Posted in amateur radio, living history, military history

PRC-25

Being both a student of military history and an Amateur Radio operator, it was natural to combine the two hobbies and put military surplus radios on the air. It was at some time in the early 1990s that one of my elmers gave me my first “green radio” as they are called.  It was a PRC-25, an earlier version of the PRC-77 VHF manpack transceiver I learned to operate in Basic Training a little before then. 

The PRC-25 and PRC-77 weigh about 14 pounds and put out a couple watts of wideband (by today’s standards, ~10 KHz. deviation) FM RF from 30-75.95 MHz. in 50 KHz. steps. I was a Technician class ham at the time, and noted that the radio would operate on the 50-54 MHz. Six Meter band.  At the time Six Meters was not very popular in the NY Metro area because of its close proximity to TV Channel 2, WCBS in New York City. Six Meters would almost certainly bleed over to TVs tuned to channel 2 (54-60 MHz.), and running FM would ensure that your neighbors would hear you and your identifying callsign loud and clear. Having no desire to earn the Worked All Neighbors TVI Award, one stayed away from Six Meters in places where there was that interference potential.

Since then, cable TV systems started becoming more prevalent, and people replaced their TV antennas with a 57+ channel feed from a service provider.  More recently, analog NTSC TV has been replaced with digital ATSC, and many of the stations on Channel 2 have switched to a UHF channel.  These three changes in American television have greatly reduced the interference potential on Six Meters.

Speaking of TV, back in the analog days, PRC-25s and 77s worked really well for hearing the audio on TV channels 2-4, and I suspect that if we ever get Five Meters back (Ireland already has it), those of us with VHF milsurp radios will be among the first to be QRV on the old/new band.  The old pre-World War II 5 Meter band was 56-60 MHz., which still remains within the frequency range of TV Channel 2 in the US.

After moving back East, and reconnecting with old friends who share similar interests, I find myself doing living history displays again, with FDR being my first event in a long time. Much like an SCR-300, the PRC-25 is one of those milestone radios that might be considered a “must-have” for a green radio collection. So when a fellow ham who is also a green radio enthusiast had a complete PRC-25 for sale, I took the opportunity to add one to my collection again, having swapped out my original PRC-25 many years ago.

The PRC-25 (and PRC-77) make a good first radio for the beginning green radio enthusiast. They are relatively inexpensive, their accessories are readily available, they are easy to power up, and are ready to go on Six Meters.  Technical information is downloadable right off the Internet, and if you are lucky a local old-skool Army/Navy store might have some of paper TMs in their inventory of military manuals.  All you really need to get one on the air is a power source that provides 12V and 3V DC, a handset, and a 6 Meter antenna.  That last item can be anything from a base antenna, to a telescoping whip used on HTs, to something you put together out of zip cord (the civilian equivalent of WD-1) from FM 24-18 or MCRP 8-10B.11.
.

fm_24-18_tactical_single_channel_radio_communications_techniques_0000
Download manuals at
https://archive.org/details/milmanual-fm-24-18-tactical-single-channel-radio-communications-techni
and
https://www.marines.mil/Portals/1/Publications/MCRP%208-10B.11.pdf.
Practicals available at https://www.n6cc.com/antenna-system-ideas.

The big question with milsurp VHF sets is whether or not they’ll be able to talk to other 6 FM ham rigs. The FM voice deviation of a PRC-25 is somewhere around 10 KHz. Modern 6 Meter ham gear is closer to 5 KHz., although I’ve seen some rigs that are pushing 7-8 KHz., usually older stuff.  If you yell into the handset mic of your PRC-25, someone listing with an FT-817, for example, would hear some clipping off the audio peaks. Likewise, someone running the standard <=5 KHz. deviation out of their civilian ham rig is going to sound a bit on the soft side when listening with your ’25. The other issue is the 150 Hz. “new” tone squelch, but you can turn it off on the PRC-25 if you’re trying to communicate with a civilian radio (or an older military radio that uses “old squelch” for that matter).

As a piece of amateur radio equipment, a PRC-25 gives you a QRP (~2 watts) FM transceiver on the 6 Meter Band. Six meters is the most fun VHF band to operate on (especially during band openings), and although the weak signal operators prefer SSB for DX voice work, anyone who listens to the VHF-Low band regularly knows that FM will also work when band conditions are right.  The radio is simplex only, and the 50 KHz. channel spacing renders it impossible to get on the 6m national simplex channel of 52.525 MHz. However, hams who are green radio enthusiasts will be found at hamfests, living history events, and vehicle rallies operating usually on 51.0 or 51.6 MHz.

In TM 11-5280-398-12, Uncle Sam specs out the range of the PRC-25 at five miles. I’m thinking that’s with the standard tape antenna.  Reports from other hams indicate that depending on the terrain, antenna used, and band conditions, you could get as much as 10 or more times that distance.

 

prc25

My PRC-25 is not “mint,”  but neither is it all beat up. It has character. I sometimes wonder where it served, and what stories it might tell. Did it spend some time in the Central Highlands of Vietnam? Did it help watch over the Fulda Gap?  Maybe it’s last tour of duty was in the commo section of a National Guard unit where it was only used one weekend a month, or maybe it ended its career as part of the inventory belonging to a post like Ft. Jackson, SC or Ft. Sill, OK where trainees used it while learning how to shoot, move, and communicate.  The stencils on the radio are very quiet in that regard. Regardless where it’s been and what it did, it’ll spend its retirement communicating with its brethren on 6 meters,  acting as a point of reminiscence for those who carried one in the service of their country, and honoring the past by helping teach an important part of American history.

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