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Re: [wsjt-eu] ISCAT and JT6M

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  • Joe Taylor
    Hi Ken and all, With some concern that this may be starting to get repetitive, I ll try to respond to your main points. ... If my understanding of ISCAT usage
    Message 1 of 7 , Apr 6, 2011
      Hi Ken and all,

      With some concern that this may be starting to get repetitive, I'll try
      to respond to your main points.

      G4IGO wrote:
      > I find that most users don’t even try using the digital modes on very long
      > distance paths ( over 2000 kms) ... I
      > have yet to see any real long distance qso’s being made with ISCAT.

      If my understanding of ISCAT usage in EU is correct, how could you
      expect to have seen such QSOs?

      ISCAT hasn't yet been widely available during a northern hemisphere Es
      season. Nevertheless, even in the first few weeks of field tests I made
      ISCAT QSOs in the 3000-4000 km range. These QSOs were sub-audible, and
      they could not have been made with JT6M.

      > For myself I find that we are having more and more different modes coming
      > along for people to try – and see which is the best – ROS, whisper – Joes
      > portfolio etc.
      > We are in danger and submerging in “what mode is best for XXX opening, what
      > mode is better than YYY mode etc”

      This is one of the reasons that when demonstrably better modes appear,
      the modes they replace will (and should) eventually disappear.

      A WSPR QSO mode was tried and tested, but for a number of good reasons
      it never gained popularity. WSPR QSO mode has disappeared. The
      beacon-like WSPR mode is extremely popular for what it does; but it does
      not make 2-way QSOs.

      ROS? Does anybody use it? I really don't know. (I never found it very
      attractive, and some of its early claims could not be substantiated.)

      > I have tried ISCAT on MS and find it is no better or worse than JT6M for
      > most qso’s – which have not exceeded 1800 kms. I pass no comment on whether
      > is it or not better than JT6M – how can you judge – if the rocks aren’t
      > there then you can’t compare. I haven’t had ANY qso’s over 1800 kms on ISCAT
      > so again reserve judgement.

      A decision to move from JT6M to ISCAT was not made until after
      exhaustive tests -- tests under controlled laboratory conditions, as
      well as on the air -- had shown it to be clearly superior.

      If you have evidence to the contrary -- evidence, not "impressions" --
      please make it public!

      > The main gripe I have about ISACT, on MS, is that it doesn’t work well on
      > weak short bursts ( that also may contain a bit of Doppler) – whereas , as
      > above JT6M does – for me

      Then I think you haven't yet learned to use ISCAT effectively. ISCAT
      can work well with bursts as short as just about any that can be useful
      with JT6M. If the signal you're trying to copy is dominated by still
      shorter bursts, you should be using FSK441.

      This is important: all WSJT modes have benefited greatly by enhancements
      to the decoders made after someone sent me recorded files with signals
      they thought should have decoded, but did not. If you have any such
      examples, please send them to me as email attachments!

      > J. These short weak bursts that can be decoded by
      > skilled use of JT6M are the backbone of MS as described above. If the
      > digital programme being used only give full decodes and therefore requires
      > long bursts – then there is no fun in it for me - as others have also
      > indicated.

      Again: if you have not yet learned to get partial decodes from short and
      marginal ISCAT signals, then you're not yet up-to-speed in using ISCAT.

      I know, of course, that better "how-to-use" instructions would be
      helpful. I hope to get to that task, perhaps including some tutorial
      files, before too long.

      > It is a pity that JT6M was dropped as others have said from the later WSJT
      > and that also the timings could not have been altered to 15 and 30 second
      > periods, as I believe have been suggested in the past. If this were so then
      > we might be able to compare apple with apples and not pears.

      Here, I don't know what you mean. You must know that JT6M and ISCAT
      both use 30-second T/R cycles. (ISCAT also offers a 15-second period,
      at least during this trial period.)

      > ... JT6M, ISCAT etc are WEAK signal modes ( as Joe designed them) –
      > are again most people are using then for STRONG signal propagation – when
      > ANY mode will do the job.

      No disagreement here. With adequate signals, you might as well use CW
      or SSB and have a real conversation!

      -- 73, Joe, K1JT
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