[ARC5] A.R.C. Type 12 and AN/ARC-60 (and AN/ARC-12)

[Mike Morrow]

Wayne wrote:

> I understand that the U-2 used the Type-12/ARC-60 sets.  I guess that
> with weight very much at a premium ... that was feasible.

It is hard to imagine why the rather poor-performing AN/ARC-60 would be
used in *any* critical application.  The 1950s AN/ARC-48 provided four
UHF-AM crystal-controlled (transmit AND receive) channels at higher output
power (2 watts vs. 0.5 watts) and with a much better receiver all in one
unit (RT-307/ARC-48) that is about the size of a "command set" transmitter.
Its DY-125/ARC-48 is about the size as a Type 12 dynamotor.  But, the
AN/ARC-48 was a US Navy set.  (It's not rare...I've come across two of
them in the past ten years without looking for them.)

> I can't imagine a lighter military VHF installation than the ARC-60...

Of course "VHF" is a correct description for the AN/ARC-60 and AN/ARC-48,
which operate well below the official UHF boundary of 300 MHz.  But both
function in the lower part of the "UHF-AM" military aircraft band.

The AN/ARC-60 is "UHF-AM" only.  Its R-508/ARC (R-19) VHF receiver *always*
gets its input from the CV-431A/AR (TV-10A) "UHF"-to-VHF-receive-converter/
"UHF" transmitter.  An AN/ARC-60 often used two CV-431A units for 16 channel
capability.  The CV-431A converter front-end has no amplification...it is
simply a mixer diode and local oscillator chain.  It is a damned poor "UHF"
receiver.  The AN/ARC-60 also requires a few more odds and ends (O-423/AR,
RE-275/AR) with associated cables, plus a MC-215 tuning spline, than does
the more elegant AN/ARC-48.  There id little or no substantive weight or
volume advantage for the AN/ARC-60, but a lot of performance and ease-of-use
advantage for the AN/ARC-48 (no receiver tuning cranks!).

> Also no doubt every Type 12/ARC-60 installation, civilian or military,
> had 121.5 MHZ.

The AN/ARC-60 does not cover 121.5 MHz.  It is possible that a generic Type 12
system could be configured for both VHF and "UHF", but it would not be the
"UHF"-only AN/ARC-60.

Around 1960 the earliest versions of the AN/ARC-51* UHF command sets appeared.
Although a little larger and heavier than the sets mentioned above, they weren't
distressingly so.  They provided 1750 or 3500 channels, 20 watts output, and
required 28 vdc input.  Everything but the control panel and the antenna were
in one unit.  There would be little reason that an early AN/ARC-51* would not also
have been ideal for U-2 service.  (The last version was the AN/ARC-51BX from the
Vietnam era.  Doubtless it was the most common UHF command set of that era.)

I don't know what the CIA/USAF U-2 aircraft used.  Some may indeed have used the
AN/ARC-60.  But there were much better alternatives.  I'm sure that the USN
AN/ARC-48 was *not* used, though there doesn't seem to be a real good reason why.
But the AN/ARC-51*...it was USAF and US Army and common.  It seems a possible
candidate.  By late-1960s, the first AN/ARC-116 3500-channel all-in-the-control-
panel UHF sets were out.  The complete radio set consists of the control panel
unit and weighs well under ten pounds.  That would be a natural. 

The AN/ARC-12 is a post-WWII U.S. Navy 10-channel crystal-controlled UHF-AM
set whose RT-58/ARC-12 could directly replace the VHF RT-18*/ARC-1 in the
existing mount to convert an aircraft from VHF to UHF with no further
alteration except the antenna.  The A.R.C. Type 12 is related in no way to
the AN/ARC-12, but one occasionally finds some websites and old ham magazine
articles that confuse the two systems.  Doubtless there would be more
confusion if there were a significant ham population that cared about this
stuff any more.  :-)
 
73,
Mike / KK5F