PRC-68 Family

Products For Sale

 

Web Page =	PRC-68	PRC-68A	PRC-68B	PRC-126	PRC-128	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
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:

• have a micro controller and frequency synthesizer (except the PRC-68 that used acustom chip, not really a uC)
  
• have a built-in Push To Talk switch
• have a combined Speaker/Microphone
• have a 10 position knob to allow selection of the operating channel
• can use either of two antennas, a short antenna to restrict the range to nearby troops and a long antenna for greater range
• have a carry pouch that attaches to a standard military pistol belt
• were all originally designed and manufactured by Magnavox in Fort Wayne, IN (FSCM - CAGE 37695)
• are intended to be used in front line military operations at the squad level, meaning they are very rugged.
• have a 6-32 threaded hole near the ANT connector that accepts the ground lead/handle of the TS-3951/PRM-34 test set.
• Plus the items listed below:
  

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.

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