[Milsurplus] ATD

[Mike Morrow]

I wrote:

>> ... I believe that the AN/ARC-8 was the best WWII-era airborne 
>> HF set in the world. ... Some active service USAF utility aircraft
>> still carried the AN/ARC-8 in 1970!  

Dave wrote:

> What do ya'll think of the late PB4-Y installations that used
> the ART-13 with a set of three RAX receivers?
> I was thinking of changing my complete AN/ARC-8 station 
> over to this one, just because it looks "cooler." ;-).

I think they would have been better off with BC-348 receivers.  Logistically one BC-348 would be easier to support than three failure-prone separate receivers, and the installation itself would take up less volume and weight.

The RAX gear is definitely cool in a 1930s sort of way (just like the RU/GF gear).  That makes it seem like an anachronism when paired with such an "ahead-of-its-time" set like the ATC.  In addition, for any given HF frequency covered by both the BC-348 and a RAX, I believe that the BC-348 would the superior performer.

You know that if you convert from an AN/ARC-8 to that PB4Y set, you'll need to get an ATC rather than a T-47A/ART-13 to make the spirits smile upon you.

A technical plus for the USAAF's AN/ARC-8 is its improved transmitter, the T-47A.  A vernier scale above the MF/HF VFO dial A allows the dial to be set in 0.1 minor division increments.  Thus, the T-47A calibration book contains cal data at 1 kc intervals throughout the entire frequency coverage range up to 18100 kc.  The ATC or T-47, in contrast, has no vernier, and the cal book data is supplied only at 1, 2, 5, or 10 kc increments as the frequency increases.

The AN/ARC-8 (like the SCR-287) uses an external MONITOR-NORMAL switch which disconnects the audio sidetone and retains HV on the receiver so that the transmitter can be netted in MONITOR, or restores normal HV-removed muting with audio sidetone in NORMAL.  USN sets, AFAIK, almost never employ any receiver muting other than grounding the receiver antenna post during key-down.  (The ARA and later versions of the command sets are the worst in this area.  On transmit, a modulator-generated sidetone is connected to the receiver audio output bus and the operator has no way of determining what's actually coming through the receivers at key-down.)

In short, its easy to see why the AN/ARC-8 had such long service life.  To me, it looks as cool as a bank of RAX receivers, not to mention how damned hard it is to assemble all the hardware for a proper CG-46115/6/7 RAX installation.

73,
Mike / KK5F