[GreenKeys] re: rtty reception woes

[tony j. podrasky]

Hi Gil;

You have found the station that cranks me off the most!

The signals come BOOMING in, but are not printable.

I don't know what the mode is called, but they are changing speed,
changing shift, and changing bit patterns.

73,
tonyp / W6ESE ex-WA2EAA
NNNNZCZC

> 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


 
--
Tony J. Podrasky   Everyone knew that as time when by they'd get 
  tony.podrasky    a little bit older and a little bit slower.
       @                                                   JL/PM
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