[GreenKeys] True FSK vs AFSK

[Ralph Mowery]

The part about running audio rtty into a ssb transceiver and class C is not really true.  As only one tone is present at a time a class C amp can be used.  

Ralph ku4pt



All this assumes that the tones are pure and the transmitter is not over driven.



-----Original Message-----
From: greenkeys-bounces at mailman.qth.net [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Richard Knoppow
Sent: Saturday, February 05, 2022 3:26 PM
To: greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] True FSK vs AFSK

     However, AFSK is really a shifting signal at audio 
frequencies that is beat up to some RF frequencies via the 
transmitter. If the transmitter is not adding distortion the 
output will be exactly the same in either case.  The problem is 
the extra circuits of the AFSK can add distortion products.
    Someone pointed out that a FSK transmitter can run in Class-C 
with somewhat higher efficiency. The power gain is probably not 
very great. The advantage of AFSK for an SSB transmitter is that 
it is simpler to implement for the transmitter itself.