[GreenKeys] Old Army Portable Communication Truck

[WA5CAB at cs.com]

AN/ARC-58 and AN/TRC-75 (Collins 618C) are apparently the early mobile ISB 
rigs.  Mechanical filters in AN/PRC-47 are the same as the LSB filters in 
those two sets.


In a message dated 02/05/2012 19:42:38 PM Central Standard Time, 
duncanancy at earthlink.net writes: 
> Roy,
> 
> I don't remember seeing anything in the AN/GRC-46 manual about 
> simultaneous voice and RTTY and was surprised at the mention of it in 
> the film.  But the T-195 is AM and you could probably talk and send RTTY 
> at the same time (the T-195 used true FSK).  On the receive side, you 
> might hear a little low frequency "hum" from the FSK; and the FSK 
> converter (being FM) would strip off most of the AM and probably copy 
> the TTY signal OK.  The voice "circuit" was probably just used for 
> "order wire" while the TTY was the major circuit.
> 
> This was before the Army had SSB radios and ISB was not typically used 
> in tactical communications systems.  The AN/GRC-46 was replaced starting 
> in the mid /late 1960s with the AN/GRC-122 &-142. It was SSB and was 
> modulated by an AFSK signal for RTTY. It did have a "Voice plus TTY" 
> mode.  It was done by using 85 hz shift at the high end of the audio 
> spectrum (around 2800 hz as I remember). But no ISB.
> 
> have fun,
> 
> Duncan, K2OEQ
> USASA 31J
> 

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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