[Milsurplus] RAX nix surveillance

[Mike Hanz]

On 10/30/2010 12:23 AM, Hue Miller wrote:
> BTW, somebody step forward and suggest a scenario where in WW2, signals
> intelligence was performed at HF from aircraft. Oh- monitoring German tanks?
> Well, some did operate in the 24-25 Mc/s range for ground-air coordination,
> but most of their traffic was in the 27-up frequencies. So, where were the RAT
> and RAV and RAX receivers used like the BC-787 / S-36 ? C'mon, i'm dying to
> know. Oh - i just thought of ONE example - in which case there was a motor-driven
> wobbulated plugin TU for the BC-375. But - this still didn't use RAX's etc. as the
> receiver.

In my Summary Technical Report of Division 15, there are only a few 
brief references to HF signals collection work from aircraft, such as an 
investigation by the 20th Bomber Command into the Japanese fighter 
control networks (which concluded that they were not very good, in 
contrast to the German networks which were superb.)  In general, the 
powers that be gradually came to the conclusion that airborne collection 
at those frequencies was best limited to detecting and characterizing 
such networks, and of course tactical jamming of ground communications, 
which moved ever upward in frequency as the war progressed.  But in 
1940, pretty much everything was below 30MHz, so the acquisition of the 
RAX probably made sense at the time.  There was a plethora of aircraft 
based ground communication jammers designed for use by both the Navy and 
Army beginning in about 1943, and some of it went down to quite low 
frequencies, including several using the GO, ATA, and ATC that were the 
equivalents of the one you mention for the BC-375.

Equipment problems probably limited some intercept work.  I found this 
snippet in the operational section on efforts in the Southwest Pacific:

"A limited program of airborne communications intercept work was carried 
on in the 21st Bomber Command.  ARR-5 communications receivers and disk 
recorders (later replaced, in part, by wire recorders) were available in 
quantity.  Lack of the ARR-7 until the summer of 1945 necessitated the 
use of the BC-348 communications receiver for frequencies between 5 and 
15 mc.  The quality of the recordings made was never very good; this was 
due both to the lack of experience on the part of the operators and to 
equipment limitations, and the program yielded little in the way of 
usable results."

At any rate, the trend toward the end of the war was that ground forces 
did their own thing, and airborne efforts focused on radar and aircraft 
protection.

  - Mike