[Milsurplus] ARC-65 (and other sets)

[Ray Fantini]

I don't know why , maybe someone changed out the power supply but my ARC-94/618T has the 28 VDC inverter and not the 115/400 cycle power supply. The top of the radio is stenciled AN/ARC-94 and not ARC-102. Also thought that my PDF of the ARC-94 manual shows the PP-3702 power supplying rack? Also why is there a different number for the control head for the ARC-94, ARC-102 and the civilian 618T when all three look to be identical? and last but not least why do some 618T heads have a data mode and others don't?
Ray F.

-----Original Message-----
Subject: Re: [Milsurplus] ARC-65 (and other sets)

Joe wrote:

> The ARC-65 was a mechanical wonder. It was very heavy. 

The RT-400/ARC-65 is just over 140 pounds by itself!

Many of the USAF RCA RT-400/ARC-65 USB units are RCA conversions of the RT-128A/ARC-21 AM set, so there seems to be few surviving RT-128A units anymore.  The R-224/ARR-36 is the associated auxiliary receiver, and overall system wiring diagrams often incorporate the
AN/APN-70 LORAN A set.  

It's interesting that the principal USN equivalent, the Collins RT-311/ARC-38 AM set, was likewise converted with an RCA design to the RT-594/ARC-38A USB set.  The R-641/ARR-41 is the associated auxiliary receiver.  I suspect that RCA created the USB conversion for the Collins USN set based on experience gained converting their AN/ARC-21 to the AN/ARC-65 for the USAF.

The AN/ARC-58 appears to have replaced the AN/ARC-65 in many SAC aircraft 45 years ago.  The
KC-135 and B-52 aircraft at Blytheville AFB in the late 1960s all used the AN/ARC-58.  The avionics service shop there was not set up for the AN/ARC-65.

> The newer 618T-3 was a great radio to work with.

The Collins 618T-series is, IMHO, the greatest HF aircraft radio design of all time.  The two major military versions are the RT-648/ARC-94 (618T-2) using a little 28 vdc and a lot of 400 Hz AC, and the RT-698/ARC-102 (618T-3) using 28 vdc only (when in the PP-3702/ARC-102 mounting rack that has a small 400 Hz inverter built in to it).

If the application did not require the 1000 W output of the AN/ARC-58, the 400W 618T-based sets could be used.  Ignoring the USMC AN/TRC-75, I believe that only the USAF used the AN/ARC-58.  All US services used the AN/ARC-94, -102, or the several other 618T-based variants.  There were even AN/ARC-102 installations on some of the UH-1D/H helicopters in Vietnam.  (Those have a short zig-zag wire HF antenna on the port side of the tail section.)

The 618T-series was introduced around 1960, and I've seen USMC documents referring to its continued use in the early 2000s, less than ten years ago.  That's a very respectable 40-year service life.

I have an almost complete AN/ARC-102 with CU-991/AR tuner, missing only the unobtainable
PP-3702/ARC-102 that I've been seeking for 15 years.  Still, the RT-698 is a beautiful set to look at.  I got mine in almost new condition (with Collins round emblem) for $50.  The
C-3940/ARC-94 control box cost twice that!  The CU-991/AR (Collins 180L-2) is only good to 25 MHz.  For higher frequencies, one needs the newer CU-1658/A.

Mike / KK5F