[Milsurplus] A.R.C. Type 12 In ER #385, By VK2NO

[Mike Morrow]

Congratulations to Ray (VK2NO) on a fine article on many of the LF/MF/HF/VHF components of the A.R.C. Type 12 equipment.  It was the first article U read.  A lot of work was obviously devoted to it.

I suggest however revising the title and text to remove ALL reference to the AN/ARC-60.  All AN/ARC-60 installations use two CV-431A/AR Converter-Transmitters for UHF-AM military aircraft frequencies between 228 and 258 MHz.  As Ray states, the CV-431A/AR (TV-10A) is omitted from the article.

US Army TMs 11-5821-205-12 and -35 describe AN/ARC-60 major components as:

JAN Nomenclature (A.R.C. Type 12 Nomenclature)
-----
CV-431A/AR (TV-10A) Converter-Transmitter 228-258 MHz (2 used)
R-508/ARC (R-19) Receiver 118-148 MHz, 228-258 MHz with CV-431A
DY-86/ARN-30 (D-10A 24 vdc) Receiver Dynamotor
C-1917/AR (C-52) Control panel with 228-258 MHz receiver tuning dial and transmitter 16 channel selector
O-423/AR (K-13) Oscillator-Relay for whistle-through.
RE-275/AR Antenna relay, swaps AT-701 between two CV-431A
AT-701/AR  (A-16) Antenna
J-502/ARC (J-10) AF Jack Box
J-506A/ARC  (J-13A) System Junction Box
MT-1140/ARC (M-12A) Mounting for CV-431 and R-508 (3 used)
MT-1677/AR (M-24) Mounting for O-423

The above are the ONLY A.R.C. Type 12 components which may be claimed accurately to be part of AN/ARC-60.  Many other A.R.C. Type 12 components are assigned JAN "COMPONENT" nomenclature, like the R-11A (R-511/ARC) and T-11B (T-366A/ARC), but they are NOT part of AN/ARC-60.  In fact, JAN nomenclatured A.R.C. Type 12 components are NOT part of any specifically designated JAN "SYSTEM" except those few listed above for AN/ARC-60.

Because the AN/ARC-60 always uses the CV-431A/AR, none of the configurations described within the article qualify as AN/ARC-60.  I suspect there is little interest for the real AN/ARC-60 in Australia because there is no amateur operation allowed in the 220 MHz region.  Nontheless, it's an interesting system.  The CV-431A UHF receiver front end is nothing more than a 1N82 mixer diode and a crystal-controlled 110 MHz local oscillator chain...there are no other RF active components.  Regardless, the published sensitivity specs for the AN/ARC-60 and the very widely-used UHF command set AN/ARC-27 do not differ greatly.

A.R.C. Type 12 systems were installed in the T-34B aircraft at NAS Corpus Christi in which I took midshipman aviation indoctrination training 50 years ago.  IIRC the components had commercial Type 12 nomenclature on them.  (I could be wrong.)

A 1953 diagram appears in the January 1955 A.R.C. Type 12 instruction book that shows a Type 12 installation for an L-19 observation aircraft.  There is a R-11A, R-19, T-11B, T-13A, and C-37, which provides 10 crystal-controlled VHF transmitter frequencies from an 11-position switch.  The 11 eleventh position on most C-37 control boxes is marked FM.  From that position control is taken of a BC-1335-A (SCR-619-A) 4-watt two-channel tactical FM receiver-transmitter (27-38.9 MHz).  However, that is a 12 vdc radio in a 24 vdc aircraft so the diagram shows an adjustable voltage-dropping resistor used to produce 12 vdc for the BC-1335-A.  It's one of the most interesting of military Type 12 configurations.  Unfortunately the BC-1335-A lacks squelch, so that might have taxed the listener a bit.

There were at least a couple of other related commercial A.R.C. systems at the same time as the Type 12:

Type 11A:  (LF/MF receive, VHF transmit)
R-11A (0.19-0.55 MHz), T-11A (121-132 MHz), L-10 Loop (MF)

Type 17:  (VHF receive, VHF transmit)
R-15 (108-135 MHz), T-11A (121-132 MHz)

There is also a very late Type 12 broadcast band receiver...the R-22 with Control C-57.  It has both wire and loop antenna inputs but unlike the R-10A and R-11A, it is not designed to work with a VHF transmitter.  It is explicitly covers the entire post-WWII AM broadcast band of .54 to 1.6 MHz instead of the .52 to 1.5 MHz of all earlier versions (RAV CBY-46103, ARA CBY-46145,  BC-946-B, R-24/ARC-5, R-10A).  Mine was made for the USAF in 1958.

During WWII A.R.C. did not blaze new trails very successfully in VHF communications.  Its semi-experimental R-112, R-113, T-89, T-90/ARC-5 sets fell way below WECO's R-28, T-23, T-126/ARC-5 and never gained acceptance for regular deployment.  A.R.C. was able to salvage some of their VHF effort with post-WWII Type 11A, 12, and 17.

I suspect the R-10A and R-11A receivers would have been much more desireable to hams 60 years ago if they had BFOs.  The most important departure from war-time versions is that no Type 12 receiver has a BFO.

It is never without value when the A.R.C. Type 12 is discussed to remind people that it has absolutely no connection to the JAN AN/ARC-12.   Unfortunately many ham sources persist in incorrect stating that they are the same.  The RT-58/ARC-12 is an early USN 10-channel crystal-controlled UHF-AM command set.  It is the same size as the RT-18/ARC-1 USN 10-channel crystal-controlled VHF-AM command set.  Both use the same mounts and control panels.  An installation of the VHF AN/ARC-1 may be changed to the UHF AN/ARC-12 simply by pulling the 40-lbm RT-18 and inserting the RT-58 in its place, plus altering the antenna.  There's no relationship to A.R.C. Type 12.  Such confusion is strengthened when people write ARC Type 12 or ARC 12 instead of A.R.C. Type 12.  The latter usage make it clear that the A, R, and C combo before Type 12 is not the JAN "ARC".

I have accumulated Type 12 gear and information for more than 45 years.  I enjoyed Ray's article and I hope that it will stir up more interest in the neglected Type 12...at least enough to slow down the rate that landfills are absorbing them (and those who collect them).

Mike / KK5F