[Milsurplus] Odd AN/ARC-27 box

[Mike Hanz]

William Donzelli wrote:

>I have quite a pile of AN/ARC-27 control boxes (without, mind you, having 
>the RT unit), and one popped up that I have never seen before. It is a 
>dual place control box, used for putting two AN/ARC-27s in relay.
>Why would anyone want to do this? Why could the military not just 
>allocate one of the 18 channels on each to be the common frequency?
>

Hi William,
I may have misunderstood your question, but the voice relay concept 
originated late in the war in the Pacific theater, prompted by the need 
to relay VHF voice comms back to the carrier CIC from strike aircraft 
and others beyond line of sight range.  The fielded systems received the 
nomenclature of AN/ARC-18 and AN/ARC-28, but were actually two 
variations on a pair of AN/ARC-1s with a control box and a box with some 
relays and squelch detection tubes (12SL7) in it.  The ARC-18 seems 
similar to what you're describing, as it has channel selection knobs on 
it, where the ARC-28 required a pair of C-45/ARC-1 control boxes to 
perform that function.  The two systems worked with the AN/ARC-12 UHF 
transceiver as well, since all the system did was control the audio and 
PTT lines of each transceiver.  You'll note the type issuance on the 
later relay was one higher than the AN/ARC-27, which took another 6 or 7 
years to get fielded because of inter-Service bickering.   (So much for 
joint cooperation between the Army and Navy...)  At any rate, the 
November 1945 ARMN has an overview and circuit diagram of the ARC-18/28 
that I can scan that for anyone who needs it.  The control box shown in 
the ARMN (same size as a command set transmitter control box) doesn't 
match the one with my ARC-28, but I suspect there were variations over 
the years, as there certainly was for the ARC-27 control boxes!

>For that matter, why have so many channels? Did missions really involve 
>more than one or two channels (plus the G channel)?
>

Again, may have misunderstood the import of your question, but one of 
the big technology drivers for the ARC-27 was the capability for more 
channels - not necessarily to use on a single mission, but to reduce the 
thousands of hours of manual labor required to keep changing crystals 
and adjustments prior to each sortie.  The avionics techs must have 
sighed a big one when the ARC-27 finally became a part of the inventory 
- no fun out in a blinding rainstorm in a dripping radio space trying to 
change freqs on an ARC-1 or ARC-4.  As the defense of the carrier became 
more complex, with a CAP (and APS-4 picket planes, along with *its* 
relay aircraft), you began to have a lot of hardware up in the air, all 
needing comms back to the carrier.  Anyway, that's my take from the 
literature of the time.

Best 73,
Mike