[RTTY] Omni and FSK now working!

[Nat Davis <ndavis@vt.edu>]

Many thanks to all of you that replied to my Friday post about trouble I 
was having getting FSK to work on my Omni VI. The response was overwhelming 
and very helpful.....

Friday  night I tried again....  I brought up MTTY on the Omni and selected 
the "reset to default values" option to clear anything that I might have 
done (wrong) in setting MTTY up.  I then followed several of your 
suggestions about which options to enable and, more importantly, which to 
turn off!

As a test, I verified that I could (still) send and receive AFSK from/to my 
Omni and my 817 that was also running MTTY but only in the AFSK mode.  This 
worked like a charm.

I then put the Omni in the FSK mode and changed the MTTY option  to send 
FSK via the TxD serial output line.  In order to zero beat to the 
transmission of the 817, I had to change (lower) the displayed freq on the 
Omni by 2.125 KHz.  This is because the 817 in the AFSK mode displays the 
LSB suppressed carrier frequency -- so does the Omni in that mode.  When 
switching to FSK, the Omni displays the _mark_ frequency -- which is 2.125 
KHz below the LSB mode's carrier frequency.  Once I made this frequency 
change on the Omni, it was zero beat to the 817 and both rigs tx/rx RTTY 
with no problems.

Next, I tried a "real" QSO.  I talked to a op in Pennsylvania and was dead 
on his tx frequency.  No problems what so ever.  I was happy as the 
Omni/FSK seemed to be working.   On Saturday before the ARRL SS contest 
took over the CW/RTTY bands, I made a long QSO to a ham in Mississippi.  We 
had a long discussion about my signal.  He confirmed I was zero beat to him 
and had a fine sounding signal.....  My conclusion is that what ever was my 
problem before, it was gone!

The only thing I can think of that might have been the problem with my 
being off frequency (not zero beat) during my QSO with XE1L Thursday night 
was that MTTY may have been set in the AFC "on" mode at some point during 
or before that QSO.  AFC being on would have permitted my receive frequency 
to drift away from the Omni's fixed transmit frequency.   So while I 
correctly tuned in XE1L thinking I was zero beat, my transmit freq could 
have been off.

I do not recall if AFC was on or not during the actual QSO with XE1L, but I 
know it had been on at some point before I made the QSO.  On Saturday, I 
found that even if you turn AFC "off," if it had allowed the receive 
frequency to drift, that drift is not reset unless you hit the "ham" button 
after you disable the AFC!

Several of you asked about my TxD to mark/space input connection.  I am NOT 
using the transistor interface that seems to be the standard 
expectation.  The Omni does not require the transistor interface (a similar 
interface is actually built in to the radio itself).  If you try to use 
this type of interface, your RTTY signal will be "reversed" -- one of the 
problems I discovered earlier last week.   Instead, I followed suggestions 
from this list and connected the TxD output of the serial port through a 
10K ohm resistor and then directly to the mark/space input on the 
Omni.  This works just great!

At this point, it looks like my Omni with MTTY and Writelog is now FSK 
capable.  I'll give it the real test next weekend by trying my hand at the 
WAE RTTY contest.

Thanks again for all the suggestions and offers of help!

73,

Nat Davis
N4EL

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