PRC-68 Family

©Brooke Clarke, N6GCE

Products For Sale

The radios shown on these pages are not for sale
 
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PRC-68
PRC-68A
PRC-68B
PRC-126
PRC-128
PRC-136
 Front
PRC-68 Front
PRC-68A Front
PRC-68B Front
PRC-126 Front
PRC-128 Front
PRC-136 Front
 
4.5" overall ht
5.5" overall ht
6 1/8" overall ht
6 1/8" overall ht
6 1/8" overall ht
6 1/8" overall ht
 Top
PRC-68 Top
PRC-68A Top
PRC-68B Top
PRC-126 Top
PRC-128 Top
PRC-136 Top
 Back
PRC-68 Back
PRC-68A Back
PRC-68B Back
PRC-126 Back
PRC-128 Back
PRC-136 Back
Frequency
Range
(step kHz)
30 - 79.95
(50)
30 - 79.975
(25)
130 - 173.9875
(2.5)

30 - 87.9875
(2.5)
30-87.975
(25)
12.5 w/compuer
130 - 173.9875
(12.5)

30 - 87.9875
(12.5)
130 - 173.9875
(12.5)
# of problem
frequencies
93
37
0 hi band


26 ?
26
0 (hi band)


26 ? (lo band)
0 (hi band)
Frequency
Display
none
none
LCD
LCD
NV backlight
LCD
NV backlight
LCD
NV backlight
Split
Tx - Rx
na
na
Yes
Yes
Yes
Yes
Antennas
7" Duck
28" AT/892
7" Duck
36" AS-3575
20" Duck (H+L)
7" AS-4094
Goosneck&AS3575
19" Tape (H+L)
36" AS3575 (L)
 ?
ANT
thread
5/16" X 24
5/16" X 24
1/4" X 28
5/16" X 24
5/16" X 24
5/16" X 24
ANT
switch
none
none
ABCDEH
ABCDE50
ABCDE50
ABCDE50
Chan
programming
controls
internal
switches
internal
switches
+ Norm-Load
pushbuttons
behind
cover
pushbuttons
on panel
pushbuttons
on panel
pushbuttons
on panel
150 Hz Tx
Disable
SVM
connector
SVM
connector
? +
SVM
connector
PTT +
INC
SVM conn
PTT +
INC
SVM conn
n.a. for
 hi band
AUDIO
connector
5 pin 
5 pin
6 pin 
6 pin 
6 pin 
6 pin 
Retrans
Cloning
na
na
Yes
Yes
Yes
Yes
Standby hrs
0.8 AH batt
17
32
 
20
80
 
Microcontroller
Functions
Synth prog
150 Hz gen
Batt Saver
Synth prog
EEPROM read
150 Hz gen
Batt Saver
Low Batt Tone
Synth prog
EEPROM read
150 Hz gen
Batt Saver
Low Batt Tone
Antenna Tone
Clone/Fill/Rptr
 Synth prog
EEPROM read
150 Hz gen
Batt Saver
Low Batt Tone
Antenna Tone
Clone/Fill/Rptr
Synth prog
EEPROM read
150 Hz gen
Batt Saver
Low Batt Tone
Antenna Tone
Clone/Fill/Rptr
Synth prog
EEPROM read
150 Hz gen
Batt Saver
Low Batt Tone
Antenna Tone
Clone/Fill/Rptr
Deviation Osc
J2-2
12 MHz
12 MHz
21.4 MHz
21.4 MHz
21.4 MHz
21.4 MHz
Manual Date
19 Jan 1981
Jan  1985
 15 May 1989
1 Sep 1988
1 Jan 1991
July 1993
Frame
   
816173-801
816173-821
5820-01-255-5631
816173-821
 816173-821
Synth Module
 
814635-801
815587-801
815587-821
5820-01-255-5630
815587-822
721599-801
5895-01-291-9286
521599-801
RF/IF Module
 
814636-801
HI 816767-801

LO 815586-801
815586-821
5820-01-257-3142
HI 721598-801

LO 721597-801
HI 721598-801
5998-01-288-2255

Squad Radio Batteries

Squad Radio DC Power Sources

U-229 Audio Accessories - Photos of Military Audio Accessoires

Specials & Prototypes

KYV-2/2A Secure Voice Module

Additions and Corrections to "The AN/PRC-68 Legacy" by Alan Tasker

Radio Shack 19-345 Repeater

Background

Before the PRC-68 there were handheld radios like the BC-611 and PRC-6 that required changing crystals and realignment to change frequency assignments.  The PRC-25 and the PRC-77 man pack Squad radios use a modular construction method.  The PRC-68 uses a very similar modular construction methods and introduced the frequency synthesizer and micro controller to the handheld squad radio. Improvements to the PRC-68 added more features and capabilities.  The PRC-68 series of Squad Radios evolved in the sequence: PRC-68, PRC-68A, PRC-68B, PRC-126, PRC-128 and PRC-136.  The PRC-136 is a Crash Fire Rescue USMC radio.  If you have any PRC-136 literature of any kind please email me.  It looks exactly like a PRC-126 or PRC-128 and operates in VHF high band only.

The seperate Army PRT-4 transmitter and PRR-9 receiver were not liked by the Marines, they wanted a single unit Squad Radio.

For more on how these radios came about see the AN/PRC-68 Legacy by Alan D. Tasker, WA1NYR and PRC Data series by Dennis Starks. "History of the Squad Radio" ECOM, Nov 1976 available from W7FG.

Olive Drab web page for PRC-68 Family

Common Features

All of the radios in the series:

Battery Interface

The key feature that all radios in the series have in common is the mechanical & electrical battery interface (Bottom of radio).  The two slotted screws hold the module cover to the radio.  The small screwdriver is stored in the radio and is used to change channel frequencies, adjust the low battery and/or squelch threshold depending on the radio model.  The two snaps connect to the battery.  Two of the four tapped holes in the corners are used for attaching the Secure Voice Module.  On the left and right are the hooks that hold the battery clasps.  The large philips head screw is a mystery.

All the radios are about 3 3/4" wide and 1 1/2" thick and use the same male and female snaps to make electrical connection to the battery and the same external latches to hold the battery onto the radio. Battery Family Portrait, Squad Radio DC Power Sources -

My 68BA Battery Adapter allows the use of commonly available AA or 9 Volt batteries to power all the radios in the family and other equipment that uses the same batteries.

Secure Voice Module

Another part of this interface is the 15 pin miniature "D" connector to allow the installation of a Secure Voice Module.  All the radios in this series are compatible with the SVM not only in terms of the connector, but also in that they have the functions to support it.

Antenna Connector

The antenna connectors are all very similar, but not identical.  They all support the use of the same 914598-801 adapter to BNC for use with external 50 Ohm impedance antennas or for test purposes.
Dennis Starks 4 part article on Shortnend Antennas for Portables.
Note that the 7" rubber duck antenna was made to restrict the range of the radio.  In general these radios operate above 30 MHz so that they can not be heard over long ranges.  The operating range is a very strong function of the antenna used.

My 68AA Antenna Adapter not only works with all the radios in the family it also has a built in DC return so the the radios that sense the DC conditions at the antenna connector will be happy using a DC open atnenna like a Ham stick or other whip.

Audio Connector

They all can be used with standard military U-229 audio accessories.  From the PRC-68B onward they utilize the 6 pin version of the U-229 with the added pin used for things like cloning and repeater/retransmission functions.
 

Frame & Panel

The radios have a panel that's the casting with all the controls and SPKR/MIC. The Frame is the part that holds the modules. The module cover slips over the frame and modules.  The PRC-68 and PRC-68A have an identical panel.  The frame on the PRC-68A and all newer radios is the same length and takes a module cover that's about 3.5" high.  The PRC-68 module cover is about 2.5" high.
The Panel height of the PRC-68B and newer radios is the same, but the PRC-68B is the only one with a cover over some of the programming switches. From the PRC-126 on, all the Frame & Panel assemblies have the same 816173-821part number.

People

By reading the title and change blocks on Magnavox, Fort Wayne drawings the following people were involved in the PRC-68 seires of squad radios.  If you are one of these or know one please email.  It is not easy to read the names on a multi genertion copy so I have put a "?" mark on those that were not clear.

A. Cox,  A. Paul,  B. L. Rettig,  C. Lilie,  C. Reid,  C. Steffen,  D. R. Moss,  F. Joiner,  G. ?er,  G. J. Zollinger,  G. Sutter,  H. Weisbach,  J. Comdon,  J. Foell,  J. L. Becker,  J. Mills,  J. Weigand,  L. Schaeffer,  L. Smith,  M. Minion?,  N. ?Nguyenba,  N. E. Minich,  O. R. Moss
R. Miller,  S. Conte,  S. Widau,  T. Karapantos,  T. Wilcoxson,  W. Miller

Mystery Antenna

This 15" rubber duck (helical) antenna fits the 5/16" X 24 threads used on most of the Squad Radios, but I don't see any reference to it.
Photo (I put the blue tape on to help stitch two images). If you know what this is email me .
I have heard that this was a replacement antenna for either the gooseneck & tape or a longer range version of the short ducky.

Mystery VHF High Band Support

The PRC-68B, PRC-128 and PRC-136 have a 130 to 174 MHz capability, but there does not seem to be any test procedures or test equipment to support this frequency range.  The use of commercial FM communications equipment must be assumed, but why the lack of test procedures?

Next Generation PRC-139

The PRC-6725 is a single band version of the PRC-139.

I am looking for schematics for all of these radios.  If you have them please contact me.

Back to Brooke's Products for Sale, Audio Connectors & Cloning - Fill - Retransmission, U-229 audio accessories, Squad Radio, Military Information, Electronics, Personal Home, Squad Radio Family Battery Portrait, Squad Radio DC Power Sources, PRC68.com page

  This is the  time this page has been accessed since 9 April. 2001.