Temporary Post – AN/GRC-109 Gasoline GENSETS

UPDATED 2/21/20

Known Gasoline GENSETS for the AN/GRC-109 system:

First photo: The UGP-12.  125 Watts, 115 VAC, 400 cps, 2-stroke (manufacturer unknown) as described in the GRC-109 manual as an alternate field power source. At the 2014 MRCG event at San Luis Obispo, Chuck demonstrated his UGP-12 (pictured). It was remarkably quiet and produced little smoke.

Second photo:  The 125 Watt, 115 VAC, 400 cps 2-stroke Homelite Model XLA115/1/400/1P as used by the Army’s 10th Special Forces Group.  Photo of a layout for a unit communications team equipment inspection, mid 1970’s.

It is presumed these generators would be powering GRC-109’s from a safe house, bunker, forward operating base or as a backup in an HQ someplace – rather than tactical “mudborne” operations.






GRC-109 teamradio 1977
Also note the GRA-71 Code Burst Keyers, the PRC-74 HF sets and the PRC-25/77’s etc. It seems reasonable that the Homelite generator replaced the UGP-12 later on in time. The Homelite Tech Manual (TM5-6115-405-15) is dated July 1967.
Special Forces comm gear inspection layout photo courtesy of W1OC, 10th Special Forces Group (E).

Here’s another look at this little gas powered military generator: The Homelite XLA115/1/400. Approximately 1531 units were delivered to the US Army in 1966-67. Made by Homelite of chain saw fame, the engine was taken directly from the Homelite Super XL chain saw. Clearly designed to meet a specific Army requirement it is an essentially “commercial off-the-shelf” item. It does not carry a usual military PU-xxx designation for generators.

XLA115 generator running from external fuel source

This little guy is rated at 125 watts, 115 VAC at 400 cps, single phase. It was designed to power military radios in the field, notably the AN/GRC-109 and the earlier RS-1 and RS-6 CIA sets that were designed to operate off 115 VAC with AC sources delivering power at between 50 and 400 cps. It will also be a good match for a PRC-47 running in the Low Power setting.

With its two-stroke engine and alternator it will also power incandescent lamps or any other resistive load not to include motors or consumer-grade transformer operated equipment rated for 60 cps power.

This Genset is conservatively rated like most military gear. Here powering a 150 watt shop light for an extended period – no problem. Note the completely shielded ignition system and all metal construction; it radiates no RFI ignition noise into nearby HF receivers. Honda take note!

Homelite XLA115 400 cps generator

It will run at full load for 1.4 hours on its internal fuel tank. It also includes a fuel selector valve that can select an external fuel source such as that 1 gallon fuel can. Very handy, one gallon will run the generator for over 12 hours. The specified lube is SAE 30 weight oil mixed 32:1. I am using synthetic oil in the mix at 40:1 as a better alternative using modern lubrication chemistry.

Just as with its chain saw “father” the engine delivers maximum torque at 4000 rpm. So despite that big muffler it is still fairly noisy, acoustically. But still quieter than the 300 watt PU-181 or PU-162 sets. So operationally, just place it in a 10 gallon-sized hole in the ground outside of your Commo Bunker. Presto!

Then there is the PU-181 Genset that was designed for a field teletype system the AN/PGC-1. This one is also a 2-stroke gasoline powered alternator that delivers 120 VAC, 60 cps. It can be strapped for 240 VAC as an alternative.

PU-181/PGC-1 Generator in the bush

This little 300 watt Genset was likely used for all sorts of alternate uses besides powering a teletype set. Mine starts reliably even with year-old gas, sips fuel and this one still has the original Korean war era spark plug installed. Here powering a GRC-109 at a campsite. Reliable gear in the field.

With its 60 cps output it will also power the RS-1 and RS-6 CIA sets as well as anything else designed for “standard” AC power.