URM-182A TS-3754/U VHF Low Band Power Meter

Brooke Clarke 2006


TS-3754 Mounted on
                  PRC-77 left handle
Front
Mounted on PRC-77 handle

Background

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.

Differences Between TS-2609 and TA-3754

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.

Manuals


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

URM-182A

TM-11-6625-2718-14-1 

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