[RTTY] MMTTY, permanently disable AFC

[Bill Turner]

ORIGINAL MESSAGE:          (may be snipped)

On 6/17/2014 8:19 AM, David G3YYD wrote:
> It
> is essential to have Net off when Running so your TX frequency does not
> wonder and Net on for S&P so you transmit on your receiving frequency.

REPLY:

That's true only if you're using AFSK. If you're using FSK, Net has no 
effect at all, and AFC should be on only when running. A further 
complication with MMTTY is when AFC is on, the Mark tone tends to wander 
around with no signal present. This can be a problem when S&P'ing 
because as you tune across the band with AFC on, it will reach out and 
lock on to a signal before the signal is correctly tuned in. As a 
result, you stop tuning and now your TX frequency is off. I see this 
happen on every contest.

The solution if you are using MMTTY with FSK is this:  On the DI window, 
under Setup>Settings, you will see a column of check boxes in the upper 
left corner. Two of the lines start with "MMTTY". Be sure both of those 
check boxes are checked.

On the other hand, if you are using AFSK, all you have to do is be sure 
both AFC and NET are on when S&P'ing, and when running, AFC is on and 
Net is off.

Complicated, I know, but if you don't get it right your TX and RX 
frequencies will be different.

AFC is actually a leftover from the days when rigs were crystal 
controlled and the crystals were never quite zeroed with each other. 
With modern VFO rigs, AFC really should not be needed at all if everyone 
tuned signals in correctly. If in doubt, leave AFC off at all times,  
get your manual tuning correct and use RIT when needed.

73, Bill W6WRT
dezrat at outlook.com