS. When the receiver is used
for headset or speaker reception, the intelligibility of
reception can be determined aurally. When the receiver
is used for teletypewriter or telegraph recorded copy,
the intelligibility of reception can be determined visually. In either instance, when reception begins to deteriorate on a particular station frequency, the remote
station should be notified by means of the associated
transmitter so that the operational activity may be
switched to some other predetermined operational frequency. If accurate indications of the received carrier
strength or the receiver audio output are desired, the
tuning meter (1) may be used [Refer to paragraph
.1-20 for the explanation of the function of the "METER" switch (18).] Table IV may be used to determine
the r-f microvolts or a-f milliwatts equivalent to the db
readings of the r-f and a-f scale calibrations of the tuning meter. With the "AUDIO GAIN" control (16) set
to provide 500 milliwatts to a 600-ohm matching load,
TABLE IV. METER DECIBEL CONVERSION CHART
08
-6
R-F Microvolts
0.5
0
08
-10
0
A-F Milliwatts
0.6
6
+6
2
+6
24
+20
10
+10
60
+40
100
+15
190
+60
1,000
-1- 80
10,000
+100
100,000
Section III
T.O. 31R2-4-101-1
Paragraphs 3-25 to 3-29
15 milliwatts are provided to an 8000-ohm headset connected to the "PHONES" jack (20). A minimum of 0.6
milliwatt of 455-kc i-f output is provided at the "IF
OUTPUT" connector (6, figure 2-2).
3-25. OPERATING PROCEDURES.
3-26. GENERAL.
3-27. The operating procedures for the receiver Involve a sequence of operations prior to, during, and
following its use in an operational activity. These operations are outlined in paragraphs :.,-28 through 3~56 for
each possible mode of receiver operation. In each instance, the control or switch referred to is identified by
its front panel designation. (See figure 3-1.) A performance check chart, table V, is provided to indicate
nounal receiver operation.
3-28. RECEPTION OF A-M PHONE OR SINGLETONE TELEGRAPH SIGNALS.
3-29. PRELIMINARY ADJUSTMENTS.
a. Plug the headset into the "PHONES" jack (20) or
connect a loudspeaker across the "AUDIO OUTPUT"
terminals (8, figure 2-2).
b. Set the "SEND/REC" switch (21, figure 3-1) to
the "REC" position.
c. Set the "FREQ CONTROL" selector switch (8) to
the "VFO" position.
d. Set the "LIMITER/OFF" switch (19) to the
"OFF" position.
e. Set the "SELECTIVITY" switch (22) to its "NONXTAL" 3-kc position.
f. Set the "AVC/MAN" switch (12) to the "AVe'
position.
g. Set the "XTAL PHASING" control (23) to the
position indicated by the diamond between positions
"4" and "6".
h. Unclamp the "TUNING LOCK" (14) by turning
it countertlockwise.
i. Rotate the "RF GAIN" control (11) clockwise
from its "OFF" position. A click should be heard, indicating that the power switch has been actuated, and the
pilot lamps should light, illuminating the main tuning
dial (4) and the verniel' dial (6). Allow the receiver to
warm up for a period of 15 minutes.
j. Set the "MOD/CW" switch (13) to the "MOD"
position.
k. Rotate the "BAND CHANGE" switch (17) until
the frequency band indicated at the "MEGACYCLES"
window (5) includes the desired signal frequency.
TABLE V. PERFORMANCE CHECK CHART
Test
Procedure
Normal Indication
A-C power source, "LINE" fuse
Rotate "RF GAIN" control clockwise from its "OFF" position.
Pilot lamps light.
Amplifier circuits, "-B" fuse
Advance "RF GAIN" control and
"AUDIO GAIN" control to maximum.
Noise output in headset or loud
speaker.
A-M reception
Loosely couple A-M signal from Ereqnency meter or accurately calibrated signal generator to receiver
antenna terminals. Tune receiver
as per paragraphs 3-29 and 3-30.
Repeat on each of the six bands.
Tone in output of receiver. With
"AVC/MAN" switch set to
"AVC", tuning meter pointer
deflects as signal is tuned in.
Dial calibration
Same as A-M reception procedure.
Tune receiver accurately using tuning meter. Note main tuning dial
indication.
Indication on main tuning dial
should be accurate to within 0.25
percent of signal frequency.
C-W reception
Loosely couple cow signal from frequency meter accurately calibrated
signal generator to receiver antenna terminals. Tune receiver as
per paragraphs 3-35 and 3-36.
Repeat on each of the six bands.
Beat note heard in output of receiver. Pitch of note varies as
"BEAT OSc." control is varied.
Zero beat obtained when "BEAT
OSc." control is set to "0".
Audio output
Same as A-M reception procedure.
With loudspeaker connected across
"AUDIO OUTPUT" terminals
and "AUDIO GAIN" control setting reduced, depress "METER"
switch to "AF" position.
Power output in db indicated on
lower scale of tuning meter.
Meter indication varies as
"AUDIO GAIN" control setting
is varied.
17
Section III
T.O. 31R2-4-101-1
Paragraphs 3-30 to 3-33
1. Turn the "RF GAIN" control to its maximum
clockwise setting. The tuning meter (1) pointer should
move upscale and noise should be heard in the headset
or loudspeaker.
m. Turn the "AUDIO GAIN'· control (16) to adjust
the receiver noise output to a suitable level.
n. Turn the "TUNING" control (15) until the maintuning-dial indication corresponds to the desired signal
frequency.
Note
Reduce the "RF GAIN" control (11) setting
slightly to avoid excessive receiver noise output while the "TUNING" control (15) is rotated through positions at which there are no
signal transmissions.
3-30. RECEPTION USING VARIABLE-FREQUENCY
OSCILLATOR. To tune in an A-M signal, perform the
preliminary adjustments outlined in paragraph 3-29,
and continue as follows:
a. Rotate the "TUNING" control (15) in the proper
direction to tune in the signal. Proper tuning is indicated by a maximum indication of the tuning meter (1).
The main-tuning-dial (4) reading should be within 0.25
percent of the frequency of the desired signal.
b. Clamp the "TUNING LOCK" (14) by turning it
clockwise.
Co Readjust the "AUDIO GAIN" control (16) as desired, to obtain a suitable audio output level.
3-31. RECEPTION OF A WEAK SIGNAL USING
VARIABLE-FREQUENCY OSCILLATOR. When the
desired signal is weak and obscured by interference of
any kind, the preliminary adjustments outlined in paragraph 3-29 and the tuning procedure outlined in
paragraph 3-30 may not suffice to provide usable signal reception. Under those conditions, tune in the desired signal by use of the following procedure:
a. Set the "MOD/CW" switch (13) to the "CW"
position.
b. Rotate the "BAND CHANGE" switch (17) until
one of the lower frequency bands is indicated at the
"MEGACYCLES" window (5).
c. Locate a strong A-M or cow signal. This signal is
required to accurately set the "BEAT OSc." control
(10) for a b-f-o frequency of 455 kc, since the dial of the
"BEAT OSc." control may not be accurately calibrated.
d. Tune in the signal by turning the "TUNING" control (15) in either direction until the tuning meter (1)
indication is maximum.
e. Adjust the "BEAT OSc." control to obtain a zerobeat audio output and maintain this setting.
£. Rotate the "BAND CHANGE" switch until the
frequency band indicated at the "MEGACYCLES" window includes the desired signal frequency.
g. Turn the "TUNING" control in the proper direction until the main tuning dial (4) indicates the desired
signal frequency; then readjust the 'TUNING" control
slightly to obtain a zero beat in the output of the
receiver.
18
h. Return the "MOD/CW" switch to the "MOD"
position.
i. Clamp the "TUNING LOCK" (14) by turning it
clockwise.
j. Readjust the "AUDIO GAIN" control (16) as desired, to obtain a suitable audio output level.
3-32. RECEPTION USING CRYSTAL-CONTROLLED OSCILLATOR. When fixed-frequency
crystal-controlled reception of phone or single-tone
telegraph is desired, follow the preliminary adjustments
outlined in paragraph 3-29, and continue with the step
sequence that follows:
a. Set the "FREQ CONTROL" selector switch (8) to
the numbered "XTALS" position whose numeral corresponds to that of the crystal socket which holds the
crystal of the proper frequency. The proper switch position can be determined from the plastic chart (9) on
which should have been recorded the switch positions
and the corresponding signal frequencies.
b. Turn the "TUNING" control (15) until the main
tuning dial (4) indicates the desired operating frequency and cal ~fully readjust the "TUNING" control
to obtain a maximum indication on the tuning meter
(1).
c. If desired, clamp the "TUNING LOCK" (14) by
turning it clockwise.
d. Turn the "D FREQ" control (7) in the proper
direction to accurately adjust the crystal oscillator frequency. The proper setting for this control is that at
which a maximum indication is obtained on the tuning
meter.
e. Readjust the "AUDIO GAIN" control (16) as desired to maintain the proper audio output level.
3-33. NOISE SUPPRESSION. To provide for the best
possible reception under noisy atmospheric or manmade static conditions, follow the preliminary adjustments outlined in paragraph 3-29 and the tuning procedure outlined in paragraphs 3-30, 3-31, or 3-32, as
applicable, and continue as follows:
a. Set the "SELECTIVITY" switch (22) to the 5witch
position which provides the most intelligible reception
for the desired mode of operation.
b. If the "SELECTIVITY" switch (22) is used in one
of its "XTAL" positions, turn the "XTAL PHASING"
control (23) for best attenuation of any interfering
signal.
Co Set the "LIMITER/OFF" switch (19) to the "LIMITER" position to reduce ignition noise or any other
pulse-type noise from the audio output.
d. During standby periods in the transmission, when
the desired signal is off the air, turn the "RF GAIN"
control (11) down from its maximum clockwise setting
to cut down on the receiver noise output.
e. During reception, when the signal fluctuates or
fades so that at intervals the signal level is low, the
receiver signal output may be favored, relative to the
receiver noise output, by careful readjustment of the
"RF GAIN" control (11).
T.O. 31R2-4-101-1
3-34. RECEPTION OF C-W TELEGRAPH SIGNALS.
3-35. PRELIMINARY ADJUSTMENTS. Perform the
procedures outlined in paragraph 3-29 for reception
of A-M signals, except, in step "i", set the "MOD/C\.V"
switch (13) to the "CW" position. Set the "BEAT OSc."
con trol (10) to "0".
3-36. RECEPTION USING VARIABLE-FREQUENCY
OSCILLATOR. To tune in a cow signal, proceed as
follows:
a. Rotate the "TUNING" control (15) in the proper
direction to tune in the signal. Proper tuning is indicated by a zero beat in the audio output or maximum
indication on the tuning meter (1). When the signal is
properly tuned in, the main-tuning-dial (4) reading
should be accurate to within 0.25 percent of the desired
signal frequency.
b. If desired, clamp the "TUNING LOCK" (14) by
turning it clockwise.
c. Turn the "BEAT OSc." control (10) in either direction to obtain a tone output, preferably around 1000
cps. Reception may be better with the control turned in
one direction than in the other. In any case, choose
the position in either direction which provides the
most intelligible reception.
d. Readjust the "RF GAIN" control (11) for the
clearest signal and the "AUDIO GAIN" control (16) to
the position providing the desired audio output level.
3-37. RECEPTION OF A WEAK SIGNAL USING
VARIABLE-FREQUENCY OSCILLATOR. When the
desired signal is weak and obscured by interference of
any kind, the preliminary adjustments referred to in
paragraph 3-35 and the tuning procedure outlined in
paragraph 3-36 may not suffice to provide usable signal reception. Under those conditions, tune in the desired signal by use of the following procedure:
a. Follow the instructions outlined in steps "b"
through "g" of paragraph 3-31.
b. Clamp the 'TUNING LOCK" (14) by turning it
clockwise.
c. Turn the "BEAT OSc." control (10) in either
direction to obtain a tone output, preferably around
1000 cps, as outlined in step "c" of paragraph 3-36.
d. Readjust the "RF GAIN" control (11) for the
clearest signal and the "AUDIO GAIN" control (16)
to the position providing the desired audio output level.
3-38. RECEPTION USING CRYST AL-CONTROLLED OSCILLATOR. When fixed-frequency
crystal-controlled- reception of cow telegraph signals is
desired, perform the preliminary adjustments referred to
in paragraph 3-35, and continue as follows:
a. Follow the instructions outlined in steps "a"
through "d" of paragraph 3-32.
b. Turn the "BEAT OSc." control (10) in either direction to obtain a tone output, preferably around 1000
cps. Reception may be better with the control turned in
one direction than in the other. In any case, select the
position which provides the most intelligible reception.
Section 11\
Paragraphs 3-34 to 3-43
c. Readjust the "RF GAIN" control (11) for the
clearest possible signal and the "AUDIO GAIN" control (16) to provide the desired audio output level.
3-39. NOISE SUPPRESSION. To provide for the best
possible cow reception under noisy atmospheric or manmade conditions, perform the preliminary adjustments
referred to in paragraph 3-35, follow the tuning procedure outlined in paragraphs 3-36, 3-37, or 3-38, as
applicable, and continue as follows:
a. Set the "SELECTIVITY" switch (22) to the
"XTAL" switch position which provides the best
reception.
b. Turn the "XTAL PHASING" control (23) to a
position which provides best attenuation of any interfering signal.
c. Set the "LIMITER/OFF" switch (19) to the "LIMITER" position to reduce ignition noise or any other
pulse-type noise from the audio output.
d. Readjust the "RF GAIN" control (11) for clearest
signal reception and the "AUDIO GAIN" control (16)
to provide the desired audio output level.
3-40. RECEPTION OF FREQUENCY-SHIFT
TELETYPE SIGNALS.
3-41. PRELIMINARY ADJUSTMENTS. Perform the
procedures outlined in paragraph 3-29 for A-M signals, except, in step "j", set the "MOD/CW" switch
(13) to the "CW" position. Set the "BEAT OSc." control (10) to "0".
3-42. RECEPTION USING VARIABLE-FREQUENCY
OSCILLATOR. To tune in a frequency-shift signal, proceed as follows:
a. Turn the "TUNING" control (15) in the proper
direction so that the two-tone output signal, heard when
the receiver is slightly detuned, is changed to a single.
tone output signal, or adjust the control for a maximum
indication on the tuning meter (1). Either procedure
may be used to tune the receiver properly. When the
receiver is properly tuned, the main-tuning-dial (4) frequency indication should be accurate to within 0.25 percent of the signal frequency.
b. If desired, clamp the "TUNING LOCK" (14) by
turning it clockwise.
c. Adjust the "BEAT OSc." control (10) to obtain a
two-tone output at 2500 cps plus or minus the carrier
shift. Reception may be better with the control turned
in one direction than in the other.
3-43. RECEPTION OF WEAK SIGNAL USING
VARIABLE-FREQUENCY OSCILLATOR. When the
desired signal is weak and obscured by interference of
any kind, the preliminary adjustments referred to in
paragraph 3-41 and the tuning procedure outlined in
paragraph 3-42 may not suffice to provide usable signal reception. Under those conditions, tune in the desired signal by use of the following procedure:
a. Follow the instructions outlined In steps "b"
through "f" of paragraph 3-31.
19
Section III
T.O. 31R2-4-101-1
Paragraphs 3-44 to 3-50
b. Turn the "TUNING" control (15) in the proper
direction until the main-tuning-dial (4) reading corresponds to the frequency of the desired signal. Then
carefully readjust the "TUNING" control so that the
two-tone output signal, heard when the receiver is
slightly detuned, is changed to ~ single-tone output signal, or adjust the control for a maximum indication on
the tuning meter (1). Either procedure may be used to
properly adjust the "TUNING" control. When the
receiver is properly tuned, the main-tuning-dial frequency indication should be within 0.25 percent of the
desired signal frequency.
c. If desired, clamp the "TUNING LOCK" (14) by
turning it clockwise.
d. Adjust the "BEAT OSc." control (10) to obtain a
two-tone output at 2500 cps plus or minus the carrier
shift. Reception may be better with the control turned
in one direction than in the other.
e. Readjust the "RF GAIN" control (11) to provide
the clearest signal and the "AUDIO GAIN" control
(16) to provide the desired audio output level.
3-44. RECEPTION USING CRYSTAL-CONTROLLED
OSCILLATOR. When fixed-frequency, crystal-controlled
reception of frequency-shift signals is desired, perform
the preliminary adjustments referred to in paragraph
3-41, and continue as follows:
a. Follow the instructions outlined in steps "a"
through "d" of paragraph 3-32.
b. Turn the "BEAT OSc." control (10) in either
direction to obtain a two-tone output at 2500 cps plus or
minus the carrier shift. Reception may be better with the
control turned in one direction than in the other.
c. Readjust the "RF GAIN" control (11) to provide
the clearest signal and the "AUDIO GAIN" control
(16) to provide the proper audio output level.
3-45. NOISE SUPPRESSION. To provide the best possible frequency-shift reception under noisy atmospheric
or man-made static conditions, perform the preliminary
adjustments referred to in paragraph 3-41, follow the
tuning procedure outlined in paragraphs 3-42, 3-43,
or 3-44, as applicable, and then follow the instructions outlined in steps "a" through "d" of paragraph
3-39.
3-46. RECEPTION OF SUPPRESSED-CARRIER
MULTICHANNEL PHONE, TELEGRAPH,
AND TELETYPE SIGNALS.
the bandwidth required for the mode of operation contemplated. Channel separations in multichannel operation are usually 170 cps, and the 3-kc position suffices
for single-sideband reception; for double-sideband reception, either the 8-kc or the 13-kc position may be
required. For double-sideband transmissions, the signal
intelligence for each side band is independent of the
other.
c. Set the "BEAT OSc." control (10) to "0".
d. Perform the procedures outlined in steps Hf"
through "n" of paragraph 3-29, except, in step J,
set the "MOD/CW" switch (13) to the "CW" position.
3-49. RECEPTION USING VARIABLE-FREQUENCY
OSCILLATOR. To tune in a suppressed carrier signal,
perform the preliminary adjustments outlined in paragraph 3-48, and continue as follows:
a. Turn the "TUNING" control (15) in the proper
direction to accurately resonate the receiver circuits to
the desired signal frequency. Proper adjustment of this
control is indicated by maximum deflection on the tuning meter (1). At resonance, the main-tuning-dial (4)
reading should be within 0.25 percent of the suppressed
carrier frequency. When it is desired to tune the receiver by listening to the audio output, attenuate all
but one channel of the transmission by setting the "SELECTIVITY" switch (22) to its "XTALS" 1.3-kc position. Then turn the "TUNING" control (15) in either
direction until the receiver audio output from one circuit is clearly intelligible as phone, as two-tone teletype
signals (595 cps for "mark" and 425 cps for "space"),
or as automatic Morse-code keying of a IOOO-cps tone,
as applicable. Then reset the "SELECTIVITY" switch
(22) to the required position as determined in step "b"
of paragraph 3-48.
b. If desired, clamp the "TUNING LOCK" (14) by
turning it clockwise.
c. Readjust the "AUDIO GAIN" control (16) to
provide the desired audio output level.
3-50. RECEPTION
USING
CRYSTAL-CONTROLLED OSCILLATOR. When fixed-frequency
crystal-controlled multichannel reception of a single- or
double-sideband suppressed-carrier signal is desired, perform the preliminary adjustments outlined in paragraph
3-48, and continue as follows:
3-47. GENERAL. To provide for single- or doublesideband reception, the signal carrier, suppressed at the
transmitter, must be reinserted at the receiver. This is
done by use of the internal bfo of the receiver to provide a 455-kc carrier which can be added to the singleor double-sideband signals prior to detection.
a. Set the "FREQ CONTROL" selector switch (8) to
the numbered "XTALS" position whose numeral designation corresponds to the crystal holder which carries
the crystal for the desired suppressed-carrier signal frequency. The correct switch position may be determined
from the plastic chart (9) on which the switch positions and the corresponding suppressed-carrier frequencies should have been recorded.
3-48. PRELIMINARY ADJUSTMENTS.
a. Perform the procedures outlined in steps "a"
through "d" of paragraph 3-29.
b. Set the "SELECTIVITY" switch (22) to its "NONXTAL" 3-kc, 8-kc, or 13-kc position, depending upon
b. Turn the "6, FREQ" control (7) in either direction to resonate the crystal oscillator precisely. Resonance is indicated by a maximum deflection on the tuning meter (1). When it is desired to resonate the circuit
by listening to the receiver audio output, attenuate all
20
Section III
T.O. 31R2-4-101-1
Paragraphs 3-51 to 3-58
but one channel of the transmission by setting the "SE_
LECTIVITY" s\Yitch (22) to its "XTAL" 1.3-kc position. Then turn the "6. FREQ" control in either direction until the receiver audio output is clearly intelligible
as phone, as two-tone teletype signals (595 cps for
"mark" and 425 cps for "space"), or as automatic Morsecode keying of a WOO-cps tone, as applicable. Then reset the "SELECTIVITY" switch to the required position
as determined in step "b" of paragraph 3-48.
c. Turn the "TUNING" control (15) in the proper
direction to resonate the r-f section of the receiver to
the suppressed-carrier single- or double-sideband frequency. Proper adjustment of this control is indicated
by maximum deflection on the tuning meter (1). Maintain the "6. FREQ" control (7) as set in step "b".
d. If desired, clamp the 'TUNING LOCK" (14) by
turning it clockwise.
e. Readjust the "AUDIO GAIN" control (16) to
provide the proper audio output level.
3-51. NOISE SUPPRESSION. To provide the best possible single- or double-sideband suppressed-carrier reception under noisy atmospheric or man-made static
conditions, perform the preliminary adjustments outlined in paragraph 3-48, follow the tuning procedure
outlined in paragraphs 3-49 or 3-50, as applicable,
and continue as follows:
a. Set the "SELECTIVITY" switch (22) to the "NONXTAL" position which provides the best reception.
b. Set the "LIMITER/OFF" switch (19) to the "LIM_
ITER" position to reduce ignition noise and other pulsetype noise from the audio output.
c. Readjust the "RF GAIN" control (11) to provide
the dearest signal and the "AUDIO GAIN" control
(16) to provide the proper audio output level.
3-52. PERIODIC AND SPECIAL OPERATING
ADJUSTMENTS.
3-53. To maintain the communication link in a condition providing for optimum reception, repeat the following operating procedures, as applicable, when required.
a. When the operational activity is two-way, set the
"SEND/REC" switch (21) to the "SEND" position during transmission intervals to prevent damage to the
receiver from the strong local transmission. When the
transmission has been completed, return the switch to
the "REC" position to provide for normal reception.
b. When the receiver is used for reception of A-M
signals, unclamp the "TUNING LOCK" (14), and retune the receiver as outlined in step "a" of paragraph
3-30 or in steps "b" and "d" of paragraph 3-32, as
applicable. Do this periodically at IS-minute intervals,
or at longer intervals, depending upon the frequency
drift noted. When noise impairs the quality of reception, repeat the procedures outlined in paragraph 3-33.
c. When the receiver is used for the reception of cow
signals, unclamp the "TUNING LOCK" (14) and
retune the receiver as outlined in step "a" of paragraph
3-36 or in steps "b" and "d" of paragraph 3-32, as
applicable. Do this periodically at 15-minute intervals,
or at longer intervals, depending upon the frequency
drift noted. When noise impairs the quality of reception, repeat the procedure outlined in paragraph 3-39.
Also reset the "BEAT OSC." control (10), if necessary,
as outlined in step "c" of paragraph 3-36.
d. When the receiver is used for the reception of
frequency-shift teletype signals, unclamp the "TUNING
LOCK" (14) and retune the receiver in accordance with
step "a" of paragraph 3-42 or in steps "b" and "d" of
paragraph 3-32, as applicable. Do this periodically at
15-minute intervals, or at longer intervals, depending
upon the frequency drift noted. When noise impairs
the quality of reception, repeat the procedures outlined
in paragraph 3-39. Reset the "BEAT OSC." control
(10), if necessary, as outlined in step "c" of paragraph
3-42.
e. When the receiver is uS2d for the reception of
suppressed-carrier multichannel signals, unclamp the
"TUNING LOCK" (14) and retune the receiver in accordance with step "a" of paragraph 3-49 or in steps
"b"and "c" of paragraph 3-50, as applicable. Do this
periodically at W-minute intervals, or at longer intervals, depending upon the frequency drift noted. When
noise impairs the quality of reception, repeat the procedures outlined in paragraph 3-51.
3-54. DE-ENERGIZING THE EQUIPMENT.
3-55. Upon completion of the operational activity,
when advised to do so, do the following:
a. Turn the receiver off by turning the "RF GAIN"
control (11, figure 3-1) counterclockwise to its "OFF"
position.
3-56. Deleted.
3-57. PRECAUTIONS TO BE OBSERVED.
3-58. The receiver is precisely aligned and adjusted at
the factory for optimum performance. The metal buttons (18, figure 2-1) cover the chassis openings used
to provide access to the various inductance tuning cores
and capacitor trimmers. These alignment adjustments,
as well as the "BFO IN]" (4, figure 2-2), "METER
ADJ RF" (5), and the "METER ADJ AF" (7) screwdriver adjustment controls, are not operating controls
and cannot be manipulated without impairing the receiver performance and the meter scale calibrations.
Revised 1 August 1956
21
Section IV
Paragraphs 4-1 to 4-6
T.O. 31 R2-4-101-1
SECTION IV
EMERGENCY OPE'RATION
4-1. GENERAL.
4-2. In an emergency, when a defect develops in the
receiver, the operator should attempt to determine the
extent of the defect through manipulation of the frontpanel controls. In many instances, while a section of the
receiver may be disabled and prevent reception using
the desired mode of operation, other receiver circuits
may remain operational and provide a means of maintaining the communications link. If a defect develops in
the crystal-controlled first heterodyne oscillator when
the fixed-frequency crystal-controlled mode of operation
is being used, operation may be maintained by using the
variable-frequency first heterodyne oscillator. If the b-f-o
circuits of the receiver are disabled, reception of A-M
signals may still be possible. Trouble may develop in
the r-f section of the receiver and affect only one of the
six bands of the receiver. In this case, if alternate operating frequencies have been assigned, the communications
link may be maintained using a frequency on one of the
operative bands of the receiver. The operator should
become thoroughly familiar with his equipment, so that
these and other alternate operational procedures may
be resorted to in an emergency.
4-3. ANTENNA SYSTEM.
4-4. For optimum results, a properly designed balanced doublet or straight-wire antenna should be used.
In an emergency, when the antenna system has been
damaged, reception may be possible using a short piece
of insulated wire stripped at one end for connections
to the "ANT" input connector (8, figure 2-1).
4-5. EMERGENCY TUBE REPLACEMENT.
4-6. The type and reference symbol designation of
each electron tube within the receiver is stamped on
the chassis, adjacent to each tube. Figure 2-1 may be
used to rapidly identify the location of each specific
electron tube used in the receiver. In the instance of
unavailability of spare tubes and specific tube failure,
table VI, when applicable, may be used in an emergency
to maintain continuity of service.
TABLE VI. EMERGENCY TUBE REPLACEMENT
Tube Identification
JAN Tube Type
S726/6ALSW/6097
6C4
S749/6BA6W
6BE6
22
Complement
of Specified
Tube Type
VI4, VIS
V20
V4, V8,
Vl3
VI, V2
V7, V9,
VIO, VII,
VI2
VS, V6
Results
Emergency Procedure
Remove
Replace For
Operation
Limited To
Effect on Limited
Operation
VIS
YI4 or V20
Any
Limiter and meter
af nonoperative
VI4
Y20
I-F output
No avc
V4
Y8 or YI3
Fixed freq
reception
None
V8
Y4 or YI3
Any below
7.4 me
None
Vl3
Y4 or V8
AM.
None
V8 and
VI3
Y4
AM below
7.4 me
None
None
V7
VI, Y2, V9,
YIO, VII,
or VI2
Any above
7.4 mc
None
VI2
VI, V2, V7,
Y9, VIO, or
YU
AM.
None
Vll
VI, V2, V9,
YIO, Y7
I-F output
Noavc
Y6
YS
Any below
7.4 mc
None
Revised
1 August 1956
Section IV
Paragraphs 4-1 to 4-6
T.O.31R2-4-101-1
SECTION IV
EMERGENCY OPE'RATION
4-1. GENERAL.
4-2. In an emergency, when a defect develops in the
receiver, the operator should attempt to determine the
extent of the defect through manipulation of the frontpanel controls. In many instances, while a section of the
receiver may be disabled and prevent reception using
the desired mode of operation, other receiver circuits
may remain operational and provide a means of maintaining the communications link. If a defect develops in
the crystal-controlled first heterodyne oscillator when
the fixed-frequency crystal-controlled mode of operation
is being used, operation may be maintained by using the
variable-frequency first heterodyne oscillator. If the b-f-o
circuits of the receiver are disabled, reception of A-M
signals may still be possible. Trouble may develop in
the r-f section of the receiver and affect only one of the
six bands of the receiver. In this case, if alternate operating frequencies have been assigned, the communications
link may be maintained using a frequency on one of the
operative bands of the receiver. The operator should
become thoroughly familiar with his equipment, so that
these and other alternate operational procedures may
be resorted to in an emergency.
4-3. ANTENNA SYSTEM.
4-4. For optimum results, a properly designed balanced doublet or straight-wire antenna should be used.
In an emergency, when the antenna system has been
damaged, reception may be possible using a short piece
of insulated wire stripped at one end for connections
to the "ANT" input connector (8, figure 2-1).
4-5. EMERGENCY TUBE REPLACEMENT.
4-6. The type and reference symbol designation of
each electron tube within the receiver is stamped on
the chassis, adjacent to each tube. Figure 2-1 may be
used to rapidly identify the location of each specific
electron tube used in the receiver. In the instance of
unavailability of spare tubes and specific tube failure,
table VI, when applicable, may be used in an emergency
to maintain continuity of service.
TABLE VI. EMERGENCY TUBE REPLACEMENT
Tube Identification
JAN Tube Type
5726/6AL5~/6097
6C4
5749/6BA6~
6BE6
Complement
of Specified
Tube Type
VI4, VI5
V20
V4, V8,
VI3
VI, V2
V7, V9,
VIO, VII,
VI2
V5, V6
Emergency Procedure
Remove
Replace For
Results
Operation
Limited To
Effect on Limited
Operation
VI5
VI4 or V20
Any
Limiter and meter
af nonoperative
VI4
V20
I-F output
Noavc
V4
V8 or VI3
Fixed freq
reception
None
V8
V4 or VI3
Any below
7.4 mc
None
VI3
V4 or V8
AM.
None
V8 and
Vl3
V4
AM below
7.4 me
None
None
V7
VI, V2, V9,
VIO, VII,
or VI2
Any above
7.4 mc
None
V12
VI, V2, V7,
V9, VIO, or
Vll
AM.
None
Vll
VI, V2, V9,
VIO, V7
I-F output
No ave
V6
V5
Any below
7.4 mc
None
23
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