[Elecraft] MMTTY FSK

[Lyle Johnson]

> ...In my setup I can switch back and forth 
> instantly between FSK and AFSK. I have done some testing with a second 
> receiver, and my K3's RTTY signal seems to be cleaner in AFSK than FSK 
> (lower odd-order sidebands).

The K3 uses continuous-phase switching between the IF (and AF monitor) 
tones, but no shaping, in FSK.  The Tx signal passes through the 2.7 (or 
2.8) kHz IF filter, of course.

During AFSK operation, the audio passes through some AF filtering as 
well as IF filtering.

The K3 also has an AFSK Tx Filter that can optionally be switched in 
(CONFIG:AFSK TX FIL ON|OFF, default is OFF) which provides a much 
narrower AF filter centered on the RTTY tones (using the FSK PITCH 
control).  If you choose to use this filter, be sure your software is 
set up in a fixed pitch mode, and not "click the waterfall" or "AFC ON" 
where your Tx tones could be anywhere in the wider audio passband as 
defined by the waterfall display.

73,

Lyle KK7P