When troubleshooting and/or
servicing military radios in the VHF Low Band (30 - 88 MHz)
it's very convenient to have a power meter that reads both
forward and reverse power. The
PRM-34
does this and more. But for most things a plain power
meter like this is all that's required. This one has two
power ranges 10 Watts full scale (just right for the
PRC-68 Family of hand held radios,
the
PRC-25 and
PRC-77 man pack radios) and a 100
Watt Full scale range that's just right for the
VRC-12 series of vehicle radios.
The URM-182A NSN 6625-01-062-3599 consists of the TS-3754/U
Test Set, Radio Frequency, Power, the CY-7733 Case and the
CG-1893C/U BNC cable. It replaces the URM-182 NSN
6625-00-148-9371 that consists of the TS-2609A/U Test Set,
Radio Frequency, Power. My guess is the the TS-2609 was
made in an expensive way with a transmission line assembly on
the back and the meter and switch on the front. The
TS-3754 mounts all the functional parts on the front panel
making it much simpler to manufacturer and to service.
I was about to get one of the URM-182 test sets that seem to
be plentiful on eBay March 2006. These all seem to be
suffering from the foam turned to goo problem. When the
URM-182A arrived it too had the foam to goo problem, but most
of the bad foam had already been removed by the prior
owner. The product called "Oops" was used to clean off
the sticky from the GL envelope.
Both the TS-3754 and the TS-2609 have a vertical "V" groove
and pinch screw so that they can be mounted on the handle of
the radio being tested. This is a good thing since
leaving the test set to dangle on the short coax is asking for
coax problems.
The TS-2609 schematic (TM 11-6625-2718-14&P Fig 5-1
TS-2609A) shows a simpler circuit (R5, R6, R7 & R8 are
factory select). The TS-3754 (TM 11-6625-2718-14-1 Fig
6-1 schematic) does not use any factory select parts.
The TS-2609 uses single diode detectors, whereas the TS-3754
uses a dual diode voltage doubler detector (Wiki)
circuit.
URM-182
TM 11-6625-2718-14&P
Operator's, Organizational, Direct Support, and General
Support Maintenance Manual Including Repair Parts and
Special Tools List Test Set, Radio Frequency Power
AN/URM-182(NSN 6625-00-148-9371) 30 June 1975