> There is an internal pull-up resistor on the FSK shift line, so
> grounding and opening the shift pin should produce a shift in the
> carrier frequency (either use a Mic PTT or the MOX button to key
> the rig).
Yes, the SHIFT pin is the FSK input. Based on suggestions from the
RITTY/K6STI manual, I ran my 1000MP and later, the MARK-V with just a 1-K
resistor in the line between the COM port FSK output and the RTTY shift pin
(no transistor, optoisolator etc) - worked VY FB.
I don't understand why Chen is suggesting using the Mic PTT or MOX button
instead of the RTTY connector PTT pin or just using rig control PTT.
Another thing to note with this rig is that the PACKET (AFSK) and RTTY (FSK)
connector PTT pins are in parallel - Depending on how you make your cables,
you can save a PTT line. (You don't need separate PTT lines for AFSK and
FSK). 73
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