TS-3951/PRM-34

©Brooke Clarke, N6GCE

This is a more modern version of the TS-3354 for use with the PRC-68 family and other radios such as the PRC-25, PRC-77, AN//VRC-12 Military Radios

The mode switch has the following positions:

OFF CHK - PTT shows Built In Test results as 01.000 in display for all pass.
SENS SQ - to test receiver squelch action
FREQ - to measure the transmitter output frequency (or deviation from channel center)
FWD PWR - to measure the transmitter output power in Watts ( 0.? to 50 Watt range)
REV PWR - to measure the reverse power, or VSWR of the antenna
FLD STR - to check the output of a radio transmitter and is used to aligh the PRC-68 ANT coupler circuit

PUSH TO TEST - activate the selected test mode
It also has an antenna for field strength measurements so that it could also be used for a number of different radios including the PRC-68

There are BNC(f) connectors for ANT and RADIO.

AN/PRM-34 Portable Tester for AN/PRC-68, 25, 77, 126 & AN//VRC-12 Military Radios This is a portable tester that checks for receiver sensitivity, frequency and transmitter RF power . It is supplied in a protective transit case and includes a copy of the operation/maintenance manual. It appears to be in very good condition. Shipping 15 Lbs.

Serial numbers of 635 and higher have a different RF cable & ANT adapter than on earlier sets and have an output every 5 MHz from 30 through 80 MHz. Spectrum of modulated 30 MHz output from PRM-34.

Battery

The original primary battery was the BA-5847 (NSN 6135-01-090-5364)
The Lithium Ion secondary battery BB-2847 (NSN 6140-01-419-8194) is the newer rechargeable version.
This battery is used in some thermal sights, AN/PRS-7 Mine Detector and other equipment.
Home made BA-5847 battery pack:

RS 270-391 4 AA battery holder with wires

RS 274-154 Big (positive) female connector

RS 274-234 Small (negative) female connector

4 AA batteries

The small PCB that is the plug for the battery has room to fit on the rubber pad that's there for the real battery. A small piece of bubble wrap placed over this battery adapter and the plug holds them in place.

The BA-5347 NSN 6135-01-455-7946 also has the same two sockets as the BA-5847 and will work in the PRM-34.

Self Test showing 1.000. Note higher battery voltages would cause different displays.
Brentronics - BB-2847 - nominal voltage 7.2, about 4 or 5 AH
Hawker Eternacell - BA-5847/U with fuel guage.

Manual & Links

TM 11-6625-3015-14 is restricted at ETM but -24P (054912.pdf) and -14-H ( 055792.pdf ) are on line.
TM 11-6625-3015-14 Radio Test Set AN/PRM-34, 14 Oct. 1983
PRC-68 Alignment Procedures with PRM-34 - GTA 11-3-21 - instead of the 75 MHz frequency for testing the squelch of the PRC-68, any frequency in 5 MHz steps can be used. Except for those that are unusable because of spurs.

Radios that can be tested

RT-246/VRC-12, 43, -44, -45
RT-524/VRC-46, -47, -48, -49
R-442/VRC-42, -44, -47, -48
RT-841/PRC-77 /VRC-64, grc/-160
RT-505/PRC-25 VRC-53, -125
RT-1113/PRC-68
RT-1547/PRC-126 (not in TM 11-6625-3015-14 but is in PRC-126 manual)
other radios in the PRC-68 family

Theory of Operation

There is a comb generator with outputs of 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, and 80 MHz at -97 dBm with a 900 Hz FM modulation for receiver testing.
There is a Watt meter with a 1 to 50 Watt range along with a digital frequency counter for transmitter testing and a reverse power test for antenna VSWR testing. What is the frequency coverage?
There is a field strength meter to align the L1 ANT adjustment on the PRC-68 in transmit mode.

Parts List

PRM-34 NSN 6625-01-094-5646
Test Cable 2249-C-24 or 393707
Antenna Adapter NSN 5985-01-097-7337 (could also use my 68AA Antenna Adapter)
Manual
Transit Case (80045) 384858 or (80045) 393662-1

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