[RTTY] Trouble getting FSK to work

[Nat Davis <ndavis@vt.edu>]

Folks,  I am new to RTTY and this list.  I hope you can help me with a 
problem I am having getting FSK to work.

I use Writelog/MTTY to run RTTY with my Ten Tec Omni VI+.  AFSK with the 
radio set to LSB is no problem and I have made contacts and had lots of fun.

To avoid the hassle of setting sound card and mic gains, I want to use the 
"true" FSK mode on the Omni.  By a search of this list's archives, I found 
that the Omni does not need the transistor circuit interface on the serial 
TxD-to-mark/space FSK input line.  I built a cable last night that seems to 
work....

I tested my Omni FSK setup by using my FT-817 as a monitor.  The 817 was 
set to the LSB mode to drive MTTY on a second computer.

I set the 817 displayed frequency to 21.100 MHz.  I then set the Omni to 
the same display frequency and transmitted AFSK (to the dummy load) with 
the Omni in the LSB mode.  The 817 received it just fine.

I then changed the mode of the Omni to FSK (and selected FSK in the "misc" 
menu of MTTY).  In this mode, the Omni displays the mark frequency rather 
than the suppressed carrier frequency that it did when in the LSB 
mode.  For the 817 to "hear" the Omni, I lowered the Omni displayed 
frequency by the 2.125 KHz mark frequency offset to 21.097.8 MHz.  The 817 
copied my FSK signal just great!

Having passed this "test," I figured I was all set to go.  I switched the 
Omni to my antenna and found XE1L in Mexico calling CQ.  I tuned him in 
using the MTTY tuning indicator and then responded to his call.  He did not 
answer.  After a second CQ response, some other op came on and told XE1L 
that I was calling XE1L "off frequency" and suggested that "maybe his RIT 
is on."  XE1L tuned me in without changing his xmit frequency.  We made the 
QSO but XE1L  confirmed that he was receiving me off of his xmit freq and 
wondered what I was doing to cause it.   Darned if I can figure it out!!

My RIT was not on and I am at a loss to explain what was going on or if I 
was doing anything "wrong"  -- especially since everything seemed to work 
as expected when monitoring the Omni using the 817....

Can anyone offer me suggestions?

Many thanks.

Nat Davis
N4EL

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