July- August 1951 - American Radio History
New Studio Consolette
.
.
.
(Uti
See Pg. 8
July- August
1951
Vol. No. 65
Annoying "Roll- over " -starts up in TV
sets
when you mix remotes with locals
RCA's TV Genlock TG -45 ends picture slipping when you
"lap dissolve" and "superimpose."
Now you can lock two entirely different programs together- remote
or local -and hold pictures steady right through switching! No
manual adjustments of phasing to fiddle with. No extra equipment
needed at remote pick -up points. Here's how the GENLOCK works.
Located in your main studio, this simple unit compares the signal
of your remote sync generator with the signal of your local sync
generator. The difference in the phasing of the pulses produces an
"error" signal which locks your local generator as a "slave" to your
remote generator as a master. This enables you to treat remote
signals as local signals-and switch back and forth without picture
"roll- over," no matter where your program originates!
The RCA GENLOCK is simple in design, completely automatic in
operation-"locks-in" much faster than you can switch. It fits any
standard 19 -inch TV rack.
Give your programming a lift. Switch as you please between
programs for variety and for special effects. It's easy with a GENLOCK.
For more information call your RCA TV equipment representative.
Or write Dept. 19AE, RCA Engineering Products, Camden, N. J.
Good -bye "Roll-over"I The RCA TV
GENLOCK tightly locks your local and
remote sync generators together -instantaneously and automatically.
-N-
'C
L.
.sî',4;
This is
the simple, automatic system that electrically locks two separate television
pick -up systems together.
RCA GENLOCK, Type TG -45.
TELEVISION BROADCAST EQUIPMENT
RADIO CORPORATION
of AMERICA
J.
ENGINEERING PRODUCTS DEPARTMENT, CAMDEN, N.
In Canada: RC A VICTOR Company limited, Montreal
this issue, is reproduced (rot a
hod:uhrome of the new Type BC -2B Audio Console. Photo was made by Rod Allen of our photographic staff. Description of this new console will
be found in the article starting on Page 8.
OUR COVER,
Broadcast News
"ABOUT TIME" is what some of our friends ( ?)
have said about the new console. They refer, of
course, to the fact that it has been some twelve
years since we've announced a completely new
console design. But is that bad? Let's look at the
AM. FM. TELEVISION
record.
In our 1939 catalog we showed the Type 76-B
Consolette for the first time. In our 1950-51 catalog it was still there
still the most popular
audio package in the business. In the intervening
years many competitive consolettes appeared. Some
enjoyed a certain amount of popularity. But the
76 -B remained the champ, year in and year out.
All told, nearly three thousand 76-B's rolled out of
our Camden plant
. and, so far as we know,
every one of them is still in use. Certainly none
has been discarded because of obsolescence .
.
for the first 76-B's made meet today's quality
standards with something to spare. And we don't
think any have been replaced because they wore
out. Old 76-B's don't wear out, they just go on
working year after year, with only very rare and
usually very minor replacements.
Originally the 76 -B was conceived as a package
audio equipment which would provide small stations with all of the quality and a reasonable de-
...
Published by the
RADO CORPORATION
OF
ENGINEERING PRODUCTS DEPARTMENT
...
AMERICA
CAMDEN, NEW JERSEY
NUMBER 65
JULY -AUGUST, 1951
Subscription Rates
ln continental U.
ln other commit
JOHN
P.
S. A.
for
issues
12
gree of the flexibility which large stations achieved
with elaborate and expensive custom-built equipments. It did this very well. But it was also found
suitable for many other purposes. For example, as
a control booth equipment in large multiple studio
layouts. With the addition of a switching console
it has been used as a master control console. It
has been widely used in large mobile units. It has
even been used as a field equipment (we well
remember our pleasure in finding ABC and CBS
using 76-B's in their booths at the 1948 political
conventions). Last, but not least, in a majority of
all those glamorous 108 TV stations on the air
today we find, believe it or not, the ubiquitous
W. O. HADLOCK, Managing Editor
GASKILL,
L.
34.00 for 12 issues
SS 00
TAYLOR, Editor
M.
-
E.
B.
MAY, Associate Editors
Contents
A CARRIER -AUDIO ALARM CIRCUIT FOR MONITORING
A NEW AM -FM -TV CONSOLE
6
\`1ILDOW AND G. A. SINGER
S
That's the record on the 76-B. It's a record that
speaks for itself, we think . . . and for the farsightedness of the engineering design work that
went into the 76-B.
TSBERG
14
NOT TOO UNUSUAL, however. is the record of
l
.o -I ;. 'l ui. if not most, of our broadcast
by ROBERT MCRANt:v
28
by J. H. Rol.:
30
by DR. C. M. MORGAN
34
by W"I'AR ENGINEERING STAFF
36
by R. L. HUCABY
48
by M. RETTINGER
55
.
I
76 -B.
by STAN BENNETT
BROADCAST TRANSMITTERS
\\
by AI.
NEW "TV PEAK" IN SAN FRANCISCO
WNAG's NEW
"250,
BTA -250M
STANDARDIZING AND MEASURING VIDEO LEVELS
IN
A TV
STATION
.
RADIO AT INDIANA STATE TEACHERS
WTAR, AM- FM- TELEVISION
A LABORATORY TELEVISION SYSTEM
TELEVISION STUDIO
ACOUSTICS
KNBC's NEW AM VERTICAL
.
by M. L. GASKILL
HAM FORUM
58
61
Copyright 1951
ofi America
Radio Corporation
p
RCA Victor Division
Camden, N. J.
www.americanradiohistory.com
equipment units have records for popularity and
longevity which approach that of the 76-B. In audio
equipments-, for instance, the 70 -B Turntable, the
72 -D Recorder, and the 77 -D Microphone all dcsigned at about the same time as the 76-B---have
been continuously, and still are, the largest selling
units of their kind.
It is significant that a large port of our sales
volume in these lines is "repeat"' business; that is.
sales of additional units to stations already using
them. Such "repeat" orders obviously are based on
experience, and as such they are the best possible
proof that these equipments really do the job.
What does the fact that RCA design stays current so long mean to you. Wll, we think it is important in two ways. First it means that the equip ment you buy does not become obsolete over
night. It not only lasts a long while-but it has a
high resale value for a long time. If you don't believe this, do a little checking in the used equipment market.
The second, and to us even more important fact,
is that when you buy a new RCA equipment you
can do so with assurance that it is not a spur-of-
the-moment idea, but rather a carefully nurtured
design based on our twenty -five years of experience
in this business. The new BC -2B Console is such
an equipment. It incorporates some new ideas, yes.
But they are all proven ideas; most of them, in
fact, pre -tested in our deluxe custom -built equip nments. You get them in the BC-2B at a "package"
price. Take a look at this new console -you'll like
it, we guarantee.
I
1
ow to get any TV
TAKE ONE
OF THESE
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all
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With RCA's complete line of transmitters
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-on
If your requirements are best met with a
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if your needs are better met with a higher power transmitter and a lower -gain antenna,
RCA has that combination too!
Ask your RCA Sales Representative to sit
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of station planning -knows TV equipment
from A to Z. He can tell you exactly what
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Call him today. Or write RCA Engineering
Products Department, Camden, N. J.
3- section
Type TF -3
TV Super Turnstile
6- section
TV Super Turnstile
Type TF -6
2
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5-section
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Type TF-5
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Type TF-12
RADIO CORPORAT/ON of AMER/CA
ENGINEERING PRODUCTS DEPARTMENT
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CAMDEN, N.J.
Type TT-10AVAHmand an
will deliver
I
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100 kw (ERP)
10-kw TV trans
high -gain antenna...
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RCA
power of any commercial TV transmitter operating today -and AT SUB-
e This remarkable new 10 -kw TV
transmitter, and an RCA high -gain
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radiated power. More than twice the
5-kilowatt
models and weighs substantially less).
The new RCA 10 -kw transmitter is
available in two types. Type TT-1OAL
covers channels 2 to 6. Type TT-10AH
covers channels 7 to 13.
For complete information on this
new 10- kw...call in your RCA Broadcast Specialist. He can show you what
you'll need to get "on the air"- with
the power you want -at lowest possible cost. Phone him. Or write Dept.
S -E18, RCA Engineering Products,
Camden, New Jersey.
STANTIALLY LOWER COST PER RADIATED KILOWATT than other trans-
mitter- antenna combinations!
Using an improved type of aircooled tetrode in the final power amplifier stages, this transmitter removes
all former restrictions on interior
cooling and floor -space requirements.
No water supplies to bother about.
No problem setting up the transmitter in tight quarters (it takes approximately half the floor area of previous
ANY T!! POWER UP TO
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CAMDEN. M.J.
A CARRIER -AUDIO ALARM CIRCUIT FOR
MONITORING BROADCAST TRANSMITTERS
By STAN BENNETT
Assistant Chief Engineer
KOMO, Seattle
Summary
simple reliable alarm device has been
developed to indicate instantaneously at
the studio location any interruption of the
transmitter carrier where the transmitter
may be located some miles from the studio
site and where "off the air" monitoring
is not continuous. Also incorporated in
the circuit is a time delay alarm which
sounds in case of audio failure for any
pre- determined time period between 10
and 30 seconds. The attachment is applicable to any - uperheterodyne type monitor receiver.
May Save Time and Money
When an emergency occurs at a trans-
mitter station that puts the equipment off
the air, the first thought of the transmitter
engineer should be to analyze the cause of
the trouble and return the equipment to
normal operation; usually, the secondary
consideration is to call the studio informing them they are off the air. This may be
some minutes later in cases of serious
trouble. Meantime spot announcements,
programs. etc., have been going into a
dead transmitter with studio personnel
blissfully unaware.
It has been the experience here at
KOMO that this automatic alarm device
has "paid off" several times during its
past two years of operation. It gives immediate warning of such things as power
failure at the transmitter site and sometimes allows re- scheduling a commercial
spot announcement or possibly delaying
the program material until the emergency
is over. Often the transmitter engineer is
not called by the studio until the station
returns to the air, knowing that he is extremely busy during moments of equipment trouble or when placing the auxiliary
into operation.
1. View of the Carrier-audio alarm (top panel) mounted in KOMO
monitoring rack. Bottom panel includes Kappler Hi- fidelity Tuner furnishing
"Off-the -air" monitoring plus AVC and audio voltage to the alarm circuit.
FIG.
"
The alarm device also offers a sense of
security in the situation of KOMO studios
where both program line and order wire
circuits are in the same submarine cable
to the 50 -kw transmitter located 15 miles
away on Vashon Island. A dragging anchor
from a ship conceivably could cut all
cable communication. Warning from the
audio- failure alarm circuit would allow
studio personnel to re -route circuits or
set up the emergency studio -transmitter
link in the most rapid manner.
There are many reasons why stations
with remote studio locations do not continuously monitor "off the air ". Some lack
high fidelity receivers, some have serious
noise pickup at the studio site, etc. Many
studios seem to ignore operation of their
transmitters unless informed it is inoperative. The device described herewith consists of two tubes, simple circuitry, made
primarily from junk box parts at a total
6
www.americanradiohistory.com
cost of a few dollars. There seems no good
reason why every remote studio location
should not have one, except perhaps the
engineering personnel are just too busy
to do the necessary experimenting on a
"gimmick" of this sort: or perhaps they
just need a bit of urging on the value and
convenience of such a device. At any rate,
that is the reason for this article.
Carrier /Audio Alarm Operation
Whim the device shown in Fig.
l
is
attached to the AVC circuit and the audio
output of any superheterodyne "off the
air" monitor receiver and sensitivity controls of the alarm circuit are properly adjusted, the following functions under the
specified conditions are performed:
-
(1) Transmitter carrier failure
instantaneous operation of relay RE -1 with
control contacts operating buzzer, fire
gong, or suitable warning device.
control contacts. The time difference of
the two clocks then gives the carrier -off
time.
Circuitry
Carrier alarm operation is controlled by
plate circuit relay RE -1 of one section of
a 6SN7, normally biased to cut -off by -3
to -5 volts available from the AVC circuit of the monitor receiver. The 50K control in the plate circuit along with relay
spring tension and armature spacing can
be used for sensitivity adjustment. The
back contact of relay RE -1 is used for the
carrier switch "off" position. When carrier
returns, the relay RE -1 opens, thus completing circuit of the carrier alarm and
warns operator that carrier is back on
the air.
FIG. 2. Chassis view of the KOMO Carrier-audio
alarm. It consists of a 5 inch by 14 inch chassis
mounted on a standard 19 inch by 51 inch panel
(2) Audio failure (any cessation of audio
either at studio or transmitter) for
pre- determined time of 10 to 30 seconds-relay RE -2 actuated with control contacts operating bell, siren or
suitable warning device distinguishable
from the carrier alarm.
Audio Time Delay
Two to ten volts of audio should be
available from the monitor receiver output
for operation of the audio time delay
alarm. In this case a zero level output was
amplified by utilizing one section of a
6SN7. The output of this tube is rectified by two 1N34 crystal diodes and used
as the charging voltage for an R -C circuit
in the grid of the second half of the 6SN7
working as a relay control tube for plate
circuit relay RE -2.
The R -C time constant can be made
any reasonable value; in this case 8 mfd.
and 3 megohms maximum resistance gave
approximately 30 seconds delay. A 1.5
megohm potentiometer allows setting of
the time constant for any variation less
than maximum delay. Care should be taken
in choosing a condenser with a high leakage resistance. Failure to do so will cause
variation in the time delay and may cause
occasional tripping of the audio alarm on
prolonged low symphony passages and similar material of low average level.
Note that the back contact of the audio
alarm is in series to ground through the
back contact of the carrier alarm relay.
Thus the audio alarm does not sound when
the carrier failure relay is operated, which
allows only the properly identified alarm
to sound.
Components can be and were in this
case mostly typical spares around a station
with exception of the two plate circuit
relays. An old buzzer and a door bell were
used for the two carrier and audio alarms
respectively powered from an ordinary door
bell transformer. Two test buttons for
checking operation of the relays were put
in the circuit and found to be convenient.
FIG. 3. Schematic diagram showing the circuitry employed for the KOMO Carrier -audio alarm.
-
a
(3) Carrier failure of several minutes
alarm sounds continuously until "Carrier Switch" is thrown to "Carrier
Off" position. Warning alarm will
then cease until the transmitter carrier is returned to the air at which
time alarm again sounds indicating to
studio engineer that the transmitter
is again on the air. "Carrier Switch"
is then returned to normal "Carrier
On" position.
By noting the time at the start of the
carrier alarm and again when the alarm
sounds upon carrier return, the transmitter outage time may be obtained for pro-
gram log purposes. The aforementioned
outage time may also be recorded automatically by operation of two electric
clocks, one of which stops and one which
starts upon actuation of the carrier relay
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1.
View of the new BC -2B Consolette shown in operating position. Eight mixer positions
are provided, colored knobs and switches enable quick identification of the important circuits.
FIG.
A
NEW AM - FM
Introduction
-
TV CONSOLETTE
By
P. W. WILDOW
& G. A. SINGER
Many
different types of audio systems
are available for use in the broadcasting
studio control room to perform the functions of amplification, mixing, switching
and regulating of the program. These systems may range from elaborate custom
built equipments utilizing rack mounted
amplifiers and control desks containing
very simple
only the operating controls
portable equipment adapted to studio use.
-to
The consolette which is in between these
extremes offers the advantage of containing in a single package all the essential
elements necessary for efficient programming. It requires a minimum of wiring at
the installation and takes up very little
space. Because regular factory production
methods are used, its cost is appreciably
lower than that of more complex equipment.
The type BC -2B Consolette described in
this article is a new design, engineered to
fulfill the control room requirements of the
majority of AM -FM and TV broadcasting
stations. The final design of this consolette
reflects the combined thinking of Broadcast engineers with long experience in the
operation and design of broadcast audio
equipment. As a result, several new operating features, and recent developments in
tubes and components are incorporated in
its construction.
Facilities
The consolette may be used to control
either one or two studios. In addition, it
will serve an announce booth, a control
room microphone, two turntables, a network and five remote lines. The monitor
amplifier may be used for monitoring,
auditioning, receiving and sending cues,
talk back to studios, and as an emergency
line amplifier. Except for the power supply,
the consolette is completely self- contained.
Simplicity of Operation
The arrangement of circuits and controls is such that operation is simple and
straight forward. Switches and faders are
clearly marked with their function, and
8
www.americanradiohistory.com
related control knobs are made of the same
color plastic material. Electrical and mechanical interlocks are provided in the
audio and control circuits to prevent improper operation. Even inexperienced or
new personnel are able to learn quickly
how to operate the consolette.
Styling and Visibility
The consolette is designed to mount on
a flat topped desk or table, yet the sloping
front panel design affords maximum visibility into the studio floor area. The con solette which is finished in two -tone umber
gray will blend in well with other RCA
television studio control equipment.
of Installation and Maintenance
All external connections are made to two
Ease
terminal blocks which become accessible
by lifting the top cover. Every electrical
component is easily accessible for inspection, adjustment, cleaning and replacement.
The front panel swings forward bringing
switches and attennuators in full view.
The amplifiers are mounted on a movable
frame which swings up, making the underside accessible. (The amplifiers are on individual chassis which can be removed.)
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FIG. 2. Simplified block circuit diagram of the BC-2B Consolette.
General Description -Electrical
be selected by means of a switch from the
Fig 2 shows the block diagram of the
BC -2B consolette. Of the six microphone
inputs, three studio microphones are connected directly to the pre -amplifiers, and
control room, the announce booth, or the
fourth studio microphone. The two turntable inputs connect directly to the mixers.
In application where a booster amplifier
is not included as part of the turntable, an
additional dual -preamplifier (MI- 11241)
the input to the fourth pre -amplifier may
may be installed in a space provided within
the consolette. One input is reserved for
a network line and one of five remote
lines may be selected by means of a
push- button switch. A line transformer
is included for isolation and impedance
matching.
FIG. 3. View of the BC -2B Con-
solette as displayed at recent
NAB Convention where it was
mounted next to companion
Master Control switching unit.
9
www.americanradiohistory.com
Each of the eight possible simultaneous
inputs is controlled by a high level mixer.
The mixer circuit is of the series -parallel
type which offers the lowest loss. Both
turntable mixers have "built -in" cueing
switches which connect the turntable outputs to an external cueing amplifier when
the mixer control is turned to the "off"
position.
By means of key switches, the output
of each mixer may be connected to either
the program bus or the audition bus. The
program bus is permanently connected to
the input of the program amplifier. The
output of the program amplifier is con-
nected through the "line -out" switch and
a 6 db pad to the output line terminals.
The purpose of the pad is to equalize
amplifier and line impedances.
MORE AND MORE BROADCASTERS
ARE
TAKING ADVANTAGE OF
FIG. 4.
forward
View of the BC -2B with front panel swung
to show how every component is accessible.
THIS SPECIAL SERVICE
The RCA Service Company maintains a complete factory
repair shop for overhauling and repairing broadcast equipment. More and more AM, FM and TV broadcasters are
taking advantage of this special service to make worn or
damaged Microphones, High Fidelity Recorder Heads, Tape
Recorder and Reproducer Heads and Test and Measuring
Equipment perform like new again.
Broadcasters like having skilled, factory- trained experts
work on their expensive equipment. They can be sure that
all replacement parts are genuine factory originals. They
like the way their equipment is repaired and returned in
only a few days. And cost -even for major rebuildingsis low.
Lengthen the life of your equipment
increase efficiency
eliminate unnecessary replacement costs. Send your
equipment in now. An estimate will be submitted, if you
wish, before work is started. Address..
...
...
RETURN APPARATUS CONTROL
RCA SERVICE COMPANY, INC.
CAMDEN, NEW JERSEY
The input of the monitor amplifier can
be selected by means of a pushbutton
switch. There are three talkback buttons
which connect the control room microphone
to the monitor amplifier and permit the
operator to talk to Studio A, Studio B and
the remote lines respectively. The fourth
push -button bridges the monitor input
across the output of the program amplifier for monitoring the outgoing program.
The fifth button connects the input of
the monitor amplifier to the audition bus
and the remaining three pushbuttons connect it to cue lines.
Sometimes it is not known over which
remote line a program will be fed. In such
a situation, the `override" feature is helpful. By operating the "override" switch
(4S13) all remote lines are connected to
the input of the monitor amplifier and a
call coming in on any one of the lines will
override the signal coming from the monitor speaker.
The monitor amplifier may also be used
to send cues over a remote line, and this
is accomplished by throwing the
"override"
switch (4S13) to the "Remote Cue" position. The remote line, over which the cue
is sent, is selected by the switch (4S11).
An electrical interlock on the line selector
switch (4510) prevents cue from being
sent over a line which is "in use" to receive a program from a remote location.
With switch 4S13 on the "phone- remote
talkback" position, the monitor phone jack
4J1 is connected through 4511 to the remote lines, the program and the monitor
amplifier. This position is also used to
talkback over any remote line. It is thus
possible to carry on a two -way conversation between the control room and a remote
location.
Should the program amplifier fail, the
monitor amplifier may be used as a line
amplifier. To do this, the mixer output
switches are thrown from the program to
the audition position. The audition button
of the monitor input switch 4S12 is depressed and the line out switch 4514 is
thrown to the "emergency" position. The
monitor gain control acts as the master
gain control under those circumstances.
10
www.americanradiohistory.com
i
The VU meter can be switched to indicate the output level of either the program
line or the monitor amplifier. Brightness
of the lamps illuminating the meter scale
is adjustable to suit operating conditions.
The two sets of pushbutton switches are
of the cam -operated type with leaf -spring
contacts which are inherently quiet, easy
to maintain and give many years of reliable
service.
Although this consolette is primarily designed for single channel operation, a remote line may be used as a second channel
Mechanical
The consolette housing is made of steel
and finished in dark umber gray except for
the front panel which is light umber gray.
The overall length is 33 inches, the depth
21%2 inches, and the height 11% inches.
The total weight is 114 pounds. Knockouts for cable conduits are provided in
the bottom and rear sides.
FIG. 6 (below). Block diagram showing the func-
FIG. 5. Rear view of the BC -2B with cover removed to
show accessibility and position of amplifiers and wiring.
STUDIO
M
I
I
tions performed by the BC-2B Consolette as used
in a typical broadcast installation.
STUDIO
A
MIC 3
MIC 2
B
MIC 4
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177,7177:2
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117
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CONTROL ROOM
50/eOASOURCE
11
www.americanradiohistory.com
Amplifiers
The amplifiers are of a new design which
utilizes miniature tubes in all stages except
the output stage of the program and monitor amplifiers. Negative feedback is employed to stabilize gain and to reduce noise
and distortion.
The preamplifier utilizes a 12AY7 twin
triode for its two stages of amplification.
This tube is designed especially for low
level amplifiers. However, to obtain exceptional low hiss, hum, microphonics and
pops, the tubes should be selected for those
characteristics. Tubes which meet these test
specifications and are equivalent to the
type 1620 in regard to these characteristics
may be obtained as MI- 11299. The 12AY7
is also used in the input and 2nd stages
of the program and monitoring amplifiers.
Two identical preamplifiers are mounted
on a chassis.
The program amplifier consists of four
amplifier stages. A potentiometer type gain
control is inserted between the first and
second stage. A 5879 pentode, which is
also a low noise tube is used in the third
stage, and a 6V6 -GT beam power tube is
employed in the final stage. The first and
second stages of the monitor amplifier are
similar to those of the program amplifier.
The third stage and phase inverter utilize
FIG. 7.
a I2AY7 twin triode. The output stage
consists of a pair of 6V6 -GTs in a push pull circuit.
Long tube life was considered in the
choice of all tubes and in the selection of
operating conditions. l'in jacks provided
for measuring the cathode voltages of the
amplifier tubes facilitate checking the condition of tubes and circuits. The amplifiers
chassis float on rubber gromets which
diminish the transmission of vibrations
and further reduce microphonics. Transformers used in the BC -2B are of the same
high quality as those employed in the
standard line of RCA broadcast audio
amplifiers.
Speaker Muting and Warning Light
Relay Circuits
As shown in the installation diagram
Fig. 6, a loudspeaker may be installed
in each of the studios, the control room
and the announce booth. These speakers
may be used for monitoring, cueing, and
talk-back from the control room. In order
to prevent acoustical feedback, it is essential that a speaker be turned off whenever
a microphone is turned on in the same
room. Also, when a studio is on the air,
it should be impossible to talk back or
otherwise interrupt the program progress.
Fast acting speaker muting relays are
therefore provided for both studio and the
Overall view of the Consolette Power Supply, MI.11313.
control room speakers. Space and wiring
are provided for the customer to add a
relay to control the announce booth
speaker if desired.
The relays are operated from a 24 volt
part of the consolette
power supply. Contacts on the microphone
selector (S-1), the mixer (S -2, 3, 4 and 5),
and the line out (S-14) switch provide the
necessary control and interlocking features.
d -c supply which is
If studio warning lights such as "On
Air" and "Audition" (MI -11706 series)
are to be used, these lights may be controlled by a set of warning light relays
(MI- 11702 -A). Power for actuating these
relays is furnished by the consolette power
supply and operation is controlled by the
speaker relays and additional contacts
on the consolette key and push button
switches.
The control circuits are normally connected for two -studio operation. If it is
desired to use all microphones in a single
studio, the circuit may easily be adapted
for this type of service by changing a few
jumpers on a terminal board.
Power Supply (MI- 11313)
The power supply furnishes plate and
heater power to the amplifiers and 24 volts
d -c to the relays. It requires an input power
of 150 watts at 100 -130 volts, 50 -60 cps.
The B voltages are rectified by a 5R4 -GY
and filtered through separate RC filters
for the preamplifiers, program amplifier and
monitor amplier. Two potentiometers are
provided to adjust the hum level to a minimum; one for the preamplifiers, the other
for the program and monitoring amplifier.
Power for the relays is obtained from
a separate transformer and rectified by a
selenium rectifier. The power supply is
housed in a dark umber gray cabinet which
may be hung from a wall, or by means of
suitable brackets (MI- 11650) be mounted
on a standard amplifier rack. The power
switch and fuses are accessible from the
front. After opening the cabinet door, the
chassis may be swung out to provide
access for installation and service. The external dimensions are 10% inches high by
1434 inches wide and
inches deep and
the weight is 32 pounds.
8/
Where extreme reliability of service is
required, a standby power supply, of the
same type as the regular power supply
(MI- 11313) may be installed. A switch is
used to transfer power from one supply to
the other.
12
www.americanradiohistory.com
at
aerara
/RCA
kt/AY
/Z40/O
provides more efficient service
and increases profits
Here's
a
booklet that describes the advan-
of 2 -way radio ..:'what it is"...
"what it does "..."how it works."
BOB
In the
... emergencies
Explains how 2 -way radio enables taxicabs to serve more people faster
cut
down on "dead" mileage
boost cab
profits. Tells you how trucking companies
use 2 -way radio to handle a greater volume of freight and maintain supervisior
of trucks en route. Shows the use of 2 -way
radio by inter -city and urban bus and
trolley lines for more efficient handlinp
service ... on problems of usage, coverage,
obtaining a construction permit. Every
transportation executive should send for a
copy. (In Canada, write: RCA VICTOR
...
Contains information about RCA's
Limited, Montreal.)
/
HOPE
Hou.,"
caused by
breakdowns or traffic jams.
...
medy
of peak loads
tages
NBC
act...
without hiding the star
RCA's
"STA'MAKUR"
... a
nhbon- pressure microphone that
so skillfully styled
so
slim
unobtrusive ... you must look twice to
see it.
is so
...
...
Despite its slim construction, the
exacting quality
standards of other RCA professional
Broadcast microphones. Pick-up is nondirectional. Frequency response is substantially uniform, 50 to 15,000 cps. It
is free from wind rumble and air blast
and virtually impervious to mechanical shock.
STARMAKER meets the
...
The STARMAKER fits any standard
can be used in
microphone stand
place of and RCA microphone. No
extra attachments needed.
...
For delivery information call your
RCA Broadcast Sales Engineer, or write:
Department QA -19, RCA Engineering
Products, Camden, N. J. (In Canada
write: RCA Victor Limited, Montreal.)
RCA ENGINEERING PRODUCTS
Dept. 129G
Camden, N. J.
Send me a copy
Name
Firm
Address
c
of
"2 -way Radio for the Transportation Industry."
Stan
ty
RADIO CORPORATION
of AMERICA
13
www.americanradiohistory.com
1
(above). The new KRON -KNBC transmitter building atop San Bruno mountain, the highest point on the San Francisco
peninsula. Towers, left to right, include: KRON television radiator, with two parabolic receiving antennas at the base and the
KNBC -FM radiator with its receiving dish installed near the steel fence. All signals reach the San Bruno site via microwave.
FIG.
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Dominating San Francisco's south skyline is San Bruno mountain, the peak of
which is marked by KRON -TV, KRONFM and KNBC -FM antennas. Recently
installed RCA equipment is now broadcasting sight and sound programs at this
point from a common transmitting plant
(one building houses the transmitters of
both KRON and KNBC).
Television Peak is not only the top of
San Bruno mountain but it is also the
culmination of a new three -lane highway
that snakes up through a residential section, an army receiving station, and pastures with grazing cattle. At the end of
the road stand the two towers and the
KRON -KNBC building. The long, low slung, light and dark green structure combines the one -story spaciousness of California ranch style with the crisp, clean -cut
lines of modern design.
The two antenna towers (TV and FM)
overlook the entire bay area just south
-
IN
SAN
AL ISBERG
FRANCISCO
transmitter site with a very low density of
population on that side of the mountain.
Electronic Systems Consultant
Chief Engineer, KRON -TV,
San Francisco, Calif.
KRON's (TF -DA) TV Antenna System
Since it appeared unwise to waste a
large percentage of the station's power
over the ocean, RCA's engineers suggested
that we consider a directional antenna and
increase the effective radiated power over
the populated areas.
-at
of San Francisco
an elevation of over
a quarter of a mile above sea level. Tips
of the towers average 1,325 feet above all
terrain within a ten mile radius. Illustrated
on these pages are the estimated 5 -milivolt and .5- milivolt coverage contours
obtained with KRON's TF -DA three section omni-directional antenna. In this
The proposed antenna was the TF -DA
with eight dipoles and screen reflectors
mounted on each of two sides of a square
tower. The resulting pattern will cover the
densely populated areas surrounding San
Francisco Bay and will provide an improved signal -to -noise ratio compared to
the same transmitter power into an omnidirectional antenna.
illustration the surrounding countryside
and terrain may be studied. The transmitter site is located near the boundary
which separates San Francisco from San
Mateo County, and this location will ultimately become the center of population
as the Metropolitan Bay Area expands.
The peninsula is rather narrow and the
The antenna gain of the directional array
consisting of eight radiators on each of
two adjacent sides of the tower is esti-
ocean is only four miles to the west of the
Overall map of surrounding terrain showing the 500 and 5000 microvolt coverage
contour lines. Note that black arrow indicates position of San Bruno mountain, KRON site.
FIG. 2.
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KRON'S (TF -DA) Antenna
System (Cont'd)
The KRON -TV Ideco tower and TF -DA
three -section antenna which will later be made
directional by moving back screens to front side.
Note gradual curve of transmission line which
follows ladder girls inside tower to eliminate
special angle and reduce discontinuity of line.
FIG. 3.
Close-up view at top of tower showing
how antenna screens are clamped to tower upright angles. The [deco tower was custom made
to fit RCA antenna screens exactly.
FIG. 4.
mated by RCA engineers from work done
on scale models and from calculations to
be 20.1. This figure includes the losses in
the feed system within the antenna and
is multiplied by the efficiency of the transmission line from transmitter to antenna
to obtain the gain of the system. This is
the gain in the maximum direction, as
distinguished from average gain through
some designated horizontal angle. The vertical beam width is empirically given as
61/ 8 = 7.6 degree.
Although the FCC freeze precluded the
erection of a directional antenna at the
time the station was built, the tower was
designed and positioned with future directionalization in mind. It will be made directional in the future by moving elements
on the ocean side to the sides facing the
densely populated areas. Early tests of
the transmitter were conducted with a
single section Super Turnstile mounted approximately 30 feet above the building
roof. A comparison of the tests with the
low antenna having a power gain of 1.2
compared to the TF -DA with a gain of
3.3 is very interesting, because it shows a
greater than expected increase in signal
strength for the higher antenna at line -ofsight locations, and sometimes a slight decrease in signal strength in shadowed locations behind hills.
The antenna arrived by air freight late
on a Saturday night, it was spray painted
on Sunday, hoisted up on the tower and
bolted in place on Monday and Tuesday,
and the electrical installation was cornpleted and tested on Wednesday.
FIG. 5. At top is E -W junction box and at top
straight length of
right, N -S junction with n
line for 90 phasing. A termination resistor on
power equalizer absorbs reflected energy from
antenna mismatch to present resistive load to
transmission line. This avoids energy reflections
back to transmitter.
FIG. 6. The power equaliser and transformer assembly is spring supported by standard transmission line brackets so that it may be separated
from the 3I/4" line for maintenance and inspection. Note long taper 3'/e" to VA" reducer used
to reduce discontinuity.
are spring clamps on each 15s
transmission sections and at right center rigid
clamps for the power equalizer are visible. At
bottom note close -up view of spring clamp.
FIG. 7.
At top
www.americanradiohistory.com
The 200 -foot Ideco tower was designed
to accommodate the Channel 4 TF-DA antenna on the sides of its upper 100 feet
of uniform cross- section framework. The
accompanying pictures show the antenna
installation as it was being made.
FIG. 8. Photo showing support of transformer sections of Fig. 7. Note additional rigid clamps are
added to reduce movement of line during high
winds. Vibrations of line otherwise cause steel
springs around inner conductor to dig pieces of
copper which short insulators, causing overloads.
o
At right top on N -S
transformer and junction box and
FIG. 10.
at center E-W transformer and
junction box. Junction boxes are
secured by rigid clamp. Cables
care dressed cnd secured so transformers and equalizer may be
raised one foot or more for checking transmission line with calibrated termination.
FIG. 9. Top view of the junction boxes and transformer assemblies for the TF -DA antenna. Each
junction box has six RG 34 U cables of equal
length which terminate at the dipoles. Coaxial
transformer assemblies are made up of sections
having different size inner conductors.
Close -up view showing
feed lines were run and
any excess cable was carecoiled and taped. Also note
clamps cre used to secure
coils in position.
FIG. 12.
how
how
fully
how
FIG. 13(A). All electrical connections to the antenna were made
by erectors under the chief engi-
neer's supervision.
FIG. 11. All work was personally supervised by
R. A. Isberg. Chief Engineer of KRON -TV, shown
here checking junction box at the center of the
antenna. The feed lines were taped to the supporting structures with Scotch electrical tape and
then painted with red Glyptal. Aeroseal clamps
were used to secure the cable to the structure.
FIG. 14 RG 34 u cables were supplied with threaded brass sleeves attached
to the shield braid for connection to the end of the dipole feed section.. The
center conductor was soldered to a fitting which connects to a strip of metal
for feeding the other half of the dipole. The workman has attached the cable
to a special "fishing line" so that it can be pulled up to connect to the dipole.
In this view riggers are showing making electrical connections to the antenna dipoles. Some of this work
was done from a bosun's chair outside the screens.
FIG. 13(B).
www.americanradiohistory.com
Transmitter Building
streamlined all- concrete building
houses the KNBC -FM, KRON -FM and
KRON-TV transmitters on Television
Peak. The building architecturally appears
to be one unit but is actually two buildings with a common wall. This construction was deemed desirable to take advantage of protection from the prevailing
winds and for security reasons. KRON -TV
occupies about half the building at the
San Bruno site. Owned and operated by
the San Francisco Chronicle and affiliated
with NBC, KRON -TV serves as KNBC's
television outlet.
A
Both KNBC and KRON -TV maintain
convenient studios in downtown San Francisco, however, KRON -TV's quarters on
Television Peak also include a 19 -by -12
foot studio for simple telecasts. The new
plant also provides dining and sleeping
facilities and storage space for filin and
slide projection equipment. Rain water collected on the roof is stored for sanitary
purposes in four 5,000 gallon tanks.
Bottled water is used for drinking. (See
building floor plan for location of equipment and facilities.)
FM Equipment
The KNBC-FM transmitter is an RCA
BTF -IOB. KNBC -FM's new eight section Pylon antenna increases the station's effective radiated power from 4,500
watts to 45,000 watts. With high power,
plus the high elevation, KNBC assures
high quality FM reception far beyond the
bay area.
10 -kw,
The KRON -FM transmitter is BTF-3B
and utilizes a directional 4 layer dipole
and screen reflector antenna which is a
prototype of the future directional TV antenna. Field strength measurements and a
FIG. 15. San Bruno floor plan showing the location of TT-SA transmitter
and video control facilities. Note that auxiliary TV studio is provided.
WATER PRESSURE
SYSTEM RADIENT
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SPLICING
FIG. 16.
View
of
the KRON -KNBC all concrete building which is situated atop San Bruno mountain.
FIG. 17. Front view of the KNBC -FM transmitter and FM monitoring
All equipment is installed "in- line." Sam Molnicoe is the
at right.
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and test equipment
engineer on duty.
Under the guidance of Mr. Charles
Thieriot, Manager of KRON -TV, and
Mr. Harold See, Director of Television,
the technical operating requirements were
determined first by studying scale models
and then by building full scale mockups.
Experienced technical operating and program personnel assisted in the "dry runs"
in the mocked -up control room and as a
The KNBC -FM transmitter operates on
99.7 megacycles and KRON -FM utilizes
96.5 megacycles. No RF interference in
video systems has been experienced.
PULSE
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This operation includes the television
transmitter two film cameras; three slide
projectors; one opaque projector; two
16mm motion picture projectors; a two
camera (fixed position) live studio; the
studio -transmitter microwave link; a sec-
Simplified diagram showing the interrelated KRON TV video equipment and facilities employed.
FIG. 18.
TG -IA
SYNC.
result an unusual "U" shaped control area
was adopted which satisfies all the requirements of efficient television station operation -with only two technicians on duty.
KRON Video Facilities
study of reception on the null side of the
antenna indicates that the proposed antenna pattern is satisfactory and that no
multipath problems are encountered. This
antenna is mounted on the same tower as
the TV antenna.
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FIG. 19. View of the KRON -TV transmitter (RCA TT -5A( and master control position which includes
both audio and video control equipment. At right, audio control and 70 -D Turntables are visible.
MULTIPLEXER
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and microwave link, and a two -channel
audio system complete with magnetic tape
recording facilities. A third man is assigned
when it is necessary to dolly or change
camera positions.
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Everything that has a switch or a knob
is within a few feet of either operator,
whose chairs are on casters. The technicians are trained to handle any function
and during periods when either of the men
is absent from his chair attending other
duties, such as, loading the automatic
slide or film projectors, taking meter readings of the transmitters, or setting up the
live cameras, the other man assumes his
responsibilities. This is possible when the
sound portion of the program has been
previously monitored as in the case of
downtown studio shows, remote broadcasts,
film programs, network programs, tone
with test pattern, long playing records or
sound recorded on magnetic tape.
Although two men are normally assigned
when switching operations involves both
aural and visual systems such as the beginning and ending of any film program,
transition from film to studio or remote,
live programming from the mountain stu-
dio, etc., the system is designed so that
one man can perform both operations
which he customarily does during test
pattern transmission.
Innovations in the film room design include automatic slide projectors which are
controlled from the video operator's console: remotely controlled 16mm film projectors with rapid braking: modification
of the 16mm film projectors to utilize reels
with up to 3600 feet of capacity; and
eliminating film make -up and splicing
from the operation function makes it unnecessary to man the film room except
for loading the projection equipment. In
the event of splice breaks or loss of a film
loop, the audio man takes over the camera control as well as audio, and the video
man covers the film room which is only
a few feet behind his normal operation
position.
Directly behind the operating console
is located a 12 -by -19 foot TV studio large
enough for two studio sets and two TK -30
cameras. By means of rolling backdrops
this studio is readily converted from a TV
news room to a set where commercial
demonstrations may be made. Hot and
21
www.americanradiohistory.com
cold water, sewer connections, and outlets
for electrical appliances are provided for
such demonstrations. This studio is especially useful on weekends, holidays and
for late night operation, and since it is
not necessary to keep the downtown studio
manned for more than five days a week,
there is considerable saving in operating
cost.
For some shows, two fixed -position unmanned cameras are often used. For shows
requiring panning and focusing of two
cameras, one technician is assigned to
handle both of them. This may seem hazardous on first thought, but in the small
studio he merely has to move three feet
to pan and focus the other camera, and
the production is directed accordingly.
FIG. 20.
Block
Most of the live productions have an established format or are entirely extemporaneous. The unusual sequences of the
shows from the mountain studio are rehearsed, but it has been found that with
the small crew of two or three skilled technicians and a producer- announcer, organization and teamwork prior to and during
the show always results in a satisfactory
performance.
The operating console and rack arrangement is shown in Figs. 18 and 19. The
RCA TG -1A Synchronizing Generator is
on the left. The video equipment rack is
adjacent and contains two RCA TRR -1A
microwave receiver control units, two RCA
TA -5B Stabilizing Amplifiers, a modified
RCA TV Jack Panel, and two RCA TA-1A
Distribution Amplifiers. The third rack
contains the RCA 86 -Al Limiting Amplifier, Audio Oscillator, Magnetic Tape Recorder, Audio Jack Strips, Video Bar Generator, Line Equalizer and one RCA TA-1A
Distribution Amplifier.
The first section of the console is the
RCA TT -5A transmitter power panel. In
the space below the operating shelf is located a circuit breaker panel for the TV
studio lights.
The second section of the console is an
RCA TM -5A Master Monitor associated
with monitoring input and output of the
TT -5A Transmitter. The third section is
an RCA 90-degree desk section which accommodates the aural and visual control
"System. diagram showing the interconnection of BRON video facilities.
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22
www.americanradiohistory.com
DRIVE
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Close -up view of part of the KRON -TV master control desk. Shown left to right are: William
Sadler at video controls, Jule Vetter at audio control position, and Marc Spinelli. producer- announcer.
FIG. 21.
panel for the TT -5A, and the intercom
equipment from master control to TV studio, film room, front door, FM studio, and
shop. The circuit breaker panel for all TV
and audio equipment (other than the film
room and the transmitter) is located under
the operating shelf on this console section.
Next are located control equipment for
two RCA TK -20 film cameras; a special
panel for remote control of all slide and
motion picture projectors a two -channel
audio mixer having a choice of ten input
circuits selected by push buttons; and an
RCA TS -10A Switcher.
;
Two TK -30 Camera Control Units are
mounted on an adjacent composite corner
console within easy reach of either the
video or audio man. While the video man
is shading a film chain, the audio man sets
up the TK -30 cameras. During a live show,
the audio man monitors audio levels and
the video man conveniently operates the
camera controls which are adjacent to the
TS -10A Switcher. The block diagram of the
video facilities is shown in Figs. 18 and 20.
The audio console contains the equivalent of a relay rack of RCA audio equipment and was specifically designed and
built for our operation by KRON -TV engineers. Two mixer channels are provided,
Channel being the two mixer channel for
the video control position, and Channel 2,
which is a six -position mixer located in the
audio console. A unique circuit arrangement permits transferring a program from
one channel to the other or simultaneous
operation with both channels feeding the
program buss. This feature is very useful
for auditioning live shows, film, etc., and
also permits feeding recorded music for
aural backgrounds into the studio and on
the air simultaneously without danger of
acoustical feedback. Fig. 22 shows the
block diagram of the audio system.
1
The remote control of the projection
equipment, turntables and magnetic tape
equipment is accomplished by means of a
12 -volt d -c power supply and relay system.
Turntables and magnetic tape machines
may be started and stopped from either
or Channel 2 audio console
the Channel
positions. Transcribed aural station identifications or sound on film are normally
used unless an announcer is available in
the studio.
1
The automatic slide projectors were
carefully selected from a number of com-
merciai models and were modified to suit
our requirements. The modification consisted of a new cam, a reversible motor, a
new lens barrel, a modification of the
blower system to keep the slides cool, a
variac for the lamp, control relays and
rewiring.
The location of the power supplies in
racks removed from the operating area reduces the heat and eases ventilation requirements for the operating personnel. All
power leads were shielded wires run in
trenches. All a -c power circuits were run
in conduit. A grid of copper strips was
laid on the ground prior to pouring the
concrete floor slab and tabs from this
ground system appear in the trenches at
intervals of approximately four feet. R -f
interference and cross talk has been a minor
problem in the entire installation with the
exception of the necessity for some additional filtering of the plate supply of the
microwave receivers to eliminate a "wind
shield wiper" on microwave programs
caused by a beat between synchronizing
generators. The ground system was planned
to avoid "ground loops," paint was removed from the rails which support rack
mounted equipment and bonding proce23
www.americanradiohistory.com
dures were given careful attention during
the assembly of the transmitter.
and likewise were checked during noisy
operating periods.
Downtown Studios
The KRON-TV studios were constructed
on the ground floor of the Chronicle Building in downtown San Francisco. The floor
plan is shown in Fig. 25, offices and a rehearsal studio are located on the second
floor. The noise isolation problems in a
newspaper building are numerous and except for other compelling factors, the construction of TV and radio studios in such
a building is not always a wise choice.
Consideration was given the ambient
noise level in a TV studio with camera
blowers, ventilation noise, rustle of clothes,
etc., as well as the relation of the microphone with respect to the source of noise.
It was decided that an ambient noise level
due to the above causes will average between 30 and 35 db below program level
under usual operating conditions with
present equipment, but 98% of the TV
receiver owners will not hear this noise
because their small loudspeakers will not
reproduce the low frequencies.
The noise levels and vibration amplitudes were measured during all anticipated
hours of operation of the station and under
every condition of noise usually encountered in the building. Test floor slab sections and wall sections were constructed
The walls enclosing the studio space were
constructed of hollow tile with plaster on
both sides, both brown and white coat, and
will isolate airborne sound levels of the
order of 40 db. However, these walls contain all the vibration in the building, and
riCONTROL
the inner walls of the studio are designed
to reduce the conducted vibration noise
as well as to provide desired absorption
characteristics.
Adjacent to the tile wall is an overlapping layer of %" celotex wallboard.
then an air space, then a free standing
2" x 4" stud wall on 16" centers with /z"
celotex panels adjacent to the air space
and bridging between studs. The bridging
serves two purposes: it stiffens the wall
and also supports the glass wool batts
which fit between the studs. The walls
were then covered with flame -proofed
white muslin and poultry netting was
stretched over the muslin as an outer protection. The stud wall rests upon a celotex
pad at its base.
The ceiling already existed as metal lath
and plaster suspended on wires but with
no isolators. Since quiet office area were
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FIG. 22. Simplified block
24
www.americanradiohistory.com
diagram
of the KRON-TV
audio control facilities.
View of the KRON -TV mountain studio in operation as seen from
the master control desk. At left. audio control position is partially visible.
FIG. 23.
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above the studio, this ceiling was not modified with isolators but was merely furred
down to accommodate the fiberglass batts,
muslin and chicken wire.
It
was decided to leave the floor isola-
tion to the last and to decide about it
after the entire studio was enclosed. Because of the fact that the printing presses
are mounted on isolators, very
little
noise
transmitted from them to the building.
The airborne noise level in the press room
is of the order of that in a subway with
two express trains passing each other, but
this noise is very effectively isolated by
the wall construction of the studio and
other partitions which exist between the
studio and the press room.
is
After several weeks' operating experiit was decided that since the studio
ence,
ambient noise was much greater than the
press room and other building noise transmitted through the floor, the isolation of
the floor would be of little value and
might aggravate the situation, since if its
natural frequency was in the range of the
building vibration frequencies, resonance
could occur.
The concrete floor was leveled with
mastic pave and then covered with rubber
tile of a light shade. The rubber tile absorbs foot falls and is more satisfactory for
studio use than asphalt tile. The light
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shade was chosen to aid lighting by reflection and for its appearance on the monitor
screens.
The studio sets are arranged so that
they may be lighted and left unmolested
from week to week. Eight sets including a
complete electric kitchen may be so arranged. A combination of 40- percent 4500
white fluorescent light for overhead and
general illumination with 60- percent incandescent flood and spotlights for modeling, back light and key lighting is used.
The fluorescent lighting is from Allen
Olsen 600 ma slim -line units, and the reactors are mounted in a cabinet in the
basement. All lighting circuits appear on
3 -wire twist -lock and Cannon receptacles
mounted on the pillars in the studio. Cords
from the lighting fixtures, which are
mounted on a ceiling pipe grid, are protected by circuit breakers located in the
control room.
Normal studio operation requires a technical staff of five men. The group supervisor customarily acts as camera control
operator and switcher, two men are each
assigned cameras, one man audio and
microwave, and a junior technician is
boom operator. All men are licensed operators and can rotate in assignments.
24. Partial
audio console with
plug-in amplifiers.
mounted on front
FIG.
An air lock between the control room
and the studio is designed as an announce
rear view of the KRON -TV
panels removed to show RCA
Two BA -4A Amplifiers are
side under operating shelf.
25
www.americanradiohistory.com
booth and permits the producer of a show
to also serve as an announcer. An off-theair monitor receiver is provided and the
announcer has control of his microphone
switching and communication with the control room.
Provision is made in the equipment
room for future film projection facilities,
but at present all film originates at the
transmitter. By comparing the phasing of
the two synchronizing generators prior to
a show, it is possible to make switches
from studio to transmitter without rolling
frames on home receivers.
For approximately the first year, KRONTV operated six days a week with a test
pattern schedule of
12 hours, a live program schedule of 20 hours, and approximately 30 hours of film including kinescope
recordings. Eight technicians and a chief
engineer comprised the technical staff; and
three producer-announcers, one film editor,
and a program director comprised the program department. The station is now in
its second year of operation and it operates on a seven -day schedule. It has
doubled its operating time; increased its
studio space 50 percent; its program staff,
200 percent; and its technical staff, 250
percent.
The achievement of the goal to make
KRON -TV an economical and practical
television station would not have been
realized without the wholehearted interest
and cooperation of Mr. Charles Theiriot,
Manager of KRON -TV; Mr. Harold P.
See, Director of Television; and the program staff. Credit is especially due Mr.
William Nielsen for the construction of
the audio consoles, William Sadler for
the video system installation, Jule Vetter
for the transmitter installation, Donald
Anderson for projection remote control,
Roger Woodruff for power circuit engineering, Fred Street for studio plans, Ed
Price and Hal Simpson for studio techniques, Lee Berryhill and Granville Esch
for the studio-audio installation.
26. The control room at the Chronicle
Building studio. Two RCA TB -30 Cameras are
normally utilized but four can be used when
necessary. Two TTR -1A Microwave Links and
STL facilities are used to send visual portion
of program to San Bruno mountain.
FIG.
Floor plan, showing the studios end other facilities located at the Chronicle Building in San Francisco.
FIG. 25.
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KRON -TV OFFICES ON SECOND
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VENTILATING EQUIP
www.americanradiohistory.com
o
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Field Engineering Service
to Broadcasters...AM, FM, TV
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FUTURE
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EXPANSION
RCA Service Company engineers are
experienced in all the latest techniques
and are equipped with the most modern
specialized measuring equipment. The
RCA Service Company has been working hand in hand with the nation's
broadcasters for over 25 Nears.
á
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OUR SERVICE TO BROADCASTERS...
Installation supervision and measure ments of transmitting, studio and
accessory equipment . . . AM, FM
or TV.
Prompt help in emergencies. Technical
Instruction and training of station operating personnel.
Performance measurements and adjustments for station compliance with FCC
regulations.
advice, service, and assistance on special problems.
Measurement and curves on FM and
TV antennas and accessory equip.
men t, including transmission lanes,
o
o
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For further information call or write
Communications Service Section, RCA
matching networks, diplexers.
Service Company, Inc., Camden, N. J.
(For service outside the U. S. A., consult your Authorized RCA Distributor)
NOW- restore the original quality of your
RCA microphones, transcription pick -ups and test and measuring
equipment under the new Factory- Reconditioning Plan.
For complete details, write: Return Apparatus Control,
Building 8-2, Camden, N. J.
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RCA Service Company, Inc.
A
Subsidiary of the Radio Corporation of America
CAMDEN. NEW JERSEY
WNAG'S NEW
"250",
250 ",
BTA -250M
By ROBERT McRANEY
General Manager
The Mid -South Network
WNAG
of Grenada, Mississippi,
which is now operating full time with a
brand new RCA BTA-250M, is affiliated
with the Mutual Broadcasting System and
the Mid -South Network. The WNAG installation represents one of the first (if not
the first) of the new RCA transmitters
to be put into service. Transmitter operation has been exceptionally stable and
FIG. 3. View of the entrance to WNAG's
station building.
ment, two studios and associated control,
lobby, offices and workshop.
FIG. I. View
WNAG's
transmitter
of
room.
Mr. Robert McRaney, General
Mid -South Network.
Manager,
reliable. It is well suited for the "combination" type of operation employed at
WNAG where the announcer is also the
engineer, etc.
WNAG Building Facilities
FIG. 2. Close up of the
BTA.250M
transmitter
which is
mounted in a
standard
cabinet rack
for maximum
convenience.
\VN.AG is housed in the building formerly occupied by the Administration
offices of the old Grenada College for
Women. The Barwin Hotel, which now
occupies the old dormitory of the school,
converted the administration building into
apartments, leaving the entire ground floor
for WNAG facilities. Because the school
had a large campus area, we were able
to locate the tower adjacent to the "studio transmitter" building to effect a combined
and compact setup.
As shown in the floor plan, the ground
floor layout provides adequate room for
the transmitter and associated test equip28
www.americanradiohistory.com
The New BTA -250M
The new transmitter occupies the central part of the "transmitter room" space
and is flanked by a relay rack containing
RCA Frequency and Modulation Monitors
and patch panel on one side -and the old
RCA 250 -D Transmitter on the other side.
The old transmitter is now employed as a
"standby" and is a converted exciter unit
of an RCA 1 -D which gave many years
of excellent service, first at KITE, Kansas City, later at WROX, Clarksdale,
Miss., and finally at WNAG.
The new BTA -250M transmitter employs a pair of 813 tubes in parallel as
power amplifier, modulated by a pair of
813's operating class B. The oscillator
employs the TMV-129B temperature-con trolled crystal unit. The output of the
oscillator feeds a single RCA 807 tube
operating as a buffer amplifier. The 807
buffer in turn drives the power amplifier.
New circuit design in the BTA-250M
simplifies transmitter adjustment and operation. There is only one tuning control
RECORDING
ENTRANCE
EQUIPMENT
STANDET
TRANS.
MANAGERS
CONTROL
ROOM
NEW
RCA
RACK
OFFICE
OFFICE
TRANS.
RELAY
RECEPTION
Staff
RCA
CONSOLE
a
TRAFFIC
OFFICE
TRANSMITTER
ROOM
STUDIO
Tom McFerrin, Chief Engineer for the
Mid -South Network, was in complete
charge of the WNAG transmitter installation which proceeded smoothly in all
respects.
The WNAG station staff includes three
LOBBY
who can double as full -time engineer -anENTRANCE
AUDITORIUM
tion. In addition, WNAG employs RCA
microphones, sound system, and remote
pickup equipment.
nouncers. Mr. Monroe Looney, Station
Manager, holds a first class license himself
and can also double as Chief Engineer and
announcer. The balance of the staff consists of a part -time announcer -salesman, a
receptionist -copy writer and a bookkeeper.
STUDIO
FIG. 5. A view of the control room of Radio
Station WNAG. The RCA console and varicoustic
mike are shown. The console operator faces a
window separating the control room and the
transmitter of WNAG. At WNAG the engineers
also serve as announcers in a "Combination
type operation.
Floor plan
showing layout of
building to accommodate transmitter
and studio facilities.
FIG. 4.
WNAG coverage contour map.
and one power output control in the entire
transmitter. The tuning control is a varia able capacitor in the plate circuit of the
power amplifier, and the power output control is a variable resistor in the cathode
circuit. For the low level r -f stages, the
807 crystal oscillator plate is broadly tuned
by an inductor with suitable taps to cover
the broadcast band. The 807 buffer plate
is also broadly tuned for the entire broadcast band.
Studios
\ \ "\.AG studio facilities consist of two
studios (one an "auditorium" type) and
a studio control room which houses the
audio control, turntables and recording
equipment. The RCA Consolette is arranged so that the operator has visibility
into the transmitter room and adjacent
studio. This facilitates operation since at
WNAG the engineers also serve as announcers in a "combination" type opera-
Monroe Looney. Station Manager
for WNAG.
29
www.americanradiohistory.com
TELEVISION LEVEL MEASUREMENTS
TYPICAL
MEASURED
REFERENCE
LEVELS
LEVELS
.- - -
100
80
Waveforms
showing significant
levels and details
FIG.
1.
the
standard
scale for measuring
of
video levels.
60
40
20
--0
WHITE PEAK
REFERENC E
WHITE LEVEL
-
ft
-
0-
-20-40
-BLACK PEAK
,
L_ _
REFERENCE BLACK LEVEL*
BLANKING LEVEL
.SY NCH
LEVEL
RONIZING
NOTE : REFERENCE BLACK LEVEL TO BE SPECIFIED IN ACCORDANCE
WITH OPERATING PRACTICES.
STANDARDIZING AND MEASURING
VIDEO LEVELS IN A TV STATION
Introduction
by J. H. ROE
The subject of video levels
in television
from standpoints of both
broadcasting,
standardization and measurement, has been
going through a slow process of evolution
ever since the early experimental broadcasts in the 1930's. At first, as should be
expected, the significance of all the factors was not fully appreciated, and, as a
result, accepted values and methods have
been changed from time to time in an
effort to keep pace with the advances in
techniques and equipment. There is no
assurance that this evolution has now
reached its final stage, but substantial
changes which have developed recently
are a sufficient reason for restating the
situation as it appears to be at present.
Review of Past Practices
In 1936, the first major installation of
television broadcasting equipment in New
York was made in the studios of NBC in
Radio City. One feature of this installation which bears on the subject of levels
was a mile and a quarter of coaxial trans-
mission line connecting the studios to the
transmitter in the Empire State Building.
With the lines and equalizers used at that
time, it was thought necessary to feed
the input of the line at a level of about
5 to 10 volts, peak -to -peak, in order to
secure an acceptable signal-to -noise ratio
at the transmitter input. This situation set
the pattern for line amplifiers at the studio
TV Terminal
Equipment Engineering
output until the approach of the development of commercial equipment during the
last year of World War II. Video levels
within the studio plant during that period
were generally set at about 1 volt, peak to -peak.
In connection with post -war developments, there was activity in technical corn mittees of the Radio Manufacturers' Association (now the RTMA) to evolve suitable standards for commercial television
equipment. Among the standards adopted
by these committees in 1946, was one
which specified that studio output amplifiers should be capable of producing a level
of 2 volts, peak-to -peak, of composite picture signal, including about 0.5 volt of
sync. At that time, there were some wire
line interconnections in use in New York
provided by the Telephone Company and
consisting of ordinary telephone cable pairs
with equalizers spaced at frequent intervals. The 2 -volt level was considered high
enough to avoid objectionable noise, and
low enough to avoid noticeable cross talk
in the telephone cables. Furthermore, it
appeared to be possible to develop this
voltage efficiently with acceptably low distortion, on a 75 -ohm transmission line
load by using a single 6AG7 tube in the
output stage of a studio amplifier. It was
also felt that the use of a 2 -volt level
30
www.americanradiohistory.com
would permit simple and economical designs of picture monitors with a minimum
amount of video signal amplification. In
RCA pickup equipment, the 2 -volt level
was adopted as standard on nearly all 75ohm interconnecting circuits carrying composite signals, and a 1.5 -volt level on 75ohm circuits carrying non -composite signals (no sync present).
The cathode ray oscilloscope (CRO) has
been used universally, during all these
various stages of evolution, primarily as a
level indicator, but in addition as an indicator of quality of the picture signal. One
typical example of its use as a quality indicator is found in the adjustment of shading signal controls where the CRO gives a
more critical indication of uniform background than does the eye by direct observation of the monitor kinescope.
Recent Trends
The rapid and continuing growth of network facilities, together with the almost
unbelievable expansion of studio facilities
in some of the larger stations with all their
highly complex interconnections, has made
evident some weaknesses in the adopted
video level standard as related to the design of equipment which is in widespread
use at present. It has become apparent
that the earlier concept of acceptable amplitude distortion limits in line amplifier
stages has to be modified when applied to
a large system where the number of equipment units is greatly increased as compared
to that involved in a small operation. For
example, a signal originating in an outlying studio of a large station may be
passed through as many as ten line amplifier stages before arriving at the transmitter. If the signal is fed through a cross-
country cable network, it may pass through
several hundred repeater amplifiers before
reaching its destination. It is obvious that
the distortion in any one amplifier must
be held to an extremely low value if the
cumulative distortion in such a system is
to be tolerably small.
Amplitude distortion of a television picture signal results in unnatural tones of
gray in the reproduced scene. The most
common type of distortion changes tonal
gradation in the light grays and nearwhites. Faces may look too white and
washed-out, and lack any appearance of
depth. In order to illustrate the significance of a small amount of distortion in a
single amplifier unit which is part of a
large system of many similar units, let us
assume that the permissible limit of compression of the whites accumulated in the
entire system is 25%. This particular value
has no special significance, but it is an
amount of compression which is observable, and may be assumed for purposes of
discussion. In the case of a system having
100 amplifiers in cascade, the compression
per unit would have to be less than 0.3
of 1% to stay within the assumed limit.
Fortunately, the network equipment is
designed to avoid distortion to an acceptable degree. On the other hand, many
studio amplifiers do not have adequate
linearity to provide satisfactory operation
in cascade in large numbers with a level
of 2 volts. Rather than recommend modification or replacement of the large number of such amplifiers now in use, with
attendant high cost and inconvenience, it
seemed preferable to recommend a reduction in the standard signal level which
would make possible a noticeable decrease
in distortion without an appreciable increase in noise.
Operating scale No.
camera controls.
Reference white at
FIG. 2.
Reference black at
Blanking level at 0
100
80
1
become the principal source of network
programs on television. Another problem
had also been adding to the confusion,
namely, that in spite of the RTMA standard 2 -volt level for video amplifiers, there
was no adherence to any operating standard
in this matter. The levels put out by the
New York stations were nearly all different, determined largely by requirements
of common carrier equipment used for interconnections and for networking. These
varying requirements resulted from the
fact that common carrier terminal equipment had grown up with the demand; it
represented, in some cases, different stages
of development, and did not adhere to one
standard in the matter of levels.
0.
Video Signal in Volts
The choice of the new level of 1.4 volts
was guided, of course, by the need for reduced distortion, but in addition, it was
influenced by the recently adopted IRE
Standard* which included, among other
things, a standard scale for measuring video
levels. This scale is shown in Fig. 1 which
is a reproduction of the diagram in the
IRE Standard. The special committee of
FIG. 3. Operating scale No.
with composite signals.
for use at
2
for
100
Practical Scales for CRO Tubes
The three scales shown in Figs. 2, 3,
and 4 were recommended by the Special
Committee for practical use on the faces
of 5 -inch CRO tubes as follows:
SCALE 1 (Fig. 2)
To be used with either studio or film
camera controls where non -composite
(no sync) signals are used. Blanking
level is at 0; reference black is indicated at 10; and reference white is at
100. Total deflection is 2 inches between
0 and 100.
SCALE 2 (Fig. 3)
To be used at studio or master control outputs, or for preview monitors,
or for any monitor where composite signals are present. Sync peaks are at -40;
blanking at 0; reference black is indicated at 10 ; and reference white is at
100. Total deflection is 2 inches between
-40 and 100.
SCALE 3 (Fig. 4)
To be used at the transmitter location
where composite signals are present and
where it is desired to measure depth of
modulation. Scale numbers on the left
*STANDARD, 50 IRE 23.51-TELEVISION : METHODS OF MEASUREMENT
OF TELEVISION SIGNAL LEVELS, RESOLUTION, AND TIMING OF VIDEO
SWITCHING SYSTEMS, 1950. This standard was published in the May, 1950 issue of
Proceedings of the IRE. Reprints may be purchased from the Institute of Radio Engineers,
East 79th Street, New York City, for $0.70
1
each.
Operating scale No. 3 for use at
a transmitter location where depth of modulation is to be measured.
Reference white at 100. 12.5% carrier
Zero carrier at 120, 0% carrier
FIG. 4.
use
Reference white at 100
Reference black at 10
Blanking level at 0
Sync peaks at -40
10
100
80
40:
40
y
Reference black at 10
Blanking level at 0, 75% carrier
Sync peaks at --40, 100% carrier
100.
60.
=
Number of IRE Scale Units
The IRE Standard Seale
100
100
+ 80
80
60
40
40
20
20
20
O
20
broadcasters and television
manufacturers decided to recommend correlating the new video level in volts with
the arbitrary units in the IRE scale.
The desired relationship is given by the
expression:
New York
The situation was given special attention by an informal committee composed
of representatives of the six television stations in New York City and of the Telephone Company and of some interested
manufacturers of television equipment.
This group held several meetings between
May and September and proposed a standard operating level of 1.4 volts, peak -topeak, of composite signal as outlined in
Fig. 1. The new level has subsequently
been adopted by the New York stations
as well as by some others. It has been
agreed that this level will be satisfactory
in the common carrier operations though
there will be a transition period required
for modernizing some of the existing equipment during which it may be necessary
to continue the use of other levels.
100
60
40
This problem came to a head early in
1950 in New York which had by that time
0
20
20.
20
0
40
40
60
0
O
5
75
20
40
31
www.americanradiohistory.com
hand side are the same as for Scale 2.
On the right hand side, the numbers
are per cent of modulation. Total deflection is 2 inches between -40 and
100, or between 100 and 12.5 on the per
cent scale.
The value of 2 inches for vertical deflection on the CRO using the new scales
was adopted after tests which indicated
that this deflection was reasonably linear
in present equipment. Units which were
not linear at 2 inches of deflection were
found to contain subnormal amplifier tubes.
A fortuitous relationship between the
IRE standard and the proposed operating
level is evident in Fig. 4. Here the numbers
on the right hand side of the scale indicate
per cent of modulation of the r -f carrier
and show how it relates to the IRE scale.
By setting zero carrier opposite 120 on
the IRE scale, and maximum carrier opposite -40, blanking level (or zero) corresponds with 75% of maximum carrier,
and reference white (or 100) corresponds
to 12.5% which is the minimum allowable
carrier level. Thus the F. C. C. specifications on carrier levels are embodied in this
same scale.
Recommended Use of New Scales
Experience over several months of operation in a number of television stations has
shown that the new voltage level and the
new scales are a substantial aid in attaining improved performance. As a result of
this experience, a recommendation has been
sent to the RTMA that its standard be
revised to specify a video level range of
1.4 volts, peak -to -peak, for studio equipment. The recommendation is now being
considered in the technical committees of
the RTMA.
It is highly recommended that all television stations adopt this level in operating
practice as soon as practicable. It will not
only improve performance, but it will do
a great deal to facilitate the interconnection of stations and the exchange of programs through the networks.
Availability of Printed Scales
For those users of Master Monitors, or
other equipment employing 5 -inch CRO
tubes, scales, similar to those shown in
Figs. 2, 3, and 4, printed in black on thin
clear plastic, may be obtained by writing
to the Editor, BROADCAST NEWS, Building
15 -7, RCA Victor, Camden 2, New Jersey.
These scales may be applied to the faces
of CRO tubes with pieces of transparent
adhesive tape. This type of scale is not as
durable nor as easily visible as is consid-
o
...-`,....
z
a
\
u)
óIoo
\
\
a
\
w
\
W
\
i020
U
25
.
t4
0.5
O.i
FREQUENCY
FIG.
5.
j40
Of
Io
tz
Ñ
50
\\\\\
8
80
01 CL
o
á
0,05
0,1
02
TIME IN MICROSECONDS
002
05
4 5 6 7 8
3
2
IN MEGACYCLES PER SECOND
Curves showing frequency and time response for a standard oscilloscope.
ered desirable, but it is being made available as a temporary measure until the design of a more satisfactory type can be
completed.
Setup
The term setup, though not officially
recognized, has been, for a long time, applied to the difference in level between
blanking level and reference black. In a
perfect television system, it might be possible to hold setup to zero with satisfactory results. By doing so, it would be
possible to obtain the most efficient utilization of video, r -f, and i -f amplifier
characteristics. However, perfect signals
would be required, without amplitude distortion (overshoots in the black direction),
and very careful adjustment of the background controls in receivers would be required to avoid retrace lines or clipping
of blacks in the kinescope.
By raising setup to some reasonable
value, it is possible to realize much more
practical operating conditions. Small black
overshoots can be present without extending into sync territory, and in the receiver
it is possible to adjust the background
control so that retrace lines are surely
blanked out without clipping black peaks
in the picture signal.
In the PICTURE LINE AMPLIFIER STANDARD OUTPUT adopted by RTMA (Revised
Oct. 9, 1946) *, the recommended amplitude of setup is 5% of the difference between blanking level and reference white
level. This corresponds to 5 units on the
IRE scale. Experience in most stations has
shown the desirability of increasing this
amplitude to about 10%. The increase reduces the utilization of amplifier characteristics, but it improves overall performance
by allowing more tolerance for overshoots
in the blacks, and by permitting final clipping at blanking level in stabilizing ampli* See "The Philosophy of Our TV System,"
by J. H. Roe, Fig. 5, BROADCAST News, No. 53.
32
www.americanradiohistory.com
fiers in order to eliminate overshoots in the
sync region. This clipping usually reduces
setup somewhat below 10%, a process
which would not be permissible if the
initial value of setup were only 5%. For
these reasons, the scales adopted for operating use include a line at 10 to indicate
the maximum amount of setup. This 10%
line, as well as the zero line, is made continuous across the scale to emphasize its
importance.
The maintenance of constant setup, at
all times, is extremely important in order
that brightness adjustments in receivers
should not require changing. This is important in successive scenes in any one
program, and it is equally important in
successive programs, whether they originate in the same station or not. It is,
therefore, urgent that all stations adopt
uniform procedures and uniform instrumentation which will make possible accurate measurement of this and other video
levels.
It is recognized that the proposed scales
do not permit a high degree of accuracy
in measurement, but universal use of the
same methods and tools will at least provide the first step on the way toward
achievement of uniformity.
Instruments for Measuring Video Levels
The cathode ray oscilloscope has been
regarded almost universally as the only
suitable instrument for the measurement
of video levels. Probably, the principal
reason for this is that the television signal
is a composite of several signals, each having levels that need accurate measurement
individually and in their relationship to
each other. Circuitry is rather well known
which would make it possible to measure
any of these quantities by means of a
meter with the same advantages that are
inherent in the use of audio level meters.
However, it is not possible to provide
simultaneous measurement of all the quantities in a single meter, and the circuit corn-
stricted and the "roll -off" at the upper
end of the band is gradual. The resultant
effect is to eliminate most of the higher
frequency components in the signal, including most of the overshoots. Corners
of the pulses in normal signals become
rounded, but the amplitudes of blanking
pulses and low frequency signal components are not affected. Because nearly all
scenes contain at least a few relatively
large areas of average contrast, the loss
of high frequency response in the CRO
Because the CRO does measure all levels amplifier does not often affect the accuracy
simultaneously, at the same time giving de- of level measurement. Practical experience
tailed information about waveshape, and indicates that use of CRO's with this rebecause it has no appreciable sluggishness, sponse characteristic does help to reduce
it can serve as a universal instrument for disagreements among operating personnel
indicating both level and quality. Its use about levels.
as a level indicator over such a long period
It should be emphasized that this type
has undoubtedly established an acceptance of restricted bandwidth is not suitable for
which would be difficult to change. In any gauging the quality of a picture signal, but
case, there has been no definite trend as only for measuring levels, and then only
yet away from the use of the CRO in tele- to minimize the errors introduced by
vision monitors.
spurious overshoots. It is rather interesting
to note that one early type of television
studio monitor (RCA Type KES, designed
The IRE Standard Frequency
in 1936) employed CRO's with a restricted
Characteristic for CRO's
pass band very similar to that in the presPost -war experience gained in the use ent IRE Standard. In later versions (RCA
of television equipment has shown that the Types 542 and TMS) the pass bands were
presentation on the face of a CRO tube is extended to several megacycles to make
easily misinterpreted in the measurement them more suitable for judging quality.
of levels if there are any spurious over- Present design trends are to make both
available
shoots in the signal. Overshoots may arise types of frequency characteristic
by switching.
from any of several causes such as faulty
circuits or tubes, or from a type of distorTo illustrate the effect of reducing the
tion introduced by single -sideband trans- frequency response, several oscillograms
mission circuits. Sometimes, the overshoots are reproduced in Figs. 6 to 9 inclusive.
may arise in the measuring instrument The wide -band CRO used to obtain the
(CRO amplifier) itself. It has been found pictures in Figs. 6 and 8 was an RCA
that when spurious peaks are present, dif- Type 715B. The narrow -band CRO used
ferent operators do not interpret their sig- to obtain the pictures in Figs. 7 and 9 was
nificance in the same way. In measuring a modified TM-5B Master Monitor. The
levels, one operator may discount the pres- signal source in every case was a TK -1B
ence of the overshoots completely, while Monoscope Camera. Overshoot distortion
another may regard them as a part of the for Figs. 8 and 9 was produced artificially,
is more severe than is usually ensignal to be measured. In network opera- and
but nevertheless, it serves to
countered,
tion, it is particularly important that levels
of the restricted band pass
show
the
effect
be measured on the same basis at all moniof the CRO. Horizontal sweep rate in
less
importoring points, and it is hardly
each case is at one half of scanning line
tant in studio equipment. A desirable solu- frequency.
is
to
tion to the problem of uniformity
make the measuring instrument insensitive
Modification of Master Monitors
to such spurious overshoots, and thus reA discussion of methods by which the
move the human factor of interpretation.
RCA TM -5A and -B Master Monitors
To accomplish this result, the previously may be modified to provide the IRE roll -off
mentioned IRE Standard also includes a characteristic will appear in a future issue
specification of a frequency characteristic Of BROADCAST NEWS.
for CRO's which are to be used for measuring levels only. This characteristic is
Oscillogram showing the same
reproduced in Fig. 5 from the IRE Stand- FIG. 9 (at right).
signal as in Fig. 8, but shown on the Master
ard. The bandwidth is considerably re- Monitor with IRE roll -off in the CRO amplifier.
plexities involved in using several meters
at each monitoring position would be
greater than those associated with a CRO.
Furthermore, because of inherent sluggishness, both electrical and mechanical, the
meter system is incapable of indicating the
presence or amplitude of isolated narrow
peaks in the signal. It is also incapable of
indicating any information about wave shape in the measured signal, and therefore
fails as a monitor of quality.
6 (above). Oscilloscope showing a normal monoscope signal on a wide -band CRO
(RCA Type 715B).
FIG.
PI
kiiw
Ì
i
reir
IEEE
7 (above).
Oscillogram showing a normal monoscope signal on CRO in a modified
TM -5 Master Monitor (CRO amplifier with
FIG.
IRE roll -off).
8 (above.) Oscillogram showing the monoscope signal with severe overshoot distortion
as shown on a wide-band CRO (RCA Type
715B). Note black overshoot in sync region.
FIG.
33
www.americanradiohistory.com
FIG. I. View of the Radio Division's Studio "B" during a regular
program. Visible in back of the studio is the audience room.
RADIO AT INDIANA STATE TEACHERS
If
one word were to be chosen to describe the new radio suite at Indiana State
Teachers College, that word would be
"accessibility."
Sixteen years of consecutive broadcasting by the college over commercial radio
station WBOW resulted in a knowledge
of basic fundamentals which should be incorporated in the construction of a radio
division. These included: (1) accessibility
to the control room during broadcast
periods; (2) ease of entrance into each
studio when on or off the air; (3) ready
movement of guests in and out of the radio
center; (4) an auditorium type audience
room to accommodate visiting listeners and
students; (5) an elevated control room to
facilitate cueing; (6) an announcer's room
from which perfect control over voice level
is possible ; (7) an air conditioning system;
(8) storage rooms for electrical transcriptions and recordings; (9) a script room;
(10) a sound effects display room; (11) a
maintenance shop; (12) an adequate office
suite; and (13) high fidelity equipment
with both rehearsal and broadcast units.
In 1949, when the "go" sign for new
radio studios was given, the floor plan
shown below was placed in the hands of
the architects. This plan fulfilled the requirements listed above as necessary for
an efficient broadcasting unit and became
the new radio suite.
To equip the radio suite, RCA equipment was used throughout. In the con-
By
DOCTOR C. M. MORGAN
Director of Radio
Indiana State Teachers College
Terre Haute, Indiana
trol room was placed an RCA consolette,
type 76 -C with an RCA recorder, type
OR- lAX /OR -IA with RCA monitoring
and recording amplifier, type BA-14A. The
floor of this control room was elevated 14
inches in order to enable the engineers
and directors to have complete visibility
of studios "A" and "B" and the Audience
Room. Studio "A ", used for -talks" programs, round -tables, and an announcer's
room was equipped with two Bantam
Velocity Microphones, Type KB -2C. These
were selected because of their sensitivity,
narrow dead sides and the fact that these
microphones do not obstruct the faces of
the speakers.
Studio "B" is the main studio of the
radio unit. From this point originates all
drama and music shows broadcast from the
college. To handle this multiple use, three
RCA Velocity Microphones, Type 44 -B
and one Type 77 -D Poly -directional Car diod Microphone were selected. A unique
feature of studio "B" is the RCA Sound
Truck built to furnish backgrounds of
mood and transitions music and sound
effects used in the drama shows. The Sound
Truck has two dual speed turntables, an
interior speaker plus connections for a re-
34
www.americanradiohistory.com
mote speaker, gain controls for each turntable, an off-on switch for speakers and
facilities for cueing transcriptions by
means of a headset. Ample storage space
is provided in the Sound Truck for transcriptions and recordings to be used on
the shows.
The Audience Room of the Radio Division serves a dual capacity. Throughout
the school day it is used as a college class
room for students enrolled in the field of
radio. During the broadcast periods, this
room becomes an audience room to accommodate visiting college dignitaries, alumni.
college students, and hundreds of children
from the listening area who come each
week to see the programs being broadcast
for their class room use. This room has
elevated tiers upon which movable chairs
have been placed. This makes it possible
for various size groups and individuals to
be accommodated. For example, small
chairs may be brought in to accommodate
children of the elementary grades. To adequately serve the listeners, an RCA duo cone Type LC -1A Speaker was installed.
To complete the equipment of the radio
suite, test equipment and supplies were
placed in the maintenance shop. Metal
files for the storage of transcriptions and
scripts were installed in the transcription
and script rooms, and the sound effects
room was supplied with manual sound
effects within the construction range of
school groups. This room is so located that
0
0
RECEPTION
ROOM
15
111'X IÓ -O'
C
ASSISTANTS
OFFICE
DIRECTORS
OFFICE
i
15.- Ir.%
10
-0
15-11 X
10-0
C
THURSDAY
11.30 a.m.
SOUND EFFECTS
ROOM
15
\Ve, the Students
Speak" (Alternate)
Dr. Fred Brengle
"Weather Analysis"
Dr. David Koch
"Peter Rabbit News Service"
College Students
-11X 14 -0'
CORRIDOR
12 0"
Mr. V. L. Tatlock
"
11.42 p.m.
T-
"Portholes to Learning"
1.45 p.m.
FRIDAY
\
STUDIO
STUDIO
I
A
,117 -5-X
AUDIENCE
B
24-0
IIf -O
X
19-0
ROO M
29 -Ó
X
IS-6
SCRIPTt-8-Ó X
I
1\
MA'NTENANCE
1.45 p.m.
/CONTROL
16 -O
X
Programs from the college are written.
directed, engineered, and produced by college students trained in the Radio Division. To give this training, the college offers
the following undergraduate courses:
ROOM
ID- 6"
Floor plan layout showing the AM
studio facilities at Indiana State Teachers.
the sound effects may be moved into the
audience room for demonstrations.
All rooms in the Radio Suite have
acoustically treated walls. The use of dual
glass in windows separating the studios and
the Audience Room satisfactorily blocks all
sound. Air- conditioning units operated from
switches within the studio guarantee an
adequate supply of fresh air any time during the day or night.
From the studios originate 16 programs
each week-programs designed to supplement construction within the classrooms in
the service area of WBOW and to provide
a furtherance of education for adult listeners. The present broadcast schedule is:
11.42 a.m.
Dr. David Koch
"The Story Princess of
the Music Box"
College Students
FIG. 2.
11.30 a.m.
"Stairway to the Stars"
"Sinfonia"
"Sigma Alpha Iota" (Alternate)
College Students
11.42 a.m. "Weather Analysis'
11.30 a.m.
1.45 p.m.
"Fun With Music"
Mr. James Barnes
TUESDAY
"Sportscasting"
"Campus News" (Alternate)
College Students
a.m. "Weather Analysis"
Dr. David Koch
11.30 a.m.
11.42
1.45 p.m.
"Guidance Guideposts"
Miss Helen Ederle
WEDNESDAY
11.30 a.m. "Places In The News"
314
315
316
317
318
319
320
421
422
423
424
Radio Music
Use of Radio in the Classroom
Radio Workshop
Introduction to Radio Broadcasting
Radio Speech
Rodio Writing
Radio Program Production
Radio Control Room Technique
Advanced Control Room Technique
Fundamentals of Radio Directing
Advanced Radio Directing
For graduate students, advanced work
is offered in each of the above fields. The
success of the program is evidenced by the
men and women of Indiana State now op-
erating behind the scenes or being heard
on stations throughout the United States.
Dr. David Koch
"Weather Analysis"
Dr. David Koch
1.45 p.m. "Science Talk"
Dr. William P. Allyn
11.42 a.m.
MONDAY
"For Parents"
Dr. Wenonah Goshorn
"'Weather Analysis"
Dr. David Koch
3 (below). View of the Announce or News
studio used for script or interview work. Recordroom
is visible in background. Personnel in
ing
the photo are: Mr. James R. Boyle, Mrs. Ruth H.
Morgan, Dr. Morgan, and Miss Peggy Molter.
FIG.
www.americanradiohistory.com
FIG. 4 (below). View of the Control Room with
Mr. Dean Cannon at the RCA 76 Consolette.
At left in Studio "A ", Miss Betty Ann Skelton
is shown operating
turntables.
WTAR, AM- FM- TELEVISION
WTARhas
grown from the tiny
15 watt AM transmitter that came on the
air in 1923 to the present 5,000 watt AM,
50,000 watt FM, 24,000 watt TV installation of the present day.
In 1947 WTAR instituted FM broadcasting with the 3,000 watt interim transmitter which was located on the top floor
of the National Bank of Commerce Building in Norfolk. The following year the
10 kw transmitter was installed at the AM
plant location and by using the 4 section
Pylon antenna, the radiated power was
upped to 50,000 watts.
by
WTAR Engineering Staff
Treasurer; Mr. C. Ralph Beamon, Secretary; Mr. Robert Lambe, General Sales
Manager. Among the managing, producing
and directing echelon are TV Operations
Manager, John C. Peffer; Chief Engineer
(AM- FM -TV), Richard L. Lindell; TV
Production Manager, Winston Hope; AM
Program Manager, Joel F. Carlson; and
Frederick N. Lowe, Promotion Manager.
Perhaps one of the most unusual qualities of the building is the purity of its
atmosphere. A Precipitron has been installed which removes all dust from the
air and electrocutes foreign objects such as
flies. Perhaps an even more spectacular
feature is the Glycol unit. This mechanism
instills triethylene glycol in vapor form in
the air being circulated in the building by
the air conditioning unit. This compound
which is absolutely undetectable, immunizes against colds and many other diseases
while in the building and for eight hours
after leaving.
In 1948, WTAR began its plans for TV
operations. After months of engineering
and planning, work was commenced on the
new AM -FM -TV Center. April 2, 1950
saw the culmination of these plans, and
WTAR -TV made its inaugural telecast on
Channel 4.
\\WTAR- AM -FM -TV is owned by the
WTAR Radio Corporation. The parent
company of WTAR- AM -FM -TV is Norfolk Newspapers, Inc., who publish the
evening Norfolk Ledger- Dispatch and the
morning Virginian -Pilot newspapers.
The president of WTAR Radio Corporation is Mr. Campbell Arnoux, who is
also the General Manager of WTAR -TV.
Col. S. L. Slover is Chairman of the Board;
Mr. Henry S. Lewis, Vice- President and
wide and three-feet deep. The exterior and
interior bearing partitions are sixteen inch
solid masonry. The lobby walls are of
black and gold Italian marble while the
black granite on the building front was
imported from Sweden (Fig. 2). All floors
are nine inches thick solid concrete. Four
inches is considered a heavy floor but the
extra thickness insures against impairing
the structural quality of the floor should
it be necessary to reach the conduits under
the floor by drilling. There are twenty -five
miles of wires in the building.
Mr.
Campbell Arnoux, President and General
Manager of WTAR Radio Corp.
WTAR's AM-FM-TV Center building
located on Boush Street near the center
of town. This new radio center houses the
AM studio installation, the TV transmitter
and two TV studios. The general business
offices are located on the third floor. The
building was planned and designed for TV
is
WTAR houses the first installation of
this kind in Virginia. Tested first by the
federal government in its office buildings,
it has only recently become available for
commercial use. The air conditioning unit
itself has a capacity of one hundred tons.
To reduce the problem of maintenance all
the walls lining the corridors are built of
from the very beginning, and has proven
ample in every respect.
Mr. John C.
Feller, Operations Manager,
WTAR Radio Corp.
The building has been built in such a
manner as to make it almost vibrationless.
The studios, AM, FM, and TV, are built
on the principal of a room within a room,
the inner room, or studio, being floated on
springs to isolate it from all extraneous
sound and the interior surfaces acoustically
treated to insure complete fidelity of reproduction. All studios must be entered
through sound locks protected at either
end by sound proof doors. The building
itself rests upon 407 forty -foot wooden
piles supporting concrete pile caps five -feet
36
www.americanradiohistory.com
Mr.
Richard
L.
Lindell. Chief Engineer.
AM -FM and Television. WTAR.
0
FIG. 1. Front view
of the WTAR new
"Radio Center" build-
ing located at 720
Boush Street in downtown Norfolk.
4I
The lobby of WTAR's
new building. Walls are of
black and gold Italian marble.
FIG. 2.
37
www.americanradiohistory.com
structural units of tile. The roof has been
so constructed of asphalt plank that it may
be used as an open air television studio for
outdoor and garden sets.
Just behind the building is the tower
that supports the Five Bay RCA Super
Turnstile. Same was hoisted into place in
one piece. The overall height is 400 feet
and the height above average terrain is
367 feet. Directly under the tower and
utilizing the space between the four legs
a brick building of two story height was
constructed which is a combination garage
and storage place.
On the 210 elevation of the tower, two
platforms with a connecting cat -walk were
installed for mounting the micro -wave receiving dish for WTAR-TV's video remotes. Each position allows the dish to
be rotated something over 200 degrees and
with the two locations the dish can be set
to pick up a signal on any point of the
compass. A two inch steel conduit carries
the various wires and coaxial cables down
to the receiver control which is located in
the TV control room.
4
WTAR.TV's micro-wave receiving dish
on the 210 foot elevation of the tower. Two platforms with connecting catwalks were provided
so that the dish can pick up a signal on any
point of the compass.
FIG. 3.
4. WTAR -TV's
mobile unit in action.
This photo shows the
unit being used to
televise a Memorial
Day parade.
FIG.
38
www.americanradiohistory.com
WTAR -TV's mobile unit is an RCA
Type TJ -50A using two RCA field cameras type TK -30A, a type TG -10A field
synchronizing generator, a type TS -30A
field switching system, an MI -26293 mobile
power control unit, a TM -5A master monitor and type TTR-1B television relay
transmitter. To date, it has been used to
cover baseball games and special events
such as parades.
The auditorium studio-complete with
stage, dressing rooms and lighting controls
-lends itself to a wide variety of radio
and television productions with the added
advantage of being suitable for studio
audiences. Seating facilities in the auditorium have been provided for seventy persons. Acoustically it is designed just as
the radio and television studios. Many
modern and unusual features have been
incorporated here. The stage itself is thirty two feet wide and forty -eight feet long,
large enough to accommodate a symphony
orchestra. The curtains are motor driven.
A set of buttons on the control panel start
and stop them at the desired place with
just the flick of a finger. The spotlights on
either wall may be trained on the audience
as well as the stage. The footlights at
the front of the stage are so constructed
that they may be made to disappear completely. The TV Mobile Unit is backed
into a space provided directly in back of
the stage and is used for the Video Control Room. A permanently installed Audio
Control Room is located on the left hand
side of the stage and utilizes an RCA 76B
consolette. Directly above this control
room the stage lighting switch room was
installed -each has sound -proofed viewing
windows facing the stage and audience.
A viewing window is also provided in the
Client's Lounge which permits viewing of
any programs taking place on the Auditorium Stage.
Network shows are not the sole delight
of Tidewater television audiences. In its
first summer of operation WTAR produced
live shows from its studios averaging not
less than nine hours of local programming
a week. The TV Studio is so constructed
that automobiles may be driven directly
from the street for televising. One man
operates the banks of overhead lights
which are mounted on a pipegrid, by cables
from a steel cat -walk on the far wall of
the studio. These lights may be rotated
vertically or horizontally. The cameras are
mounted on rubber wheeled dollies for
quick maneuvering as the action demands.
Just to the rear of the studio is the prop
room where scenery and stage properties
are stored. A viewing room on the mezzanine permits visitors to watch TV shows
in the process of production.
The TV Control Room is located on the
first floor with wide view windows that
look into the TV studio. It was built with
a two foot higher elevation than the studio
so as to give the operating personnel a
better view into the studio. The equipment
shown includes the console studio -type
camera controls, two film camera controls,
two studio camera controls, TS -10A type
switcher, and preview monitor. The audio
console includes a 76B TV consolette with
BCS -3A TV switcher. The talk -back
switches have been mounted between the
consolette and the preview monitor for
convenience to the switchers. The whole
audio installation is so arranged on its
custom built table to give the entire operating position an unbroken appearance.
The arrangement of the camera control
monitors and audio consolette was made
as per accompanying picture bearing in
mind that a program man was to do the
M
WTAR's auditorium studio. The stage
32 feet wide
by 48 feet long. Seating facilities are provided for 70 persons.
FIG. 5.
measures
39
www.americanradiohistory.com
7=1=7
video switching and that the audio man as
well as the video switcher should have unrestricted view of the preview monitor. It
also permits one man to take care of the
studio camera controls as well as the shading on the film camera controls. From left
to right, the monitors are as follows: #4
and #3 are the film camera controls;
#2 and #1 are the two studio camera
controls; next is the switcher or "on air"
monitor and to the right of that we have
the preview. The equipment racks were
placed far enough from the wall to permit
easy accessibility for trouble -shooting from
the back as well as the front. The racks as
shown, include the first, which holds the
synchronizing generating equipment. The
second rack contains the monoscope, miscellaneous power supplies and grating generator. The third in line contains the microwave receiver control, the network stabilizing amplifier, the switcher stabilizing amplifier, jack panels and TS1A switcher;
below the switcher are 2 banks of distribution amplifiers. The fourth, fifth and
sixth rack contain power supply equipment for studio cameras and more dis-
PROPS
REMOTE EQUIP
&. STORAGE
B. SCENERY
TRUCK
BACK - IN
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LOBBY
VESTIBULE
II
FILM
First floor plan of WTAR layout showing auditorium studio, stage, and other studio
facilities.
FIG. 6.
PROJ
DOTTED LINES INDICATE
WIRING TRENCHES
FIRST
FLOOR
FIG. 7. This closeup
shows a corner of
WTAR's studio set up
ready for a show.
40
www.americanradiohistory.com
M
FIG. 8.
another
This shows
corner
of
WTAR -TV's
studio
with the steel catwalk in the background. From this
point the
lighting
man can switch the
lights on or off and
rotate same vertically
or horizontally.
9. Floor plan
showing the utilization of the mezzanine
floor for clients and
director's accommodation and film and
props storage.
FIG.
tribution amplifiers. The seventh and final
rack contains the TV audio equipment.
(Fig. 11.) Just behind the control room
is the film projection room. Located in this
room are the two RCA TP-16C 16mm
projectors, two RCA TK -20 film cameras,
and the new super Projectal Belopticon
with two 35mm slide projectors. (Fig. 14.)
Directly above this room is the film room
where films are previewed, spliced, etc. A
coaxial switch is provided in the Projection Room so the projectionist can select
the video output of either the two film
chains or the TS10A switcher for his
monitor.
COL
MEN
PROPS
&
TELEPHONE
PERSONNEL
STORAGE
REFRIGERATING
MACHINERY
ELEV.
TELEPHONE
PERSONNEL
TELEPHONE
PERSONNEL
TV STUDIO
UP
CLIENT
ROOM
UPPER
PART
AUDITORIUM
All the a -c power, video and audio wiring was run in steel trenches (6 inches
wide and 4 inches deep) which extend underneath the audio console and the various
camera controls and from there under the
racks which house the power supplies, etc.
From there it extends on to the projection
room and thence into the announcer's
booth. Wherever the trenches were exposed, they were covered with removable
linoleum covered steel plates making for
ease in assessibility. The a -c power wiring
was isolated from the audio and video by
running same in steel conduit and in some
cases removing from the trenches entirely.
COL
WOMEN
TELEPHONE
EQUIP ROOM
WOMEN'S
PROD DIR.
MIME
MIT
E
_
E
CLIENTS LOUNGE
FILM DIR. AND
STORAGE
Up
MEZZANINE
STORAGE
FLOOR
41
www.americanradiohistory.com
WTAR -TV's
room. From
left to right. the monitors are: =4 and
c3, the film cam
1.
eras; =2 and
the studio cameras;
next in line is the
switcher monitor with
the preview to the
right of it. An RCA
76B Audio Consol.
ette with a BCS -3A
switcher is used.
FIG. 10.
ccntrol
NETWORK LINE
SPARE
I
MONOSCOPE
WAVE
NETWORK CAMERA
STAB
CONTROL
AMP
RECEIVER
STUDIO
CAM.
CAM.
MONITOR
3"
4*
MICRO-
STUDIO
FILM CAM FILM CAM
MONITOR MONITOR
SWITCHER
CAMERA
CAMERA
CONTROL
CONTROL
CONTROL
IN TRUCK
DIST. BOX
PREVIEW
MONITOR
PROJ.
MONITOR
I
_
CAMERA
PULSE
MONITOR
MONITOR
AUDIT.
CR.MON
-IANNC.
MON.
LINES
STUDIO
FIG. 11. Block schematic diagram showing WTAR's video
system.
MON.
TSIOA
SW.
J
STAB.AMP
3 °DFLOOR
GRATING
GENERATOR
13
F-MON.
4
14
5
15
-
6
16
7
17
J---<-
18
1-(-
il
SYNC.
SWITCH
11111
TG-IA SYNC
GENERATOR
-°FLOOR
MON.
8
9
19
10
20
<
MON
,o.c.
TO .XMTR:
42
www.americanradiohistory.com
MON.
>---
COAX
SW.
TERMINATED IN
VIDEO JACK
VIEW RM
(-)-TO
STUDIO
XMTR.
75-4
-<-)-
The wiring coming to the racks containing the power supplies, stabilizing amplifiers, D.A.'s etc., (except the video) was
brought up to terminal strips mounted in
the lower back part of said racks. From
there the wires branched off in forms to
the various pieces of equipment. When
completely wired all forms were laced up
giving a neat workmanship appearance.
A record was made of what appeared on
the various terminal strips which greatly
simplifies trouble -shooting.
The video wiring
I
best explained by
referring to the accompanying diagram.
The use of an RCA TS -1A line switcher
makes it possible to switch the output
on network, micro -wave, film cameras or
Monoscope direct to the transmitter on the
second floor, freeing the TS1OA switcher
for audition purposes. The TS1A switcher
also provides for direct feed from these
points mentioned to the preview and projection room monitors. The use of two
banks of video jacks and 20 distribution
amplifiers gives extreme flexibility to the
operation.
NEWS
ROOM
II
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II
TT-5A
-rr
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STUDIO -B
CHIEF
AVNCR.
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T.V -FIN %MT
EQUIP) ROOM
RECORD
BOOTHS
is
dark room was provided for and was
located on the second floor. It was made
sufficiently large to house a Houston film
developer although present plans do not
call for its installation in the near future.
ANNCR
11
LOCKER &
OPERATORS
LOUNGE
ANNCRS
CONTROL
BOOTH
rr
u
TUBE STORAGE
& SHOP
PERSONNEL
ROOM
UTILIT
CLOSET
CH. ENG
OFFICE
STUDIO-A
LADIES
RECEPTION
ENTRY
ENTRY
A
ASST.PROD
MGR. E. PUB
T.V. WRITERS
PROD.
PROD
RELATIONS
DEPT.
MGR.
LINES INDICATE
WIRING TRENCHES
DOTTED
L
Second floor layout
plan showing the location of TV
master control. rack equipment,
studio "A ". transmitter and associated offices.
FIG.
i
12.
41
FIG. 13. Front view of the eight
TV equipment racks located in
the master control room.
43
www.americanradiohistory.com
FIG. 14. The projection room
directly
back of the TV control room. Two RCA
TP -16C 16mm projectors, two RCA TK -20
film cameras and a
Super
OFFICE'
MANAGER
CLERICAL
ELEV.
IAM CONTINUITY
The TV transmitter room is located on
the second floor and space has been provided for future expansion as well as spaces
for an additional TV transmitter in the
future. The coaxial lines come out of the
transmitter room and are supported by a
bridge across the street behind the building to the TV tower.
FILES &,
STATIONERY
TRAFFIC
i
1
SALES CONF.
I
SALES MGR.
MEN
i
MI
WOMEN
SEC
Y
TOL.
UTILITY
MI
OPERATIONS
MANAGER
are
However, recognizing the necessity of having the slides used on the air of uniform
specifications and standards, equipment
for making these was installed and today
WTAR -TV makes up practically all the
slides used. W. Browning, the video supervisor devotes one day per week for this
work.
DOOR TO
TERRACE STUDIO
SALESMEN
Projectal
shown.
PRESIDENT
The client's lounge located on the mezzanine is designed to afford the maximum
of gracious comfort to WTAR's patrons.
A wide viewing window on the left wall
enables visitors to see clearly the auditorium stage below.
Just to the left as you enter the lounge
but completely furnished kitchenette from which light refreshments may
is a small,
be served. WTAR strives not only to fulfill its essential duties to its audience and
advertisers, but also in the performance of
those duties to fulfill the tradition of true
Southern hospitality.
PROG. DIR.
FIG. 15.
Plan
devoted
44
www.americanradiohistory.com
to
of
WTAR's third floor which is
sales and executive offices.
FIG. 16. Front view
of the RCA TT -5A
television transmitter.
Charles DuVal, TV
Supe:
Transmitter
visor, c the controls.
t
WTAR's new Center Building is furnished with two large AM -FM radio studios located on the second floor. From
these studios most of the local programs
are broadcast. Local programs account for
43 per cent of WTAR's time on the air.
Separating the two studios is the control
console, designed and built by WTAR
engineers, the announcer's booth, record
turntables, and broadcasting equipment
for all kinds of programs including line
terminations for remote broadcasts.
Each of the studios is equipped with
six mike outlets, each of which has associated with it cue lines into which any
desired program may be fed. Each mike
outlet appears on jacks and circuits are
normalled complete through its associated
pre- amps-keys -relays -pots and console. The
input and output of each stage appears
on jacks so that cross patching makes the
operation versatile. The announcer's mike
circuit is so set up that it can be controlled
from the control room, or, as is normally
FIG. 17. Back view of the television transmitter.
Each individual cabinet has the warm air removed by means of duct -work as shown. The
dummy load is mounted on the side of the vestigial side band filter. The water cooler is also
connected to air exhaust and is located behind
the side band filter.
45
www.americanradiohistory.com
the case, may be set so the announcer on
duty can open and close his own mike.
This is the only control he has over his
mike while operator is on duty as the
operator rides gain.
The operator on duty spins discs as required and the turntables for this are
r:adily available. These turntables are provided with foot -pedal control cueing circuits. These foot controls operate a twelve
(12) volt vacuum sealed relay which, when
operated, feeds the output of the turntable amplifier to the cueing circuit. When
pressure is released from foot -pedal, circuit returns to normal and is again clear
to air. The use of vacuum sealed relays
here has reduced to practically zero the
loss of transcriptions due to faulty relay
contacts.
An RCA tape machine is available with
remote control to make possible the transcribing and playback of programs off the
line possible by the operator on duty.
Installed in the console are two identical control panels referred to as control
room #1 and control room #2. Number 1
faces studio A and #2 faces studio B.
Though these consoles are exact duplicates
in every way, interference of one with the
other is prevented through a priority system. Control room #
facing studio Ahas priority over control room #2 for all
1-
FIG. 18. Looking into the AM announcer's booth and the recording room at
right. Marybelle Darden, WTAR's hillbilly disc jockey doing her daily show.
#2-
facing
studio A circuits. Control room
studio B -has priority over control room
#1 for all studio B circuits. This system
follows throughout to best advantage.
Each console and announcer's booth has
its own monitor input selector, its own
monitor amplifier and its own monitor gain
control. Head phone jacks are also pro-
FIG. 19.
The recording
room. Two RCA type 73B
recorders are used. Choice
program is achieved
through selector switches.
of
FIG. 20. "Looking down
on the AM master control
console,
designed and
built by WTAR engineers.
Richard King at controls.
46
www.americanradiohistory.com
or units of speakers are terminated on
jacks and thus any program desired may
be fed to any location in the building. The
program of WTAR normally appears on
these speakers.
In order that there might be a common
ground system for the radio and television
equipment, a solid sheet of copper ten feet
square was placed twelve feet under the
center of the building. To this were soldered
several heavy copper straps which branch
off to the various parts of the building
and appeared in the trenches of the various
equipment rooms. To this all the individual pieces of equipment were bonded.
The overall technical planning and the
technical installation was under the direction and supervision of John C. Peffer,
who was Chief Engineer of WTAR at this
time. He was assisted greatly by Richard
L. Lindell, who was assistant Chief Engineer at the time of taking to the air on
Channel 4.
Since then, Mr. Lindell has been promoted to Chief Engineer of the combined
operation and Mr. Peffer, as Operations
Manager has been given the responsibility
of directing all TV departments.
The architect for the building proper
was Mr. George Van Leeuwen, who worked
in the closest cooperation with the engineers in developing one of the most modern
and compact television installations in the
country today, that really
vided across each of these circuits to be
used according to individual requirements.
Talkback facilities are provided so that
the operator on duty may talk to each of
the studios, the announcer's booth, the recording booth and the announcer's lounge.
The announcers, from their booth, can
talk back to control room and both studios. The recording booth can talk to the
control room only.
In the center of the console we have
three channels of line amplifiers and our
line selector channels to select our feed
to the transmitters. We are set to be able
to feed to any line the output of any of
the consoles or any of the channels. We
can feed a total of twelve lines with six
different programs simultaneously should
the occasion arise.
Our twenty -four remote lines are all
terminated on our ring -down panel which
will bring up both signal buzzer and light
whenever anyone comes across the lines
to contact us. Through this same ring down panel also connects the AM operation with every other operational point
throughout the building and our transmit-
ter at Glenrock. This ring -down panel is
located in the control console and an exact
duplicate is in the announcer's booth.
The announcer's booth is also equipped
with a complete console and when control
is turned over to them, they have readily
accessible two mikes in each studio, six
remote lines, incoming network, and two
turntables in addition to their own mike.
This operation is used only when program
schedule is light or in case of emergency.
Our recording booth is within easy
reach of the control room, but is a complete operation within itself. We have two
of the RCA Type 73 -B Professional Recorders, each with its own associated amplifiers, equalizers, and matching networks.
Choice of program is achieved through
selector switches to bridging inputs of
line amplifiers. Should the occasion arise
where the program desired is not available
on selector switch, it is readily available
through simple patching as input and output of all circuits appear on jacks.
The thirty -three monitor speakers
throughout the building are fed by six
monitor amplifiers. Each of these speakers
is an
engineer's
d ream.
The general contractors on the job were
the R. R. Richardson Company of Norfolk, who did a most commendable job on
the entire project.
Other engineers of the staff who worked
hard and diligently are:
Stanley S. Busby, Video Supervisor (now
in the U. S. Armed Forces)
William I. Browning, Jr., Present Video
Supervisor
Willis J. Robert, Mobile Unit Chief
Charles N. DuVal, TV Transmitter Supervisor
Julian W. Craps, AM and FM Transmitter Supervisor
Zack Yates, Audio Supervisor
Patrick C. Arnoux, Cameraman
Orville K. Gibboney, Video Engineer
John O. Bishop, Jr., Audio Engineer
Jlyrle 1I. Harrison, Audio Engineer
Richard King, Audio Engineer (now in
the U. S. Armed Forces)
William D. Hayth, AM and FM Transmitter Engineer
William L. Herndon, AM and FM Transmitter Engineer.
47
www.americanradiohistory.com
A LABORATORY
TELEVISION SYSTEM
STUDIO
CAMERA
(I MAGE
A VIDEO
ORTHICON)
)-
By R.
L. HUCABY
Television Terminal Engineering
General
Atelevision
system for a development
laboratory is unique in that it must provide a degree of flexibility not ordinarily
needed in a broadcast station installation.
Recently, we were confronted with the
problem of designing such a system in the
Television Terminal Equipment Laboratories. The installation was required to
perform three primary functions. First, it
was to provide a dependable source of
synchronizing and driving pulses, video
signals-both with and without sync -and
other necessary signals and was to distribute these signals to the various laboratory locations for use in the design and
development of television broadcast equipment. Second, the system was, as far as
possible, to take the form of a typical television studio that could be used in demonstration for Broadcast Station Personnel.
As such, it was to include at least one
sample of most items of equipment designed in these laboratories, all co- ordinated
into an operating system similar to that
found in any medium-sized television station. This demonstration function was to
be independent and self- contained so as
to provide a minimum of interference with
the laboratory distribution function. Third,
but by no means the least important, the
facilities were to provide a means of lifetesting the equipment since it would be
in practically constant use during a forty hour week. Fig. 1 shows a simplified block
diagram of the system that was developed
to fulfill these three requirements. This has
now been in use for over a year with very
good results. Various sections of this f unctional diagram will be referred to and discussed in the following sections.
Signal Sources
Any laboratory television system must
have several dependable picture sources of
high quality. The four primary video signal
sources may be found at the extreme left
of the block diagram in Fig. 1. These consist of a studio camera, a film camera, a
monoscope camera, and a modified television receiver that produces an "off -theair" signal. They will be discussed in the
order mentioned.
The image orthicon studio camera is located in a small studio (shown in Fig. 2),
complete with lighting equipment and the
other facilities necessary for the production of small television shows. The camera
is mounted on a movable dolly which allows the cameraman to adjust the elevation of the camera or to move it about the
studio floor to obtain views from different
angles and distances. An electronic viewfinder is incorporated in the camera, permitting the cameraman to view the picture
being televised. The camera control and
monitor are located in the control room in
the extreme right hand console section as
shown in Fig. 3. The signal source has
been very useful -particularly for the
presentation of demonstration programs to
customers, and for the investigation of
new camera circuits and studio lighting
techniques.
In order to provide facilities for the investigation of film pickup, a small room
is equipped for a film studio. The film camera, employing an iconoscope pickup tube,
is located in this studio with the projectors
(see Fig. 4). A mirror arrangement called
a "multiplexer" makes it possible to feed
one film camera with any one, or any combination of three optical images without
changing the physical location of either the
48
www.americanradiohistory.com
FILM
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COFF
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projectors or the camera. The three picture
sources consist of a 35mm film projector,
a 16mm film projector, and a 2 x 2 inch
slide projector for transparencies. The control rack shown in the background of Fig.
MASTER CONTROL SWITCHING
STUDIO -A SWITCHING
PROGRAM DIRECTOR'S CONSOLE
LINE
PREVIEW
MONITOR
MONITOR
MIXING
AMPLIFIER
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MANUAL SWITCHING SYSTEM
STUDIO B SWITCHING
- VIDEO SWITCHING, POINTS
- COMPOSITE VIDEO.SIGN AL
FIG.
1.
Functional Diagram of Video Facilities.
to any one of three predetermined signals
for video cueing purposes. The projector
control panel provides facilities for re-
motely starting or stopping either film projector or for effecting an optical change-
over between projectors. The slide projector
lamp may be turned on or off or its
brightness controlled from this panel also.
'I'he film camera control and monitor are
in the second console section from the right
49
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in Fig. 3. These film facilities permit the
testing of new ideas and improvements on
equipment identical with that in general
use. They also make possible experimentation with new film camera tubes, and provide film pictures for use in demonstration
programs for customers.
The third signal source is a monoscope
camera which is rack -mounted in the control room. It employs a tube containing a
fixed test pattern and provides a signal
which may be used to check other equipment for scanning linearity, resolution in
both horizontal and vertical directions, and
low frequency phase shift. The fact that
this camera delivers a constant signal of
fixed amplitude and quality makes it the
most -used test signal by the laboratory
engineers.
The rack -mounted television receiver
shown in Fig. 5 forms the final signal
FIG.
2
source of this television system. It is a
standard home receiver that has been
modified to provide both video and audio
outputs for connection to the picture and
sound switching systems. This picture
source has been indispensible for demonstrating the capability of the switching
facilities to handle programs originating
from a remote point as well as those of
local origination. It has also been useful
to those engineers engaged in the design
of equipment to handle remote signals that
have been subjected to disturbances such
as those often encountered in coaxial network or microwave relay transmission.
Switching Systems
To realize maximum flexibility, provisions must be made for quick selection of
any signal source for distribution to any
given point in the laboratories. For this
purpose, three different types of video
switching equipment have been incorporated into the design of this layout. Fig. I
designates these three as "Studio A"
Switching, "Studio B" Switching, and
Master Control Switching, all using the
various video sources described above.
"Studio A" Switching will be discussed
first. This is composed of RCA's standard Type TS -20A relay equipment. The
switching is done by means of remotely controlled, rack-mounted relays, and the
fades and lap dissolves are effected electronically through the use of a mixing
amplifier which is mounted together with
the relays and which is also remotely controlled. A Program Director's Console (extreme left of Fig. 6) is a part of these
facilities and contains three video monitors
to assist the technical and program directors in conducting the program. The Technical Director, seated at the left, has at his
(below). Small studio containing Lights, Microphone Room. and Image Orthicon Camera.
50
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before they are routed to Master Control
Switching. A monitor output from this
amplifier feeds a line monitor in the console so that the directors may observe the
outgoing picture at all times. The third
console monitor is a spare monitor to be
used as the occasion demands.
"Studio B" Switching is less elaborate,
but performs the same basic functions as
that of "Studio A ". Here RCA's Type
TS -10A switching equipment (fourth console section from the right in Fig. 3) is
used and is denoted on the block diagram
of Fig. 1 as a manual switching system.
This means that all video signals are
brought directly to the switching unit instead of being routed to rack -mounted relays as in the "Studio A" system, and that
fades and lap- dissolves are done by means
of potentiometers in the video circuits
rather than electronically in a mixing amplifier. The TS-10A output is fed to Stabilizing Amplifier #2 which functions in this
arrangement as Stabilizing Amplifier #1
does in the "Studio A" system. A monitor
3 (at left). Video Console containing Camera
Controls. "Studio B" Switching, and Master
Switching Preview Monitor.
FIG.
fingertips all the remote controls for operating the relays and fading amplifier, while
the Program Director, seated on the right,
has ample desk room for scripts, etc.
Both have adequate intercom facilities for
talking with all pertinent points in the
laboratories.
The rack-mounted relay chassis contains
special video relays accommodating six inputs and three outputs. One output is used
to feed a preview monitor in the console
with which the Directors may preview any
of the six inputs prior to using them "onthe- air ". Mixing Amplifier #1 (see Fig. 1)
serves as a sync interlock amplifier by adding local synchronizing pulses to all local
video signals but passing any composite
remote signals to the monitor without sync
addition. The other two outputs are connected to the inputs of Mixing Amplifier
#2 which serves as the electronic fade and
lap-dissolve amplifier. Its output is in turn
fed to Stabilizing Amplifier #1 where any
switching transients and low frequency disturbances are removed, and synchronizing
pulses are added to all local video signals
FIG. 4 (at right). Slide Projector in the Projection
Room being adjusted by the Author. Film Camera
in foreground, l6mm Projector at right, 35mm at
left, and Control Rack in background.
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output drives a line monitor so that the
program director, who also serves as technical director, may have constant check
on the outgoing picture. Preview provisions
are limited to remote signal inputs only,
of which there are two in the TS -10A.
Since this switching unit is located where
the director may view all local signals on
the camera control monitors, it is not
necessary to provide preview facilities for
them. Intercom circuits are built into this
switching equipment enabling the director
to talk to all necessary points.
Distribution Amplifiers #6 and #7 thus
providing a total of ten signal outputs
that may be routed via the jack panel to
the various laboratories through permanent
trunk lines. Sections A, B, and C of Distribution Amplifier #5 serve as "buffers"
between the TS -1A and its distribution system. Although extremely simple, this master switching system is quite adequate and
dependable.
The Master Control Switching System
(Type TS -1A) is a rack -mounted panel
with provisions for six inputs and three
outputs. Push buttons on the panel permit
the manual connection of any input to
any or all outputs. This unit is shown directly below the video jack panels in Fig.
7. The six inputs consist of the four pre-
Planning the distribution of the four signal sources to each of the three switching
systems presented no special problems, but
a discussion is given here to provide a clear
understanding of the installation. For an
example of the necessary interconnections,
refer to the studio camera chain in Fig. 1.
The studio, film, and monoscope cameras
have two outputs each; one of these connects directly to the "Studio A" switching
equipment. The other terminates at the
inputs of sections A and B of Distribution
viously described signal sources plus the
outputs of "Studio A" and "Studio B ".
Of the outputs, one feeds a master -control
preview monitor, and the other two feed
FIG.
5
(below).
Interconnections Between Signal Sources
and Switching Systems
Operator adjusting Rack -Mounted Television Receiver.
Amplifier #1. The output of section A
then goes to the "Studio B" switching
facilities. Since only composite signals are
fed to Master Control Switching, synchronizing pulses must be added to the
camera signal before it is sent to the
TS-IA. This is done in sections B and C
of Distribution Amplifier #1. Section B
carries the video, section C supplies the
sync, and the two are mixed to form a
composite signal by simply tying these
amplifier outputs together. This same interconnection procedure is used with the
film camera and monoscope with the exception that an extra sync mixer is used
with the film camera to supply a composite signal to the film room monitor
switch.
The interconnections used with the "offthe-air" receiver are somewhat simpler.
Since this signal is already composite
when received, no sync mixing sections are
necessary.
The flexibility of this television system
has been kept to a maximum by the extensive use of coaxial video jack boards.
Equipment failures may be quickly patched
out, additional signal sources may be
patched in, signals may be re- routed
through the system, and many other unusual situations and requirements are
easily met through the medium of the
patch panel shown in Fig. 7.
Pulse Distribution System
The heart of any television installation
generator and the
pulse distribution amplifier. In this layout
it was not only necessary to supply pulses
to the camera chains, but also to supply
them to all laboratories for use in equipment design. The pulses distributed include
sync, horizontal drive, vertical drive, blanking, and positive vertical drive -the latter
is the synchronizing
being used to key the power supply for the
35mm projector pulsed light source. (An
improved design of this power supply using
negative vertical drive is now available but
has not yet been installed in this system.1
The source of these basic pulses is an
RCA Type TG -1A Sync Generator which
occupies one of the racks shown in Fig. 5.
A sync generator switch makes it possible
to switch instantaneously to another generator which can be connected and operated as a standby. By referring once more
to Fig. 1, it is fairly easy to trace the
52
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FIG. 6.
Program Director's Console at left with Audio ConsoLette and Turntables in foreground.
pulse routes after they leave the sync generator switch. Due to the rapid accumulation of input capacity, only a limited number of distribution amplifier sections may
be bridged across a given coaxial line
without disturbing rise -time or wave -form.
For this reason, Distribution Amplifier #8
was included as a "buffer" to isolate from
the coaxial lines the input capacities of
Amplifiers #11, #12 and #13 which supply the laboratories with the basic pulses.
Distribution Amplifier #9 supplies the
pulse signals to the jack panels so that
they may be patched to the various labs
to take care of unusual requirements that
arise from time to time in development
programs. Amplifier #10 provides the
pulses that are used by the monoscope,
film and studio cameras. Since Section E
of this Amplifier performs a special function, it is worth mentioning here. The normal amplitude of the sync signal from the
generator is approximately four volts,
peak -to -peak. The sync mixing amplifiers,
such as Section C of Amplifier #1, require
only 0.5 volt to add to the nomal 1.5 volts
of video in order to produce the standard
2.0 volts of composite signal fed to Master
Switching. Therefore, some means must be
utilized to reduce the 4.0 volt signal to
0.5 volt. This was accomplished by placing
a variable attenuator at the output of the
above mentioned Section E.
Special Considerations
It might be of interest here to explain
why so many distribution amplifiers have
been used in this system design by giving
a brief description of the amplifier and its
uses. Each amplifier chassis contains five
individual amplifier sections, each of which
has unity gain (a small amount of gain
variation is possible), high input impedance
and an output designed to work into a
75 ohm load. Their characteristics make
them especially useful for isolation between
a signal source and its load, for bridging
a 75 ohm line without upsetting its termination, for providing multiple outputs
from a single input, for mixing video and
sync to obtain a composite signal, and for
increasing a signal amplitude by paralleling two or more amplifier sections. Three
of these chassis may be seen at the bottom
of the rack shown in Fig. 7.
In this television system, spare distribution amplifier sections have been brought
out to the jack panel for use in meeting
special requirements. One section (Section E of #12) has been modified to serve
as a signal inverter for changing the polarity of a video signal from negative to
positive, or vice versa
situation that
occasionally arises.
-a
Power Supplies
The five racks of regulated D.C. power
supplies necessary to operate this system
have been located in a separate room primarily to isolate the heat from the working
area of the control room. The D.C. load
has been distributed among the power supplies with an eye to maximum efficiency
and the ability to shut down certain parts
of the system independently without dis-
turbing other parts.
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Nine RCA Type WP-33B supplies (600
ma at 280 volts), fourteen Type 580C
(400 ma at 280 volts), and three Type
TY -25A (300 ma at 280 volts) were used
in this installation.
Audio Facilities
The primary objective of this discussion is that of describing the video system,
but brief mention should be made of its
companion audio system. It was designed
by Mr. R. E. Bailey of RCA and embodies most of the latest equipment types
and techniques. The facilities are built
around a Type 76B Consolette which provides for auditioning, monitoring, switching, and mixing the audio signals associated with this television system. The
input signals to the consolette are derived
from two turntables, four microphones,
two film projectors, a communications receiver, and a television receiver. Fig. 6
shows the consolette and turntables located
between the "Studio A" and "Studio B"
video switching consoles to promote close
coordination with the program director at
either console. The rack -mounted audio
equipment may be seen in Fig. 8.
Video Equipment Rack with
door opened to show Jack Panels, Master Control Switching, and the Distribution Amplifiers.
FIG.
7
(at left).
The audio system design is quite conventional with one possible exception. Arrangements were made to permit feeding
a turntable output into the studio loudspeaker even though a studio microphone
is in use. This is useful for providing a'
low level of music in the studio to aid
a vocalist who wishes to sing with the
transcription on the turntable. This technique is used occasionally in certain types
of programming. No attempt has been
made to allow simultaneous switching of
both audio and video signals since this
presents specialized problems which vary
with each installation. The audio facilities
are entirely independent of the video and
have given excellent results to date.
Conclusion
The system described here has worked
very well and has shown itself flexible
enough to meet 95% of all the conventional and unconventional situations that
can and do arise in a television engineering laboratory. However, some additions
and modifications (as described below)
could be made to increase the flexibility.
Experience has indicated that, in addition to feeding the video from each camera chain to each of three switching systems, a fourth output, without sync, appearing at the jack panel would be very
useful. A stabilizing amplifier, placed between the "off- the -air" television receiver
and distribution amplifier #4, would allow
gain, sync stretching, and other adjustments to be made prior to using the signal
with any of the switching systems. Another output channel could be added to
the relay switching system of "Studio A"
and used to make the spare monitor in the
Program Director's Console function as a
second preview monitor. More spare distribution amplifier sections could be provided as well as more coaxial lines between
the control room and the laboratories. Six
lines to each lab might be considered as
a workable minimum.
Acknowledgment
The writer wishes to express his appreciation to Messrs. W. J. Poch, John H.
Roe, H. N. Kozanowski, and Eric Lind
of the Radio Corporation of America for
their assistance in the preparation of this
article.
FIG.
8 (at left).
Audio Equipment
Racks and Portable Oscilloscope.
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TELEVISION STUDIO ACOUSTICS
Sound recording
in television studios differs from that in radio studios chiefly by
the greater microphone distances which
have to be employed to keep the pick -up
device outside the camera angle. In order
to maintain, for maximum intelligibility,
a low enough ratio of reflected to direct
sound at the microphone, the reverberation
time in television studios must be made
considerably shorter. This applies both to
the television stage proper, as well as to
any auditorium area, if such exists.
The acoustic treatment of the stage
should be highly absorbent as well as
durable and fire -proof. Perforated hardboard or asbestos board backed by 2 inches
of rock wool constitutes an effective treatment, if large flat surfaces of the board
are avoided. A large perforated hardboard
panel gives rise to very pronounced high
frequency echoes, even when the board is
backed by rock wool. For this reason it
is desirable to install the material on the
stage walls and ceiling in the form of triangular corrugations, none wider than 3
feet, and at least 6 inches deep; or better
still, to apply it in the form of cylindrical
sections. In this manner the sound becomes
dispersed, and the effect of echoes is re-
by
M. RETTINGER
RCA Victor Division
Radio Corporation of America
Hollywood, California
duced to a negligible degree. As is well
known, the wavefront of a beam of sound
reflected from a convex surface is considerably longer than that from an equally
large flat surface, provided that the wavelength of the incident sound is small compared to the dimensions of the reflecting
surface. Fig. 1 shows this relationship
graphically, and it is seen that the wave front reflected from the convex splay is,
for the condition illustrated, several times
longer than the sum of the two reflected
from the flat panels. The figure shows also
the construction of the wavefronts, analogous to the optical case. The center of
the reflected wavefront coming from the
curved surface is one -half the radius of the
convex splay (assuming the source to be
at some distance from the surface).
Fig. 2 shows how, in Television Studio
E at NBC Hollywood, a convex reflective
stage splay is being planned to be converted to a convex absorptive splay em-
ploying perforated hardboard for the
"facing" and 2 inches of rock wool for
the sound absorbent. This studio had
previously been used for radio programs
only, and was found to be too live for
television programs.
Many television programs employ the
music of a band for accompaniment or
effect. If the orchestra is placed in front
of the stage, the intelligibility of the performers' dialogue is sometimes markedly
reduced in the auditorium during high
music levels. This is so even when the
transmitted program has considerable intelligibility, because music and dialogue
microphones can be controlled individually,
although in small rooms and at moderately
high music levels it may become difficult
to secure enough acoustic separation between speech and music at the dialogue
microphone to obtain there an adequate
balance.
For this reason an orchestra pit or lateral placement of the band in the room is
desirable. The latter means is not too effective, since some scenes may at times have
to be laid on the same side of the room
where the orchestra is located. An orchestra
pit, on the other hand, may extend partly
1. Vector diagram illustrating the relationship between
wavefrcnts resulting from convex and from flat surfaces.
FIG.
55
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below the stage, and provides considerable
acoustic screening between the individual
pick -up units.
It is a frequent complaint of television
program attendants that their attention is
distracted and their sight to the stage obstructed by the various booms and lights
and their operators on the stage. For this
reason it may be desirable to have a suspended platform along each side of the
stage some 10 or 12 feet high on which
these devices can be placed, together with
the personnel. At the KECA Studio in
Hollywood, for instance, (previously the
"Tom Brennaman Breakfast Studio" and
converted by the writer), the sides of the
stage are dressing rooms, the roofs of
which are strong enough to accommodate
light, booms, and operators.
Television cameras appear far less disturbing, however, and may be assumed to
be part of the show. Even so, an auditorium level which is higher than the stage
does much to improve observation for the
spectators as shown in Fig. 3. For this rea-
son, television studios of the future, which
are intended to accommodate an audience,
may have a balcony, even when the studio
is not very large.
not be made concave, even when it is intended to treat it heavily acoustically, and
the side -walls should not be parallel but
should be angled and /or splayed.'
No less important than the acoustic
treatment of the stage is that of the auditorium proper. Durability of wall and ceiling treatment appears somewhat less important in this part of the studio, however,
while decorativeness or appearance become
Television stages without audience accommodations should have as low a reverberation time as possible. The reason
for this is that, in general, the ratio of
(set -) reflected -to- direct sound at the microphone is sufficiently high to provide
enough of an impression of reverberation
quality so that the pictured scene will
have a natural character. If the stage walls
are insufficiently absorptive, the added reflections will tend, not only to destroy the
illusion of the picture, but also to reduce
the intelligibility of the dialogue. It has,
therefore, become almost customary to line
the stage walls either by nailing a 2 inch
rock wool blanket to the wall studs or by
packing the space between the studs with
rock wool. As a protective measure, muslin and wire mesh are usually applied over
the wool. Fiberboard, hair felt, cork, acoustic plaster, etc., are useless for the purpose
of treating the stage acoustically. A glance
through absorptivity tables of acoustic
materials will quickly show that mineral
wool, also called rock wool, has by far
the highest absorption for the frequencies
in the recording spectrum.
more significant. For this reason a fireproof tile which is soft, and hence a good
low- frequency absorbent, represents a desirable material. Many such products can
be painted without impairing their absorptivity, quite unlike porous ceramic
tiles.
Much as in a theatre, the rear wall
should carry the most effective treatment.
The side -walls as well as the ceiling should
be covered with sufficient treatment to secure in the house a reverberation time no
longer than two -thirds that accorded to the
auditorium were it used for radio shows
only. Needless to say, the rear wall should
FIG.
2.
Cross-sectional
diagram showing how
Hollywood TV
Studio construction is
planned to be converted to a convex
absorptive splay.
NBC's
PERFORATED
HARDWOOD
2y
ROCKWOOL
Rock wool is made by melting silica and
other compounds (notably magnesia, alumina, and lime) and shredding the molten
mass into fine fibers by one of many
patented processes. Some manufacturers
prefer to use glass for the raw material,
calling the final product either glass wool
or referring to it by a trademarked name
(Red Top Insulating Wool, for instance).
This type of wool is characterized by a
relatively low density (1.5 -3 pounds per
cubic foot) and a very clean, white appearance. Ordinary mineral wool varies in
density from 3 to 12 pounds per cubic foot,
the average run being 7.5 pounds per cubic
foot. In color, it ranges from a very dark
gray, almost black, to a white resembling
that of glass wool. The density of the material has a considerable bearing on its absorptivity, the light wools being less absorptive than those of higher density.
Regarding its color, it can be said that
dark wool indicates the presence of certain elements (phosphorus, sulfur, etc.) or
the lack of silica, which may have a bearing on the longevity of the wool. A recently
examined installation of very dark wool
design,
1 For further details of auditorium
see "Applied Architectural Acoustics," by M.
Rettinger, Chemical
Brooklyn 2, N. Y.
56
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Publishing
Company,
a motion picture sound stage over
twelve years old, showed that a considerable portion of the wool had disintegrated
and had settled, in a more or less powdery
form, to the lower portions of the structure. However, other portions of the same
installation, either because of less contact
with a moist atmosphere or because less
subject to vibrations, had stood up considerably better.
in
Regarding the texture of the wool, socalled shot (solid globules of material) is
of course useless for sound -absorptive purposes. Studio specifications usually exclude
wool with shot having a diameter in excess of % inch. Another shot restriction
excludes wool having solids in excess of
30 percent by weight or 2 percent by
volume.
The preferred method of applying rock
wool to stage walls consists in nailing
2 -inch thick blankets directly to the studs
of the walls, rather than packing the space
between the studs with the wool. The latter method is undesirable from a workman's point of view (since the incident
mineral dust is injurious to skin and lungs),
and also because it provides neither increased absorptivity nor a saving in cost.
This is true even in the case where the
blanket carries heavy wrapping paper on
one side (the one facing the studs) and
muslin on the other, instead of muslin on
both sides, as did the early and more
expensively manufactured mineral wool
blankets. The use of the paper in no way
detracts from the absorptivity of the product, and even tends to increase it at the
low frequencies. Some manufacturers (particularly of low- density wool) glue the
paper to the wool, and then merely stretch
muslin over the face of the blanket after
its application to the studs. For heavier
wools, however, muslin and paper are
sewed together, approximately every four
inches, with a special sewing machine, the
stitch running the length of the (usually)
four -foot -wide and fifteen- foot -long blanket. The type of paper used varies from
forty-pound (per ream) basis Kraft paper
to the very strong sixty -pound paper. The
muslin is frequently specified as 44 -40
count, weighing six ounces per square yard.
If a blanket has been fabricated this
way, it can be nailed to the studs with
ordinary box nails, although so- called
foundry nails (large- headed nails) are
sometimes thought to provide greater security. Certainly the use of 1 -inch diameter
tin washers in conjunction with the nails
to give greater security to the installation
appears superfluous, judging from the
many blankets which have been nailed
FIG. 3. An auditorium level higher than that of the stage and the removal of mike
booms and lights to a raised level at the sides improves the viewing for spectators.
2/
-inch
to the studs with no more than
long plasterboard nails 2 feet on center.
The use of a wire mesh over the blanket
for protective purposes is recommended.
This mesh need not extend from floor to
ceiling, but may be applied to a height of
approximately 16 feet from the floor.
Ordinary 1% -inch chicken -wire is frequently employed for the purpose, although
1 -inch
hexagonal wire mesh (somewhat
more expensive) is used by some studios.
A 6 -inch baseboard and a 2 -inch by 6 -inch
nailer 4 feet from the floor usually corn plete the treatment of such a stage wall.
If for any reason the recorded dialogue
reverberant, this can be accomplished by means of a reverberation
chamber. The sound is reproduced in this
chamber and the output from a microphone
in it is mixed with the original. Unlike
other methods, electrical or mechanical, of
adding a reverberating note to a recording, the chamber method provides both the
proper growth characteristic and the decay
quality of sound in a live enclosure. Delay
networks, magnetic tape recordings, and
other devices for achieving synthetic reverberation usually permit only provision
for the decay characteristic; no attempt is
made to introduce the growth characteristic since the latter is held less essential
in an approach to total reverberation.
is to sound
The following recommendations for reducing acoustic difficulties on television
sets are presented as a guide in set design
to reduce sound pick-up difficulties often
encountered during programs.
I. All alcoves, window recesses, concave
spaces of any type, should be made of
cloth to eliminate boominess.
parallel walls in sets such as
kitchens, offices, boat interiors, etc., unless opposite walls are made of cloth.
When opposite hard walls are angled,
the slope should come to 1 foot in 10
feet.
2. Avoid
3. Where ceilings are used, they should be
made of cloth. It may be noted that
dialogue can well be recorded by placing the microphone on the other side of
the "ceiling ", that is, above the thin
cloth representing the ceiling.
4. Whenever possible, the treads of
stair-
ways should be covered with soft material and the stairs so constructed as to
eliminate squeaks.
5.
The use of glass in windows should be
kept to a minimum. Wherever possible,
black gauze or narrow glass borders
should be used. Large plane surfaces reflect a large percent of the incident
sound which reinforces the direct sound,
particularly at the low frequencies,
causing these frequencies to be over accentuated. Indeed, "boominess" of recorded dialogue is probably the most
common acoustic defect experienced on
television sets.
footsteps, vehicles, etc., on
gravel walks can be reduced through the
use of chipped cork in place of gravel,
which gives the identical appearance of
gravel when televised.
6. Noise from
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KNBC'S NEW
AM VERTICAL
..
1
_\{
-'
....
1.
Dramatic close -up view of the new vertical "articulated joint- AM radiator
installed at Belmont. Distance between the upper and lower guy wires is 150 feet. The
"articulated" joint is just a few feet above the point of attachment of the lower guy wires.
FIG.
"
KNBC,
the 50 kw NBC station in
San Francisco, recently completed the installation of a new vertical antenna tower
having unique features of design. Located
at the edge of San Francisco Bay near the
foot of San Bruno Mountain, the new
structure rises 550 feet above the Belmont
Marsh flats. Operating on the frequency
of 680 kc the new tower adds 10,000 square
miles to the KNBC primary service area
and during the evening and night hours
greatly increases the area free of fading.
The New Vertical
The new structure incorporates an "articulated joint" at the 400 -foot level which
in effect provides two separate guyed sections one above the other. The lower section is supported by a single set of three
guy wires. At the top of this section there
58
www.americanradiohistory.com
another porcelain cone insulator. Rising
above this point, there is an additional
150 feet of tower, supported by an additional single set of three guy wires. At the
top there is'a "top hat" to increase the
effective electrical height. To further increase the effective electrical height loading is provided across the upper insulator.
Fig. 1 shows the stub provided to accomplish this loading.
is
To increase the conductivity of the steel
structure, NBC engineers incorporated
3 -inch copper tubing bonded to each corner of the tower throughout the entire
length of the steel members. The ground
system consists of 1 -inch copper ribbon
.02 -inch thick which extend 500 or more
feet from the base of the tower. One hun-
dred and twenty radials are incorporated,
spaced three degrees mechanically. In addition, the center pier is shielded and connected to a 50 -foot square copper mesh
ground screen around the base.
The design and erection of the structure was executed under the supervision
of Raymond F. Guy, NBC Manager of
Radio and Allocations Engineering. An investigation of earthquake hazards in this
area indicated the possibility of horizontal
wave motion through the mud flats in
the event of severe transverse earthquake
shocks. In order to contain the tower sec (Continued next page)
FIG. 2. A closeup of
the base of the verti-
cal radiator, showing
equipment used to
increase conductivity;
three- quarter -inch copper tubing along each
corner of the tower,
copper radials extending outward from
the base, and fifty
feet of copper mesh
screen
surrounding
the base. Structure at
left houses condenser
and induction coils.
59
www.americanradiohistory.com
AN
,'
)k
r
tions in the event that transverse shocks
were to destroy the porcelain cone insulators, a circular steel rim is provided
to confine the tower sections on their
pedestals.
The 600 -foot long transmission line is
the familiar RCA 6 -wire type of 230 ohms
impedance insuring high efficiency transfer
and low radiation.
The tower is of the familiar welded type
of construction having structural specifications designed further to give protection
against transverse earth shock waves.
The construction of this new vertical
radiator insures radiation efficiency in keeping with a 50,000 watt non -directional,
clear channel station -the only one north
of Los Angeles, south of the Canadian
border, west of Salt Lake City and east
of the Orient.
FIG. 3. The ten -inch insulator cone at base will support the entire 90 tons
of KNBC's new vertical radiator tower. The tower shown in the background
is part of the old antenna and was kept intact for use during construction of the new radiator. It is now available for future emergency use.
-dtt-
Close-up view of the insulator
cone which will support upper part
the
tower
at the articulated joint.
of
FIG.
FIG.
4.
5.
Close -up photo showing the
impedance matching network for
KNBC's new vertical radiator at
Belmont. California.
www.americanradiohistory.com
HAM
FORUM
A DEPARTMENT FOR THE BROADCAST RADIO AMATEUR
Latest news from Florida indicates
plenty ham activity in Coral Gables and
Miami. Larry Mennitt, W4IVF, Chief Engineer of WVCG, Coral Gables, is on 10
tone with 15 watts. He also has a mobile
30 -watt Nemo (26 mc.) rig into which he
plugs a 10-meter crystal for ham work.
The rig in the transmitter building uses
a vertical antenna suspended from a tower
guy.... Larry would like to see a broadcast calling frequency on 10 meters... .
We do not know of any on 10, but on 20,
14260 kc is held down every Saturday at
10 am by W3HUV, "Grif" Griffith of
RCA; W4SW, Wilson Raney, Chief Engineer of WREC, Memphis; W5GSY, Harold
L. Sudbury, owner and Manager KLCN,
Blytheville, Ark. ; and W5AY, K. Tracy,
Chief Engineer of KLRA, Little Rock.
Can anybody supply a 10 -meter
calling frequency?
Dave Traer, W4AZK, of WIOD,
Miami, says someone is pouring QRM on
his dx
while he is having fireside chats
with the rare ones
blames it on 50 kw
QSY stations.
...
...
...
...
EAST COAST TELETYPE
W2JAV, Phil Catona, Supervisor of RCA
Test Section, is South Jersey's "King pin"
in the 2 -meter Teletype Net which is gradually being extended up and down the East
Coast from New England to Virginia. Phil,
whose QTH is Hammonton, N. J., has been
keeping regular skeds with W3LMC, Baltimore and W4JCV, John Gill, BC Consultant Engineer, 153 miles away in Leesburg,
Va. High gain antennas and fairly high
power are used by practically all stations
in the net. However, as Phil points out, low
power is practical too. From High Point,
N. J., using a 20-watt mobile rig, he succeeding in starting auto -printer of W2PAU,
some 100 miles distant in Westmont, N. J.
(also an active member of the net).
There are several other hams active in
this (147.96 mc.) net. Among them Charles
Brown, W2ER, Chief Engineer, and Dave
Winter, W2AUF, Transmitter Supervisor
of WEVD and WEVD-FM, Long Island,
N. Y. Dave is also President of the Amateur VHF Institute of New York, which
was organized in 1947 to advance VHF
techniques, and comprises several of the
local clubs in the Long Island area. The
Maspeth Radio Club was the orginal group
to which was added the 235 (mc) Club, the
Brooklyn VHF Club and the VHF Teletype Society.
Pioneers in Teletype
According to Dave, the latter group has
greatly increased its membership due to a
tremendous interest in Amateur Teletype.
First successful Radio Teletype contact on
meters was carried out between this club
and W2BFD, John Williams, pioneer of
Amateur Teletype.... Also with WEVD
is Vern Calame, W2YSO.
2
The teletype system on the net utilizes
carrier shift for calling. The receiving apparatus is on "auto- call" during intervals
(clock -controlled) during which the calling
station can lock the printer on. At the close
of transmission, the sending station can
close the printer down. This system is useful for call-back signalling, should an operator be away from his station.
HORIZONTAL OR VERTICAL FOR VHF?
\\ 'TAU, \Ales Brown, RCA Engineering, and W4AO, Ross Bateman (National
Bureau of Standards) Falls Church, Va.,
have been keeping regular skeds on 2 for
the past year over 120 miles using first
horizontal and then vertical beams... .
"Brownie," who packs up to 500 watts to
a pair of 4- 125A's, says he is squarely on
the fence as to which polarization is the
best
he uses a mechanical "flip -flop"
arrangement since both vertical and horizontal antennas are widely used.
...
...
It is with regret that we record the
passing of W2GX, Russ Valentine, Chief
Engineer of WQXR, N. Y. Russ will be
remembered by many because of his keen
interest in the Amateur Fraternity and his
technical contributions to its progress.
73 W2BCV
Address correspondence to:
HAM FORUM
Marvin L. Gaskilt (W2BCV)
Associate Editor, Broadcast News
RCA, Camden, New Jersey
The rack in the center of the W2JAV operating room contains the original teletype gear
which has been superseded by the very small unit partially visible at the extreme right.
To the left of this is a teletype Model 14 tape printer. and on the left side of the rack
is a Model 12 roll printer. The rack in the background is Phil's low.frequency transmitter.
www.americanradiohistory.com
Whe
fried etato4n
maid
...(tie
KOMO, Seattle. This master control console -with 9 deluxe audio equipment
racks (at rear, not visible) -is one unit
of KOMO's completely new and modern
7- studio system. It incorporates complete
center panel switching for 10 studios
and 6 outgoing channels (KOMO-AM,
KOMO-FM, network plus 3 emergency).
IF NEW, New York.
This master con.
trol installation -in WNEW's 7-studio
lineup is flanked on each side by 5
deluxe audio equipment racks. It has
complete facilities for contro: and
preset switching of 7 studios to 10
outgoing lines . . . and for feeding
cue from any channel to any studio.
tM***
t!R:
4**
WJPG -FM, Green Bay. One of the
specially -built studio -control consoles in
WJPG -FM's 4- studio arrangement. Complete two -channel operation (AM and
P31), simultaneous audition and broad cast from any combination of studios,
remote lines, cueing and talkback are
provided.
www.americanradiohistory.com
RCA
WIBP, Baton Rouge. Here ,s a
speciallybuilt console which combines master and studio control
operations at one location. Mester
control incorporates mechanically
interlocked push-button switches
to avoid the possibility of program
overlap.
WMGM, New York. This deluxe
custontbuilt studio console provides complete facilities for the
control of auditorium -type studio
"A ". largest of 16MGM's 6 studios.
WJAC, Johnstown, Pa. In this
speech input layout, custom -built
matching -end consoles contain aux.
iliary switches and controls. They
are used in conjunction with a
standcrd 76- series consolette to
provide increased flexibility and
convenience.
.,
www.americanradiohistory.com
=
,
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Srjw,,, T,sz.ar:w
1
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H-f voice coil, aluminum win-wound,
to deliver full h -f range
2
Heavy ALNICO V magnets
3
Cross -over condenser
4
Centering adjustment for h -f cone
5
Centering adjustment for -f cone
6
Sturdy die -east aluminum frame
7
Shallow cone for smooth response
and greater angle of distribution
8
H -f
9
H-f cons. Diaphragm diameter
only 2% ". Wide -angle distribution
to 15,000 cycles
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and -f cones coaxially- mounted,
mechanically independent
1
11001:
LC-1A Loudspeaker Mechanism
MI -11411
www.americanradiohistory.com
10
Ample gap clearances
11
Massive 15" -f cone. Bass response
35 to 2000 cycles at all volume levels
12
Cone rim
13
Offset mount eliminates front cavity
insures smooth response
1
treated to minimize edge
reflections for smoother response
-
...... next fo perfect!
The Famous
LC-1A Speaker
A mong the great achievements of the RCA
Princeton Laboratories is the development
of the most advanced speaker in the world
-the RCA Duo -Cone, Type LC-1A.
Expressly designed to give sound its true
translation, this professional speaker is
matched by no other high-quality sound
reproducer.
Unique duo -cone design (originated by
Dr. H. F. Olson of RCA Princeton Labs)
provides a smooth response from 50 to
15,000 cycles
with no resonant peaks,
-transient distortion.
harmonics, or
New Wall -Ceiling Housing for
Ideal for sound reinforcement in control rooms, auditioning booths, hallways, talkback positions, elevators,
i
--
ann..
rumor
r
It's Easy to mount
;%
The Wall -Ceiling Housing
can be
mounted for long or short "throw;"
-makes the wall and ceiling a part
of the acoustical system.
Full
power is radiated over 120 -degrees at 15,000
cycles -makes it possible to enjoy high fidelity sound any place in the room!
Smooth crossover response around 2000
cycles eliminates all undesirable interference between the high -frequency unit and
the low-frequency unit. Controllable "roll off" at 5 and 10 kc... when used with the
MI-11707 filter... restricts the h -f distortion
and surface noises present in many recordings.
Today, more than 3000 of these speakers
are serving in station control rooms, listening rooms, auditioning booths, lobbies,
clients' offices, and private homes.
For more information, mail the coupon.
LC -1A
executive offices. Port prov;ded for
increasing bass response. Finished
in harmonizing 2 -tone umber gray.
The
LC -1A
Monitoring Speaker,
with Console cabinet and
MI -11707 filter
The finest reproducer in the business.
Available in
a
choice of
2
-tone
umber gray or walnut finish.
Department 19 -IC,
RCA Engineering Products
Camden, N. J.
Send me price and information on
LC-1A Speaker Mechanism, MI -11411
LC-5A Wall- Ceiling Cabinet, MI -11406
LC-IA Speaker with Console Cabinet,
AUDIO BROADCAST EQUIPMENT
RADIO CORPORATION
t
of AMERICA
MOEN, N.J.
ENGINEERING PRODUCTS DEPARTMENT.
In Canada, RCA
CA
VICTOR Company Limited, Montreal
MI-11411/11401
Name
Station or
firm_
Address
City
State
The Fountainhead of Modern Tube Development is RCA
ri
The
att of Modern Television
The extraordinary picture quality your
television audience sees is due in great
measure to RCA research and engineering in developing pickup tubes for specific TV broadcast services.
The three RCA pickup tubes you see
here meet the requirements of modern
TV stations. Each tube has features
which make it particularly suitable for
delivering superior pictures in its special field of service.
For general -purpose use. The RCA 5820 has exceptional sensitivity and
ability to handle a wide range of brightness in the scene. It portrays colors in
appropriate gradations of gray tones
has good resolution capabilities.
...
For "live" work in the studio. The
RCA -5826 with its high sensitivity and
improved signal-to -noise ratio is ca-
pable of producing excellent picture
quality. It portrays colors in the same
gray tones as RCA -5820 ... can he used
with low studio light levels...has good
resolution capabilities.
For film pickup. The RCA -1850 -A
has good sensitivity and resolution ..
can handle a wide range of light levels
in the same scene. Its cost factor is low.
In addition to pickup tubes, RCA has
a complete line of electron tubes for
every type of broadcast service. The
entire line is available through your
local RCA Tube Distributor.
RADIO CORPORATION of AMERICA
ELECTRON TUBES
218120
HARRISON, N.
I.
Awree
uïr.
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