[RTTY] software question

[Kok Chen]

On Apr 6, 2012, at 10:11 AM, Ed Muns wrote:

> But, if you are tuning the band
> with AFC enabled you will likely be transmitting off-frequency unless you
> disable AFC or enable NET which is a second function in MMTTY that also
> moves your transmit audio tones to match your received tones.  This, of
> course, only works with AFSK transmission which is one of the advantages of
> using AFSK instead of FSK.

Transmit frequency agility is easiest to implement in AFSK.  As Ed mentions, you simply match the transmit tone pair to the receive tone pair. 

However, the use of transmit agility is not restricted to AFSK.  It can also work on FSK.

As long as you have CAT capabilities to offset tune the transmitter, you can implement transmit agility in FSK.  Many transceivers have the ability to apply XIT through CAT.  With the transceivers that don't, you can use A/B VFOs.  

With FSK, the VFO offset stays fixed at the 2125/2295 pair, instead, you change the RF synthesizer by the amount you wish to move.  Just send the CAT command right before you commence transmission.

73
Chen, W7AY