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7038RE: [wsjtgroup] Need help with decode problem on my end

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  • Russ K2TXB
    Mar 3, 2010
    • 0 Attachment
      Hi Bob. The obvious answer that comes to mind is; are you sure the signal you are trying to decode is on frequency?  If the signal is 400 Hz or more off frequency it is unlikely or impossible to decode.  You need to study the peaks of the spectrum that WSJT shows in the small window at the upper right corner.  If the signal is tuned in 100% correctly then the peaks will all be directly below the four yellow lines at the top.  If there is a tuning error the peaks will be shifted one way or the other, showing how far off frequency the signal is.  WSJT can handle small tuning errors (less than about 200 Hz) with little difficulty.  Even errors between 200 to 400 Hz can be handled, but with increasing difficulty.
      If the signal was 441 Hz off frequency then you would see the peaks lining up with the yellow lines - except that the lower peak or the upper peak would be missing.  That indicates an extreme tuning error and you will have to retune your receiver before the signal can be decoded.  And of course, you cannot ever decode the signals received before retuning, even if you saved them in .wav files.
      Once the signal is close enough for WSJT to start decoding, you can see the frequency difference as the DF value in the textural display.  You should usually adjust your receiver's RIT control to reduce DF to near zero on future receptions of that signal.  It's easy.  If DF is reported as -250 then simply reduce your rx frequency by 250 Hz with the RIT, etc.  WSJT may well decode the signals even if you don't do this, but it will suffer a loss of sensitivity and weak signals may not be decoded.
      Once you get used to operating FSK441, you may develop a sense of what the signal is supposed to sound like.  Then you can recognize when a signal is off frequency by the sound - and quickly adjust the receiver by the approximate amount required.  I'd also like to point out that it is almost always a bad idea to use the main tuning dial to adjust your receive frequency.  If you do, of course, it changes your transmit frequency too.  But it may very well be the case that the other station has already heard you and adjusted his RIT accordingly.  If you change your transmit frequency you will "screw him up".  If you recognize a frequency error before you start transmitting it might be a good idea to adjust both receive and transmit frequency to compensate before starting.  But I have seen circumstances where even then it is a bad strategy.  (Consider that the station at the other end suddenly realizes his VFO is set wrong and corrects it. - better then for you to be on frequency.)
      You said the received signal was very strong.  Does that mean the pings or bursts were very strong, or are you hearing him directly (not via meteors).  If you have a direct signal that you can hear all the time then FSK441 does not usually decode it very well.  This is by design, as FSK441 is designed only for meteor scatter communication and is optimized for signals that arrive in short bursts.  You can try clicking on various portions of the displayed signal.  Each time you click, FSK441 will attempt again to decode, at the frequency indicated by the mouse position.  By trying various positions it is often possible to make FSK441 decode even very strong signals.  But sometimes strong signal receptions can be impossible to decode.
      Hope this helps,
      73, Russ K2TXB

      From: wsjtgroup@yahoogroups.com [mailto:wsjtgroup@yahoogroups.com] On Behalf Of Bob KD7YZ
      Sent: Wednesday, March 03, 2010 10:22 AM
      To: WSJT
      Subject: [wsjtgroup] Need help with decode problem on my end


      I was trying to work FSK441 with W3XS this morning. I've tried before.
      I've heard him in skeds before on 6m.

      No time do I ever decode an obviously *strong* signal. He's usually so
      strong here that I need to back down the "Ex" control on the
      SignaLink-USB device.

      Today I even re-loaded the wav files to see if I could teach myself how
      to decode them. No luck.

      As a test, I used the "Sample" wav files and they decode nicely.

      If anyone wants to help, I can email one, or more, of the wav files
      from today. Maybe someone can decode and then tell me how to configure
      the WSJT7 here " mo betta " than I have it now.


      Bob KD7YZ EM88ii

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