[GreenKeys] rtty reception woes

[gil smith]

Hi folks:

Well, I finally got my Kenwood TS-430S -- not that I have much time to play
with it, since we are moving (again) this month.  But I did spend a few
hours last night trying to fing some rtty signals.  I downloaded mmtty,
read up enough to hook it up, and poked around the spectrum.  Please recall
that rtty is entirely new to me, and I only sorta know what I am doing.  I
got a live demo from Larry the other day and saw mmtty in action, as well
as a TU driving his 28, so I'm rather excited to dig something out of the
air myself, especially when the Dovetron gets here.

I don't have an owner's manual for the 430, and a service manual CD I
ordered is not here yet.  I poked my scope probe on all the rear-panel
connectors, and even the mic connector, to find a fixed-level audio out --
none to be found.  So I put a Y-cable in the external speaker jack, hooked
up headphones, and a cable to the pc input.  It was still variable-level,
but I was able to adjust for a decent level on mmtty's display and still
hear the signal ok on the phones.

I tried most of the freqs recommended by folks lately, especially the ones
that Larry has had good luck with locally, but none seemed to have a decent
signal.  Of course, this is mostly due to my late-night last-minute
antenna:  a wire attached to my garage door frame (frame had better signal
than just the wire).

Anyway, as I twiddled around, I did find a few signals that sure seemed
like rtty.  The problem is, I never saw anything but garbled text, even
though I could get a decent signal on the displays.  That is, I could get
mark/space peaks on the fft display, select the appropriate shift, and see
a decent xy pattern.  I tried both AFC off, manually fine-tuning the peaks
to the mark/space bars, and AFC on, where it appears that mmtty shifts the
freq domain to maximize the signal peaks (which is quite a cool use of
software).

So, having tuned in a signal, it seemed that the only other parameter to
adjust would be the baud rate.  Based on what people have told me, on 170
Hz shift signals, I would expect 45.45 baud, and on 850 Hz shift signals, I
would expect 75 baud.  But varying baud rate still left garbled text on the
screen.  What am I missing?  Is there something else to tweak on mmtty?  I
tried reverse m/s as well.  Is this stuff coded differently?  Here is the
only activity I found (I am in Arizona):

 freq     signal  shift   baud     text
7.58121    fair    170    45.45?   garbled
7.59515    good    850    75?      garbled
7.45614    fair    850    75?      garbled
6.45163    good    850    75?      garbled

I also found a 170-Hz signal (forget where) that was not keyed constantly;
in fact it was keyed at a periodic rate of about a second on, three seconds
off.  Does that make any sense?

mystified yet intrigued,

gil



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