BR4 D CAST - American Radio History

BR4 D CAST - American Radio History
BR4 D CAST
N
P
NEW AM TRANSMITTERS
FEATURE IMPROVED SOUNDABILITY
AND COLOR STYLING
VOL. No. 100
APRIL 1958
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A
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TYPE BA -26A
TRANSISTORIZED
TURNTABLE EQUALIZING PREAMPLIFIER
The BA -26A is designed
to mount in same position and space previ-
ously occupied by RCA
Type MI -11877 passive
equalizer.
Designed to provide both amplification and equalization of turntable output!
This compact equipment makes a modern
replacement for bulkier combinations of separate amplifier and equalizing filters. Designed
to provide both amplification and equalization
of output of studio transcription turntables
employing either the RCA Type MI- 11874 -4 or
RCA Type MI- 11874-5 Pickup Heads. The
entire unit is completely self -contained including a -c power supply. Built-in equalization conforms to new industry standards of both NAB
and RIAA. A three position switch compensates for variations in transcriptions and records. Etched wiring circuits provide stable,
trouble -free operation. Transistors are employed
throughout to assure freedom from micro phonics. Absence of inductances make the BA -26
insensitive to stray hum field pickup, greatly
simplifying installation. Mounts easily in turntable, provides essentially noise-free operation
and long equipment life.
For full particulars about the new BA -26A Transistorized Turntable Equalizing Preamplifier, see your RCA Broadcast Representative. In Canada: RCA Victor Company, Limited, Montreal.
RADIO CORPORATION
of AMERICA
BROADCAST AND TELEVISION EQUIPMENT
CAMDEN, N.
J.
Vol.
April,
No. 100
1958
BROADCAST NEWS
published by
RADIO CORPORATION OF AMERICA
BROADCAS T & TELEVISION EQUIPMENT DEPARTMENT
CAMDEN. NEW JERSEY
In U.S.A.
- - -
-
4.00 for
12 issues
PRICE
In Canada
- - -
$5.00 for 12 issues
C O N T E N T S
Page
HOW THE RCA VIDEO TAPE RECORDER WORKS
6
PROGRESSIVE STEPS TOWARD TV AUTOMATION
14
WTPA -TV MAKES CONVERSION FROM 12 TO 25 -KW
TRANSMITTER FOR MEGAWATT OPERATION
18
WFIL -TV AND WRCV -TV MULTIPLE
ANTENNA SYSTEM
.
THE APPLICATION OF VERY PRECISE FREQUENCY CONTROL
NEW 500 AND 1000 WATT AM TRANSMITTERS
.
.
KBKC REVEALS ITS MODERN APPROACH TO RADIO
.
.
.
HOW TO DESIGN THE COMBINATION CONTROL ROOM -ANNOUNCE
BOOTH TO GIVE GOOD ACOUSTICAL PERFORMANCE
NEW
WIP
2 -KW
GETS
UNIVERSAL
VHF TELEVISION
UNIAXIAL MICROPHONE
.
NEW 5 -KW TRANSMITTER
.
COAXIAL TRANSMISSION LINES
.
GROUND WEATHER RADAR FOR BROADCAST STATIONS
Copyright 1958. Radio Corporation of America. Broadcast
&
Television Equipment Department. Camden. N. 1.
nrEa
15e.
www.americanradiohistory.com
.
.
36
44
56
.
TRANSMITTER
32
52
.
THE NEW BK -10A BIGRADIENT
26
58
63
64
69
ow to Get Coverage
with
RCA
Transmitter -Antenna Combinations
FOR OVER -ALL UNIFORM COVERAGE
10 KW TRANSMITTER with 12-Section Antenna
An RCA TT -10AL Transmitter
Antenna for channels 2 and
The above combination
for low- channel operation, used with
or a TF -12AM for channels 4 to 6.
a TF -12AL
3
assures:
...
More uniform coverage
without wasting it.
Low operating cost.
Minimum space requirements.
Other combinations:
In locations where ERP is limited by antenna height,
a number of combinations can be provided
utilizing RCA Transmitters with powers from
2 KW to 25 KW and RCA Antennas with gains from 3 to 12.
www.americanradiohistory.com
Where It Counts
for Maximum Power..
.
!
LOW BAND
FOR CLOSE -IN SATURATION COVERAGE
25 KW TRANSMITTER with 6- Section Antenna
An RCA TT-25CL Transmitter for low- channel operation used with a TF -6AL
Antenna for channels 2 and 3 or a TF -6BM for channels 4 to 6.
Ili1!i1111
The above combination assures:
Close -in saturation coverage.
Low operating cost.
Reserve power
extended tube life.
...
Whether for low -band or high -band operation, RCA Transmitter- Antenna
combinations are available to suit your requirements.
Ask your RCA Representative. In Canada: RCA VICTOR Company Limited, Montreal,
RADIO CORPORATION
of AMERICA
BROADCAST AND TELEVISION EQUIPMENT
TmklslD
CAMDEN, N. J.
www.americanradiohistory.com
Type BK -1A Pressure Microphone -Highfidelity "Commentator" pressure microphone,
non-directional in character. An ideal announce mike for speakers. It assures clear, crisp
speech and is well suited for remote pickup.
O
Type BK -5A Uniaxial Microphone with
Desk Stand -Standard of the television
industry, highly directional, with high front
to back ratio. Unidirectional characteristic
simplifies microphone and camera placement. (See boom -type below.)
Type 77 -DX Polydirectional Microphone
Excellent for both voice and music. The
standard of the broadcast industry. Variety
of directional characteristics, with high sen-
-
sitivity over entire frequency range, assures
high quality reproduction.
Microphone
Immediately Available
from RCA I
Whatever your special microphone requirements, RCA can meet them exactly.
Look at the variety of models now offered. You
can get pressure -type microphones-such as the
BK-1A, SK -45, or BK -6B -and velocity- typesthe BK -5A, 77-DX or SK -46. There are microphones for radio or TV station use; for intercom,
paging, or PA use. Also mikes for announce,
music, or both; for desk, boom, personal use
unidirectional, bidirectional, polydirectional.
Type BK -5A Uniaxial
Microphone with Boom Mount.
Specially engineered for the television industry
to reduce camera noise and interference.
Newly designed boom mount combines superior mechanical isolation with rugged durability. Also available with wind screen for
outdoor use.
-
Also A Complete Line of Microphone Accessories...
TYPE
"P"
TYPE
"XL"
WALL RECEPTACLE
MI. 4624 -A
'f
-
RECEPTACLE
MI-11069
MI-12055
MICROPHONE
ADAPTORS
MI-12051
MICROPHONE
MICROPHONE PLUG
MI- 4630.8
CORD
CONNECTOR
MI- 4620 -B
RECEPTACLE
MICROPHONE
MICROPHONE
IMALEI
MI. 11087 -B
PLUG
(MALE/
MI- 11089 -A
RECEPTACLE
(FEMALE)
MI- 110888
MI-12053
The
advent of the RCA Video Tape
Recorder has been long awaited. Its advantages over film for immediate playback
and re -use of the raw stock speak for themselves. Moreover, the quality of the picture
is much closer to that of the original live
presentation. Not the least of its numerous
conveniences lies in the relief from chemical processing; furthermore the video tape
recorder is relatively simple to operate.
To this impressive list of advantages. the
RCA Video Tape Recorder has added a
number of additional features:
1.
2.
3.
4.
5.
6.
7.
8.
Rack mounting, for ease of maintenance;
Master erase head which obviates the
necessity of using a bulk eraser;
Tape -footage counter, for use in logging the exact position of any recording on the reel;
Continuously variable rewind /fast
forward speed control for ease of
cuing;
Cue channel, for voice or special control signals;
Edit pulses facilitate the splicing of
tape;
Special signal monitoring facilities for
operational reliability;
Remote control of operating functions.
The RCA Video Tape Recorder has been
designed for both color and monochrome,
having had the ultimate use always in
view. Color is not an added accessory.
Nevertheless. if so desired. the RCA Video
Tape Recorder may be obtained without
the color processing rack -which then
provides a high fidelity monochrome recorder. To this may be added, at any
time, the color processing equipment.
Basic Recording Principles
The RCA Video Tape Recorder will record and immediately play back a color or
monochrome television signal along with
program sound with a quality that closely
approaches that of the original signal. The
tape speed is 15 inches per second and a
standard 12% -inch reel will provide 64
minutes of recording time. A one hour
recorded program will play back in one
hour plus or minus a fraction of a second.
The storage medium is 2 -inch wide magnetic tape made of 0.001 -inch thick mylar
base with a 0.0003 -inch magnetic oxide
coating. At the time of tape manufacture
the magnetic particles are oriented in the
transverse direction, i.e., across the width
of the tape. This transverse orientation
gives a playback signal level about 6 db
higher than if the tape had longitudinal
orientation.
Figure 1 pictures the actual tracks recorded by the video tape machine. The
recorded tape was immersed in a volatile
suspension of very fine carbonyl iron par
tides, whereupon, the iron particles adhered
to the magnetized areas. The tape was
pulled out and after it had dried, the iron
particles were lifted off onto a piece of
transparent adhesive tape. This resulted in
a permanent display of the recorded tracks.
The transverse video tracks can be seen
very clearly; the thin white transverse
areas being the separation between successive tracks. The program audio track is on
the left; the control track and cue track
on the right.
The signal in the video tracks is a frequency modulated one. The FM signal
deviation is roughly 5 to 6 mc. This is a
vestigial sideband signal. Because of the
unusual nature of this FM signal, there
is some amplitude modulation present. This
AM accounts for the fact that the horizontal sync pulses and vertical blanking
interval can be seen in Fig. 1. By using
FM in the recording and playback process
any tape signal amplitude variations are
limited out.
The mechanism for recording transverse
video tracks involves a 2 -inch diameter
wheel with four magnetic heads spaced 90
VIDEO TAPE RECORDER WORKS
h t'
JEROME
L.
GREVER, Rrnudi a.cl und Telei isiwt En! fine. rirai
HEAD
2 INCH WIDE
WHEEL
TAPE
VACUUM
SHOE
3.
Another view of the video head wheel
panel assembly. The vacuum shoe when closed,
positions tape to contour of the head wheel.
FIG.
7
www.americanradiohistory.com
Close -up of the video head wheel. Four
video recording heads are located 90 degrees
apart around the head wheel.
FIG. 4.
Cutaway view showing details of a
5.
video recording head. Note size of head block,
core and coil as compared with pencil.
FIG.
\/
GAP
COIL
POLE TIP
CORE
CLAMPING
SCREW
CLAMPING
BLOCK
8
www.americanradiohistory.com
Type
SK
-45 Pressure Microphone
-
Rugged, announce microphone of the
dynamic type, suitable for talk-back or
cue -in purposes. Economical, light in
weight, small in size. Designed for high
or low impedance use.
Type BK -6B Miniature Microphone
-
Small but tough, this new personal microphone is easily concealed in hand or clothing. Only half the size and weight of
previous models. Offers excellent speech
balance when talking "off mike." Wide
range frequency response.
Type SK -46 Velocity Microphone -Good
low -cost studio velocity microphone for speech
or music. Provides bidirecticnol characteristic over wide frequency range. Designed
for high or low impedance use.
for Every Need. s
For the finest microphones that money can
buy, or for quality, low -cost, utility microphones ... when you come to RCA, you know
the microphone will be right- whatever the
type. It has to reflect the standards for which
the RCA symbol has long been famous.
-4t...
mau
_
*Rolm
........
available for immediate delivery. All represent
.
.
today's greatest microphone values. For information concerning any of the microphones illustrated, write today
for descriptive literature. Bulletins describing desk stands,
floor stands, and booms, also available.
.
Ask your RCA Broadcast Sales Representative
irr
RADIO CORPORATION
BROADCAST AND
TELEVISION EQUIPMENT
CAMDEN, N.
In
Canada:
of AMERICA
J.
RCA VICTOR Company Limited, Montreal
www.americanradiohistory.com
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FIG. I. Display of actual tracks as recorded by the
ACA Color Video Tape Recorder.
TONE
WHEEL
Close -up of a portion of the video head
wheel panel assembly with vacuum shoe in the
open position to expose details of construction.
FIG. 2.
'
6
www.americanradiohistory.com
SLIP RING 8
BRUSH ASSEMBLY
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MODULATOR
AIR PRESSURE
VIDEO EQUIPMENT
EQUIPMENT
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HEAD WHEEL
TRACKING SERVO
SPEED SERVO
CONTROL PANEL
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PICTURE MONITOR
COLOR
Q
PHASE
PANEL
RECORD AMPLIFIER
CORRECTION
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TAPE
TRANSPORT
OSCILLOSCOPE
EQUIPMENT
SCOPE /MONITOR
PLAYBACK AMPLIFIER
SWCH'R.
OVIDEO EQUIPMENT
TONE WHEEL
4 CHANNEL EQUALIZER
PROCESSOR
SYNC. RESTORER
PROGRAM AUDIO
POWER SUPPLIES
4
SHOE POSITION SERVO
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SWITCHER
a
CUE
SYSTEM
2
DEMODULATOR
REF GENERATOR
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VIDEO EQUIPMENT
AUTO COLOR/MONO SW.
FIG. 6. Rack layout of RCA Color Video Tape Recorder. The three racks at the
right form the operating position. The other three racks may be remotely located.
degrees apart. The error in this angle must
he less than 30 seconds. The tape is curved
along its width by means of a vacuum shoe
which holds it in an arc. approximately 113
degrees long. Details of the head wheel
panel assembly are shown in Figs. 2 and
3. The arc distance between program audio
and control tracks is about 100 degrees.
The plane of head wheel rotation is perpendicular to the motion of the tape. As
the wheel rotates at 14.400 rpm (240 rps)
and the tape is pulled through at 15 inches
per second, transverse tracks are recorded
with a pitch of 0.0156 inches (15.6 mils).
The width of the head and hence the width
of the track is 10 mils and there is a 5.6
mil blank space between tracks.
The length of one TV line along this
track is about 5.5 degrees of arc or 0.1
inch. Therefore, about 18.4 TV lines are
recorded on each transverse track. The
actual number of TV lines used on playback is either 16 or 17 depending on their
position on the track. The 18.4 TV lines
are recorded in order to allow suitable
overlap of information for reliable switch-
ing between heads during the horizontal
blanking interval. The long term average
number of TV lines used on playback is
16.40625. One TV frame (525 lines) comprises 32 transverse tracks or
inch along
the direction of tape motion. The distance
between vertical blanking periods is 16
tracks or % inch. In Fig. 1. the tape
tracks were enlarged more than three times
so that the details which have been discussed can be readily seen.
The magnetic video head is a tiny assembly held together by much larger clamping
blocks. Figure 4 shows the video heads in
place on the head wheel assembly: Figure
5 includes a highly magnified sketch of the
head itself. The recording /playback gap
is formed by a 100 micro -inch spacer held
between the pole tips. The flat area
formed by the top of both pole tips is
0.010 inch wide and 0.060 inch long. The
two clamping blocks are made of a nonmagnetic metal.
/
Equipment
The complete video tape recorder is contained in six standard cabinet racks (see
Fig. 6). The tape transport panel is conveniently located between a control panel
and 5 -inch oscilloscope on the right, and
a 17 -inch monitor on the left. The three
racks shown associated with the tape transport must remain together. The other three
racks in Fig. 6 contain the color phase
correction equipment, servo amplifiers, and
power supplies which can be remotely
located. The master control panel in the
rack can delegate operating control to a
remote control panel for convenience in
operation. The CRO- monitor switcher is
a very handy device which allows the
selection of a number of important signals
for display on the scope. When one of
these signals is selected by a pushbutton,
the proper synchronizing signal is automatically fed to the scope. Similarly, other
buttons allow the display of video input,
monochrome output, and color output pictures on the monitor. These switching circuits are arranged so that no transients are
allowed to feed out on the program line as
the switch occurs.
The tape transport mechanism is shown
in Figure 7. The 12 -inch diameter reels
9
AIR
GUIDE
MASTER
ERASE
HEAD
HEAD
WHEEL
VACUUM
SHOE
REWIND
TAPE
LIFTER
CONTROL
TRACK
HEAD
TENSION
ARM
AIR
GUIDE
PGM. AUDIO
HEADS
ERASE
REC./PLAY
Close -up of the tape transport mechanism. Call -offs identify key components for record
and playback functions.
FIG. 7.
hold 4,800 feet of tape, providing 64 minutes of playing time. The main tape guide
posts do not rotate; they employ the
technique of air flotation. Air is forced
through tiny holes in the post so that the
tape rides over the post, touching it only
at the very edge, where flanges are used
to guide the tape. This results in very accurate positioning of the tape. Also the
tape edge is protected from damage because
only a minute amount of guiding pressure
is
required.
Recording Operation
The following discussion concerns the
technical function of recording on tape:
Figure 8, a simplified block diagram of the
AIR
GUIDE
CAPSTAN
SIMUL. PLAY
complete color tape recorder, and Figure 9,
an expansion of the video system block
will be helpful in following the operation.
The color phase corrector is not treated in
detail here since it was described separately
in a previous article.'
The tape is driven at the rate of 15 inches
per second. During the record cycle the
supply and take -up reels function mainly
to provide proper tape tension. The tape
is actually driven by the capstan assembly.
(During rewind and fast forward modes
the reel motors drive the tape.) The capstan motor is supplied with a constant
"Color Processing in RCA Video Tape Recorder." BROADCAST NE \VS, Vol. No. 99,
February, 1958.
10
www.americanradiohistory.com
PINCH
ROLLER
amplitude 60 -cycle voltage and the tape is
driven at a very constant rate of 15 ips. At
the same time. the head -wheel servo controls the head -wheel motor speed and hence
the head -wheel to 14,400 rpm or 240 rps.
This is accomplished by comparing the frequency and phase of the 240 -cycle tonewheel pulse with a reference 240 -cycle
pulse. If there is an error in the tonewheel signal, the servo amplifier adjusts
the head -wheel motor speed to remove the
error. The 240 -cycle reference pulse is
actually derived from incoming video as
shown in Fig. 8. Also derived from this
video signal is a 30-cycle editing pulse.
(How the editing pulse is visually identified and used to facilitate tape splicing will
be described later.)
At this point the capstan is pulling the
tape at 15 ips and the head -wheel is rotating at 240 rps. The tape is held in an arc
by the vacuum shoe and the magnetic
heads in the wheel scan across the tape
at the rate of 960 scans per second. The
linear scanning speed of the heads is nearly
90 miles per hour.
Before the tape gets to the head wheel
it first passes over the master erase head
which cleans the entire 2 -inch width. The
clean tape then passes between the vacuum
shoe and head -wheel where the video signal on its FM carrier is recorded. The
motor shown connected to the vacuum shoe
(Fig. 8) is not active during the record
cycle, the shoe being locked in position.
The tape next passes over the control track
head where a 240 -cycle saw-tooth signal
is recorded. This signal will be used during
playback to insure that the video heads
scan along their recorded tracks. The 30cycle editing pulse, which is only about
100 micro-seconds wide, is merely added
to the saw tooth. This does not interfere
with the subsequent tracking operation, but
is used later for tape splicing.
Next the program audio track is recorded: the area first having been erased
by a separate erase head which is a little
wider than the following record head. The
simultaneous playback head, adjacent to
the record head, allows the operator to
monitor the signal being recorded.
On the opposite edge of the tape the cue
channel record head provides a means for
recording cue information. This can be in
the form of voice cues or some other form
of signal which could later be used for
automatic control of the tape machine. A
special feature of the cue channel is its
operation in either record or playback mode
MOTOR
PROGRAM
AUDIO HEADS
VAC.
15
IPS
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CMASTER
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HEAD
SUPPLY
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WHEE-
TRACKING
SERVO
SPEED
SERVO
VIDEO
VIDEO
SYSTEM
INPUT
COMPOSITE
VIDEO
SHOE
POS.
SERVO
W
PHASE
COLOR
CORRECTOR
i
AUTO
COLOR
MONO
COLOR
SWITCH
FIG. 8. Simplified block diagram of the complete
Color Video Tape Recorder.
MONOCHROME
MONITOR
OUTPUT
b
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V DEO LINE
OUTPUT
MON TOR
COLOR
OUTPUT
11
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MODULATOR
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RO
RECORD
AMP
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F
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4
CHANNEL
PLAYBACK
AMP
CHANNEL
II
2I
4
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4
CHANNEL
EQUALIZER
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4
4
3
21
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SWITCHER
4 M
2 X
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960
N
1
SWITCHER
MONITORING OF
F M
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ó
SYSTEM
DEMODULATOR
DURING
RECORD
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RESTORER
TO
AUTO.
COLOR
O
O
-MONO. SWITCH
MONOCHROME
MONITOR
OUTPUT
TO
COLOR
PHASE
CORRECTOR
FIG. 9. Functional diagram showing the details
of the video system block of Fig. 8.
12
regardless of the mode of operation of the
tape machine. This allows the recording
of cue information while playing back or
previewing the video signal.
The composite video signal is on an FM
carrier which is recorded on the tape (see
Fig. 9). The incoming video signal goes
directly to a frequency modulator whose
carrier frequency is about 30 mc. The
resulting FM signal is heterodyned with a
35.5 mc local oscillator, resulting in a final
FM signal having a carrier frequency of
about 5.5 mc with a deviation from about
5 to 6 mc. (For the sake of simplicity,
assume a carrier frequency of 5.5 mc.
Actually, there is no "center frequency"
since the moduiator is clamped; that is, the
tip of sync always corresponds to an instantaneous carrier frequency of about 5
mc regardless of the duty cycle of the
video signal. Similarly, peak white corresponds to a frequency of about 6 mc.)
It is the FM signal which is recorded on
the tape. The magnetic head and tape
response is such that the actual playback
pass band is roughly to 7 mc. This results
in a vestigial sideband FM signal -the
lower sideband plus only a part of the
upper sideband is passed.
1
The FM signal goes to a record amplifier
which essentially drives all four video heads
in parallel through a slip ring /brush assembly. Therefore there is no need of head
channel switching during the record cycle.
It is the playback operation which is more
involved. This is fortunate from the standpoint of equipment complexity and system reliability. If a tube or component
failure occurs in the video system, there is
a good chance that the signal would be
properly recorded on the tape and the
failure would merely have to be corrected
before playback.
Playback Operation
The head -wheel in the playback mode
again rotates at 240 rps by virtue of the
same servo control as used in recording.
The only difference is that the timing
reference is now local sync. The 240 -cycle
tone wheel pulse is the main timing signal
for the rest of the machine. The most important servo function during playback is
the tracking servo (see Fig. 8). Its job
is to see that the control track signal
passes over the control track head in exactly the right phase, so that the video
heads are reading right on top of the
transverse video tracks. To accomplish this
the 240 -cycle tone wheel signal phase is
compared with the phase of the control
track saw tooth. The speed of the capstan
motor is controlled by the servo amplifier
to establish the proper phase relationship.
The FM signals which are being picked
up by the four heads in the wheel are fed
through the slip ring /brush assembly to
the video system (see Fig. 9). These signals are fed to a 4- channel amplifier and
in turn to a 4- channel equalizer. The
equalizer essentially adjusts the frequency
response in each channel so that the 4 channels are identical.
Next the signals go to the 4 by 2
switcher. The 240- cycle, tone -wheel signal
operates this electronic switcher so that
head signals No. 1 and No. 3 feed out
channel A, while No. 2 and No. 4 feed out
channel B. Because of the 90-degree spacing of the heads, No. 1 and No. 3 are
never reading signals at the same time and
therefore can share channel A. The same
is true tor No. L and No. 4 on Channel ti.
There is about a two '1'v fine overlap in
the transverse track signals which means
mat immediately before head No. 1 leaves
the tape, head No. 2 has entered and is
reading the same information as head Nu.
1
(except it is near the opposite edge ui
the tape). Junilarly, there is overlap between Heads No. 2 and No. 3; No. 3 and
No. 4; No. 4 and No. 1. It is the function
of the 2 by 1 switcher to select the final
signai during these overlap periods. This is
accomplished by the 960 -cycle gate which
identities the overlap interval in combination with horizontal sync pulses derived
from the video signal itself. The demodulator feeds the video signal back to the
switcher for this final switching operation.
The actual switch is made during the
horizontal sync period which occurs during
the horizontal blanking interval. The composite video signal out of the demodulator
goes to a sync restorer which clamps the
signal, removes the switching transients,
and provides three parallel outputs. One
of these outputs goes to the color phase
corrector and another goes to the automatic switch which instantaneously selects
the proper line depending upon whether the
signal coming off tape is color or monochrome (see Fig. 8). This switching chassis
then provides a 75 ohm sending -end terminated program line feed.
Splicing
Special provisions for tape splicing have
been included in the video tape recorder.
As mentioned earlier, the reference generator of Fig. 8 has a 240-cycle pulse output which is derived from the incoming
video signal. This pulse, in conjunction
with the head -wheel servo, causes vertical
sync to be recorded in the same position
on the transverse tracks on all machines.
The 30-cycle editing pulse is derived from
the incoming video signal, and is recorded
at half-inch intervals on the control track
between the sharp edges of the control
track saw tooth (see Fig. 1). The edit pulse
is positioned near the track which contains
alternate vertical sync intervals. The position of this pulse is fixed relative to vertical sync and will be the same in all RCA
Video Tape Recorders.
When a splice is to be made, the tape
púlled out of the head wheel /shoe assembly and the edge of the tape sprayed
with a carbonyl iron suspension. An inch
or so of sprayed area is all that is needed
to easily identify the editing pulses which
are clearly visible every % inch along the
control track. The edit pulse is used to
position the tape in a simple cutter so that
the tape is cut right through the vertical
blanking interval. When the spliced pieces
(joined by adhesive splicing tape) later
pass through the head wheel assembly on
playback, the sync will appear essentially
as a continuous signal and will prevent
vertical rolls from occurring in TV monitors and receivers.
is
The shoe position servo shown in Figure
helps provide a continuously usable signal as a splice passes through. The two
pieces of tape which were spliced may have
been recorded at slightly different head
wheel -to -tape pressures (remember that the
head wheel is actually pushed into the
tape a few thousandths of an inch). if the
transverse tape stretch (due to head wheel to -tape pressure) is slightly off, tiny jogs
will appear in vertical lines in the picture.
These jogs can be removed by correcting
the transverse tape stretch through adjusting the head wheel-to -tape pressure. This
is what the shoe position servo does by
slightly moving the position of the vacuum
shoe, depending upon the presence of an
error signal which is derived from the playback video signal.
8
Convenient Operation
Design of the RCA Color Video Tape
Recorder has incorporated numerous techniques which result in straightforward
operation. All components have been rack
mounted for ease of installation, operation
and maintenance. Both color and monochrome operation are accommodated. By
eliminating the rack of color processing
equipment it is adapted for monochrome
operation only. Thus, this RCA Video
Tape Recorder fills every requirement for
television broadcast and closed- circuit ap-
plications.
13
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PROGRESSIVE STEPS
TOWARD AUTOMATION IN
TELEVISION PROGRAMMING
Building Blocks Consist of Products Designed for Automation,
Equipment
and
for Controlling the Station -Break Period
The Basic
by A. H. LIND, Manager,
.
I
udio and
jI
cIauiiral Devices Engineering
The
advantages of the use of automation
techniques in radio and television stations
are threefold: First, automation can make
possible increased income for the broadcaster since the improved performance
makes a station's programs more appealing
to viewers and sponsors alike. Second, automation can eliminate operating errors by
reducing the confusion attendant to the
station break or commercial insert (during
which time most switching errors occur).
Third, automation can permit more efficient usage of skilled personnel, thereby it
may be possible to hold high caliber people,
who are presently being attracted to more
lucrative jobs. Because of these advantages,
many radio and television stations are
planning now for automated operation. In
considering use of automatic devices, many
of which are available now, it is well to
note that the broadcast plant can be automated to a high degree in a series of
planned progressive steps, each of which
will produce immediate benefits.
Generally, TV programs can be classified
into the following kinds:
Programming Task for Automation
In a broadcast plant there are three
types of 'l'V signals to be handled. First;
there are signals derived from recorded
programs: These include motion -picture
film, slide transparencies, positive prints
or opaques, magnetic tape and disk recordings. Second, there are direct live -pickup
pictures. Third, from the standpoint of
signal handling, there is the master control or program assembly function where
the signal arrives in "packaged" form via
cables from either local or remote sources.
In the first two cases there are control
functions which must be performed in the
process of generating the signals, both picture and the accompanying sound. In the
third case it is a matter of switching the
correct signals at the correct time.
A program day is usually made up of a
variegated mixture of these different kinds
of programs. The program material, live
or recorded, is transduced in appropriate
TV machines into television picture and
sound signals which are next subjected to
program switching for signal selection to
establish the program output (see Fig. 2).
It is important to note that in addition to
signal selection switching, machine control
switching is often required. This includes
such functions as starting and stopping
motion -picture projectors, changing slides,
switching optical paths by means of an
optical multiplexer, starting and stopping
tape and disc recordings. The pattern indicated here, in greatly simplified form, is
representative of the basic television studio
system as it is generally used today.
Short precisely timed sequences. In
the vast majority of cases these short
sequences are station break or commercial inserts. Also used are short
film inserts in live programming such
as news scenes, slide titles and program announcements. Station -break
programs are the most rigidly scheduled with respect to clock time. Other
types might be scheduled to occupy
a precise time block, but not so rigidly
scheduled with respect to clock time.
2. Feature film. Motion -picture films
frequently provide programs of several minutes to several hours duration.
3. Direct pickup live programming. This
is a broad area of programming ranging from carefully planned and rehearsed studio pickups, through indoor and outdoor athletic events and
a multitude of other unrehearsed
on- the -spot pickups.
1.
14
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Three Steps to Automation
It is logical to propose that automatic
equipment be used to move forward in this
era of automation. But where should one
start? Fundamentally each machine should
be as automatic or self-controlled as possible. This minimizes the amount of external control required. Once the machines
are available in a broadcast plant, they
are of immediate use and benefit, in that
manual operation can be streamlined and
simplified.
A second step is the introduction of automatic "station break control" to handle
programming of the so-called "panic period" in which several events of short duration take place in rapid -fire sequence. The
third logical step is adding an automatic
"system control" to handle extended periods of operation. With the first two steps
as background, the automatic system control can be accomplished without becoming
overwhelmingly complex. It can provide a
system capable of unattended operation
for either brief or extended periods.
Step 1: Automatic Machines
In the area of automatic machines, programming from recorded material lends
itself most readily to automation.
Automatic Cuing of Projectors
The cuing or positioning of motion picture film in a projector to assure that
picture and sound will start at the instant
the program schedule indicates, is a problem which involves careful operating practice. Since the projector requires a finite
period of time to accelerate to stabilized
running speed, the frame placed in the gate
of the projector must be ahead of the first
frame to be used. The amount of leader
depends upon the start -to- stabilization time
VIDEO
SIDE PROJ
TAPE
TO VIDEO SWCHR
VIDEO SWITCHER
FILM CAMERA
MULTIPLEXER
RECORDER
TO AUDIO SWCHR
WC
STUDIO
PROJ
TO VIDEO
I
PROJ 2
SWCHR
SWCHR
I
ST CAM I
NETWORK
VIDEO TAPE
REMOTE
16 MM
PROJECTORS
FAST
X
STUDIO
START
X
X
X
VIDEO
MONITOR
X
PREVIEW
X
X
X
X
X
AUTO START
AUTO CUE
AUTO LIGHT CONI
VIDEO
MONITOR
PROGRAM
X
X
SOF TO AUDIO SWCHR
VIDEO
AG6
VIDEO
AMPLIFIER
PROGRAM
READOUT
CONTROL
PANEL
PANEL
AUDIO SWITCHER
STUDIO
AUTOMATIC
ANNO STUDIO
TO AUDIO SWCHR
TURNTABLE
AGNETIC
DIS
TURNTABLE
-
SOF I
SOF 2
AUTO TT
TO AUDIO
TO AUDIO S WCH'R
TAPE
1. Simplified system diagram of automated television operations
including control and switching functions of audio and video signals.
FIG.
MATERIAL
TV PROGRAM MACHINES
i
PROGRAM
Flow diagram outlining conversion
program output.
FIG. 2.
to
PROGRAM
AND
OUTPUT
SWITCHING
of
program
material
Conversion of TP -6 projectors for fast start and automatic
cue can be accomplished by station engineers using RCA Kits.
FIG. 3.
NETWORK
X
MAG
MAGNETIC
CONTROL
X
X
X
PREVIEW
MONITOR
SPEAKER
V
TAPE
REMOTE
AUDIO
PROGRAM
MAG DISK
VIDEO
SWCHR
X
X
X
TAPE
X
X
PROGRAM
MON TOR
SPEAKER
AUDIO AGC
AUDIO
AMPLIFIER
PROGRAM
required for a given projector. In present
practice this is a manual operation. It requires that an operator be at the projector in use prior to every film sequence to
be run. However, an automatic cuing facility can be added to the film projector to
perform the cuing function. This mechanism detects the presence of a suitable cue
mark on the film leader and in turn actuates controlled stopping mechanisms to
bring the film to a stop with the specified
frame in the gate. It now becomes possible
to run through a series of film sequences
spliced together on a reel, with projector
start being the only operation required.
This, of course, can be performed remotely.
Following the completion of a given sequence, the program line is switched to
another picture source, but the projector
continues to run until the cue mark for
the following sequence is detected and the
machine is brought to a controlled stop
with that sequence cued for starting. Automatic cuing for RCA Type TP -6 and TP35 Series Projectors has been designed and
will be available in attachment form in
the near future.
Fast Starting
of Projectors
In addition to cuing the film for proper
start, the start -up time of the machine
must be accommodated by activating the
machine several seconds prior to switching
its output to the program line. Three interdependent functions must be accomplished
before satisfactory picture and sound can
be obtained. The film and rotating parts
of the machine must be accelerated to the
24 frames -per- second synchronized speed
to establish proper intermittent motion of
film at the gate. The light shutter must be
rotating at the proper speed and locked in
the proper phase with respect to the film
intermittent. Finally the film must reach
stabilized, uniform motion at the sound
take-off point, which is separated by 26
frames from the film gate (where the film
motion is intermittent). A modification
that provides for very fast starting of RCA
TP -6 projectors will shortly be available.
With this modification, start -up time is
reduced to less than one second and the
TP -6 prepared for automatic operation.
Automatic Turntables
The Type BQ -103 Automatic Turntable
is presently available to provide means for
storing one hundred 45 -rpm records and,
when actuated, selecting records in sequence or in random order. The record is
removed from the storage rack and placed
on the turntable. The pickup arm is next
positioned so that the stylus is in the
lead -in groove of the record. The turntable
platter is then de- energized and quickly
braked to a stop. The machine remains
in this ready condition until a start -switch
circuit is closed. Upon completion of playing a record the machine returns it to the
proper place in the storage rack and goes
on to ready the next record for playing.
Automatic Slide Projectors
Slide transparency projectors, such as
the TP -7A, are now available with a substantial slide capacity (which is a requirement for an automatic system). The TP -7A
is a rugged, reliable projector designed for
remote control service. The machine is
basically sequential in operation. It is
capable of showing a rapid succession of
slides with very fast slide -to-slide transitions. If sequential operation through a
series of slides will fit the programming
desired the TP -7A will lend itself to auto-
mation immediately.
A machine which will permit the selection of slides in random order makes for
more flexible and efficient programming because slides can be used repeatedly without
rearranging the loading of the drums. Such
random selection facility is soon to be
available in the TP -8 slide projector. This
unit is designed basically for pushbutton manual, remote -control operation, but it
will be possible to readily integrate it into
automatic control systems.
Automatic Gain Control
The need to keep the transmitted signal
levels within proper bounds is, of course,
always present. Automatic gain control
amplifiers such as the BA -6A and BA -25A
for audio and the TA -21A for video are
also available. They are beneficial in relieving operators of much of the gain riding
that otherwise may be necessary. Such
amplifiers are essential to satisfactory unattended operation.
Automatic Light Control
Optimum operation for vidicons in film
cameras is obtained when the highlight
16
www.americanradiohistory.com
brightness of the optical image on the
photo surface of the tube is such that the
target voltage is optimized and the beam
just discharges the highlight. Excessive
beam current will produce deterioration of
resolution. If the sensitivity is varied to
accommodate variations in the film image
brightness by changing the target voltage,
spurious effects can appear due to deviations from field flatness, distortion of the
transfer characteristic, and shifts in black
level behavior. The present method of
maintaining constant highlight brightness
at the vidicon by manually controlling the
position of a neutral density filter disk in
the projector light path works very satisfactorily. Development work is currently
in progress to make the neutral density
light control automatic. A servo loop including the vidicon camera chain, a level
measuring and error detecting amplifier
plus power amplifier and servo motor to
drive the neutral density filter disk can
reduce the need for manual operation.
A word of caution is in order about both
automatic gain control and automatic light
control devices. It is not practical, at least
at present, to build into such servo equipments the kind of subjective judgment
that can be exercised by a human operator.
Thus, some extremes in pictures and sound
may not be aided (in some instances may
even be deteriorated), because the auto-
matic device uses a very objective judgment with limited IQ instead of an acs thetic subjective judgment.
Once automatic machines are available,
fewer control switching functions are re-
quired. Thus, the addition of future automatic control is made more practical and
straightforward.
Step 2: Automatic Station Break Control
The station -break period of programming is normally a very hectic time which
is frequently referred to as a "panic period." Station breaks and commercial spots
are of short duration thus they follow one
another in rapid succession. An approach
using a preset control of adequate capacity which will automatically control programming for a period of several minutes
constitutes the second step in automation.
The automatic station break control
system is illustrated in Fig. 5. The coded
control memory in this case consists of
preset groups of relays. Each group of
relays stores information to control one
"event" which expresses all switching functions that are required for a program output change. The programming operation
may be as simple as selecting the sequence
in which the automatic machines are
started. The actual switching may be manually carried out. Or, in a more comprehensive system the switching can be
automatically accomplished on a preset.
time- duration per event basis.
In order to handle last -minute changes
in program content that cannot be preprogrammed due to lack of time, and provide
emergency means of control, a manual control panel which can supercede the automatic control is provided.
Step 3: Automatic System Control
The third step is an extension and expansion of the second. Functionally the
diagram of Fig. 5 still applies. In general
the system is expanded in capacity of
stored information and manner of time
control. If perforated paper tape is used
for the coded control memory. automatic
control for periods of 24 hours or more is
quite possible.
Random Selection Slide Projector. Type TP8, may be readily integrated mto
automatic control systems.
FIG. 4.
While it is possible and practical to
utilize many standard product components
as building blocks in an automatic control system, a given broadcast station's
requirements must be studied on an individual basis and a system plan tailored
CODED CONTROL MEMORY
PROGRAM MATERIAL
accordingly.
Step -by -Step Approach Logical
and Economical
DECODING, TIMING, ETC.
I
build toward automatic programming
by obtaining individual basic equipments
that are automatic, or in some instances
modifying existing equipments to make
them automatic, is the first step. Next.
the station operator can take further advantage of the automatic machines by
PROGRAM
AND
MANUAL CONTROI
PROGRAM OUTPUT
CONTROL SWITCHING
automatically controlling them to ease the
human operating problem during station break periods. Finally, based on the foundation of the first two steps, the automatic
system control can be expanded if desired
and the goal of automatic programming
achieved through system evolution.
S.
Functional diagram of automatic control system showing relationship
and timing devices to basic program equipment.
FIG.
of
memory
17
WTPA -TV,
FROM 12 TO 25 -KW
Advance Planning Permits Conversion
/,,v PAUL D. GROSS,
7uß'1
6n,ineer, II'TP.1 -TI'
Transmitter conversion from one to twelve
and then to twenty -five kilowatts, adding
RCA amplifiers all the way, has been accomplished at WTPA in a block -building
plan which required no modification in
building layout. Man hours were kept to
a minimum, much of the original installation was re -used, and savings amounted to
thousands of dollars.
From the first, our plan has been to
attain high power as equipment to do so
became available. With the installation of
an RCA Ultragain Antenna, Type TFU46AL, early this year, the station has begun operation at one megawatt FRP on
Channel 27.
Station Operation Began 1953
Station WTPA transmitted its first television signal on June 19, 1953, and regular
programming was initiated July 6. At that
time, WTPA was operating with a 1 -KW
Transmitter, Type TTU -1 B. Installation of
the transmitter by the station engineering
staff had begun as soon as the transmitter
building was under roof, but was still far
from completion. In fact, the finishing
touches were not put on the transmitter
plant until after programming had begun.
WTPA operated with the TTU -1B
transmitter for a period of 16 months. On
October 19, 1954, sixteen months to the
day, the station put into operation a 12KW Transmitter, Type TTU -12A. This
combination of original 1 -KW transmitter
with 12 -KW amplifier was in service for
about the next three years.
1.
Chief Engineer, Paul D. Gross, installs the 6806 UHF
Tetrode in the visual PA of WTPA's 25 kilowatt transmitter.
FIG.
18
Conversion to 25 -KW in 24 Days
Consistent with original plans for highest power, WTPA applied for and was
HARRISBURG, PA., MAKES CONVERSION
TRANSMITTER FOR MEGAWATT OPERATION
Without Building Changes; Enables Station to
granted a Construction Permit to increase
ERP to one megawatt. Immediate delivery
of transmitter and antenna equipment was
accepted from RCA, and on July 22, 1957,
conversion of the 12 -KW transmitter to
25 kilowatts was begun. After 24 days
(and nights) of constant work, WTPA
engineers put into operation the first TT1:25B transmitter converted from the station's existing TT -12A.
Both mechanical and electrical modifications were completed according to a
cabinet -by- cabinet plan, which would allow
the transmitter to operate at a full 12 -KW
R emain
On -Air While Equipment is Being Modified
output during most of the modifications.
Each cabinet was modified, first mechanically then electrically, starting with the
thyratron and rectifier cabinets. By completing this work in one operation the
12 -KW transmitter output was maintained.
Next the plan called for modification of
the main control cabinet, which involved
the mounting and changing of several
switches and relays. At the same time the
main control cabinet was separated from
the visual PA and the auxiliary control
cabinet from the aural PA. Power was cutback to one kilowatt. and a new wiring
Modifications were made cabinet by
cabinet and the output of the 12-kilowatt transmitter was maintained. Checking blueprint are
Assistant Chief Engineer Charles Baker (left), and
Operating Engineer, Raymond Julian.
FIG. 2.
harness was installed so that the transmitter could be returned to 12- kilowatt
operation. The cabinets were separated a
fixed distance to permit mounting the water
columns at the proper intervals in the
water compartment.
By August 1, mechanical and electrical
modifications to the aural and visual PA's
were begun. The aural PA was taken out
of operation and the aural transmitter
operated at one kilowatt output. This was
facilitated by the coaxial switching panel
shown in Fig. 3. The arrangement permits
rapid manual switching between one and
twelve kilowatt outputs.
On August 7, the aural and visual PA's
of the 12 -KW transmitter were taken out
of service, and WTPA went on the air
with the original 1 -KW driver for a period
of seven days. Immediately, the plumbers
and electricians went to work. The old
plumbing was removed as was the old
3.
Manual coaxial switching panel permitted rapid manual switching between 1 and 12 kiloand 25 kilowatt outputs after conversion
watt outputs during conversion, and ultimately between
was completed.
FIG.
1
wiring, and new plumbing and electrical
wiring installed. By August 12, this work
had been completed, with new transformers
and high -voltage cables being installed. On
this date the power company changed the
primary service from 230 to 480-volt service. This was accomplished in record time:
Service was cut at 6 A.M., the existing pole
transformers were removed and new pole
transformers installed. By 10:30 A.M., just
472 hours later, WTPA was back in business, operating on the 480-volt service.
Testing of the transmitter and its associated equipment began on August 13. First
the water system was completely checked
out, flushed and declared sound. Power
then was applied to the high -voltage transformers and a complete check of the high voltage system was performed. One bottleneck developed at this point; the water
columns had not been delivered for the
final cavities, however, they were delivered
on the following day. These were installed
immediately and early on the morning of
August 15 the complete, final checkout of
the system was performed. Fortunately,
everything had been previously checked
out and there were no bugs to be found.
On August 15, at the start of the day's
operations, WTPA put into operation its
TTU -25B transmitter.
Power equipment for operation of 25kilowatt transmitter. Modifications called for
changing primary service from 230 to 480 volts.
FIG. 4.
FIG.
5.
WTPA transmitter building. A standby tower and antenna were used during conversion.
Advance Plans
Simplify Antenna Installation
A stand -by tower and antenna were
erected south of the WTPA transmitter
building and operations were shifted to this
location, so that the original 400 -foot guyed
structure which supported a TFU -27B
antenna could be removed and a larger
tower erected to support the new high -gain
antenna. Meanwhile, transmitter conversion
was undertaken despite the fact that a
TFU -46AL antenna was not immediate)
available. A special temporary authority
was granted by the FCC permitting WTPA
to operate with a 5 -to -1 power ratio between visual and aural transmitters, thereby
permitting the high visual ERP produced
by the TTU -25B transmitter. Originally
the tower base was made large enough to
support the new tower and antenna, hence,
a tremendous saving was effected because
the tower base and guy anchors could be
used for the new tower. A TFU -46AL
antenna was installed on the new 400-foot
tower, completing the facilities for mega-
PANELS
CABINET
TRANS.
VAULT
PWR
PAN
nRECTIFIER
CABINET
FILTERPLEXERS
OCONTROL
CONSOLE
MEAT
watt operation.
Transmitter Building
Houses New Equipment Without Change
Original plans for the transmitter building provided sufficient room for expansion.
The block diagram. Fig. 6, shows how
each succeeding modification was accomplished without additions to the building. In each case a section of false wall,
PWR
PA N
THYRATON
EXCHANGER
RACK
EQUIPMENT
PUMP
WATER
LI
Block diagram showing how modifications from
watt transmitter were accomplished without additions
FIG. 6.
1
TANK
to 12 to 25 kilo.
to
the
building.
21
www.americanradiohistory.com
FIG. 7. Initial 1- kilowatt transmitter installation.
A false wall provided roam for expansion.
FIG. 8. The 12- kilowatt transmitter installation.
The false wall has been removed to provide space
for the extra cabinets.
22
www.americanradiohistory.com
dividing the building into two parts, was
removed to accommodate additional transmitter cabinets. In Fig. 7 the initial onekilowatt installation is pictured. Figure 8
shows the 12 -kw installation, and Fig. 9
the 25 -kw installation.
The transmitter building is located on
Blue Mountain overlooking the Susquehanna River and the city of Harrisburg.
It is a 30 by 80 -foot building with the
transmitter room itself measuring 30 -font
square. The TTU -25B transmitter is installed down through the middle of this
room. A false wall is built around the transmitter, separating the operating room with
control console from the rear of the building where the filterplexer, water-cooling
system, thyratron and rectifier cabinets and
other associated equipments are installed.
The transformers are installed in a row
(see Fig. 6) within a vault at the back of
the building. Standard 4 -by -4 -inch ductwork, (as supplied by RCA on the original
TTU -12 installation), is used to carry the
primary and secondary voltages to and
from the vault.
The remainder of the transmitter building houses a shop, kitchen, bedroom and
lavatory areas. A three -car garage is located
at the one end of the building.
9.
The 25- kilowatt transmitter installation. No new cabinets have been added, however,
spacing of the cabinets has been changed slightly to make room for the water columns.
FIG.
23
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Elevated Control Room
Serves Two Studios
The studio building at 3255 Hoffman
St., in uptown Harrisburg, houses WTPA
offices, studios, control and film rooms
as well as storage and workshop areas.
The building measures 80 by 100 feet
and includes two operating studios. Largest
of the studios is Studio A, measuring 35 by
55 feet. A smaller area, Studio B, measures
21 by 31 feet. Both have 14 -foot ceilings.
Large double doors at the end of Studio
A allow automobiles to be driven into the
studio and provide easy access for large
properties. Studio equipment includes three
field camera chains, Type TK -31, which
may be used in either or both studios, or
in the station's mobile unit, a converted
bus shown in Fig. 13.
Studio A. largest of the station's two studios, accommodates
several sets and has access for automobiles and large properties.
FIG. 10.
FIG. 11.
Studio
and Donald
24
D.
The control room is elevated above the
studios by a height of four feet. It measures
20 by 30 feet and contains extra large
windows which look into each of the studios
(see Fig. 12). The control desks include
two film camera controls, remote control
panels, switcher and line monitor as well
as portable control units for the three field
cameras. Built into the wall along the front
of the desks are six monitors, providing
signals off -air, from the three live cameras
and two film cameras. The location of the
monitors, immediately above the set of
windows which look into Studio A, provides
an unobstructed view to all program and
B is used for weather, news and other small set programs. Shown are Tom Weitzel, Staff Announcer (left).
Wear, Station Manager behind desk. Cameraman is Bob Hice.
technical personnel.
control room are all
for both studios
panel and electronic
-a
in the
the lighting controls
90- circuit Rotolector
dimming board.
Also housed
Directly below the control room is a
projection room (having the same dimensions as the control room). The area is
equipped with two complete RCA film
camera chains.
Ample room has been allowed in the
studio building for storage and construction areas. The entire back portion of the
building, the full width of 80 feet and a
depth of 25 feet, has been allocated to set
storage and construction. This area is provided with large overhead doors so that
the station's mobile unit can be driven
into this area.
FIG. 12. Th WTPA control room includes portable control units for
three field cameras and controls, and two film cameras. Also housed
here are lighting controls for both studios.
Initial Planning Pays Off
The initial planning and layout preparation along with careful consideration of
future developments has enabled WTPA
to take the successive steps from low to
high power UHF operation most efficiently
and economically. Each increase in power
has been accomplished without building
modification. The tower base was initially
designed so that it and the guy anchors
could be used with the station's new tower
and ultragain antenna. Thus, we reduced
the number of man -hours required for the
conversion and kept our station on -air all
during the conversion.
FIG. 13. WTPA mobile unit. Field camera chains have been selected
so that they may be used either in the studios or with this mobile unit.
FIG. 14. View from control room looking into Studio A during local production of weekly
"Capitol Correspondents" program. Guest at telecast shown was Harold E. Stassen.
25
FIG. 1. Over-all view of the new WFIL -WRCV
joint lower. The structure is 917 feet high, and
the antennas increase the total height to 1109 feet.
WEIL -TVand WRCV -TV
MULTIPLE
ANTENNA SYSTEM
The
key outlet of Triangle Publications,
Inc., WFIL -TV, and the local NBC station, WRCV -TV, have combined facilities
atop a new 1109 -foot tower in Roxborough, the highest point in Philadelphia.
Both stations estimate that an additional
279,000 homes have been added to their
service area that now extends to Asbury
Park, N. J., to Stroudsburg and Mahanoy
City, Pa., and to Havre de Grace, Md.
Service has been greatly improved in the
Philadelphia area, and better reception is
apparent in the Allentown- Easton section
of Pennsylvania.
Stations WFIL and WRCV jointly presented a special half-hour colorcast on
December 15, 1957, to inaugurate operation of the new antenna system. The program, titled "The Big T," explained the
increased benefits of a multiple tower, and
in laymen terms showed how the TV signal
is transmitted. During the program the
public was given a close -up inspection tour,
via TV, of the new tower, also a ride on
the two -man elevator that runs up and
down the side of the tower. A representative of the City of Philadelphia welcomed
the mayors of ten other cities that have
joined the increased viewing audience of
the stations.
26
Philadelphia Stations Combine
Antenna Facilities to Increase
Coverage and to Improve
Picture Quality
FIG.
2.
The new 1109 -foot tower is shown in comparison to WFIL "s former tower structure.
FIG. 3. The WFIL -TV Type TF -6BM Superturnstile Antenna being raised to top of tower.
Note the 1000 -watt beacon on top of the antenna structure.
New Antennas
Station WFIL installed a Type TF -6BM
Superturnstile Antenna, which is fed with
the new 3A -inch Universal Transmission
Line. This six -section superturnstile is
phased to provide uniform coverage with
excellent null fill in. With an antenna gain
of 8.13 db, WFIL continues to operate at
maximum power atop the new tower.
1
Station WRCV selected a Type TF -6AL
Superturnstile Antenna, which is split in
half electrically. Provisions have been incorporated to feed either the upper or the
lower three sections of the antenna in an
emergency. In normal operation WRCV
uses all six sections with a power gain of
7.85 db. The TF-6AL also provides excellent null fill in and uniform coverage.
Tower
Structure
The entire 917 -foot tower was fabricated
by Dresser -Ideco, and shipped to Philadelphia in six trucks. The remaining 192 feet
(the total height of the structure is 1109
feet) is made up of the TF -6BM and TF6AL antennas. Approximately two miles of
steel sections are used in the tower, if laid
end to end, and weigh over 300,000 pounds;
when combined with antennas the total
weight of structure is 421.000 pounds.
www.americanradiohistory.com
FIG. 4. Base of tower is an ll -foot deep, reinforced concrete foundation. six feet square with only two feet extending above ground.
The two -man, radio-controlled elevator. noted by letter A. is shown in above photo.
Another view of the foundation showing the transmission line feed from WRCV. Cabinet at right contains the tower -lighting
control and the radio -control unit for the two -man elevator.
FIG. 5.
28
WFIL constructed these support posts for the new 3'8.inch Universal
Transmission Line. The lino runs approximately 600 feet from the WFIL building.
FIG. 6.
Tower Supports
Fifteen guy wires support the 917 -foot
tower. Two and one half miles of galvanized stranded bridge cable is used to
guy the tower at five levels. The upper
guy cables at 917, 630, and 420 -foot levels
are anchored at a point 700 feet from the
base of tower. The two lower guy cables
are on the 360 and 180 foot levels, and
these are anchored 465 feet from the tower
base. The guys are anchored in a 15 -foot
concrete foundation, 11 feet of which is
WIGARO
AVE.
underground.
Tower Foundation
The triangular tower is
feet wide
on each face, and it is set on a hexagonal
foundation. The 11 -foot, 2 -inch deep reinforced concrete foundation is 6 feet on
each side, and only 2 feet of the base is
above ground. The tower legs are secured
to the foundation with three leg bolts imbedded deep in the reinforced concrete
foundation.
7/
Tower Maintenance
A radio -controlled, two -man elevator provides transportation to within 50 feet of
the WRCV antenna. The enclosed -cab
elevator control is operated by a battery
powered transmitter located in the cab.
This transmitter sends stop- and -go signals
to a receiver on the ground. In the event
of cable failure, an automatic safety, locks
the elevator to the guide rails.
Rest platforms are located at the obstruction and beacon light Ievels to make maintenance easier. The platforms allow a man
to make needed repairs swiftly and safely.
FIG. 7.
Layout
of WFIL
and WRCV buildings with respect
platform is also located at the ground
level elevator landing, and an enclosed
platform has been placed at the top elevator landing (872 feet high).
A
Tower Lighting
The height of the structure and its location demand strict compliance with CAA
lighting regulations. However, a joint antenna does reduce the hazard that would
to the tower is
shown.
be created if these stations were on separate towers. A flashing 1000 -watt beacon
is mounted on top of the WFIL, TF -6BM
antenna with other 1000 -watt beacons
mounted at the 810, 540, and 270-foot
levels. One- hundred -watt obstruction lights
were placed on the 150, 420, and 690 foot levels; an additional set of two 100 watt obstruction lights was placed on the
WRCV antenna.
29
WFIL continues to use existing facilities
which are considered more than adequate. A
complete workshop and a small kitchen are found
here in addition to all transmitting equipment.
FIG. 8.
New Equipment
3/
Station WFIL installed the new
-inch
Universal Transmission Line. This type of
line operates uniformly over all channels
with low loss and high efficiency. Station
WRCV installed a new Type TT -6AL
Transmitter to drive its existing 25 KW
amplifier, and another TT -6AL as a standby unit.
The new tower site is located a few hundred yards from the former WFIL tower.
On the other hand WRCV moved from its
former site in Wyndmoor, Pa., to a new
building at the present site. While WFIL
continues to use its existing facilities,
located about 600 feet from the new tower,
WRCV's new building is approximately
200 feet from the tower.
Co-operation Pays Off
Both stations are proving by this venture
that co- operation does produce greater
benefit by improving their picture quality
and coverage. Since both WFIL and
WRCV are equipped for live local color,
this new joint antenna has also done much
to strengthen color quality. Furthermore,
the viewers as well as the stations benefit
from this joint installation: the viewers
receive better pictures, and the stations
split the costs of installation.
Edward Neville, WFIL Transmitter Engl.
neer, checks the TT -25BL amplifier.
FIG. 9.
Richard Marshall, WFIL Transmitter
Supervisor, takes readings on the TT -5A driver.
A TT.25BL amplifier is shown on the right.
FIG. 10.
WRCV-TV has constructed this new transmitter building that incorporates many desirable
features, including a garage, a complete workshop, a complete kitchen, and ample office area.
FIG. 11.
Co-operation does pay off. Left to right:
Fred Everett, Station Engineer, WRCV -TV: William
A. Howard, Manager of Technical Operations,
WRCV, WRCV -TV; Henry Rhea. Director of Engineering for Triangle Stations; Richard Marshall.
Transmitter Supervisor, WFIL-TV. These engineers
have worked together to make this a ¡oint in-
FIG. 12.
stallation.
Oscar Jimerson, WRCV Transmitter
Engineer, takes readings on one of WRCV's new
TT -6AL drivers.
FIG. 13.
FIG. 14. Henry Shaw, WRCV Transmitter Engineer. on duty at the custom -built WRCV transmit-
ter control console.
THE APPLICATION OF VERY PRECISE
TELEVISION COCHANNEL INTERFERENCE
by WENDELL C. MORRISON, Chief Ertyinrer. Telecomnuuninrfions Division
The
ABOUT THE AUTHOR
Wendell C. Morrison came to RCA in 1940
as a Student Engineer after receiving the
MS Degree in EE from the State University
of Iowa. He joined the Research Department
and moved to the RCA Laboratories in
Princeton, New Jersey, when that organization was established in 1942. Here he worked
in the fields of speech privacy systems, antennas, antenna pattern calculators, utilization of radio frequency power, television
transmitters, and television terminal and test
equipment. He participated in the development of color television and was active in
the work of several panels of the National
Television System Committee.
In 1957, Mr. Morrison returned to Camden as a Staff Engineer to the Chief Engineer, Industrial Electronic Products. On
January 16, 1958, he was appointed to his
present position as Chief Engineer, Telecommunications Division, I. E. P.
first television channel assignments
made in this country utilized the geographical separation between stations to
provide the necessary protection against
cochannel interference. The increase in the
number of stations, together with the
gradual increase in power of the stations,
demonstrated that the original plan was
not entirely adequate. The search for a
method to minimize cochannel interference
resulted in our present system of allocations, which utilizes an offset between visual
carrier frequencies of cochannel stations.
Recently, it has been demonstrated that
precise frequency control is of real value
in reducing this interference and that it
is practical to make stable oscillators to
be used for this purpose with television
transmitters.
Present System
Early experiments demonstrated that the
greatest amount of improvement is obtained when the offset frequency is near
an odd multiple of one -half horizontal -line
frequency of the television system, while
the greatest amount of interference occurs
when the beat is an even multiple of onehalf horizontal -line frequency. To make a
practical system in which more than two
cochannel stations are involved, it was necessary to make a compromise between these
two values. The present system fixes one
station on the nominal carrier frequency;
the second station 10 kc higher; and a
third station 10 kc lower. This makes
the beat between the second and third
stations 20 kc which gives essentially the
same improvement between each of the
three stations.
TT
11rn
L= HORIZONTAL LINE
FREQUENCY
L
L
OFFSET
3L
4f
FREQUENCY
The offset of cochannel visual carriers is shown; note the fine structure that is super.
imposed. The maxima and minima points occur at multiples of one -half the line frequency.
FIG.
32
1.
At the time these early experiments were
performed, it was noted that an additional
improvement could be obtained for certain
frequencies near the 10 and 20 kc offsets,
but the frequency tolerance required was
so small that the existing methods of
transmitter frequency control made it impractical to try to utilize this additional
improvement. An illustrative sketch show-
FREQUENCY CONTROL TO MINIMIZE
PART
I
THEORY OF OPERATION
DESIGN OF STABLE OSCILLATORS
EXPERIENCE IN THE FIELD
ing this trend is illustrated in Fig. 1. It
will be noted that in addition to the
maxima and minima occurring at multiples
of one -half line frequency there is a fine
structure superimposed.
Recent Investigations
Recent advances in the art of manufacturing quartz crystals with long term
stability along with novel circuitry for
making crystal oscillators independent of
circuit components other than the crystal,
made a re-evaluation of the cochannel interference problem worthwhile. The first step
was a detailed investigation of the improvement that could be obtained if the fine
structure noted in Fig. 1 could be utilized.
A laboratory setup was made, and statistical data was obtained. Figure 2 shows the
characteristics around 10,000 cycles and
Fig. 3 the characteristics around 20,000
cycles. These curves show the required dif
ference in decibels between the desired
signal and the undesired signal in order to
obtain a tolerable picture for the offset frequencies shown. It can be seen that an
improvement of at least 10 db can be obtained at each of the two offset frequencies.
A more important observation is that in
the region of maximum improvement the
desired signal need be only 21 db stronger
than the undesired to produce a tolerable
picture. This variation in interference is
not unique for the frequencies shown. The
curves are duplicated at frame frequency
intervals and change slowly to conform to
the variation related to line frequency as
shown in Fig. 1. This gives a clue to the
basis for the improvement obtained. The
interfering signal is not reduced, but the
beat pattern produced is related to both
the television line and field frequencies in
such a way as to interlace out or. in other
words, to produce a fine-structure pattern
which is less visible. This points out a
basic requirement for the proposed system.
the offset frequency must be related to
the television line and frame frequencies.
Specifically, for the frequency domain being
9960
9980
10,000
10,020
OFFSET FREQUENCY -CPS
10,040
AVERAGE -10 OBSERVERS
21" COLOR RECEIVER - SAILBOAT SCENE
INTERFERENCE -COLOR TEST CHART
8 -I VIEWING DISTANCE
The difference in db required to produce a toter.
able picture with carriers offset by approximately 10 kc.
FIG. 2.
40
O
0
a:
36
32
Lu
a
u
28
24
20
19,980
20,000
20,020
20,040
2 0,0 60
OFFSET FREQUENCY- CPS
AVERAGE -10 OBSERVERS
21" COLOR RECEIVER- SAILBOAT SCENE
INTERFERENCE -COLOR TEST CHART
8 -I VIEWING DISTANCE
FIG. 3. Note the difference in db required to produce
a tolerable picture with the carriers offset by 20 kc.
33
www.americanradiohistory.com
REACTANCE
TUBE
-%
000
-
- SYNCHRONIZED
SWITCHING
AMPLIFIER
Here is an oscillator circuit that is ;'table enough
produce the required frequency control tolerances.
FIG. 4.
to
considered, the requirement is met by making the offset an even multiple of frame
frequency. A simple method for providing
the required stability of the field and frame
frequencies is to lock the station synchronizing signal generators to a color sub carrier frequency crystal. This equipment
is commercially available, and already installed in many stations.
The indicated improvement can be used
in two ways. If the separation between
stations is unaltered, the use of precise frequency control will improve the pictures in
areas where the quality is limited by cochannel interference. Where present quality is considered adequate, the use of
precise frequency control would allow stations to be closer together without creating
increased interference in the cochannel
limited areas.
An examination of Figs. 2 and 3 indicates that the beat between the visual
carrier frequencies should be maintained
within -x-10 cycles to obtain the major part
of the improvement possible. This allows
a change of ±-5 cycles for each station.
Thus it can be seen that the stability required varies from i-1 part in 107 for
the lower VHF channels to ±5 parts in
10" for the higher UHF channels. The
time during which this stability must be
maintained without check or adjustment
depends upon the period of time that is
considered necessary for a practical system. A frequency check once a month is
certainly not unreasonable.
Oscillator Stability Improved
Concurrent with the observational tests,
work was started in the laboratory to produce crystal oscillators of the required
stability. One oscillator that is capable of
the required performance is shown in Fig.
4. In this circuit it will be noted that the
amplitude of the oscillations is limited by
a diode in the plate circuit. The plate circuit is decoupled from the crystal circuit
by a transformer, and the grid circuit is
isolated from the crystal by a low -value
shunt resistor. This combination alone
would make a reasonably stable oscillator.
The additional equipment allows the
crystal to operate as a phase detector, in
addition to its normal function as an oscillator. A reactive change in the circuit would
normally cause a change in the frequency
of oscillation, but with this circuit it will
unbalance the bridge and produce a control
voltage on the reactance tube which compensates for the original change. It is apparent that if a crystal with good long -term
stability can be provided, the circuit will
adjust automatically in an appropriate
fashion to make the frequency of oscillation very stable.
Stable crystal characteristics can be obtained by first utilizing a crystal that has
been manufactured with the best techniques commercially available. and then
this crystal must be operated in a good,
constant -temperature oven. One oven control circuit with the desired characteristics
is shown in Fig. 5. Whenever the tempera-
34
www.americanradiohistory.com
ture of the bridge, which constitutes the
heating element of the oven, is below the
balance temperature, a small a -c signal is
produced which is amplified and detected.
This rectified signal is used to control the
d -c supply which provides the power to
heat the bridge. If the bridge overshoots
and goes too high in temperature, the
phase detector prevents additional power
from flowing into the bridge.
Field Tests
Two crystal oscillators were built. One
was installed at WRCA -TV, the Channel
4 station in New York, and the other was
installed at WRC-TV, the Channel 4 station in Washington, D.C. The system was
tested for several months. When the units
were first installed, one oscillator was arranged so that during color shows (when
line and field rates were accurately controlled) the offset frequency could be
changed with the snap of a switch from
one of the best frequencies near 10 kc to
one of the poorest frequencies near 10 kc.
The signals were observed at several locations between New York and Washington,
during many different shows. Due to propagation differences, cochannel interference
was not always a problem. However, when
cochannel interference could be observed
there was never a time when changing to
the desired offset did not either clear up
the interference or materially improve it.
Regarding the relative stability of the
crystal oscillators, almost daily checks of
the beat between the two signals were
made at the David Sarnoff Research Center in Princeton, N. J. The results are
shown in Fig. 6. It will be noted that for
the first forty days considerable aging is
apparent, since the beat changed by 5
cycles out of 67 million cycles. By this
time the initial aging was essentially complete and the frequency remained quite
stable for the next 20 days. At the end of
this period it was decided to readjust the
beat frequency to about 9950 cycles as
shown. The next 15 days show an aging of
only about one -half cycle. At this time one
of the ovens became inoperative. Although
the crystal kept oscillating, the unit was
taken out of service. It was repaired, and
restored to service 135 days after the beginning of the test. For the next two months
there was very little aging and the frequency held within ±0.5 cycle. Operation
without adjustment continued for several
weeks, beyond what is shown in Fig. 6,
with essentially the same results. This
represents a relative stability of ±4 parts
in 10° for each oscillator for a period of
two months. Since this time. the two oscillators have been in continuous use for over
TEMPERATURE
SENSITIVE BRIDGE
Diagram of the oven.control circuit. Changes in ambient tempera
lure unbalance the bridge and modify the power flow to keep the oven
temperature constant.
FIG. 5.
a year with simple periodic frequency
checks to maintain the offset.
Summary
Laboratory tests have established the
fact that an improvement in the order of
10 db can be obtained with precise offset frequency control. In order to obtain
reduced visibility of the cochannel interference, it is imperative that the beat
frequency between the visual carriers be
related in a particular fashion to the line
and field rates of the video signal. With
the required conditions established, this
means that the desired signal need be only
about 20 db larger than the undesired signal to produce a tolerable picture. It also
has been demonstrated in the field that the
system is effective under actual operating
conditions. Two improved crystal oscillators have been built and operated which
have a relative stability more than adequate for the VHF television channels. The
reduction of interference obtained with
this system can be used to move cochannel
stations closer together, or to improve the
fringe area service of existing stations when
they are limited by cochannel interference.
It is interesting to note that in such areas,
if any station were to increase its service
area by means of a power increase, additional viewers would be obtained at the
expense of the cochannel stations. If the
cochannel stations also increased their
power by the same factor. the service areas
would be back to the original condition
On the other hand, with the application of
precise frequency control, each station
would obtain the same improvement as
though it alone had increased its transmitter power.
Bibliography
1. \V. L. Behrend, "Reduction of Co- Channel
Television Interference by Precise Frequency
Control of Television Picture Carriers." RCA
Review. Vol. XVII, p. 443. December, 1956.
2. G. L. Fredendall, "A Comparison of Monochrome and Color Television with Reference to Susceptibility to Various Types of
Interference," RCA Review, Vol. XIV. p.
346. September, 1953.
RCA Laboratories Division, "A Study of
Co- Channel and Adjacent- Channel Interference of Television Signals, Part I," RCA
Review, Vol. XI, p. 99, March. 1950.
4. Norman Lea. "Quartz Resonator Servo -A
New Frequency Standard." The Marconi
Review. Vol. 17, p. 65, 3rd Quarter, 1954.
5. P. G. Sulzer, "High- Stability Bridge- Balancing Oscillator," Proc. 1.R.E., Vol. 43, p. 701,
June, 1955.
3.
Editor's Note: In our next issue (June, 1958)
we will present Part II which will he entitled
"Equipment for Achieving Precise Frequency
Control of Television Transmitters."
B
/
Actual field tests were made with this system,
and this graph indicates the relative stability obtained.
FIG. 6.
35
1.
Complete metering of all stages and simplified tuning are
inherent characteristics of the BTA -500R and BTA -1R transmitters.
FIG.
36
www.americanradiohistory.com
NEW
500
AND 1000 WATT
AM TRANSMITTERS
Type BTA-500R and BTA -1R Provide Outstanding Performance; Provision for
Remote Control; Ease and Economy of Operation, and Color Styling
by I. NOV/K, RCA Broadcast
.Sot,'s
The
latest trends in broadcasting, calling
for increased power, remote control, and
Conelrad requirements, have dictated a
new approach in transmitter design. As a
result, RCA engineers have designed an
altogether new AM transmitter that integrates these modern requirements but uses
standardized circuitry. With this technique
either the BTA -500R or the BTA-1R
transmitter has the facility of simplified
power change. Remote -control provisions
have been incorporated in both transmitters so that operational control is easily
obtained by making proper connection to
a remote- control unit. Also included in the
design, with the addition of a few accessories, is remote Conelrad switching. While
retaining all of the quality, performance
and reliability contained in the previous
RCA transmitters of the same power level,
these new transmitters have many additional advantages.
Attractive functional styling plus ease
access make the BTA -500R and BTA -IR modern
economical transmitters.
FIG. 2.
of
Features of Type BTA -500R and BTA -1R Transmitters
No Neutralization Required
Tetrodes throughout simplify the tuning.
Built -in Provision for
Remote Control
Terminal strips are provided in the transmitter for connection of a remote-control
unit.
Bi -Level
Modulation
The very low order of distortion results
in improved soundability.
Fewer Tubes
Smaller tube inventory means reduced
cost of operation.
Accessibility
Vertical construction permits easy access
for maintenance.
Simplified Tuning
Only one tuning control -and it's on the
front panel.
Modern Styling
Fits into any surroundings through choice
of color and functional design.
37
www.americanradiohistory.com
Burgundy Red
Functional Color Styling
In hand with the modern day emphasis
on functional styling, the BTA -500R and
BTA -IR transmitters have been designed
to combine an attractive appearance with
the utmost in utility. Both the cabinet design and the colors will adapt themselves
to various types of surroundings. The
cabinet that houses the transmitter is made
of aluminized steel, and this combination
of metals fuses the electrical properties of
aluminum with the strength of steel to
provide a rigid, well -shielded cabinet. In
order to provide an attractive appearance,
and yet maintain functional operation, the
two panels on each side of the door are
designed to provide front panels for mounting all normal operating controls (see Figs.
I and 2). This type of construction per-
mits installation of the transmitter against
a wall, or allows other equipment to be
placed on either side of the cabinet. As an
additional and altogether new feature, the
doors of these new transmitters are available in several colors: red, blue, green and
dark umber gray
order to harmonize
with the colors of the surroundings. Since.
in many cases, today's transmitter is located directly in the studio building, this
emphasis upon styling and color lends
luster to the appearance of a station.
-in
of Access
Although there is no back door, access
to the rear is provided through two interlocked panels behind the transmitter. These
interlocked panels are easily removed with
thumbscrew fasteners (see Figs. 3 and 4).
Ease
38
www.americanradiohistory.com
Peacock Blue
Vertical construction permits easier maintenance and service. The larger power components are mounted at the base of the
cabinet. One beneficial electrical aspect of
vertical construction is the unobstructed
manner in which the air will travel upward,
providing the most effective and uniform
cooling.
The cabinet is 84 inches high, 34 inches
wide and 32 inches deep. A 4 -inch base on
either the BTA -500R and the BTA -1R can
be removed by taking out the three leg
bolts on each side of the base plate. This
removable base makes it easier to move
the transmitter through doorways, and to
fit it into existing transmitter buildings.
Careful design has produced a rugged, well shielded cabinet that will give years of
outstanding service.
Dark Umber Gruy
Emerald Green
3.
The rear panels on the BTA500R and 1R are easily removed with
these thumbscrew fasteners to permit
FIG.
speedy access to all chassis.
FIG. 4. Rear view of the BTA -500R
and 1R. Note the easily removable
panels. An air filter is mounted behind
the grillwork on the lower panel, and
by keeping dust out of the transmitter
maintenance can be reduced.
This is the oscillator chassis. The terminal strip on the right
contains all of the oscillator connections, and the entire chassis is held
in place with six thumbscrews. The three crystals are switchable from
a front panel control.
FIG. 5.
r
0
S
BUFFER
C.
I
5763
6AK5
P A
6146
DRIVER
2
E26
AUDIO
INPUT
TO MODULATOR
DRIVER
2E26
TO AUDIO FEEDBACK LADDER
The basic exciter subassembly is shown in this block diagram.
Only three RF tubes are used. and the modulator input uses two tubes.
FIG. 6.
40
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Electrical Advantages
As was previously mentioned, both the
BTA -500R and the BTA -1R have been designed around standardized circuits. These
circuits have been incorporated in the basic
transmitter unit, and it is used in the production of either transmitter. Included in
the basic transmitter is an exciter unit, low voltage /bias supply and a portion of the
control circuits. By adding to the exciter
unit the proper RF, modulator units, high voltage rectifier and power -determining
components, a BTA -500R or BTA -1R
transmitter can be supplied.
FIG. 7. The underside of the oscillator chassis is shown here.
The relays are used to switch the crystals. Etched wiring simplifies servicing and also helps to improve oscillator stability.
Unique Exciter
exciter nucleus of the basic transmitter combines in one unit the oscillator,
low -level audio and RF stages. This new
standardized exciter contains a new type
of oscillator, developed by RCA engineers
(see Figs. 5 and 6). Three switchable, temperature- controlled, crystal units make up
the oscillator. Any of the crystal units will
remain constant within i-5 cycles. Any of
three crystals can be selected by means of
a front panel switch, or by means of relays
built into the transmitter for remote control operation. The use of three crystal
units provides a spare on the main channel,
as well as provisions for automatic Conelrad switching. This new oscillator and
1
h
buffer incorporate broadband circuits that
require no adjustment. A 6AK5 is used as
oscillator tube with a 5763 as the buffer.
This unit is built on an etched circuit panel
(see Fig. 7), easily accessible for service
by simply removing the connecting plug
and retaining screws (see Fig. S). Also
a part of the basic exciter is the 6146
IPA stage, which is operated very conservatively, and a pair of 2E26 tubes are
used for modulator input.
FIG.
8.
The entire oscillator subassembly is shown from the rear.
Vertical construction provides ease of maintenance. The oscillator
chassis is easily removed with six thumbscrews. Note the convenient plug -in terminal strip on the oscillator chassis.
41
www.americanradiohistory.com
EXCITER
0
S C.
6AK5
POWER AMPLIFIER AND MODULATOR SUBASSEMBLY
SUBASSEMBLY
BUFFER
5763
TO
ANTENNA
B+
DRIVER
2E26
MODULATION
B+
REACTOR
DRIVER
2E26
B+
Simplified diagram of the new transmitter.
Power change of the final amplifier and the modulator
stages from 500 to 1000 watts is easily accomplished
by changing the 4 -250A power amplifier and modulator
tubes to 4 -400A tubes.
FIG. 9.
BTA -500R Circuit
From the exciter subassembly we connect to the next subassembly which consists of the power amplifier and modulator
tubes (see Fig. 9). Each subassembly is
a complete unit with terminal board terminations for ease of installation. l'he BTA 500R power amplifier consists of two Type
4 -250A tubes connected in parallel, fed by
the 6146 IPA from the exciter subassembly. From the same exciter subassembly
the two 2E26 tubes in push -pull are
resistance coupled to the two 4 -250A
modulator tubes.
BTA -1 R Circuit
Again the basic exciter is used, but by
adding a different power amplifier and
modulator tubes the BTA -1R transmitter
is produced. A pair of 4 -400A tubes con42
nected in parallel are used for the final
amplifier, with another pair of 4 -400A
tubes for the modulator. As with the BTA 500R, an IPA 6146 drives the r-f power
amplifier and a pair of 2E26 tubes drives
the modulator tubes (see Fig. 9).
Power Supply Features
The low- voltage, power supply used with
both these transmitters utilizes selenium
dry -disc rectifiers for the plate, screen,
and bias. Lower power drain and cooler
operation are the reasons for using this
type of rectifier for the low -power stages.
The high -voltage supply for the power
amplifier and modulator plate circuit is
built around a pair of 8008 tubes. Their
reliability and performance dictate their
choice in this application (see Fig. 10).
Noteworthy Design
The design philosophy behind these
transmitters is based on years of experience
in building the most reliable of broadcast
transmitters. Simplified tuning, reduced
installation time, and provisions for remote
control are only a few of the outstanding
benefits of these two new transmitters.
Tetrodes are used throughout to eliminate
the need for neutralization, and improved
soundability results from using Bi -Level
Modulation. Choice of red, green, blue,
and dark umber gray doors add a distinctive touch that, combined with functional styling, permit these transmitters to
lend themselves to the decor of a station.
Altogether, these unusual features add up
to produce many major benefits such as:
outstanding performance; provision for remote control; ease and economy of operation and color styling.
OSC
IPA
BUFFER
P A
A
MOD
DRIVER
VOLTAGE
POWER SUPPLY
LOW
BIAS
POWER SUPPLY
HIGH VOLTAGE
POWER
SUPPLY
This block diagram shows the power
supplies. The low voltage and bias power sup.
plies use selenium dry.disc rectifiers, while the
high voltage supply uses two.
FIG. 10.
Front of BTA -500 new transmitter permits easy tube change. Power amplifier and
modulator tubes are located on the top chassis, and just below this is the exciter chassis. All
normal operating controls are shown on the two side panels.
FIG. 11.
The transmitter cabinet is made of
aluminized -steel for better shielding and strength.
The rigid construction is shown here: note the
additional supports across the side of the cabinet.
FIG. 12.
43
REVEALS ITS MODERN APPROACH
TO RADIO BROADCASTING
Pick a Growing Market, Program to Its Tastes,
and Provide a High-Quality Technical Installation
TOM
E.
and ROY D.
BEAL, !'resident and General alanu,t,r
STANLEY, Station )tanager and Technical Director
Station KRKC. Kansas City
This
is our recipe for success in the radio
business: First, we carefully researched
and selected our market. Next, we designed
a program format to appeal to the intelligent, adult segment of today's huge buying market. Finally, we made no compromises insofar as technical equipment was
concerned, because we were interested in
getting complete coverage and a high fidelity signal. And, this approach is paying off.
The Market
We selected the fast -growing metropolitan Kansas City area as our market-especially Johnson County. This county is reported to have the largest average income
in the U.S.A. -$7291. It has a population
of 120,000, but no newspaper and no
radio station. Many cities are located in
sprawling Johnson County, for example.
the northeast area in itself has 16 cities.
Furthermore, it's a prosperous market,
probably one of the fastest growing suburban areas in the country. There are
many large shopping centers, giving concrete evidence to the demands of the residents. Here, we decided, is the place to
locate our radio station.
Contemporary Programming
Our program format is a contemporary
one -aimed at this unique local market.
It's tailored to the tastes of our markets,
and it's designed to have an individual
flavor all its own- somewhat like the NBC
concept of "Monitor."
44
www.americanradiohistory.com
ISBKC
FIG. I. RUC building entrance, with lobby on
the first floor and studios on the second.
The daily format is built around one
main program. This daily program is called
"The Day of the Week" and runs from
5:50 a.m. until sign -off. Friday, Saturday
and Sunday are known as "Weekend." A
carefully chosen music format with wellbalanced themes is used to produce daily
programming that consistently receives
good comment. In fact, the advertising
agencies are tying this in with their accounts. Newscasts consist of two daily
ten-minute segments: "Morning News
Desk" from 7:20 to 7:30 a.m. and "Evening News Desk" from 5:20 to 5:30 p.m.
(when sundown schedule permits). In addition, each hour there is five minutes of
news, twenty-five minutes after the hour
time when no other station has news
(KBKC has music while other stations
have news). Introducing and pointing up
this hourly five -minute newscast is a piano
keyboard selection
few minutes prior
to the news. After each newscast, KBKC
features five minutes of uninterrupted
music called "Monday Music," "Tuesday
Music," etc., or "Weekend Music."
-a
-a
"News Highlights" featuring local and
national news. These two -minute specials
are to be done via mobile unit and telephone beeper. It may be a hot news report,
the local Red Cross drive, the Community
Appeal or any other local event that represents a public service. No more than two
minutes is to be used for each.
Sponsorship of the newscasts is rotated
in order to give all advertisers an even
break. Provision is also made for "hitchhike" of one sponsor's commercial on that
of another in these newscast announcements. Sponsorship of KBKC "Hourly
News" has been so attractive to advertisers
that it has produced 30 per cent of our
station revenue, during the second month
of operation.
Music Format
We offer an adult approach to music
programming that is refreshing, we believe, as one considers the usual concepts
of music selection. There is no block programming at KBKC-the music is interwoven throughout the entire broadcasting
day . . music that includes big bands,
ballads, mood, contemporary jazz, musical
comedy hits and the good current hit tunes.
.
Furthermore, we plan, directly before
each hour, there will be a two -minute
Typical One Hour Music Format
On the Hour:
Band (Instrumental)
Ballad
Mood (Instrumental)
Pop
Band (Instrumental)
Ballad
Jazz (Instrumental)
On the Half Hour: Hourly News (5 minutes)
Band (Instrumental -five
minutes
of uninterrupted music)
1. Latin
American
2. Mood
3. Piano
Rhythm
Band (Instrumental or bright piano
jazz)
Ballad
Mood (Instrumental)
Pop
Band (Instrumental)
Ballad
Mood (Instrumental)
We have one show tune per hour at a
varied time. We never have vocals back to -back, but always separate them with
instrumental selections.
45
Common reception room which KBKC shares with another
tenant in the building. Left: Tom E. Beal, Pres. -Gen. Mgr., KBKC.
FIG. 2.
Promotion
At the outset we are "buying our audience" in a way of speaking. By this we
mean that contests and prizes designed to
stir local interest are costing us a considerable outlay. For example, we are offering
two fully paid, round -trip tours to Europe
as prizes.
tional streamers in their windows everywhere. And since it's the first new radio
station in Kansas City in five years, it is
news and something to be talked about.
The Jaycees held a parade with queen
cars, balloons and all the color of a Mardi
gras during the first broadcast day of
KBKC.
Of course, we are getting a great deal
of free promotion also. Local pride is being
Another promotional item which we designed is a metal plate, the size of an
automobile license plate, for use on cars
of staff, stockholders and sponsors. Our
call letters are silk screened on this plate
tremendously stimulated. KBKC is the first
radio station in Johnson County. Jaycees
and local dealers are putting our promo-
Offices and studios are on second floor.
Shown is Margaret Ann Shaw, Traffic Manager.
FIG. 3.
in color. It makes a durable and lasting
promotion piece that goes everywhere that
we and our customers go. We have also
reproduced this plate on cardboard stock.
This is to be used on remotes for identification purposes. We can afford to spread
these around liberally.
Furthermore, we have created an all metal highway sign with our station call
letters on it. The support consists of a
piece of angle iron, seven feet high, pointed
at one end and sprayed with aluminum
paint. The sign itself is a 12 by 30 -inch,
silk- screened, metal plate. This is small
enough to get by without restrictions but
large enough to be identified as one drives
by. It is especially designed for use on
fence lines.
Studios and Offices
Centrally located, KBKC studios and
offices are in the Dickinson Building in
Mission, Kansas. This two -story building
is jointly occupied by Dickinson Theatres
and KBKC. A common reception room is
enjoyed by both on the first floor. In addition, KBKC has its own reception area in
a second -floor suite of rooms.
Newsroom, traffic, continuity, office,
combination studio -control room and production studio are all housed on the second
floor. In addition, KBKC has use of a
52 -seat, private theatre on the first floor.
Here it is planned to hold sales clinics.
FIG. 4. The sales office. Left to right: Tom Mannion and Ron
Douglas. Account Executives; Edith Sacco, Continuity Director.
46
KBKC plans to help its advertisers to
merchandise in the most effective ways.
There will be clinics for various businessmen: One for auto dealers, another for
appliance retailers, etc. Subjects will be
"How to Sell," "How to Advertise," "How
to Create Traffic in the Store."
Linda Lewi, Director of Women's Activities, and Tom Beal in second-floor hallway.
FIG. 5.
Studio A
The main studio is equipped with professional equipment but exhibits the decor
of a den or recreation room rather than
a work area. Not by accident has this
been occasioned. Our station management
believes in creating a homelike atmosphere
for the enjoyment of the staff.
No equipment racks are seen in the
studio-all are built in. Wall-to-wall carpeting covers the entire floor area. Record
storage and parts storage are in completely
enclosed areas. Furnishings are not bulky
but of attractive modern design, fitting
well into this 13 by 17 -foot studio.
Even the control console and turntables
are part of the unusual design. For the
operator's convenience, the equipment is
arranged in a "U "- shaped pattern. The
console is directly in front of him. with
turntables on the right -hand side and tape
players on the left.
The control console, Type BC -3B. is
mounted on a free -shape table. Three
BQ -2B turntables are built into an attractive cabinet. This provides a convenient
in -line arrangement for the operator. Three
preamplifiers, the BA -25 Automatic Gain
Control, the cue and speaker are all accommodated within the custom -built turntable
cabinet. (These equipments can be easily
serviced from the rear of the cabinets.)
Two portable tape recorder players, Type
601, are mounted on a record cabinet.
Above the control console hangs a 77D
microphone supported by a Dazor type
mounting. The turntables and tape recorders are operated by remote control with
finger-tip switches mounted on the console
table. We custom -built our studio installation this way and designed it ourselves for
economy and for ease of operation.
Studio "A" (control room). Seated is Ben Weaver. Corn
municator (d.).). Note the convenience this setup affords.
FIG. 6.
-
Jerry Fullerton, Commu
nicator, doing a beeper report
through console of Studio "A."
FIG. 7.
FIG. 8. Studio "A" (control room)
is equipped with BC -3B conso
lette. Note two tape recorders on
left, and three built in BQ -2B
turntables at right.
Production Studio (B)
0111:ssov
!
Adjoining Studio A is a room 12 by 17
feet, designed for production purposes. It
serves for making tapes in advance, for
preparing spot announcements, and for
readying live shows. Thus it constitutes an
auxiliary to the main studio, and is equipped with a small control console, two turntables and tape recorder in order to carry
on a completely independent operation,
when required.
A modernistic styled control console is
employed in Studio B. The consolette and
turntables plus monitor and tape machines
are entirely portable. Thus, they may he
moved to remote broadcast locations in a
very short time, providing a complete
studio wherever needed.
41E4
FIG. 9. Studio "B" (production studio) is being us ed to produce commercials and special programs.
Left: Marvin Bredemier, Engineer, using Type BN -6A, 4- Channel Remote Amplifier. Right: Chuck
Goodman, Newsman, recording special news features. The equipment is portable and can be taken
out of the studio for special remote broadcasts, setup for any type.
News Center
Just a few feet away from the production
studio is an irregularly shaped area approximately 10 by 14 feet which serves as
the news center. Here is the AP teletype
machine and the office of the newscaster on
duty. Equipment includes Type 77DX
Microphone, and monitor for police and
fire frequencies. (Plans are now in process
for a two -way radio unit for contact with
our proposed mobile unit.) Facilities are
also here for telephone beeper recording.
Station Staff
Studio "W' (production studio) showing program
director's desk to the left and control center to the right.
FIG. 10.
FIG. 11.
Ron Douglas,
news center.
Newscaster, at work
in
KBKC
Our initial staff consists of the following
nineteen persons:
General Manager
1
(and Acting Commercial Manager)
Station Manager
1
(and Acting Tech. Director)
Program Director
1
1
Chief Engineer
Transmitter Engineers
2
Salesmen (Account Executives)
4
Traffic- Receptionist
1
Continuity Director
1
News Director
1
Assistant Newsman
1
Women's Activities Director
and Music Librarian
1
Sports Director
1
Announcers -DJs (Communicators)
3
We like to think of our announcers as
communicators-talking with the people,
not to the people. They are high level men,
sharp and quick of mind, but also personable and communicative. The kind who
take people places and who do things. The
kind that strike immediate response in the
adult mind.
We also have one inflexible rule: "No
talk to last over two minutes." This, we
believe, provides a modern, fast- moving
pace. It is one of the essential ingredients
of our radio format.
RECEPTION
CONTINUITY
SALES OFFICE
EXECUTIVE
OFFICE
NEWS DISH
H
NEWS CENTER
A
L
L
W
A
Y
CONTROL ROOM
(STUDIO Ä)
NEWS TELETYPE
BO-3B
CONSOLETTE
PRODUCTION
000
BO
-2B TURNTABLES
(STUDIO "B °)
STORAGE
-
O M4IIINES
O
TAPE
-41111
TURNTABLES
SCALE IN FELT
o
-0
0 0Io
MONITOR
'TAPE PLAYERS
SPEAKER
ANNOUNCERS
ABLE
CONSOLE,
TRANSCRIPT ICI
AND TAPE
"'LCOROS
MONITOR SPEAKER
FIG. 12. Floor plan showing all KBKC offices and studios, located on second
floor of building. Large common reception room and lobby is on first floor.
Transmitter Installation
The transmitter is located approximately
six miles (4% miles airline) from the
studio. Since it is eventually to be remotely
controlled from the studio, no personnel
will be required at the transmitter. This
means a very small building (see Fig. 13)
with no need to install septic tank, water
connections, etc. (Until the first year of
operation is concluded, in accordance with
FCC requirements, an operator must be
retained at the transmitter.) For this
situation, temporary facilities are made
available but, at the end of the year,
the transmitter operator will become our
studio engineer.
A 500 -watt RCA Transmitter, Type
BTA-500MX is employed. The antenna
system is a three -tower directional array,
designed to cover the metropolitan Kansas
City area. Towers are 185 feet high, insulated guyed affairs. Transmission lines,
power lines and telephone cables are all
buried.
Phasing equipment was custom -built by
RCA. Instrumentation and radiation of
our array have proved to be very stable.
There is practically no need for adjustment.
Part of this stability is due to design: part
by the buried lines.
Three pair of wire lines are run by the
local telephone company to the transmitter.
One pair is a Class "A" 15.000 cycle audio
line for program purposes. Two pair are
dc lines for use with the remote- control
Transmitter building showing center tower in rear. Note compactness of
building and inexpensive type of construction which is typical for remote operation.
FIG. 13.
49
WINDOW AIR
CONDITIONER
STORAGE
HEATING UNIT
(BELOW)
PHASING
UNIT
BTA
-500
MX
TRANSMITTER
SPEECH
RACK
DESK
Layout of KBKC transmitter building showing all
facilities required for remote operation.
FIG. 14.
FIG. 15. Three -tower directional antenna system designed to cover Kansas
City area. Towers are 185 -ft. high, insulated guyed affairs.
unit. In addition, there is a telephone line
for continuous communication purposes.
Station management foresaw the advent
of remote control, placed a contingent order
for equipment and when FCC legalized
this type of operation, KBKC was among
the very first to further its plans. It is
this type of operation that is very efficient
in providing effective coverage of large area
with low power. Further, the economy of
unattended operation often makes the difference between operating in the red and
operating at a profit.
Essential Investments
Good money is being paid for staff and
equipment- higher than usual for a station
of its class. This is justified on the basis
that what people hear is important. This
is the identity of our station. We believe it
constitutes a good business investment. We
aim to be a first-class station with firstclass accounts, and to do this we have
acquired first -class equipment.
We deliberately planned to start on the
top level. It is easier to start there than
to try to get there later. All our plans are
made on that basis. Therefore, from the
outset, everything is of high quality-personnel, programming, advertising and technical equipment.
Transmitting Equipment
There are three racks in the transmitter
building (see Fig. 16). Rack No.
contains the custom built phasing equipment.
Rack No. 2 contains Type BTA- 500MX
Transmitter. Rack No. 3 contains equipment as follows (from top down):
1
View inside transmitter building showing engineer tuning speech rack (No. 3 rack).
Cabinet No. 1 (extreme left) contains phasing equipment. Cabinet No. 2 is the BTA.500MX.
FIG. 16.
50
a.
Limiter Amplifier
b. BW -66E Modulation Monitor
c. I08E Phase Monitor
d. BW -11A Frequency Monitor
e. Monitor Speaker
On the top of Rack No. 3 is a Conelrad
receiver. The transmitter building is electrically heated and cooled for efficient
equipment operation and comfort of engineers on
duty.
Inception of KBKC
The idea was born in our minds while
working for a radio station in Kansas. We
foresaw the future possibilities for a station in this 18th market of the U. S. which
had only eight stations. There are markets
of much smaller size which have as many
as 14 stations. And this example could be
multiplied by many more. But Kansas City
has not had a new radio station for many
years. Since radio is making a highly successful resurgence elsewhere, why not in
Kansas? The idea grew apace and we had
the necessary study made in Washington
by a consultant, then papers were prepared
and filed before the FCC. Within a short
time, we obtained the CP (construction
permit) for a new station and, in October
1957, the idea became a reality! Now.
KBKC is an ideal suburban radio station
having nice relations with local merchants.
Business Outlook
Because of the advance promotion and
selling before going on the air, KBKC
started broadcasting October 26, 1957,
with considerable business. During the first
month of operation, the station operated
in the black. This is a real success story.
Our station went on the air with a total
of 32 accounts. We had four accounts
signed for a total of 2000 one- minute spot
announcements a year: six with 1200 spots:
and eight with 600 spots a year, while the
rest of the accounts varied. We had six
of the daily newscasts sold on a 13 -week
basis before going on the air.
Business is far greater than we had ever
expected. Effective March 1, 1958, we will
have as our national representative, The
George P. Hollingberry Company.
Future Plans
Foremost on the list of things to be done
acquisition of a mobile unit for remote pickup. It is envisioned that this shall
be a station wagon equipped for on -thescene news reporting. Equipment will include tape recorders and two -way radio.
Thus, programs can originate live from the
mobile unit.
is the
Executive office of KBKC. Left: Roy D.
Stanley, Station Manager and Technical Director.
Right: Tom E. Beal, President and Gen. Manager.
FIG. 17.
Next, we are presently applying to FCC
for an increase of power from 500 to 1000
watts. All phasing equipment and the transmission line were designed for 1 KW
operation. The transmitter is easily converted from 500 to 1000 -watt output, having facilities of power increase built -in with
only a power conversion kit needed for the
KW conversion.
1
The third step in station expansion will
he conversion to nighttime operation. For
this it will be necessary to install two additional towers, giving the necessary 5 -tower
array to produce the required pattern.
Again provision for this was made at the
outset. Sufficient ground was acquired for
the 5 -tower installation and sufficient space
was allowed in the transmitter building to
accommodate an additional phase unit so
that nighttime conversion could be conven-
John Herrington, KBKC News
Director, displaying a metal highway
sign used for station promotion.
FIG. 18.
dial 1480
kan as
city
iently installed.
In addition, it is eventually planned to
install auxiliary power generating equipment at the transmitter building, since the
suburban area where the transmitter is
located is more subject to commercial power
failure than a central city location. When
all these future plans are consumated, we
feel that KBKC radio will become not
only a fine business proposition but an
excellent asset to the metropolitan area of
Greater Kansas City.
51
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HOW TO DESIGN THE
ANNOUNCE BOOTH TO GIVE
by JOHN
F.
PALMQUIST, Broadcast Field Sales
Many
present clay radio control rooms
are not only used for this purpose, but also
act as announce booths where most of a
station's announcing is carried on. In many
cases the control room may be the only
studio area in a station, and it will contain all the station's audio equipment. Frequently, a transmitter and a record library
will also be located in the control room.
This makes the problem of acoustics more
complex but since radio sells with sound.
good acoustics are a must when the best
sound possible is desired.
Design Factors
Combination control rooms are at best
a compromise of the several design factors.
When designing this control room, consideration must be given to the following:
Location of the control room within
the studio building;
Isolation -elimination of unwanted
sound and noise, both internal and
external;
Construction -dual wall, floating
wall, single wall;
Reverberation control, elimination of
unwanted reflections, and floor treatment;
Ventilation and air conditioning;
Size and arrangement of equipment.
1.
2.
3.
4.
5.
6.
TI:
: :::.
1.
:
:aWSKIKr.av
Location
The combination control room must be
located so that it is convenient to the office
areas, but traffic in and out of the room
should be minimized in order to reduce
distractions to the announcer. The location
selected must have as little external acoustical and electrical noise as possible. The
control room should be located away from
street noise, or noise that may be generated
in other parts of the building, because it
may become difficult and costly to reduce
unwanted noise that enters through the
floor and walls. Air -conditioning compressors and other rotating machinery should
be well isolated and kept as far away from
the control room as possible.
It is not wise to locate a control room
next to a power transformer vault, or other
large electrical equipment that may produce strong electrical fields. These strong
electrical fields may cause noise problems
in audio equipment. If the control room
contains the transmitter, great care should
be given to the grounding of all audio
equipment including equipment racks, con solettes, turntables, pickup arms, and other
metal objects. In some cases, it may be
desirable to shield the control room with
copper screen to reduce noise generated
from high power RF fields of the nearby
transmitters and antennas.
Is
r
::CIKCIM:o:r.11tT
PLASTER
2"x 4'STUDS
LATH
STAGGERED 16"O.C.
ON 2 -X 6" PLATE
::::::::::::::::::C:::»::v:::v::::::C:::::
1.
This shows a cross section of a sound.insulating partition. Wooden
walls should be constructed in this manner to reduce external noise.
FIG.
52
www.americanradiohistory.com
COMBINATION CONTROL ROOM GOOD ACOUSTICAL PERFORMANCE
Isolation
Ideally, a control room should be a
sound -isolated room within a room. Cost
considerations in a small station may make
such construction impractical, but it should
be considered when possible. The floors and
walls should be built from materials that
will minimize the transfer of sound into
the control room. Many new stations use
concrete block walls and concrete slab
floors, that are isolated from the building
walls with asphalt impregnated glass fiberboard. This type floor construction is very
practical since it reduces outside vibration
in the control room floor.' A stable floor
will improve turntable operation by reducing vibration that enters the pickup system
from external sources.
1
"Impact Noise Isolation in Television Studios,"
BROADCAST NEWS, Vol. 97. Oct., 1957.
Construction
The ideal control room wall would consist either of a dual masonry wall, or a
masonry wall with a sound -isolated floating
inner wall2 In the smaller stations, cost
considerations usually preclude this type
of construction. A single wall of masonry,
cement, gypsum, or pumice block is a good
compromise, which is completely satisfactory where external noise is reasonably low.
Wood wall construction should not be
used unless double walls are used. Staggered
2 by 4 -inch studs can be set on 16 -inch
centers on a 2 by 6 -inch plate for the
double wall construction (see Fig. 1). Rock
wool bats can be interlaced between the
studs for additional sound isolation. There
t "Applied Architectural Acoustics."
Rettinger, Chemical Pith. Co.. Inc.
by Michael
should be at least 2 inches of rock wool,
or other sound -absorbing material, above
the ceiling surface, and if external noise is
of large magnitude, the ceiling should be
sound isolated.
If care has been given to the location of
the control room in a given building, the
offices and other quiet areas surrounding
the control room may screen it from unwanted sound. Control room doors should
be the heavy soundproof type (see Fig. 2),
or double doors should be used. Observation windows should be kept to a minimum.
Each such window should consist of two
panes of heavy plate glass of different
thicknesses to break up resonance conditions. The glass plates should be set in
rubber or felt gaskets, and usually the
glass plates are set about 10 degrees off
vertical (see Fig. 3).
FELT OR
RUBBER
STRIP
METHOD OF SEALING DOOR CRACK
AGAINST SOUND LEAKAGE
PLASTER
METAL BACKED
FELT STRIP
TRI M
THRESHOLD
FLOOR
FIG. 2. Here are the normal methods for sealing the control-room door. The door itself should be of the heavy type
to improve isolation of the control room.
Sound -insu ating window construction showing
structural separation of double wall. G ass windows in
studios and control rooms should be offset about 10 degrees
and they should be mounted as shown on a double wall.
FIG. 3.
.
53
acoustical consultant should design the
studio and supply the proper materials.
RELATIONSHIP BETWEEN REVERBERATION
TIME AND FREQUENCY
18
1.6
14
N
ñ
2
10
64
256
FREQUENCY
512
128
IN
1024
2048
4096
8192
CYCLES PER SECOND
FIG. 4. These Morris -Nixon curves show the relationship between the reverberation time and the frequency. Reverberation time should remain fairly
constant between 100 and 5000 cycles.
o
z
ó
1.4
1.2
w I.0
F..
8
O
.6
¢
.4
m
fr .2
>
o
1000
10,000
100,000
STUDIO VOLUME- CUBIC FEET
1,000 000
OPTIMUM REVERBERATION TIME AT 512 CYCLES
FOR RADIO BROADCAST STUDIOS
FIG. 5. This curve shows the variation in reverberation time as the size of
the room increases with a 512 cycle reference signal.
Reverberation Control
Some form of reverberation control
should be employed within the studio. If
a studio has to long a reverberation period,
the sound may blur and speech may lack
intelligibility. Such sound characteristics
are not pleasing to the listener. Generally
a studio should have an approximate reverberation time of 0.4 seconds for a
volume of 1,000 cubic feet rising to 0.6
seconds for 10,000 cubic feet$ (see Fig.
5). The reverberation time should be about
the same from 100 to 5,000 cycles, but it
may rise slightly at 5,000 cycles (see Fig.
4). This type studio characteristic helps
eliminate low- frequency boominess.4 An
3
4
"NBC Studio Design." Journal Aeons. Soc.
AM.. Vol. VIII (Page 31, 1936).
"Acoustical Design and Treatment for Speech
Broadcast Studios," by Edward J. Content and
Lansdale Green. Jr., Proceedings of the IRE,
Vol. 32, No. 2, Feb., 1944.
54
Consideration should be given to all wall
and equipment surfaces in the control
room in order to eliminate unwanted reflections. Perforated hardboard or Transite may be used for wall coverings with
rock or glass wool placed behind it for
sound absorption (see Fig. 6). Hardboard
may be painted, and it is easily maintained with occasional washing. The hardboard may be used for wall panels set at
various small angles of 5 to 10 degrees to
produce greater diffusion of sound.
All glass surfaces should be set on an
angle to reflect sound into ceiling's sound absorbing surfaces. Glass surface should be
kept to a minimum, and large corner areas
of glass should be avoided. The floor covering should be of a soft material, such as
cork or vinyl tile, to reduce surface noise.
A rug may be necessary to produce required deadening in control rooms having
many glass surfaces and other reflecting
areas. The surface of the operating table
should be made of some soft material such
as linoleum or vinyl. This will reduce
table -top noise.
Microphone Requirements
A good microphone with proper directional characteristics is important in the
control room. A 77 -DX microphone operated in a unidirectional pattern is recommended (see Fig. 7). The BK -5A microphone is also an excellent microphone for
the control room. The distance between the
speaker and the microphone will be determined by the acoustics of the control room:
however, good microphone technique is
important for all air personnel if natural
reproduction is desired.
Ventilation
To do a good selling job, an announcer
must sound alive. It is important to provide air conditioning and ventilation so that
announcers have a good environment in
which to work. A central air -conditioning
system is recommended. The air is brought
in through ducts from the coolers. The air
ducts should be lined with a sound- absorbing material for a distance at least 20 times
the average width of the duct. A separate
duct should be run to each studio and to
each control room to avoid sound transfer
through the ducts. Low -velocity air should
be used to prevent air noise from the
duct openings.
If the control room contains a transmitter, it is usually possible to exhaust hot
transmitter air to the outside, and to cool
the transmitter with spent -room air. If this
is not possible, the transmitter should be
partitioned off from the control room, and
a separate source of air should be used to
cool the transmitter. The transmitter may
be remotely controlled if it is in another
room, some distance from the control operation. Such a procedure may save many
dollars in construction costs, and also eliminate a source of noise in the control room.
WOOL TYPE
2 -X 2 FURRING ON 2 C.C.
INSULATION
IN BOTH DIRECTIONS
PLASTER
SHIMS
STUDIO
IELEMENT
q
s...a_v..a_.
\alll?/`%`/G
j`\`Illuìu.!: !:iw
a'CROSS
FURRING
¡X
2
Ig'X 18 FURRING ON 2' C.C.
IN BOTH DIRECTIONS
LATTICE STRIP
237"OIR 24'
8C. TO C.
ix
Equipment Arrangement
The equipment selected will, to a large
extent, determine the physical aspects of
the control room. The size of the control
room should be adequate enough to contain all required personnel and equipment.
At the same time thought should be given
to possible future expansion, extra space
should be provided with this in mind. A
control room that is a little larger than
necessary at the outset makes it easily expanded later. Furthermore, it is always
more difficult to acoustically treat a small
room than a large room.
2' FURRING
ON
2' C.0
FIG. 6.
Ñ
INSULATION
2 X2'FURRING ON 2'C. C. IN BOTH DIRECTIONS
1\`
These are drawings of typical
acoustical panels and how they are
mounted. Excellent isolation can be obtained if this type of wall material is
backed up with glass or rock wool.
WOOL TYPE
2"X 2"FURRING
STRIPS ON 2 C.C.
IN BOTH
1,DIRECTIONS
-
Planning it Right
A good architect should be consulted
when planning a studio -control room. After
a general station plan is formulated and
equipment selected, the architect and the
consulting engineer should work out the
specific construction details for the station.
hX
ON
0000
0000
0000
0000
0000
0000
0000
0 0 0 0 0 0 o 0000
o o 0 o o o o 0000
oG00000 0000
o o o o o o 0000
o o o o o o o 0000
000000 0000
2 FURRING
2'
C.C.
ill
kW
A careful
acoustical planning combined
with good equipment will enhance the
sound of any station, and make its sound
sell more.
ALL SURFACES
PAINTED BLACK
OPEN CIRCUIT RESPONSE
OF A TYPICAL
TYPE 77DX MICROPHONE
t5
o
a)
J
W
M
5
m
W
10
o
15
UNIDIRECTIONAL
POSITION
20
UNIDIRECTIONAL
POSITION
60
IOO
1000
10,000
15
000
This is the unidirectional response curve for the RCA Type 77 -DX
Microphone. A good microphone is necessary for combination control rooms.
FIG. 7.
55
www.americanradiohistory.com
THE NEW BK -10A BIGRADIENT
UNIAXIAL MICROPHONE
/
High- quality sound is an important consideration in the broadcast industry, hence
microphone selection and design plays an
important part. It is not always easy to
maintain an atmosphere that is suitable
for quality sound pickup, especially considering the added equipment and personnel required for TV. In addition, acoustics
of television studios have not kept pace
with the visual possibilities except in the
recently engineered TV centers. Although
the polydirectional microphone and the
uniaxial microphone overcome many difficult noise situations, there are circumstances that can render their performance
ineffective. The Type BK -10A Bigradient
Uniaxial Microphone' was specially engineered to supplement the 77 -DX and
BK -5A in high -noise areas. It features a
second order gradient directional characteristic which may be used to increase the
signal-to -noise ratio.
Advantages
The size and weight of the BK -10A are
fully compatible with present boom equip]
-Bigradient Uniaxial Microphont ' RCA Review. Vol. XVII. No. 4, Dec.. 1956.
'
J.
W. O'NEiLL, Industrial I?IrcNnurr I'rndu ,..
ment. Shock mounting and a new cable
provide excellent isolation from stand noise.
Low-gloss finish and a compact mounting
arrangement provides minimum light reflection and minimum shadow. Field tests
have indicated that the BK -10A is ideal
for controlling the level of the leading voice
in a choral group. It can also be used very
effectively when the solo voice is upstage
and the choral group is downstage.
Using the BK -10A on the solo voice, it
will be found that the downstage choral
group is attenuated to a level that permits the use of a separate microphone
for the downstage group; thus the levels
can be mixed to any desired degree. The
BK -10A is also good for picking up weak
voices without getting the microphone in
camera range.
Design Features
The second order gradient directional
characteristic of the BK -10A is made possible through the electrical combination of
the outputs of two mechanically integrated
microphone elements. The microphone elements are patterned after the quality per-
o^
BK -10A DIRECTIONAL
CHARACTERISTIC
270°
190"
l
nuisdu
r
/!r.ri
ur
i
;ran /,
formance and rugged construction of the
Type BK -5A Uniaxial 1llicrophone.2 The
electrical combination of the outputs of
these two axially located microphone elements result in a directional pattern with
wide angle forward response, with a null
at the sides and rear. The two microphone
elements are carefully matched in the
manufacturing process to derive the desired response, sensitivity and directional
characteristics. The two ribbons are adjusted to have fundamental resonance
within two cycles per second of each other.
The output of the microphone over the
entire rear hemisphere is 12 db less than
the output for "on axis" sounds with the
nulls providing 18 to 20 db of attent'ation.
The directional efficiency of this order may
be most readily demonstrated with the following comparison. For identical conditions
the ratio of signal to random noise or reverberation when a nondirectional microphone is replaced with a cardioid microphone may be increased by 4.75 db. The
signal to noise ratio improvement is 8.75
db when it is replaced by the BK -10A.
If the sound source is sufficiently loud
the distance from the talent to the microphone may be increased 14 times when
the nondirectional microphone is replaced
with a cardioid type microphone. For the
same performance with the BK -10A the
distance may be increased
times the
distance required for nondirectional microphones. This feature allows quality reproduction during problem "wide angle" shots
in areas of relatively high random noise.
2/
The microphone elements include the
RCA designed blast filtering to reduce the
possibility of damage caused by gun blasts
and other violent noises. The electrical
circuits are carefully balanced for hum
pickup, and the transformers are exceptionally well shielded to maintain a minimum
of stray magnetic field pickup. This careful design reduces the over -all hum pickup
to a level of -127 dbm.
The output impedance of the BK -10A
is 200 ohms for use with preamplifiers
FIG. 1. At left, the conventional drawing shows the bigradient characteristics of the BK10A.
On the right, this bigradient characteristic is shown in a three dimensional configuration.
56
"The New RK -5A Uniaxial Microphone.BROADCAST NEWS, Vol. 83. May. 1955.
An Ultra- Directional, High - Quality,
Ribbon Microphone; Designed for TV
Boom Use and Especially
Effective in High -Noise Areas
This is the Type BK -10A Bigradient
Uniaxial Microphone. Note center grill; the
second microphone element is located here.
FIG. 2.
having 150 and 250 ohm unloaded input
transformers, but may be changed at the
terminal board to 40 ohms for use with
30 and 50 ohm input transformers.
tilt encountered in television boom use. The
mount is compact and does not detract
from the performance in any manner.
Feedback and Noise Reduction
3.
For situations where feedback from
monitor speakers is a problem the BKlOA may be used successfully if the speaker
is located in a null in the plane perpendicular to the axis or in the rear null. Thus,
for the solution of feedback problems, the
BK -10A is more versatile than either the
velocity or cardioid microphones. The null
plane at right angles to the microphone also
serves another purpose when used in the
television studio. The normal position of
a TV boom microphone is overhead in front
of the talent. In this position camera crew
and cameras are approximately in the null
plane. This means that for a cardioid type
microphone, attenuation of direct sounds
from camera and crew is only 6 db, but the
BK -I0A will attenuate these noises by 18
to 20 db. Both of these comparisons are
made with respect to the performance of
a nondirectional microphone.
Mounting Noise Reduced
The cable supplied with the microphone
is 18" long and is designed to give a maximum attenuation of cable transmitted
noises. The cable consists of tinsel cord
conductors braided together. Cables of this
type have served continuously for five years
in television boom use without failure.
The mounting supplied with the BK -10A
follows the modern styling of the microphone. It provides for all normal angles of
The frequency response is shown in Fig.
No low -frequency compensation is
included: the BK -10A was designed for
use at distances greater than three feet as
would be encountered in boom operation.
Proximity of large obstacles may have a
deleterious effect upon the directional characteristics in some cases. The output level
is maintained at -55 dbm.
'
The "Ultra- Directional" characteristics,
of the BK -10A, make it the ultimate for
high -quality reproductions in those situations where premium performance is a
must. The directional properties of the
microphone will provide excellent noise rejection even under adverse conditions. The
BK -10A is a superior acoustic tool that
will find numerous applications in the
television and radio broadcast fields, as
well as in the recording and public
address systems.
1 __IL
5
0
-5
-l0
-IS
...
-20
Q
la
-
Applications
RESPONSE
BK -10A
AND DIRECTIONAL CURVES
FOR THE RCA TYPE
ULTRADIRECTIONAL MICROPHONE
'
minuffilli.
I
LIMMIMIllrall
,mea uN
ililiiila
,
1
25
-30
?leo/
0DB125 UV /DYNE/CM
loo
1000
10000
FREQUENCY - C.P.S.
FIG. 3. The frequency response curves for the BK -10A are
shown for various incidence angles of sound pickup.
57
NEW 2 -KW VHF
TELEVISION
TRANSMITTER
TYPE TT -2BH
A High -Band, Economical, Low -Power Transmitter for
Medium - Coverage Applications and Standby Use
1.
Front view of new TT -2BH, 2 KW, tele
vision transmitter. Note sloping meter panels,
FIG.
by H.
E.
SMALL, lPrnudi us7 und 'frlrrisdun Engineering
band VHF channels without the installation of frequency- determining
components, and this ease of tuning is
a feature that should win the acclaim
of station personnel.
for remote control, fewer tube types, and built -in
linearity correction for color TV, make the
new TT -2BH 2 -KW, high -band VHF television transmitter a compact, economical
low -power unit. The TT -2BH is an ideal
transmitter for the medium -coverage station or as a standby for the high -power
station. The design is based on proven performance of the TT- 2BL /6AL low -band
transmitter; however, the TT -2BH has
many exclusive features necessary for high -
4. Complete overload
band operation.
5. A
Space- saving cabinetry, provisions
Distinctive Features
The TT -2BH has many features of which
the following are outstanding:
1.
New style cabinetry offers excellent
accessibility to all components, and
it allows a great saving in floor space.
2.
The TT-2BH was designed to meet
stringent color TV specifications.
Built -in linearity correction can eliminate the need for a stabilizing amplifier at the transmitter site. Accurate
intercarrier frequency control is used
to get better color performance.
3. Only two tube types are used in the
r -f stages following the exciter. These
stages will tune to any of the high58
protection is provided for all circuits. The circuit at
fault can be readily detected by means
of a row of indicating lights which
are visible through the window in
the control rack door.
sloping illuminated meter panel at
the top of the transmitter makes it
easy to read the meters.
6. The temperature of all mercury vapor
rectifier tubes is thermostatically con-
trolled to permit operation at lower
ambient temperatures.
7.
Remote control provisions have been
included in the design. (Although remote control has not yet been authorized for domestic television service, it
is possible that it might be authorized
within a few years.)
Space Savings
The typical floor plan, shown in Fig. 2,
indicates the small floor area required for
the installation of a TT -2BH transmitter.
and convenient placement
of
operating controls.
The size of the room indicated is not an
absolute minimum, but is the recommended
minimum to allow ample freedom of movement for personnel and test equipment.
As can be seen in Fig. 2, no additional
floor area is required for the harmonic
filters, vestigial sideband filter or diplexer,
since these units can all be suspended from
the ceiling as indicated.
The rear of the transmitter enclosure
can be placed directly against the wall
since there are no components or access
doors at the rear. All transmitter components are contained inside the enclosure,
and they are accessible from an aisle directly behind the front line racks. All
power- supply components are inside the
enclosure and to the rear of the aisle; it
is not necessary to encase any of the transformers, since they are behind an interlocked door. This effects a reduction in
space requirements as well as improving
accessibility.
If space in the operating room is very
limited, the rectifier enclosure can be separated from the front line racks and placed
in another room, or in the basement. In
this event rear doors are then added to
the control and r -f racks, and a front wall
is added to the rectifier enclosure. A typical
floor plan using this alternate arrange-
156"
(13-Ó)
6
VESTIGIAL SIDEBAND
FILTER-MI- 19114-8
MIN
DIPLEXER MI-19390
TO
-
ANTENNA
1:-=
mÑ re.I
'X'
010
11
EXTERNAL A R DUCT
TO TRANSMITTER
v
HARMONIC
FILTERS
MI- 27317-7
OR 10
LOAD MI -19196 IS
PORTABLE AND SHOULD
BE PROVIDED WITH A
CONVENIENT STORAGE
R.F.
PLACE._
-..J
TT2BH
TRANSMITTER ES -19287
INPUT ec MONITORING
EQUIPMENT RACKS
ES- 19237 -
72"
E
EW
TTC5A CONSOLE
ES- 27274
to
1
24-
18.
36°
384
402
3'
I16
Typical floor plan arrangement for the TT -2BH. The entire transmitter is only 72 inches wide and can be located in a small
floor area. At points marked by "X:' provisions should be made for connection of a dummy load for testing and tuning the TT -2BH.
FIG. 2.
59
I3
ment is shown in Fig. 3. Variations in the
rectifier enclosure installation are shown
in Fig. 4. The blower can also be mounted
in the basement, by itself, if provisions
are made for filtering the intake air.
MIN.
EXHAUST FAN
500 CFM
AIR INTAKE
BLOWER
II
I
I
I
RECTIFIER
ENCLOSURE
I
Provisions for Remote Control
In addition to the thermostatically controlled heaters for the mercury vapor rectifier tubes to allow operation at temperatures as low as 0 degrees C, a thermostatically controlled blower cools the tubes at
I
I
I
I
UNDERFLOOR
AIR DUCT
An alternate floor plan arrangement for the TT -2BH. In this
case the vestigial sideband filter
and diplexer locations are optional.
FIG.
3.
CEILING
EXHAUST
FAN
MIN.
``.
r
UNIT
11
4.
high ambient temperatures. For remote control operation, a saving in heating of
the transmitter room could be realized
because of the lower permissible ambient
LJ
UNIT
NTR
ql
FIG.
S
I
2000 CFM
R.F.
TRANSMITTER
CONSOLE
Various possibilities in
temperature.
SUGGESTED UNDERFLOOR
DUCT LAYOUT
NPUT AND
MONITORING RACKS
To make the TT -2BH transmitter completely controllable from a remote location,
motor -driven controls are included for adjusting aural and visual excitation, as well
as video gain and pedestal level to the
visual modulated amplifier. Also, meter
shunts with external terminals for all FCC
required meters are included. Additional
meter functions have been incorporated to
(OPTIONAL)
(OPTIONAL)
which the rectifier enclosure of the
TT.2BH transmitter may be installed.
AIR VENT FOR ROOF
INSTALLATION
LOUVER
FRONT FACE
PARTITION
FRONT
FACE
PARTITION
TT2BH
TRANSMITTER
TT2BH TRANSMITTER
W
O
zW
î
00
O
U
Y
STANDARD INSTALLATION
TRANSMITTER
ROOM
r7
STANDARD INSTALLATION EXCEPT
SUPPLY DUCT IN FLOOR Bc EXHAUST
AIR THRU CEILING OR FLOOR
BLOWER UNIT LOCATED IN
RECTIFIER ENCLOSURE
FRONT FACE
PARTITION
RECTIFIER
TT2BH TRANSMITTER
ROOM
LOUVER
SEPARATE
ALTERNATE
METHOD.
AIR DUCT
RECTIFIER
ENCLOSURE
LOUVERS
AIR
SUPPLY
MAY BE
MOUNTED
ON THE
.---
f
INSTALLATION
ON
THE
FLOOR
I
-J.1
1
---.-já
A
WITH SEPARATE
SAME FLOOR
INSTALLATION WITH SEPARATE
RECTIFIER ON FLOOR BELOW
AIR
SUPPLY
RECTIFIER
60
www.americanradiohistory.com
make possible the monitoring of all r -f
stages following the exciter. It is also possible to switch visual crystal oscillators
remotely. Even if the transmitter is not
controlled from a remote location, these
features can be utilized to control the
transmitter from the console or other local
positions.
Proved Design
A block diagram of the TT -2BH transmitter is shown in Fig. 5. The common
aural and visual exciter is basically the
same as the TT- 2BL/6AL exciter; however, in the TT-2BH output frequencies
are one third the aural and visual carrier
frequencies. The 4.5 me separation between
the aural and visual carriers is very accurately maintained with an automatic
frequency control circuit." The visual
modulator is on the same size chassis as
the exciter, and it is mounted beside the
exciter behind Dutch doors in the r -f rack.
Both units are made to tilt outward for
accessibility to components on the rear of
"A New Aural and Visual TV Exciter,"
BROADCAST NEWS, Vol. 99, Feb., 1958.
FIG.
5.
A
block diagram of the
TT -2BH 2 -KW TV
Transmitter.
-500
ri_ L 1 1
Il
+
VIDEO
INPUT
VISUAL
,jMODULATORH
REFLECTOMETER
L___J
VISUAL
TRIPLER
6AL5
IST VISUAL
AMPLIFIER
7034
VISUAL MOD
AMPLIFIER
7034
TO VSBF OR
HARMONIC FILTER
6076
MONITORING,
AUDIO
INPUT
8a--
EAA URAL
VISUAL
+250
+700
NO.1
-50
0 TO
I
OTO+ 600
NO.2
-50
REG.
+250
+250
LXCITER
+600
4-1900
-50
4-1900
+3800
L DIODE)
+3800
AURAL
REFLECTOMETER
6AL5
AURAL
TRIPLER
AURAL
- AMPLIFIER
7034
+700
+250
0 TO
+250
+250 0 TO
NO.2 +600
REG
it'
VOLTAGE
SUPPLY
2- 866A's
TO DIPLEXER OR
HARMONIC FILTER
NO.1
+600
LOW
6076
LOW VOLTAGE
REGULATOR
-6AS7s 2 -5651s
I
-6SL7
ootn
otnn
r
0 0ill 0In
+.
M
MODULATOR &
BIAS SUPPLY
2 -866As
I
-
-5R4GY
61
www.americanradiohistory.com
the chassis. Figure 6 shows the chassis
in a lowered position for servicing. The
units can be easily removed, without using
tools, and placed on a bench for servicing if desirable.
Fewer Spare Tubes Required
The aural and visual r -f chains following
the exciter use only two tube types, thus
minimizing the number of spare tubes required. The first stage in each chain is a
tripler using a type 7034 tube. The visual
tripler drives a type 7034 class "C" amplifier which in turn drives the modulated
amplifier. Both output stages employ type
6076 tubes. The aural output stage is a
class "C" amplifier driven by the aural
tripler. The r -f circuitry is simple and
straightforward. All stages are single-ended
using a minimum number of components.
and are all easy to tune.
-:t'411PRIAIXtF,
)
9 4 S
..
i
9 S
Only Four Power Supplies
Common power supplies for aural and
visual stages have been employed to reduce the number of rectifier tubes and
components. The 3800 -volt, high -voltage
supply is a three -phase, full -wave rectifier.
A 1900 -volt supply is also obtained by
using three of the same rectifier tubes as
a 3- phase, half -wave rectifier. The entire
transmitter operates on only four d -c power
'upplies, and each is individually protected
against overloads. The complete exciter
power supply is contained on the exciter
chassis.
1
1
î .
:
This new design adds a high-channel,
low -power transmitter to the RCA line
of space- saving, VHF transmitters.- The
new style of cabinetry has not only made
possible a reduction in floor space require-
I
ments but, at the same time, has improved
accessibility. The ease of tuning and the
low cost of operation of the TT -2BH,
along with remote control provisions are
some of the outstanding features that make
it an economical. low -power transmitter
for medium -coverage stations.
"Latest Development in VHF Television
Transmitters," BROADCAST NEWS, Vol.
No. 91. October, 1956.
J
............
62
Note "Dutch door" design of TT -2BH
transmitter. The modulator and exciter tilt out
for ease of servicing.
FIG. 6.
i
Benedict Gimbel, Jr., President and General Manager of radio stations WIP and
WIP -FM, signed a contract on February
26, 1958, for an RCA Type BTA-5H
Transmitter. With the purchase of this
new 5000 -watt transmitter, \VIP plans to
inaugurate a new high -fidelity concept in
its programming.
Modern demands for high -quality sound
in broadcasting are being felt everywhere
and WIP is doing something to improve
its position. Since first going on the air
in Philadelphia in 1922. \VIP has been
keeping pace with the latest developments
in the broadcasting art. This newest addition will enable WIP to offer its listening
audience the best sound possible.
The 5000 -watt, BTA -5H. transmitter
will be installed at \VIP's present transmitter site in Bellmawr, New Jersey. The
transmitter now in use will be used for
auxiliary operation. \VIP was among the
first stations to operate continuously and
the present schedule is 24 hours a day,
seven days a week. With this type of operating schedule only a highly reliable
transmitter like the BTA-5H would offer
the performance required and at the same
time offer the finest in sound.
In today's highly competitive market
WIP realizes the need for high fidelity in
AM radio broadcasting. In its search for
the best sounding and most reliable AM
transmitter, the station has selected the
BTA-5H. This will spell another success
story for \VIP.
FIG. 1. Benedict Gimbel, Jr., President and General Manager of radio stations WIP and
WIP -FM, signs contract for new RCA Type BTA -5H, 5000 -Watt Transmitter. RCA Broadcast
Field Sales Representative A. W. Power (left), and WIP Technical Supervisor Clifford C.
Harris look on.
WIP GETS NEW 5-KW TRANSMITTER
TYPE BTA -5H
Philadelphia's Pioneer Voice
Gets New and Improved Sound
This is the type of transmitter purchased
by WIP, which will be installed at Bellmawr,
New Jersey. The BTA -5H transmitter offers WIP
the finest sound possible with minimum distortion
and low -operating cost. RCA's bi -level modulation
provides true high fidelity frequency response.
FIG. 2.
63
www.americanradiohistory.com
UNIVERSAL
COAXIAL
TRANSMISSION
LINE
After a study of experience gathered
from hundreds of transmission line installations over the past several years, the Universal Transmission Line was developed
to incorporate all possible improvements
over the present lines. This new coaxial
line is electrically capable of covering the
UHF as well as the VHF channels (hence
the term "Universal ") at no increase in
cost over comparable "VHF only" lines.
The new line of universal coaxial transmission line is available in three sizes:
3já -inch, 50 -ohm line (MI- 27791); 6%inch, 75 -ohm line (MI- 27792); and
93 /10-inch, 75 -ohm line (MI- 27793). In
addition, there is a complement of elbows,
fittings and adapters.
Exhibits Very Broadband Characteristics
Mechanical Improvements
Improvements were made primarily with
Covers Both VHF and UHF Channels
Easier to Assemble
Is
and Assures a Lower VSWR
Rroath.a
i
by W. N. MOULE
and Trlrri.ciun Engineering
respect to making the installation "foolproof" since errors in assembly were possible with previous types, especially if
inexperienced personnel were making the
installation. For example: the assembly of
the bolted flange was time consuming, requiring 6 to 12 bolts, nuts and lockwashers
to assemble. Pinching of the "O" ring
could occur (unless extreme care was exercised) and this would result in poor flange
contact, with high VSWR (voltage standing wave ratio). Occasionally complete
disregard of centering pins cause similar
results. The resulting faults were very difficult and expensive to locate on a long
run of line because the contribution of one
CLAMP
GASKET
(O -RING)
LJ
.4111.
FLANGE
(FEMALE)
CONDUCTOR
Ft1...
(OUTER)
CONNECTOR
(INNER)
CONDUCTOR
(INNER)
FLANGE
(MALE)
FIG. 1. A view of the 3' 8.inch Universal Transmission
Line showing inner conductor, support insulator, Marmon
clamp, and the inner conductor anchor insulator.
INSULATOR
(ANCHOR)
This is a cutaway drawing showing the flanged
connector assembly of the Universal Transmission Line.
FIG. 2.
64
www.americanradiohistory.com
such fault is small but the combination of
several can result in a high VSWR causing
ghosts, etc.
The problem of slow, tedious assembly
was solved by using the new quick connect flange (see Figs. 1, 2, 3). Quick and
positive assembly is obtained by using a
\Iarman -type clamp, requiring only one
or two bolts to tighten (depending on the
line size). This flange assembly consists
of a male and a female outer connector,
which helps speed assembly by inherently
providing a guide as the mating parts are
pulled together. Thus, expensive rigging
time is saved and proper assembly is
assured.
Alignment of the two halves of the flange
was greatly improved by making a sexed
flange with mating concentric surfaces
(see Fig. 2). Thus, it is impossible to assemble the flange misaligned.
Pinched "O" rings are avoided by holding the "O" ring captive in a deep grove
on the male flange (see Figs. 2 and 3).
minimizing the possibility of damage during assembly. Since the "0" ring is held
between the cylindrical surfaces it is removed from the electrical contact surfaces
so that even a damaged "O" ring cannot
prevent good electrical contact in the flange.
Electrical Improvements
The important electrical improvement
on the universal line is the increased band-
FIG. 3.
section
width of the compensation of the support
insulators, thus resulting in lower VSWR
over the whole VHF and UHF band. The
method of improving the compensation of
electrically transparent insulators was to
put holes in the insulators to reduce the
effective dielectric constant of the insulation. The reason for the increased bandwidth is as follows: The Teflon insulators
supporting the inner conductor are of the
electrically transparent type as shown in
Fig. 4. In order to make the characteristic
impedance of the section of line containing the support insulator equal to the
characteristic impedance of the line, hence
transparent, we must consider the following equation for the characteristic impedance of a lossless coaxial line:
Z_
where
E-
log. DI
D2
Z = characteristic
impedance
(1)
of
the line
E
=
dielectric constant of the medium (equals one for air)
DI
= inside
D -.
= outside
diameter of the outer
conductor
diameter of the inner
conductor
It can be seen from the foregoing equation that the support insulator will lower
the Z in the insulator section of line. To
raise the characteristic impedance of this
An exploded view of the flange connector on a
Universal Transmission Line.
of 91í6-inch
138
section of line we can use the well known
relation for lossless lines that:
,L
Z=
(2)
where L = the series inductance per unit
length
C
= the
shunt capacitance per unit
length
Since we have increased C by the multiplying factor E we must, therefore, increase
L so that the L -to -C ratio is still the same
as for the air part of the line. The series
L is increased by undercutting the inner
conductor (see Fig. 4) until the correct
L -to -C ratio is obtained. In the practical
case the undercut portion of the inner
conductor will have a characteristic impedance slightly greater than the air dielectric portion of the coaxial line to compensate for the additional step capacity
caused by the sides of the undercut.', 2
Thus an undercut insulator can be developed to have a characteristic impedance
very nearly equal to the air dielectric portion of the coaxial line over a large frequency range.",
"Equivalent Circuits fur Discontinuities in
Transmission Lines," Proc. I.R.E., Vol. 32.
pp. 98-115. February, 1944.
2 "Coaxial Line Discontinuities," Proc. I.R.E.,
Vol. 32. pp. 695 -709, November, 1944.
"A Coaxial Line Support for 0 to 4,000 Mc.,"
Proc. I.R.E., Vol. 37, pp. 94 -98, Jan., 1949.
' "Notes on a Coaxial Line Read," Proc. I.R.E.,
Vol. 37, pp. 1249, November, 1949.
Here is a cross section of an undercut insulator
showing the spacing of inner and outer conductors.
FIG. 4.
65
Attenuation curves for the three sizes of
universal transmission lines are shown along with
frequency limits, from 50 megacycles to the upper
frequency limit of the lines.
FIG. 5.
90
80
.70
ATTENUATION OF
RCA UNIVERSAL
VHF/UHF COAXIAL LINE
60
50
40
30
/25
20
38 -50
OHM
88-75
OHM
15
10
09
08
11
05
05
04
6-75
03
.0
OHM
25
02
115
01
10
15
20
30
40 50 60
80 100
150
200
300 400
600 800 1000
FREQUENCY MEGACYCLES
1000
900
800
700
600
II
POWER RATING
RCA UNIVERSAL
VHF/UHF COAXIAL LINE
500
400
300
250
9r-75
OHM
200
150
68-75
OHM
100
90
80
70
60
50
40
38-50
OHM
30
25
20
15
The power ratings for universal transmission lines follow a descending curve as frequency is increased. The larger the size of the
line the lower the attenuation per 100 feet.
FIG. 6.
10
10
15
20
30
40 50 60 80
100
150
200
FREQUENCY MEGACYCLES
66
www.americanradiohistory.com
300 400
600 800 1000
Now the equivalent circuit of the transparent section is approximately that of
a low pass "T" network operated considerably below cutoff. We can see by the
following formula that f,. (cutoff frequency
of the network) is increased if L and C
are kept as small as possible:
fe
= \/L
l
(3)
C
In the new universal lines, Teflon was
used for the support insulator because of
its low dielectric constant, approximately
2.08. The capacitance of the insulator was
further reduced by putting large holes in
the disc insulator so that the effective dielectric constant was considerably lowered
(see Figs. 1 and 3). As can be seen from
equation (2) reducing C also reduces the
L required for compensation. Therefore,
from equation (3) we see that the cutoff
frequency is raised further above the operating band creating an almost perfect impedance match from channel 2 to 83.
Designed for
5 Megawatt UHF Installations
The universal lines come in three sizes,
a standard 3%-inch S0 -ohm, 6%-inch 75ohm, and a new 9' /I6-inch 75 -ohm size.
The reason for choosing the 75 -ohm impedance for the 6% -inch size is to cover
all the UHF television channels without
encountering the TEII coaxial waveguide
mode as would be the case with a 50 -ohm
impedance level. Also the 75 -ohm impedance is nearly the optimum for minimum
attenuation. The reason for developing the
new 9' /16-inch coaxial size was to provide a means of achieving a maximum
effective radiated power (ERP) of 5 megawatts at UHF using a high gain UHF
antenna (see attenuation and power rating
curves Figs. 5 and 6). At the present state
of the art, greater precision is obtainable
from drawn copper tubing than from fabricated rectangular tubes as used in a wave guide system, hence a substantially lower
VSWR is obtainable by using a coaxial
system. The 9`I /-inch line can be used
through UHF channel 40.
Low VSWR Achieved
Figure 7 shows a VSWR versus frequency plot of an 800 -ft. test run of 3!sinch, 20 -ft. sections of universal line. Note
that the VSWR tends to peak up on this
long run at those frequencies where the
20 -ft. sections are an integral number of
half wavelengths long. This occurs approximately every 24.5 megacycles. Because of
manufacturing tolerances the compensation
cannot be perfect and there will remain
a small reflection at every insulator and
flange which repeat in every line section.
VSWR VERSUS TV CHANNELS
OF 20FT. gSECTIONS
38 -501L LINE
RCA MI -2779 -I
800 FT. RUN
1.4
1.3
1.2
I
1.0
VA M nhnMrvltfr,,f,
2 3
4 5 6
7
8 910
II
12 13
tk«hg Aikit.ltjiA>st.40 Am. i44444"4L,
4
20
25
30
35
40
45
50
55
60
LA, ,r44 +,A..otrO
65
70
75
80 84
TV CHANNEL NO.
The VSWR peaks on long runs of line at frequencies where 20 -foot sections are an integral
half a wavelength. Spikes can be avoided by using 19' a -foot sections.
FIG. 7.
of
67
www.americanradiohistory.com
CHANNEL SELECTION
TABLE OF LENGTHS
2, 3
4, 5
6, 7
8, 9
11, 12
CHANNELS
REQUIRING
13,
15,
19,
23,
27,
31,
35,
39,
43,
47,
51,
56,
60,
64,
68,
72,
76,
80,
20 -FOOT
SECTIONS
14
18
22
24
28
32
36
40
44
48
52
57
61
65
69
73
77
81
9.
A 90- degree miter elbow for 6,/e-inch Universal Transmission Line is shown with its inner conductor and Teflon insulator.
FIG.
10, 16
17, 20
21,
26,
30,
34,
38,
42,
46,
50,
54,
58,
62,
66,
70,
74,
78,
82,
CHANNELS
REQUIRING
191/2 -FOOT
SECTIONS
In order to avoid this recurring VSIVR
spike, 19 % -f t. sections are provided, as
in previous RCA coaxial lines, for those
channels which fall on the spikes caused
by the 20 -ft. sections. Figure 8 shows
those channels requiring 20 -ft. sections
and those requiring 19V2-ft. sections.
25
29
33
37
41
45
49
53
55
59
63
67
Measured Attenuation and Power Rating
The attenuation and power rating of the
three sizes of lines are shown in Figs. S
71
75
79
and 6. These are actual measured power
ratings of the three and six -inch sizes to
maximum safe operating temperature rise
of the inner conductor. They represent the
83
steady state power required to heat the
inner conductor to a 70 degrees C rise
above a 50 degree C ambient temperature.
The power curve for the 93/16 -inch line
is calculated from data based on extensive
calculations and power measurements on
the
-inch sizes. The at-inch and
tenuation curves for the three line sizes
are actual measured values on an 800 -ft.
test run for each line size.
6/
3/
A complete line of elbows (see Fig. 9)
and fittings is provided for each line.
Adapters are also available to connect the
universal line to all conventional VHF and
UHF flanged lines.
FIG. 8. Table shows channels that require 19, zfoot and 20 -foot sections to avoid a high VSWR.
FIG. 10.
The electrical and mechanical specifications for the RCA Universal Transmission Lines.
SPECIFICATIONS
MECHANICAL SPECIFICATIONS
ELECTRICAL SPECIFICATIONS
/e"
Standard
61
Line
93Çÿ' Lino
MI-27791
MI-27792
MI-27793
table above)
50 ohms
75 ohms
75 ohms
Outer Conductor.
0-1000 me
0 -890
0 -632 me
Characteristic Impedance
Frequency Range
me
20 unti 19
20' and 19,
20' and 19
O.D.
3
125
6.125
9
166
I.D.
3.027"
5.281
9
000
VSWR*
1.1/1 or less
1.1:1 or less
1.111 or
Attenuation
See Fig. 5
See Fig. 5
See Fig. 5
Power Rating
See Fig. 6
See Fig. 6
See Fig. 6
O.D.
1.315"
1.711"
2
580
Velocity of Propagation
99.8%
99.8%
99.8%
I.D.
1.231"
1.661"
2
516
56 b
130 lbs.
220
*
63
Length (see
31/e" Line
VSWR of transmission line run terminated
in its characteristic impedance.
less
Inner Conductor:
Weight (per section
a pp rox.)
I
s.
Ibs_
GROUND WEATHER RADAR
FOR BROADCAST STATIONS
Provides Accurate Local Weather Information for Radio and TV
Stations; Serves as Valuable Adjunct to Other Weather- Forecasting Services
Lr
R.
C. STRANG, Cuxlnm
:frialinu Engineering
The
accurate and timely transmission of
complete local weather data has become
an increasingly important responsibility of
all radio and television stations and with
this responsibility has come the need for
improved local weather surveillance equipment. The RCA Ground Weather Radar
is such an equipment. providing its operator the means for viewing and tracking
storm fronts, thunderheads, squalls, and
heavy cloud formations as well as other
forms of precipitation and weather disturbances located up to 150 miles away. By
proper interpretation of this radar it is
possible to accurately forecast the time of
arrival and relative magnitude of a weather
disturbance in a specific area.
Equipment Description
The RCA Ground Weather Radar system consists of the antenna, the receivertransmitter, the indicator, the accessory
unit and a control group. The antenna and
receiver-transmitter are housed in a spe-
cially constructed radome which measures
5 feet in diameter and 6 feet in height.
This radome contains provisions for a
heater -blower unit to facilitate cooling and
prevent condensation. The indicator, accessory unit and all controls necessary for
operating the system are contained in a
control console which is completely wired
and ready for installation. A repeater indicator unit can be supplied when viewing
is also desired at a remote or secondary
location. The repeater indicator is identical
to the indicator installed in the control
console, and no internal circuit modifications are required in the radar system for
its incorporation.
Operation
This radar is very simple and straightforward in operation. External controls are
located on each indicator as well as in the
controls section of the console. Controls
located on the indicator are for the purpose
of varying the brilliance of the indicator
69
www.americanradiohistory.com
Normal Presentation
50 Mile Range
Time 12:00 Noon
Storm Located at 47 Miles
1.
The radome is about five feet in
diameter and six feet in height and may be
mounted on a building or tower. Here is
located antenna and receiver- transmitter. Radome also contains provisions for a blower
heater unit to prevent moisture condensation
and facilitate cooling.
FIG.
-
2.
The control console contains the indicator,
accessory unit and all controls necessary for operat.
ing the system. Console may be remotely located
in an office, studio or control room.
FIG.
70
www.americanradiohistory.com
Indicator unit mounted in control console
3.
gives operator continual weather surveillance. A
repeater indicator unit can be supplied when viewing is desired at a remcte or secondary location.
FIG.
Normal Presentation
50 Mile Range
Normal Presentation
50 Mile Range
Normal Presentation
20 Mile Range
Time 12:40 PM
Storm at 37 Miles
Rate of Travel 15 MPH
Time 1:20 PM
Storm at 25 Miles
Rate of Travel 18 MPH
Direction SW
Thunderstorms
Time 1:50 PM
Storm at 17 Miles
Travel 15 MPH SW
Storm due to arrive
at approx. 2:40 PM
Contour Presentation
20 Mile Range
Time 2:20 PM
Storm at 10 Miles
Corridor indicates area
will be covered with
light to medium rain.
Storm centers will bypass
to NW and SE at a
distance of 5 to 10 miles
FIG. 4. Weather changes or developments can actually be "seen" on
viewing screen providing forecaster with accurate and reliable information.
sweep and, therefore, all targets seen on
the indicator screen, adjusting the intensity
of the range marks, adjusting the indicator
edge lighting, and a control with which
it is possible to determine accurately the
azimuth of any given target. Controls are
provided on the console to energize the
system, select the range, vary the receiver
gain, elevate or depress the direction of the
transmitted beam, and energize the Iso
Contour circuitry.
How It Works
The basic principles of the system are
those of an ultra -high frequency radar
system consisting primarily of an antenna.
pulse modulated transmitter, pulse reception receiver and an indicator. The transmitter feeds the antenna with pulses of
energy modulated at a frequency of 5400
me /s. These pulses are radiated on a line
of sight transmission, reflected by a suitable target (e.g. precipitation) back to
the same antenna, amplified by the receiver
and displayed on the indicator. The travel
time of these pulses is a measure of the
distance from the radar system to the
target. This distance is indicated by the
separation of the target presentation from
a fixed point in the center of the indicator
lace. The area and azimuth location of the
largets is obtained by radiating the transmitted beam in the horizontal plane as
the indicator sweep is rotated about its
origin in synchronism with the antenna.
The azimuth of each target is thereby
located by its angular deflection from the
top of the indicator. The indicator display
is, in effect then, a reduced scale plan
view of the area scanned by the transmitter beam. Three range scales are provided, 0 -20, 0 -50, and 0 -150 nautical miles.
Electronic range marks can be superimposed on the display to occur at 5, 10
or 25 nautical mile intervals, according to
the range in use.
Interpretation
The interpretation of relative storm intensities is facilitated by the use of Iso
Contour circuitry. The results, as far as
the target display is concerned, is the appearance of a dark center in an otherwise
all light target. 'I'he size of this dark center
relative to the size of the target accurately
determines the degree of moisture present.
This radar system operates in the "C"
frequency band at 5400 megacycles (5.5
centimeters wavelength) with a peak power
output of 75 kw provided by a magnetron.
The pulse width is 2.0 microseconds with
a pulse repetition rate of 400 cps synchronized to the line frequency. The total radar
system with one indicator requires approximately 850 VA of 115 volt, 380 to 420
cycle power and 30 watts of 27.5 volt DC.
The antenna, equipped with a 34 -inch reflector, has a 360 degree continuous scan
rate at 15 rpm. It is possible to vary the
direction of the approximately 4.5 degree
beam width from 0 degrees to 85 degrees
with respect to the horizontal. The indicator display tube is S inches in diameter
and gives a 360 degree, PPI type of presentation. The electronic range mark spacing is 5, 10 and 25 miles dependent upon
the range that is employed.
Developed for Broadcasters
'1'he advantages of radar for use in detecting and plotting weather disturbances
was initially discovered as a detrimental
by- product of early military bombing and
navigation radars. Since World War II.
large sums of money have been devoted to
exploiting this characteristic and corn mercial airborne weather radar such as
the RCA AVQ -10 and AVQ -50 Weather
Radars has been the result. In recent years
commercial airborne weather radar has
made a very significant contribution to the
safety and reliability in the operation of
all major airlines and oth -r members of the
air transport industry. Partially as a result
of the enthusiastic acceptance and proof
of radar as a weather surveillance instrument in the air transport industry, it is
now possible to provide a weather radar
system specifically configured to meet the
needs of the ground based operator at a
cost consistent with commercial radio and
television station requirements.
VtrrE: For more information write to: RCA
Broadcast and Television Equipment, Camden.
N. J.
71
GETTING THE MOST FROM
Good Films are
Only HALF the story
If you have complete system equipment to provide
showmanship in your film programming, you'll be ready
for bigger film profits. That's why it's a good idea to
take a long look at your station's film room facilities
before you invest a lot of money in films.
g. s
SINCE
HOW
STATION'S
FILM ROOM
WA
WAS MODERNIZED
?
YOUR FILM DOLLAR
.
.
.
//
i//`aso1
-
....
.....
+`ae
...
.A
1411/11
.
l'_....
(tj,ujOh..
How an RCA Film System
Will Enable You to Spark
and Hold Viewer Interest
Here's how one of the most successful users of film shows gets excellent
results. He employs several carefully planned steps made possible by
the use of an extremely versatile film system. First, the program
starts with a 20 -sec. film commercial followed by a 10 -sec. VSI- fading
to a 30 -sec. film teaser strip. The feature is then announced with a
super -imposed "presentation" slide with record music. Feature is
begun and film commercials are inserted at appropriate times
to the end of the showing. This kind of expert programming
that sustains audience interest is only possible with the proper
combination of film equipment.
You have creative people who can do a similar job for you if given
the right tools. An RCA Film System will provide them with these tools.
It will enable you to offer a variety of film presentation formats for
sparking and sustaining program interest. It will also help
you prepare for future expansion.
of long -range planning will obsolete equipment
before its time
leave you unprepared for color.
Investigate the quality and cost -saving of an RCA Film
System-we'll be glad to help you check at typical
stations. And ask the RCA Broadcast Representative to
show you our latest film literature.
Lack
...
RADIO CORPORATION of AMERICA
BROADCAST AND TELEVISION EQUIPMENT
CAMDEN, N. J.
Tmk(s)
In Canada RCA VICTOR Company Ltd., Montreal
O
.
A new stanc and of performance
for color television systems...
The RCA TM -21 Color Monitor
This new color control monitor is a reference standard for evaluating the quality of color
television pictures from any source. Providing the most precise and brilliant color picture available ... this new monitor accurately reproduces the scene as the camera sees it.
OLIAL!TY CONTROL OF COLOR PROGRAMMING -The TM -21 is used in Color
Camera Chains, Switching Systems, .Master Control and Transmitting Control for
monitoring color picture quality. It is the basic instrument for checking registration,
...
shading and deflection linearity
color fidelity of the entire TV system
to monochrome ratio
color phase or hue adjustments.
...
.
..
chroma
BEST POSSIBLE COLOR -When used to display color pictures in clients' rooms and
executive offices, the TM -21 lets the station put its "best color foot forward." Clients
will be impressed by the bright, high definition picture.
COLOR ACCURACY AIDS PROGRAM PRODUCTION -Production
departments can
use the new monitor for accurate continuity control of color programming. Producers
and directors will get a true color picture of what's happening on the set. Costume and
background colors can be seen in proper relationship. Lighting can be accurately
evaluated, production aided.
-
Initial adjustment is extremely simple. Built-in
test switch reduces set-up time to minutes. Screen grid selector switch provides quick
viewing of primary colors.
SIMPLIFIED MONITOR ALIGNMENT
LONG -TIME STABILITY -Once set up, monitor adjustments "hold." Extra stability
has been designed into brightness, contrast, decoder, convergence, and linearity circuits.
Get maximum return from your color TV investment! Ask
your RCA Broadcast and Television representative for further
information on the new TM -21 Color Monitor. In Canada:
Write RCA VICTOR Company Limited, Montreal.
Check these additional technical features:
Feedback techniques and precision components
All components and tubes easily accessible.
provide long -term stability.
Automatic brightness tracking for color balance.
Convergence circuits designed for rapid setup.
restoration at
feed back.
DC
black level, stabilized
Stabilized diode demodulators.
by
Automatic wide -band operation during monochrome picture intervals.
Stabilized black level shows effects of pedestal
adjustments, aids close control of color in
picture low- lights.
RADIO CORPORATION of AMERICA
BROADCAST AND TELEVISION
Tmk)s) ®
CAMDEN, N. J.
EQUIPMENT
A NEW PUBLIC SERVICE
FOR TV AND RADIO STATIONS
The transmission of accurate local weather information from TV and Radio stations can prove to
be invaluable as an adjunct to other general
weather forecasting services. Many agricultural,
commercial, and industrial projects, as well as
public activities, are seriously affected by weather.
In the capacity of rendering a public service, considerable interests can be generated by enterpris-
ing broadcasting stations with accurate and timely
reporting of local weather conditions. The promotional advantages possible with RCA's Ground
Weather Radar are unlimited.
See your RCA Broadcast Representative
for complete information about the RC.4
Ground Weather Radar.
RADIO CORPORATION of AMERICA
Broadcast
&
Television Equipment
www.americanradiohistory.com
Camden, N. J.
Planning a Radio Station?
Plan
"B"
is a design
a
for
medium -size station!
This plan fulfills all of the requirements for a
low -cost, community -type radio station. It provides space and facilities for handling a very
diversified program schedule. It incorporates
technical features that make for adequate, yet
economical operation. It is just one of three
basic plans that can be modified to meet your
needs exactly.
Plan "B" differs from the minimum investment
design (Plan "A ") by including a more spacious
studio, an announce booth and a record library.
It provides for expanded programming to include
the origination of a fairly substantial live studio
With the announce booth serving as
another origination point, it becomes very convenient to record announcements and other
program material while on the air.
The plan offers many other features which are
show.
discussed at length in a new brochure, along with
general planning considerations for the entire
radio system. Building layouts, together with a
discussion of equipment requirements and current trends, are also offered in the new brochure.
For your free copy, write to RCA, Department
C -22, Building 15 -1, Camden, N. J. In Canada:
RCA VICTOR Company Limited, Montreal.
... your first source of help in station
vsfr
planning
RADIO CORPORATION of AMERICA
BROADCAST AND
TELEVISION EQUIPMENT
CAMDEN, N.
J.
www.americanradiohistory.com
Waveform -Oscilloscope Pattern Showing Signal
Output and Uniform Sensitivity of the RCA -7038.
RCA -7038 Vidicon Without Side
Tip (tube shown actual size).
FOR NEW TV- CAMERA DESIGNS
New, improved
...with much
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ILLUMINATION REQUIRED ON TUBE FACE-FOOT CANDLES
RCA -7038 Provides Higher Effective
Sensitivity in New Camera Design.
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Already being considered for new compact camera designs, RCA -7038 opens new
possibilities in live and film pick -up camera techniques matched by no other Vidicon.
Here is a new Vidicon that can deliver broadcast -quality pictures -with as little as
1 foot -candle of illumination on its faceplate. An improved photolayer is capable of
providing uniform sensitivity-over the entire scanned area. All "front-end" parts
are non -magnetic to facilitate registration in three-vidicon color TV cameras.
RCA -7038 utilizes a 750 -mesh screen. It has a resolution capability of 600 lines, and a
spectral response covering the entire visible spectrum.
For a bulletin containing technical data and application information on the RCA -7038,
write RCA Commercial Engineering, Section C -12 -0, Harrison, N. J.
OA
RADIO CORPORATION OF AMERICA
rp
3.13310
Electron Tube Division
Harrison, N. J.
r.,..._.
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