manuals: military AM sets, 100W, 200-400MHz, plate modulated 4X150's @ 950VDC

[Opcom]

posted at http://bunkerofdoom.com/lit/mil_uhf_01/index.html

A rare old instruction book:

"UHF Military Equipment"

covering theory and alignments of:
Receiver R-278B /GR
Receiver R-361 /GR
Transmitter T-217 /GR
Transmitter T-282 /GR
Modulator MD-129 /GR
Modulator MD-141 /GR

- as well as two manuals for the GRT-3 and an explanation of which unit goes with which set.

Each of the two sets is composed of a RX, TX and PSU/Mod.

These old FAA/military sets are of interest because the power supplies/modulators use 811's or 4-65's, and the transmitters use two 4X150's in class C. All run at 950VDC, an excellent example for a 100W station using higher-voltage tubes at rather moderate voltages.

Of further technical interest are the T-R set that is servo-tuned to preset channels with remote control.

Of canonical interest is the iron in the MD-129 modulator, being nearly all Collins. The modulation transformer in the other set is no slouch, being larger and a Freed unit. The mod iron in them is good for 200-20,000 cycles and rated 150W, and the power rating is very conservative. The chassis of the modulators is also extremely tough but light made of thick aluminum, designed to be supported by the front panel despite its 140 lb. weight.

[K3ZS]

I used to work with these monsters with the USAF/Air Guard during the VietNam era.   From what I remember, two complete sets were mounted in two racks in one portable shelter and was referred to as GRC-27 or "Jerk 27".   Each rack was set to one channel and was remoted to the radar control center, where each military controller had a small box as the interface.  You could also test the units locally with a PTT mike.

[WQ9E]

Patrick,

If you want to archive another military manual I have a Technical Radio Co. T-50-M CW transmitter from late WWII that came with a good manual copy.  I can scan it in the near future and send you the PDF if you are interested.  There doesn't seem to be much info about this one on the web.

The transmitter is a fairly low power CW only rig that covers from 1.5-12 Mhz. in 3 bands.  It uses a 6SK7 master oscillator, two 807 buffer stages, and a pair of 807 finals.