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RE: [wsjtgroup] Lyrids activity "Mode for RH"

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  • Randy Tipton
    Question: I was under the impression that as long as DF is less than 50% of Tol, adjusting RIT to minimize DF makes little difference. Is this not the case?
    Message 1 of 4 , Apr 23 6:27 AM
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      Question: I was under the impression that as long as DF is less than 50% of Tol,
      adjusting RIT to minimize DF makes little difference.  Is this not the case?

       

      Snip: from the manual …In the FSK441 and JT6M modes, if DF lies outside the range ±100 Hz it will help to retune

      your receiver to compensate. Do this with the RIT control, or by using split RX/TX VFOs.

      In general you should not change your transmitting frequency during a QSO, since your

      partner will be trying to tune you in at the same time.

       

      Bob I always set the Tol on 100Hz after adjusting the RIT for the offset for FSK441 modes. Actually with six meters I

      generally start off with the Tol set to 200Hz since most six meter rigs are closer to each other in frequency.

       

      Bob, if you are on Saturday before random hour or right after six meter random hour I would like to work some back-to-back qso’s using modes B & C on six meters for comparisons.  

       

      Tip

       

      -----Original Message-----
      From: Bob Poortinga [mailto:bobp+yahoo@...]
      Sent: Thursday, April 22, 2004 5:07 PM
      To: wsjtgroup@yahoogroups.com
      Subject: Re: [wsjtgroup] Lyrids activity "Mode for RH"

       

      "Tip" <wa5ufh@...> writes:

      > When you first received a decoded message at 05:19 and the DF was down
      > 180 Hz to improve copy I think it helps to immediately adjust the RIT to
      > -180 Hz and quickly reduce the TOL setting to 100 Hz.  The next ping you
      > receive will then show a DF very near zero and the decoded text should
      > be much better. Also if you're using single tones it will place the
      > tones on the appropriate "TIC" marks on the displays.  I know some
      > operators never make adjustments to the TOL / RIT but it does help.

      I was under the impression that as long as DF is less than 50% of Tol,
      adjusting RIT to minimize DF makes little difference.  Is this not the case?

      > The next issue is which mode is best for "Random Hour". As you know
      > FSK441B is being used for two meters and FSK441C is being used on six
      > meter random hour. These selections may not be the best mode for each
      > band during random hours. I have noticed that longer pings like the ones
      > you posted from WD4KPD sometimes don't give both calls especially if it
      > also has the reports embedded with calls. But I have experienced that on
      > mode "A" before also especially on two meters where the width is
      > generally narrower.

      My understanding of the newer modes is that Modes B & C use Reed-Solomon
      encoding to provide forward error-correction.  The amount of error
      correction depends on the number of redundant symbols in the stream.
      Mode C has more redundancy than Mode B and therefore provides better error
      correction.  On the flip side, more redundancy means a lower overall
      data rate so Mode C is slower (contains less data per time unit) than
      Mode B and Mode B is slower than Mode A.  At this point, Mode B seems
      to work best with the conditions I have been experiencing on 6m lately.

      Here are some (unedited) decodes from last weeks Random Hour (FSK441C):

      150331  7.4  200  4  2 -139     Q W9SE CQ WD/
      150531  5.6  100  3  0 -107      K1MAM7
      150631 17.7  120  6  5   49     S2$2TX 8
      150631 19.9  320  6  5  -92     K8MD CQ K8MF RQQQMMX4
      150701  8.2  320  3  1   12      W9SE WA5UFHV8KLYURG#
      150731 21.3  220  3 -1  -86     9SE CQ W9S3 ZB
      150731 27.6  120  2 -1  -85     K8M1 C46
      151001 19.2  120  3 -1    3     E WA5U.V
      151431 12.4  280  3  0  -60      W3KWH CQ W3KWH CQ
      151431 16.0   80  3  0  -55     3KWH H
      151531  7.6  160  3 -1  -74     K8MD CQ T/3
      151731 15.2  180  2 -2  -74     K8MD #Q $8MT
      151731 17.6  440  4  2  -93     D CQ U,WD CQ K8NTMW4 GFMW 65
      151731 18.3  100  4  1  -88      CQ K8W
      152230 22.0   60  3  0  -70     K8MD
      152230 28.9   80  5  3  -79     K8MD .
      152330 16.8  100  3 -1 -126     E CQEJL
      152330 17.6  180  3  0 -130      W9SE CQ/MQD

      Notice that most pings are less than 300ms and many are less than 150ms.
      These shorter pings rarely decode the entire message and the longer ones
      sometimes don't give much more.  For these conditions, I believe that
      Mode B would be a better choice than Mode C.

      > Myself, I prefer the modes B & C but do not like the Sh messages. I
      > could use my ears before but with Sh messages I don't have a clue what
      > is sent until it decodes or I see  the tones in a display.

      Yes, one can easily hear ST pings and our ears can tell the difference
      between birdies/QRM and a ST message.  However, WSJT has problems decoding
      birdies/QRM in FSK441A even with Zap checked.  There are also other issues
      with ST messages especially when a CW station (or CW ID) comes on
      frequency.  So I like the SH messages better than the ST ones.  The one
      thing that ST has going for it is the low signal level needed for a
      decode.

      > I am not stuck on any particular mode but would like to get some
      > agreement / more data before changing. The unknown is; will Joe keep
      > FSK441A as part of WSJT and what other new modes are coming for
      > evaluation?

      Good question.  I think FSK441A is still useful in some situations.

      In addition, I really, REALLY, **REALLY** wish that WSJT would not clear
      the decode window when switching between FSK441 modes.

      73 de
      --
      Bob Poortinga  K9SQL
      Bloomington, Indiana  US


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