[GreenKeys] RTTY in WW-II

[Duncan M. Brown]

Even in the 1950s/60s using R-390s there were apparently drift problems. 
In the AN/GRC-26D, the CV-116 diversity FSK converter used the IF out of
two R-390s and mixed them down to two separate low IFs (around 25KC & 85 KC
?).  The mixer oscillators were AFCed to take in any drift in the system. 
If the drift was more than it could accomodate, a doorbell inside the unit 
would ring to alert the operator to retune the system!!  It sounded like a
real doorbell, very loud. (I guess they wanted it loud enough for the
operator to hear over the TTYs and/or to wake him up!)  

  --Duncan


> [Original Message]
> From: Jim Haynes <jhhaynes at earthlink.net>
> To: Larry Tighe <larryradio at worldnet.att.net>
> Cc: <greenkeys at mailman.qth.net>; Jim Haynes <jhhaynes at earthlink.net>
> Date: 31-Dec-08 14:43:04
> Subject: Re: [GreenKeys] RTTY in WW-II 
>
> It seems like both audio and IF type converters were used.  The AN/FGC-1
> and the ones in the Press Wireless article use audio frequency, as does
> the one in the AACS article.  But there are plenty of examples of IF types
> as well, especially the Navy units.
>
> Certainly the BFO adds another source of drift.  I've seen a SP-600
> receiver that had external inputs for the main oscillator and also fo
> the BFO.
>
>
> jhhaynes at earthlink dot net
>
>
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