[Elecraft] K3 and Datamodes

[Vic K2VCO]

Julian G4ILO wrote:
> On 6/5/07, FISCHER,GREG <ab7r at cablespeed.com> wrote:
> 
>> I believe the only time you will need some other external
>> interface would be for true FSK.  The line for this is on
>> the ACC connector and should be keyed via an open
>> collector at less than 5 volts.
> 
> Why would one want to use true FSK if you are using for receive a
> modern datamode program that is capable of AFSK anyway? With AFSK you
> can net on a station by clicking on the waterfall. With FSK you have
> to tune the radio to the exact frequency.

I must be missing something. I thought AFSK was an FSK signal produced 
by feeding an audio tone which is switched between mark and space 
frequencies to an SSB transmitter, resulting in a single RF carrier 
whose frequency changes.

This signal, if the tones are clean sine waves and the transmitter has 
good carrier and opposite sideband suppression, should be *identical* to 
a 'true' FSK signal, which is produced by varying the frequency of a VFO 
in the exciter.

If you mean that it's easier to tune an AFSK signal that has some 
residual carrier, that's a poor signal.
-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco