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Cranking Up the GRC-109 R-1004


While everybody else yesterday was running around looking for foot bras and the world’s smallest volcano (more on which in the next Odd Lots) I was tidying up my shop/shack, and pulled down my AN/GRC-109 Special Forces radio system. I’ve had it since the mid-1990s, but hadn’t fired it up literally since we left Arizona in 2003. I don’t have the full list of accessories so I had to do a little lashing-up to get the R-1004 receiver connected. It didn’t disappoint me.

I have the CW-only T-784 transmitter as well. I don’t use it because I’ve largely lost my CW chops and the only guys still pounding brass are whistling along at 20+ WPM. Not having an antenna that won’t set off my security system is the other issue. (Shielding the heat sensor it triggers it is not an option due to insurance regs.) My outdoor dipole will go up as soon as we have a few leaves on the tress, whenever that actually happens.

So. What we have here is a vintage all-tube spy radio, where the spies either have stealth jeeps or very strong backs. The design came out of the CIA in the late 1940s, and was adapted for more general use in the 1950s. It was used until the end of the Vietnam War. The receiver weighs 8.75 pounds all by itself. The PP-2684 power supply will weigh you down another 25 pounds or so. (There’s a lighter, smaller power supply, the PP-2685, that I don’t have.) The receiver uses conventional 7-pin miniature battery-filament tubes in a fairly simple superhet circuit. The only glitch there is the 1L6 converter tube, which is hard to find and costs a small fortune when you find it. The 1L6 is scarce enough so that people have designed solid-state replacements for it.

The R-1004 tunes from 3 MHz to 24 MHz in three bands. Selectivity is good, hardly single-signal but a reasonable compromise for a set designed to receive both AM and CW. I had to grin at how spoiled I’ve gotten by modern digital rigs like my IC-736, which can tell you to a single cycle where you are. The dial is pretty accurate, reading bang-on for WWV at 5 and 10 MHz, but it’s a wide dial, and lacks a vernier. Sensitivity seems lower on the 12-24 MHz band. No matter; in the evenings all the action is at 12 MHz and down.

SSB was still pretty exotic when the R1004 was designed, and yet its BFO is solid enough that I didn’t have to “chase” sideband signals on 40 and 75 meters with either the tuner or the BFO knob. AM quality was good, considering that it has caps to roll off audio response past 3 KHz. I tuned the entire range from 12 MHz down to 3, stopping at the ham bands or anything else unusual. I used to do that a lot before I was licensed as WN9MQY in 1973. I was hoping to find a numbers station (are there still numbers stations?) or one of those long-extinct semi-musical beacons that I used to hear in 1965. SWBC hasn’t really changed much since 1970: Christian stations, national stations, some German and French, and a lot of things too far down in the noise to quite make out. Canadian time station CHU is no longer on 7335 KHz, but a quick Google check pointed me to its new location at 7850 KHz. I listened to an AM net on 7290, and was startled when K5MIL’s big signal came up and forced me to turn down the gain–he’s only 5 miles north of me, and running a fair bit of power.

Talk about old times, whew.

My R-1004 hasn’t seen much hard use; I’d almost call it pristine. Serial number 25. By contrast, the power supply has been around the block–or maybe the world–a few times, and when I bought it I had to do some fussy needle-file work to get the corrosion off the power connectors. It sounds goofy, but I love how this gear smells: bakelite and black rubber, with undercurrents of oil and perhaps solder flux. (Radio terroir!) If ever there were a canonical Dieselpunk radio, well, here it is. My only gripe is that my high-Z “cans” headset gave me a headache after squeezing my ears for an hour, and I really need to lash up an audio transformer to take the R-1004’s 4000 ohm output impedence down to whatever my cushy padded headset likes. I’ve done this before, but alas, the adapter unit (built into a 70s contacts case I got from Carol) is hiding somewhere.

No matter. You’ve seen my shop and my collection; it will be done. When we can manage a nerd party here sometime this summer, I’ll put it out on the deck and drop a wire over the edge if I haven’t done so already. Put the black thing up against your ear, young’un: That’s what the Internet was when I was mowing the lawn and not chasing you off of it!

One Comment

  1. […] proved diabolical, but I got a lot more into fewer boxes than I ever have in the past. I got my entire GRC-109 Special Forces radio set into a single 12″ cube, though it’s so heavy I fear for the box’s life. (The […]

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