[Elecraft] RTTY filter for K3

[Lyle Johnson]

> Yes but it won't change the center fq. to 1500Hz so it will be like DATA 
> A. I'm not sure what the purpose of changing the pitch is.

DATA A is a general purpose mode. It is SSB with some features that 
could cause distortion (like the speech processor) disabled.  It is data 
mode agnostic: you can run RTTY, PSK, Olivia, DRM, ...

We also put some specialized modes under the DATA umbrella.  AFSK, FSK D 
and PSK D are the current ones.

AFSK and FSK D assume you are probably running RTTY, or at least an FSK 
mode with similar data rate and the same shift.  The dual tone filter 
(DTF) is thus available for AFSK and for FSK D, but not for DATA A or PSK D.

The reason for the various tone pairs is that some of you will likely 
want to run an external decoder and/or encoder (MTTY, or HRD+DM780, for 
example) and these programs often assume certain standard tone pairs 
will be used.  We put the most popular of these as selectable pairs.

73,

Lyle KK7P