[GreenKeys] tapping ST-6 for RS232

[WA5CAB at cs.com]

OK.  After looking at the ST-5 schematic, I now understand.  It's a minor 
terminology error or truncation that has crept into the standard vocabulary.  
Like saying or writing kilocycles instead of kilocycles per second.

The ST-5 schematic output intended to go to the transmitter is labeled "To 
FSK, AFSK".  What he means is "To FSK, AFSK Keyer, Generator, Etc.".  In the 
case of FSK at the time, that line would probably have been run to something like 
the simple diode and a few other components modification that was commonly 
applied to CW transmitters or VFO's that didn't have built-in FSK capability.  I 
once used the circuit in a modified rack mounted BC-221 to drive a BC-610-F.

FWIW, although I don't know how it's done in current sets, when both military 
and civilian rigs began showing up with SSB or ISB capability, the most 
common method of generating FSK output to the antenna became to inject an AFSK 
signal into one or the other of the sideband channels.  Which had the advantage of 
not diddling with the RF generating circuits at all.  This in turn led to 
some oddball ways of designating the operating frequency.  At least on the 
military side.

I'll fade back into the woodwork now, my curiosity satisfied.

In a message dated 1/26/2009 1:08:18 PM Central Standard Time, k0bx at arrl.net 
writes: 
> I am the first to admit that I am more of an operator than a technical 
> person.  But maybe WA5CAB is referring to more commercial equipment instead of 
> the popular ST-6 series that was used in Ham Radio.
> 
> Here is a link to RTTY.Com and shows a clear diagram on how the FSK was 
> generated from the current loop.  This is from a ST-5.  The Hal ST-6 uses the 
> same circuit.  In the ST-5 circuit it show that the FSK output would go to the 
> transmitter or AFSK keyer.
> 
> Back then, most commercial made ham transceiver did not have the ability to 
> operate FSK.  So we used AFSK on both HF (LSB) or VHF.
> 
> http://www.rtty.com/development/tu/st-5/st-5_basic.htm
> 
> Joe K0BX
> 

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