Tandy Radio Shack Realistic PATROLMAN PRO-3A User manual

Please read before using this equipment
OWNERS MANUAL
PATROLMAN PRO-3A
VHF/UHF 3 BAND MONITOR RECEIVER
PROFESSIONAL
SERIES Catalog No.
20-452

PRO-3A Monitor Receiver
PRO-3A Monitor Receiver
General Description General Specifications
Your PRO-3A Patrolman Receiver tunes th ree bands allocated by the FCC to
service and business communications. They are:
The
PRO-3A is an extremely sensitive receiver. With a full complement of circuits
and cornponents, it is nearly as sentitive as any receiver for its tuning ranges can
be.
lts natural noise level is comparable to a one-third microvolt signal-and that
limiting noise can be heard merely by turning up the audio volume control.
These bands carry a remarkable variety of business and emergency radio
services. Best known are Fire and Police, but others include Forestry/Conservation,
Hospitais, Physicians, Emergency Communications. A list of sixteen general classes
appearing in
the FCC regulations is given on page '2, and every class includes
several users. No individual allocations are given there because generally 'all bands
are used by all services.
This great sentitivity is necessary for remote areas and in emergency operating
conditions. But circuits designed for high sensitivity are often subject to
intermodulation problems if used in very strong-signal areas. Also, adjacent-channel
transmitters are more likely to be operating in urban and metropol itan areas than
in remote regions. The PRO-3A features a really effective 10.7 MHz filter, placed in
its IF
input circuit. This reduces or eliminates adjacent-channel or strong-signal
interference.
Note: These are given in general form only, since REALISTIC does not believe
in
buying ro or designing to numerical specifications. The latter are subject to
variables not c1early related to performance, just as selectivity, the number of
transistors or IC's indicate in an average way the quality of a circuit but do not
prove one circuit will outperform another in real operating conditions. Our
philosophy is that a piece of equipment should be evaluated in terms of what it
does for the purchaser, its quality and relative value being based upon merit and
observed
performance in real life. Thus REALISTIC designs toward achieving a
certain result, ... regardless of cost, regardless of lab measurements, regardless of
competitive advertising claims. Results are determined by your application of our
finished result. Good installation is extremely important since a poorly installed or
a
wrongly placed antenna can result in a 90% or even greater signalloss. And an
inadequate speaker system can be
almost as effective in reducing equipment
performance. The following figures are offered only as a guide, not as a guarantee
of equipment performance:
This equipment is designed to operate from either 117 VAC or 12 VDC
negative ground. If it fails to operate, and there is no c1ear reason for the failure,
first check the supply switch. This switch entirely disconnects the supply
components that are not in use. Also, before connecting the PRO-3A receiver to a
DC
power supply, check the voltage polarities. Attempting to operate the
negative-ground PRO-3A from one of the rare positive-ground automotive or boat
electrical systems, or from a wrongly connected battery, will at least blow a fuse.
It may do further damage, so that expensive and time-consuming repairs are
necessary
before the PRO-3A can be used again. The Radio Shack warranty does
not apply to any damage caused by this, inadequate lightning protection, or other
improper connections.
30 - 50 MHz
152 - 174 MHz
450 - 470 MHz
VHF LO
VHF Hl
UHF
Designed for the user, the PRO-3A offers more utility than any other receiver
in its class.
It is large enough for base station operatien. and has all necessary
features
of SQUELCH, narrow-band filter, and several-band operation. It also is
light enough to be carried into hard-to-reach areas or mounted in cars, trucks,
boats or airplanes. And it uses a remarkably small amount of power. For example,
a single car battery should power the PRO-3A for better than 200 hours of
continuous operation before needing arecharge.
Another filter is included to improve the readability of very weak signais. A
low-pass
audio filter, also controlled from the front panel, can be switched in to
reduce the effects of inherent circuit noise when listening to avoice signal that is
"buried in the noise." By reducing the audio bandwidth of the receiver, the filter
emphasizes the desired audio signal.
The
PRO-3A is remarkably easy to use. But it is an up-tc-date, complex circuit
consisting of 25 separate transistors pi us 20 more in its integrated-circuit IF
section, 10 diodes and one zener. All are mounted on a steel chassis, which in turn
is instalied in a steel cabinet provided with a mounting bracket designed for mobile
installation. The PRO-3A is an important engineering achievement, but designed
for practical appl ications.
GUARANTEE: The REALISTIC guarantee is stated on the Fact Tag packed
with the equipment. It is in effect from coast to coast. At any time, REALISTIC
equipment may be restored to new condition with original parts with MINIMUM
delay anywhere in the U.S.A., usually in your own neighborhood. It is NOT
necessary to return REALISTIC equipment to our laboratories in 98% of the cases.
General Specifications List
• Tuning Ranges: VHF LO, 30-50 MHz. VHF Hl, 152-174 MHz. UHF, 450-470
MHz.
• Antenna Connections: 50-ohm coax. One for VHF LO and Hl bands. Another
for UHF band.
• Sensitivity: 1 microvolt for 20 dB quieting.
• Selectivity: 5 KHz position-6 dB @±5 KHz. 15 KHz position-3 dB @ ±35
KHz.
• IF frequency: 10.7 MHz.
• Audio Output: 2 watts into 8ohms. The PRO-3A will operate into a 4 thru 16
ohms load.
• Solid-state Components: 25 transistors, 2 IC, 10 diodes and 1 zener.
•
Power Input: 117 VAC 60 Hz or 12-15 VDC, negative ground only.
-1-

How To Operate The PRO-3A Monitor Receiver
The PRO-3A Monitor Receiver is a remarkably easy receiver to use. Basicallv, it
is an FM receiver, and
works Jike one. lts additional SQUELCH and filter controls,
bandswitching capability, and antenna and power requirements are easily met.
Highly stable, the PRO-3A, once mastered, is areliabie and useful communications
tooI.
A good installation will make the most of the PRO-3A's capabilities. Loss of
the tiny signaI at the antenna is avoided bv correct antenna adjustments and by
installing a good quality foam coax cabie. Where noise problems must be
overcome,
the PRO-3A's audio output can be fed to low-impedance audio
headphones or to an external loudspeaker.
The PRO- 3A is powered by either 12-15 volts DC or by 117 VAC 60 Hz,
whichever is most convenient. In case of difticulty or uncertainty, the installation
prablems are best handed over to an experienced technician or engineer. The
following assumes a good PRO-3A installation, and is appropriate for first-time
operation or for determining if a possible malfunction might actually be a result of
improper control settings.
The
first step is a quick check of the installation. Antenna jacks are checked
for connections to the correct antennas. The AC or DC power souree should be
operating, and providing the correct voltage. If DC is to he used, it must be of the
correct polarity. (See page 5)
On
the front panel the controls should be preset as follows before turning on the
receiver. Tuning controls are at any setting. The VOLUME contra I, SQUELCH,
SELECTIVITY controts are full counterclockwise. The AF FIL TER switch is pushed
down on the OUT side.
It is suggested if one can anticipate the frequency band to be used at turn on
time, that the band switch be pre-selected to th is LO, Hl or UHF position as even
when the power switch is turned OFF, the tuning section for this band is
electrically energized and will thus provide lowest frequency drift possible when
the receiver is turned ON.
Turning the VOLUME contral clockwise should result in a mechanical click as
the knob goes past the power switch detent, and the power goe.s on. Gradually
advancing the knob clockwise will result in a soft and then increasingly loud
rumbling hiss from the PRO-3A's monitor speaker or from the external headphone
or speaker. Af ter getting the feelof this control. it should be turned back to a
setting that gives a perceptible but quiet hiss fram the speaker.
The next step is to tune the band for a signal. Several passes may be necessary,
since
stations in the communications bands transmit only when they have a
message and
do not radiate even a carrier between transmissions. At this point
other stations should be sought out, and their positions logged using the 0-100
logging scale. These stations can be identified later.
The
familiarization with tuning can be repeated on all bands. Slight variations
in noise level will be noted as the PRO-3A is tuned over its ranges.
Next, the PRO-3A should be tuned to any station and the SQUELCH control
slowly advanced by turning it c1ockwise. Two key settings will be found. The first
is the setting at which receiver noise is no longer heard but the station is heard at
normal volume when it comes on the air. And the second setting will be one at
which the station is not heard at any time.
-2-
These settings change with receiving conditions and with the band in use. For a
strang station they are far apart, comi ng close together for weak signais. And a
too-high accidental setting of the SQUE LCH control will cause the PRO-3A to act
as
if it is not working. In case of trouble the first step is to return the SQUELCH
knob to its full counterclockwise position. After practicing with this control it
should be returned te its fully off position.
To practice with the SELECTIVITY control. tune in a station with this control
in its 15 KHz positron. Then advance this control to its SHARP or 5 KHz position.
If the signal disappears the receiver tuning should be corrected. The PRO-3A's
tuning is now very sharp, an indication of how close an unwanted signal can be
without causing interference. This filter should also be tried if the PRO-3A is
troubled by noises of uncertain origin. If these originate in strong-signaI
intermodulation, this setting should remove them. The 5 KHz position of this
switch mayalso be tried when listening te an extremely weak signal.
This completes the "guided tour" of the PRO-3A receiver. In practice, all
contrals are used whenever their functions seem to be required.
Table of Fee Listed Services
Using VHF and UHF Bands
• H ighway Maintenance Radio
•
Forestry /Conservation
•Special Emergency
hospitals
ambulance and rescue
physicians and veterinarians
disaster
relief
communications standbv
school buses
beach
patrots
• Power Radio
• Petroleum Radio
• Forest Products
• Motion Picture
• Relay Press
• Special
Industrial Business Radio
• Manufacturers Radio
• Telephone Maintenance
• Motor Carrier
• Railroad Radio
• Taxicab
• Automobile Emergency
• ESSA Weather Broadcasts on 162.55 MHz and 162.450 MHz

Cutting instructions tor UH F and VH FAntennas
•
o
CUTTING 20- I 77 ANTENNA
UHF 450-470 MHz
15" ~-----'---_-L.
450 460 470
OPERATING FREQUENCY
MHz
11"
ANTENNA
LENGTH 16'
152-174 MHz
160 170
OPERATING FREQUENCY
MHz
IS'
16"
14' L- -'- --""'--
150
ANTENNA
LENGTH
The Radio Shack No. 20-177 antenna is a one quarter
(152-174 MHz) or five-eighths (450-470 MHz) wave vertical
designed tor automotive trunk lid mounting. A special clamp
in the antenna base fits into the space between lid and car
body so that no hole cutting is required. Complete installation
instructions are suppl ied with the antenna.
Minimum distance from antenna to edge of the metal
mounting surface is preferably five or more antenna lengths.
The
two charts at the right indicate most efficient lengths, as
measured
from the tip of the antenna to the top of the set screw
fitting.
The antenna length is adjusted to 5/8 wavelength at 450-470 MHz to improve
its horizontal gain at a slight cost in high-angle gain. lts practical effect is about
equal to a doubling of the transmitter power.
Antenna reliability will be improved if at assembly all contacting metal surfaces
are cleaned and
then coated with a thin layer of water pump grease or equivalent.
The base fittings hould be dismantled, cleaned, and checked about once per year.
14' ....... -'----''----'---'---'-
150 160 170
OPERATING FREQUENCY
MHz
5.0"L....- __ -L ...L-
450 460 470
OPERATING FREQUENCY
MHz
ri
The Radio Shack No. 20-176 antenna is a wideband quarter-
wave gound-plane antenna for 152-174 MHz or 450-470 MHz. It
is designed to be used at fixed or portable stations. For best
performance at a given frequency its whip and radials should be
cut as follows.
During installation all four radials are cut to 20 1/4" (152-174
MHz) or 6 1/2" (450-470 MHz). They are removed from the
assembly, the four end balts pulled off, and each radial is cut to
the correct over-all length. Then the balls are tapped back on.
Next, the vertical radiator top plug is removed, and the
radiator overall length trimmed to the value given in the cutting
chart. After cutting, the antenna is ready for assembly and
installation.
For best performance this antenna should be instalied ten or
more vertical radiator lengths away from any large metal objects.
Wires, lightning proteetion svsterns, metal roots. and large vehicles
moving or stored nearbv may influence qual ity of the received
signal.
If performance of the receiver system seems poor compared
with th at of other similar installations, the anten na should be
moved.
UHF BAND
450-470 MHz
RADlALS 6y';"LONG
ANTENNA
LENGTH
RADlALS
20J,{" LONG
CUTTING 20- I 76 ANTENNA
VHF Hl BAND
152- 174 MHz 6.0'
17"
15'
ANTENNA 16'
LENGTH
UHF and VHF Antennas
Dual Band Ground Plane
For outdoor use. 3 heavy-duty,
low resistance aluminum ele-
ments. 2-section vertical radiator,
matching transformer. Mounting
bracket. Accepts PL-259. 20-015,
6 Ibs.
I
I
J
Indoor Hi-Lo Antenna
Plug-in type. For indoor use.
Ru
gged construct ion, center
loaded coil. Telescoping whip,
40" extended, 16" collapsed.
Termi nates with pi n-type plug.
21-161, 2 Ibs.
Dual Band Cowl-Mount
For mobile use. Chrome tele-
scopic
whip (55" extended, 36"
cotlapsed}, mounted on swivel
base. Center loaded weatherproof
coit. 5' RG-58/U cabie. Termi-
nates with pin-type plug.
Omnidirectional Indoor
Antenna
For indoor or portable use. Plugs
directly in to back of PRO-3A
receiver. 22" overall. Decoupling
skirt improves efficiency.
Chrome-plated. 20-451, 1 1/2 Ibs.
-3-

FRONT AND REAR PANEL CONTROLS
FRONT
REAR
FIG-l
-4-
A -llluminatad slide-rule dial ,
B
-Separate dial pointers for 30-50 MHz/450-470 MHz and 152-174 MHz.
C -Tuning knob for 30-50 MHz and 450-470 MHzband.
o -Tuning knob for 152-174 MHz band.
E -Power switch and audio volume control.
F -Squelch eliminates no-signaInoise.
G -Selectivity switch chooses broad or sharp characteristic.
H -Band switch.
I -Low impedance audio Jack for phones or external speaker.
J
-Audio filter improves weak signaI readability.
K -Easily removed knurled mounting screws.
L
-Steel mounting bracket.
M -Antenna connection for 30-50 MHz and 152-174 MHz band.
N
-Antenna connection for 450-470 MHz band.
o ~For P.A. or Tape Input.
P -OC Power Connection Secket.
Q -AC Power Cord.

ELECTRICAL INSPECTION
Set controlsas follows: (Ref. FIG - 1, page 4)
1. Volume Control (E): Off position
2. Squelch (F): Minimum position (Counter c1ockwise)
3.
Selectivity Switch (G): 15 KHz position
4. Band Switch (H): Low band position
5. Audio Filter (J): Out position
6. Antenna Jack (M,N): Conneet anten na to jack
7. AC Power Cord (O}: Line cord to AC outlet (120 V)
Turn the Squelch Control to the minimum position. Turn the Volume Control to
"ON" and a rushing sound will be heard in the speaker. Advancing the volume
clockwise will increase the loudness of the noise. When the Squelch Control is slowly
turned clockwise, a point will be reached where the background noise will disappear.
This indicates normal squelch and also normal operation of the unit.
INSTALLATION
A good installation will make the most of the PRO-3A's capabilities. Loss of the
tiny signaI at the antenna is avoided by correct antenna adjustments and by installing
a good quality foam coaxial cabie. The antenna that you choose, and how you install
it, wi II have a great effect on how weil your unit will work.
a. Base Station:
To install the PRO-3A in a base instellation. simply connect the AC line cord into
a 110-120V AC 60 Hz power source.
b.
An antenna, such as a ground-plane (Cat. No. 20-176l mounted as high above the
ground as practical will greatly increase the signal strength. For proper input
matching, a 50 ohm lead-in coaxial cable such as RG 8/u (Cat. No. 278-970)
should be used. A Motorola type antenna adapter plug (Cat. No. 278-208, or
equivalent to Cinch-Jones No. 13B or H.H. Smith No. 1200) will have to be
instalied on the receiver end of the cable in order to utilize the antenna connector
located on the rear (back) panel of the unit.
c. Mobile Station: CAUTION: BE AWARE OF THE BATTERY POLARITY.
For a vehicle with a 12V DC negative ground system, use the OC power cable
supplied
with the unit. Simply conneet the cable into the cigarette lighter
receptacle (Cat , No.274-331) or directly to the OC power supply source. The
red lead is to be connected to the positive terminal of the power souree and the
black lead to the Negative.
IMPORTANT: If your car has been burning out headlamps and other bulbs at a
rapid rate, have the voltage regulator checked for proper output. Excessive voltage
(more than 16 volts) may cause serious damage to your Receiver.
-5~
d. Safety and operating convenience are the primary factors to consider when
mounting any piece of equipment in an automobile. Be sure that the Receiver
controls may be easily reached by the operator. Also be sure that connecting
cables do not interfere with the operation of the brake, accelerator, etc.
The Receiver may be mounted to the underside of the instrument panel or
dashboard of a car. truck, boat, etc., bv means of the special bracket that is
supplied with the Receiver.
e. Keep
the foilowing points in mind when installing your mobile antenna.
1.
Mount the anten na as high as possible, mounting in the center of the roof is
the best possible location.
2. Mount it rigidly, 50 it will remain vertical while in motion.
3. Mount as far as possible from the engine compartment; mounting on the rear
of the car is preferabie to mounting in place of the AM antenna.
MOBILE NOISE SUPPRESSION
Noise:
This receiver is very sensitive, and will pick up signals th at are extremely weak.
With this extreme sensitivitv , you will find th at the receiver will amplify weak signais,
along with any noise that may be present.
When
operatinq areceiver in a vehicle, you will find that the vehicle generates
noise, and
this noise can become very objectionable. Mobile operatien will not be as
quiet as base station operatien. but steps can be taken that wi 11 greatly improve the
noise
situation.
Electrical System:
Generally speaking, noise can be generated by any device or conneetion that
carries electrical current. Any device that generates aspark should also be suspected.
Bypass
any suspected wire to ground with a high quality 11.Lf coaxial capacitor.
Probably the next most common souree of noise is the generator, or alternator .
This type of noise will sound like amusical whine, and will also varv with speed of
the engine. Generator and alternator noise can usually be reduced bv placing a
coaxial-type capacitor from the armature termi nal to the metal case.
Ignition System:
The ignition svstern is the most common souree of noise. This noise can be
identified by the fact th at it varies with the engine speed. Ignition noise will sound
like a series of "poppinq" sounds, while that engine is idling, and will speed up to a
buzzing sounds as engine speed is increased.
There are a number of things that can be done for this type of noise.
1. Use
radio suppression-type ignition wire, and resistor spar k plugs.
2.
Check high-tension lead etc. for leakage, cracks, etc. Replace any old wiring.
3. In extreme cases, kits may be pur chased, that will completely shield all ignition
wiring. This will provide maximum noise suppression.

Model PRO-3A Bloek Diagram
Tp1
~---------------flII'J) ~~PE OUT
AUDIO OUT
FM
DETECTOR
D2,3
IF AMP
IC 1,2
S2
WIDE BAND
FILTER
010
NARROW BAND
CRYSTAL FILTER
011
Sl
VHF La
FRONT END
30-50 MHz
01,2,3
VHF Hi
FRONT END
152-174 MHz
04,5,6
1------ --,-
I
I
I
I
I
,
,
I
~
1 :
VHF I
ANTENNA 0
JACK Sl 0Sl
SOUELCH
J4
PHONE JACK
J2
VOLUME
UHF SOUELCH AF
UHF BUFFE R NOISE AMP, DC AMP Hl CUT
ANTEN NA CONVERTER SWITCHING AMP AND
FILTER
AUDIO AMP
AMP DETECTOR
JACK
450-470 MHz
023,24
013,24,D4,5 015,16,17 AF
FILTER
020,21,22,D7
Ol,8,9,D1
D6 SWITCH
018
~o--
SPEAKER
S4
REGULATED DC TO ALL
EXCEPT AUDIO ClRCUIT
PILOT
LAMP
S4
POWER
SWITCH
POLARITY
PROTECTOR
D13
J5
PLUS
12-15 VDC
NEGATIVE
GND ONLY
VOLTAGE
REGULATOR
025, DB
RIPPLE
FILTER
026
POWER SUPPLY
RECTIFIER
f-----l
D9,1O,11,12 117 VAC
60 Hz
-6-

Model PRO-3A General Schematic
Q'D,II 25C371101
'--------"(3)
SPK
PHONE
JACK
Q22 2SB435101
Q2I 2S0235 la1Q20 2SC735IY I 07 HV Ba J3
,,--ri--------------------=~_«JI TAPE OUT PUT
53
S2-d
D4,5 IN 60 QI5,16,,72SC373
06 HV-SO
52-0
- - ~
R25
18K
~,
1F
H IG H
FRONT EI\D
(152 -174MHz )
Q4 Q5 Q6 AGC(
C43.01(M)
Q25.26 2SC 1173(0)
54
De 12~15V
NEGATIVE GND.
ONLY
AC '17V 60Hz
ZBI-IO De
iS.
RGG
330
Q 23,24 2SC 394 «»
UHF
CO NVERTE R
(4~ ~ 47QMHzJ
IF (
Q7 08 09 0 I
VHFLOW.UHF,VHF HIGHBAND SWITCH
SELEcrtVITY SW'TCH (5KHz 15KHz)
AF FILTER SWITCH (I N - OUT)
PCNlER ON-OFF SWITCH
SQUELCH CONTROL
VOLUME CONTROL, W/POWER SWITCH
RESISTANCE VALUES IN OHMS
K=IOOO
CAPA$ITANCE VALUES IN MF P~MM F
De VOLTAGE (MEASUPED BY V.T,V.M,)
De VOLTAGE (SQUELCH CJNTROL AT MAXIMUM CONDITION I
ALL VALUES AND RATING ARE SUBJECT TO CHANGE FOR IMPROVEMENT
WITHOUT NOTICE.
REMARKS
I S r-e _d
2 S2~a - e
3 53
4 $4-0- b
5
VRI
6 VR 2
7
8
9
la
"
UHF ANT
-7-

Schematic of VHF LO front end. 30-50 MHz. Schematic of
VHF Hl front end. 152-174 MHz.
Schematic of UHF converter.
450-470 MHz.
ANT
L2
CTl
L3
CT2
-8-
L5
C~3
KlJ
eI9
I
LG
ü