[KG3V] RTTY Transmissions Off-freq with MMTTY
 

Kg3v Ham Radio Blog

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RTTY Transmissions Off-freq with MMTTY

Posted: 25 Feb 2018 11:32 AM PST
https://kg3v.com/2018/02/25/rtty-tra...eq-with-mmtty/


I participated in the NAQP RTTY contest this weekend. I normally use 2
radios in contests. In this one, I setup for RTTY and started the contest.
Nobody could hear me with one radio (IC-7600) using an all-band
dipole/doublet that normally works quite well for US contacts. The Radio
was setup using N1MM+ with the common MMTTY RTTY Engine. I have used this
several times in the past, and it worked well. Not this time.

I stopped and took a few minutes to see what the problem was. The other
Radio, an FTDX-3000 was working fine. The difference between the radios is
that one was using true FSK and the other was using AFSK from an internal
sound card. The IC-7600 was using the AFSK, Since I only have the USB
interface to the radio for RTTY, I cannot use the internal FSK demodulator.
I finally discovered that my Transmit frequency was offset from the Receive
frequency. To use AFSK, I set the Receive Tone frequency to 1445 Hz instead
of the actual 2125 Hz used in true FSK. But when I would transmit, the Tone
appeared to change to the default 2125 Hz, and I could see no way to change
that setting.

I ran the contest with one radio for a while, but also pulled-up some MMTTY
documentation. Buried far down in the document was a comment that you must
turn ON the NET button in the dislayed MMTTY Engine screen if you are using
AFSK and want to Transmit and Receive on the same frequency. Â* Well, I cant
imagine anyone using AFSK RTTY that would not want to do that, and I doubt
that I ever changed that button setting (on purpose). So I clicked the
button and got back to two radios.

The one benefit of this problem is that I took some time and read the MMTTY
documentation. I also discovered that you can click and grab not only
callsigns, but exchange information (Name and State/Province in this
contest) using the mouse. That really speeds-up the RTTY contest QSOs.