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December 21st 05, 11:59 PM
posted to rec.radio.amateur.policy
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Definitely Not Qualified
From: Frank Gilliland on Tues, Dec 20 2005 12:42 am
On 19 Dec 2005 20:41:35 -0800, wrote in From: Frank Gilliland on Dec 19, 1:28 pm On 19 Dec 2005 10:38:46 -0800, wrote in From: Frank Gilliland on Dec 18, 6:54 pm The AN/PRC-104 HF manpack transceiver (operational 1986, will be replaced soon by an updated unit) by Hughes Ground Systems has an automatic antenna tuner integral to the manpack R/T. One can physically shorten the whip by removing sections to cut down visibility and the antenna tuner will compensate for the shorter sections. Won't be quite as efficient as the full whip but it is less visible on the ground. The lil 20 W PEP transmitter will shove as much RF into the whip as it can without damaging itself. We had the PRC-104 in the early '80s; the RT was used as the exciter for the MRC-109/110 (400/1000W) jeep radios. Mechanical push-button tuning from 2-30 MHz. I still want one. I'm not familiar with the MRC-109 or MRC-110, but a reference on C4I has that compatible with the AN/VRC-49 which is FM in the 30 to 76 MHz region. The AN/PRC-104 basic R/T was used in the AN/GRC-213, a vehicle mount configuration with audio amplifier and DC vehicle power supply conditioning, 20 W PEP SSB output. The AN/GRC-193 is also for vehicle mounting, uses the basic R/T, but includes a 100/400 Watt linear amplifier for transmitter and a higher- power antenna coupler/tuner. I'll have to amend what I said on the PRC-104. Hughes Aircraft Ground Systems got the initial development contract for it from the USMC some time between 1975 and 1977; seems there was a bit of disagreement between a couple of ex-HAC people who worked on it south of here as to exact year. :-) The Army got into the act on seeing field performance of the first USMC ones and they wanted one, too. :-) Army changed a few things (not much) and - probably - they added the "IHFR" moniker to the series ("Improved High Frequency Radio")...which meant an "A" suffix to the original PRC-104 and its R/T unit (RT-1209). Not to be outdone, the USMC wanted some changes after that with a resulting "B" suffix. :-) USMC had them first in the latter half of the 1970s, Army got theirs in the first half of the 1980s. :-) Somewhere in the era between 1977 and 1985, Hughes incorporated a microprocessor in the synthesizer. One result was the change from a single push button per digit with mechanical display to an LCD screen with rubber-sealed push buttons on frequency control of the R/T. That, plus some more minor revisions inside resulted in a re-issue of TMs in 1985 - 1986. Same basic R/T that is a full SSB receiver plus Tx exciter (the 20 W PEP Amp is in the automtic tuning unit alongside the manpack, higher power Amp and auto antenna tune in the vehicular or "ground" version (GRC-193). I tried to find a better description of the MRC-138 but could not. Maybe that was the Marines' own version of the GRC-193? Either way, it was described as selectable 100 W or 400 W PEP on HF. Note: A lot of "MRC-" radios out there but all for Marines; I find no direct Army "MRC-"s described. Well hell, I guess I -am- getting old. I found references to the 400 watt MRC-138 but not the 1000 watt version. I could have sworn they were called the MRC-109/110....... Given a mere 64 years since we got into WW2 until now, there's a whole potfull of different radios, radar sets, transponders, gizmos that have gotten the U.S. military nomenclature. A few of those were civilian developments, bought intact, and given MIL monikers (AN/FRC-93 for the Collins KWM-2 all-band HF transceiver; AN/FRC-23 and FRC-35 for a GE microwave terminal). I'm glad I "took notes" with my camera during my 4 active years just to jog the memory much later; came easy enough with visual clues to pull out certain technical details. :-) The basic R/T has digit push-wheel frequency selection (like digit thumbwheels but with a single button mover). The AN/VRC-11 through AN/VRC-49 had, variously, 10 push-button or rotary switch selection of frequencies in the 30 to 76 MHz region, FM, and were compatible with the AN/PRC-25 and -77 VHF FM sets. The lower number VRCs I've seen all have chromed push buttons, something left over from WW2. :-) Got a couple of tuners like that in the parts pile. Probably from the old BC-603 and BC-604 "tank radios." [add 80 to the numbers for corresponding non-tank radios] Those were all-tube, FM, and definitely crystal-controlled using 1 to 10 FT-241 holder crystals with "channel numbers" on them plus the air frequency (highest end of HF). Those just selected the crystal and cam-operated a couple variable capacitors. Those "tank radios" were among the first to get their nomenclature changed to "AN/VRC-" in the last year of WW2. In 1967 the U.S. military had three field models of NODs. Electro-Optical Systems division of Xerox in Pasadena produced one of those models. Three were stolen/turned-up-mission that year, feds in there asking questions after. The production manager "resigned." I have no idea where those missing NODs wound up but I read reports in 1970 where the USSR military now had them. First ones were "blotchy" in imaging and sensitivity didn't have any automatic gain control but they could enable anyone to "own the night." They have improved considerably since 1967. Sounds about right. On this one the lens is pretty good quality but the electronics are nothing more than a noisy inverter and a finger trigger. Suprisingly sensitive tho, especially to short IR. The sensitivity is due - according to a PhD in Optics I worked under at Rocketdyne - an innovative expansion of the basic photomultiplier tube still used for light level measurements down to single photon level. The difference with the NOD is that it does it as a wavefront of EM light as opposed to the "stages" of the photomultiplier tube with a small target area. That requires the higher voltages from the internal battery supply. Sensitivity is best at IR due to less wavefront energy there, thus the photon multiplication has higher gain at IR. Weird science! First time I looked through one at EOS in Pasadena (test area completely enclosed in double black plastic sheet), the "illumination" came from a guy's radium- marked wris****ch dial! "Eye opening" experience! :-) |
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