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Re: [wsjtgroup] Re: [wsjt-eu] ISCAT and JT6M

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  • Joe Taylor
    Hi Chris, ... No need for any transatlantic flames -- or indeed any flames at all. The words you worried about are from Tom, LA4LN, and I m sure he ll speak
    Message 1 of 7 , Apr 5, 2011
      Hi Chris,

      GW4DGU wrote:
      > I really don't want to start a transatlantic flame war, but...
      ...
      > One of the several reasons why we in Europe don't like the idea of single-tone
      > reports and confirmations is that due to the much higher levels of activity
      > over here, there is a very significant chance that the signal heard doesn't
      > come from the guy you are trying to work!

      No need for any transatlantic flames -- or indeed any flames at all.
      The words you worried about are from Tom, LA4LN, and I'm sure he'll
      speak for himself if he wants to. But I can assure you, nobody has been
      promoting any claims of valid copy on the basis of an odd single
      character here and there.

      Of course I'm well aware of the reasons single-tone reports are not used
      in Region 1. Why do you think I've taken such care to make their use
      optional, and indeed regional???

      Over here, when we do use these signals, we've learned to do it in a way
      that virtually *never* leads to broken or invalid QSOs.

      > Although the data from 2009, looked-at in the raw FSK441 decodes, seemed to
      > provide evidence of more than a few very short bursts. The burst lengths were,
      > as might be expected, very short - tens of ms at best - and the signal levels
      > rather low. Quick sanity checks seemed to indicate that I wasn't fooling
      > myself. If I had time, I would run some proper statistical analyses on the
      > data, but extracting the information is very time consuming, and due to a
      > change in my personal circumstances, I can't see that I will be able to look
      > further for some time.

      You were kind enough to share those files with me, and I did some
      analysis. As I said at the time, I did not find statistically reliable
      evidence for any detected signal in the files.

      So, as far as I can see, we're in perfect agreement about this.

      While we're at it, do you have any response to my original questions
      about ISCAT and JT6M mode?

      With best wishes,

      -- 73, Joe, K1JT
    • Chris Bartram
      Hello Joe Can I make it very clear that there was no negative criticism of any kind of your work intended in my last email. Quite the opposite! However, I m
      Message 2 of 7 , Apr 6, 2011
        Hello Joe

        Can I make it very clear that there was no negative criticism of any kind of
        your work intended in my last email. Quite the opposite!

        However, I'm afraid that I remain a sceptic regarding the use of single-tone
        reports. If I recall the tests with VO/DM7MM, there was a period when I
        received a single tone, which from its fading pattern appeared to be
        propagated by meteor reflection - it sounded, and looked like a classic
        'overdense' burst. Until I was able to speak to Joe, I had that marked as a
        potential signal from him. It wasn't, as he was sending callsigns at that
        time. But for about 48hours, I was optimistic!!

        > You were kind enough to share those files with me, and I did some
        > analysis. As I said at the time, I did not find statistically reliable
        > evidence for any detected signal in the files.

        I don't think I ever received that reply, although it may have been lost in
        the unrelated events which led to my close-down later in the year.

        > So, as far as I can see, we're in perfect agreement about this.

        Certainly about the 2009 tests! Notwithstanding that, I still have a sneaking
        suspicion that there may be some marginal indications in those files. However,
        your use of statistics is clearly much more practiced than mine!

        I still wouldn't discourage other people from trying MS into the (for want of
        a better term) second-hop range. When I look at the potential improvements
        which could have been made - particularly with regard to location at my end of
        the circuit, transmitter power, and antenna gain - it should be possible to
        improve the system by nearly 20dB.

        > While we're at it, do you have any response to my original questions
        > about ISCAT and JT6M mode?

        No. Unfortunately, I've been QRT since before ISCAT became available, and my
        only experience of JT6M was briefly to see if it was useful for ionoscatter on
        2m. (It was ...) Once I'm able to become active again, I'll probably once
        again concentrate on microwave/mmwave EME, although if I'm finally able to find
        a new QTH on a good site, I may just start playing on 144 and 432 ...

        Vy 73

        Chris
        GW4DGU
      • Joe Taylor
        Dave, Jan, and all, Thanks for your messages. ... Of course, users can still choose. JT6M is available in WSJT7, ISCAT is in WSJT9. ... Feature requests are
        Message 3 of 7 , Apr 6, 2011
          Dave, Jan, and all,

          Thanks for your messages.

          G4RGK wrote:
          > Having read all the comments, leaving aside the technical issues,
          > there are a significant number of people who want to use JT6M, so
          > would the best option be
          > to reinstate JT6M alongside ISCAT in the next revision and let the
          > users decide which one they prefer to use.

          LA3EQ wrote:
          > I agree with dave, G4RGK, Lets have both [ISCAT and JT6M] in the next
          > rev. and let users choose.

          Of course, users can still choose. JT6M is available in WSJT7, ISCAT is
          in WSJT9.

          > 1) What about an "auto detect" mode when listning to random
          > frequency...That way the program would choose automaticly the
          > correct protcol (JT6M, ISCAT,etc) for ¨replying a random CQ call.

          Feature requests are always welcome. You should be aware that this
          particular one may not receive a very high priority when the inevitable
          time for "cost-benefit analysis" arrives.

          Nobody would like it if the decoder took three times as long because it
          had to try three different modes to see which matches a weak signal
          best. Sure, you could add a mode-ID header to every WSJT signal, to
          make this determination easier; but then there would be a significant
          cost in threshold sensitivity. From its beginning, WSJT has been all
          about sensitivity.

          > 2) What about changing the TX/RX rate from 60 (or 30 sec) sec
          > to 15 or even 10 sec. Timing would be thight, but the PA would
          > be happyer due to less heat strain. And you would have faster qso's too...

          ISCAT already offers a choice of 30 s or 15 s T/R cycles.


          Now, some philosophy:

          User feedback is highly desirable, and I appreciate all received
          comments and suggestions. My own decisions about what's included in
          WSJT are never taken lightly, and they depend to a considerable extent
          on feedback about real-world experience from users.

          WSJT celebrated its 10th birthday last month. The program's development
          has been a great learning experience for me (and for others who have
          contributed to the code base). I'm happy that thousands of hams have
          enjoyed using WSJT and its siblings. Perhaps many have learned good
          things from that use, as well.

          During its 10 years, WSJT has gained a number of new modes. It has lost
          some modes when they were superseded by something better. "Survival of
          the fittest," you might say.

          JT44 was a good mode, but JT65 is certainly better. So JT44 was
          dropped. FSK441-B and FSK441-C seemed like good ideas, but neither was
          clearly superior to the original FSK441 over a wide range of conditions,
          so they were dropped. Instead, performance of the original FSK441 was
          improved.

          JT2 worked well in controlled circumstances, but required better phase
          stability than could be assured on its most interesting target
          propagation paths. It was therefore dropped. On the other hand, JT4
          has been kept, in part because some clever users found unanticipated
          applications different from those I had envisioned.

          The same thing is happening now with ISCAT. JT6M was dropped because
          ISCAT is clearly better -- even in its original released form. And
          ISCAT is still improving in a number of significant ways, thanks in part
          to good user feedback. Some of that good feedback was received this
          week, in response to my request.

          One final thought:

          It should be obvious that I won't be doing these things forever. When
          it comes to matters under discussion here, I'm more like an architect
          than a builder. I've always hoped that others with better programming
          skills will take some of the ideas in WSJT, build on them, and create
          more polished software than I can produce. That's one of the main
          reasons that WSJT and its sister programs are open-source software.

          One good example of this sort of cross-fertilization already exists: the
          excellent program JT65-HF, by Joe Large, W6CQZ. Please, some others who
          are interested and have the skills, accept my invitation to contribute
          in this way to our wonderful hobby!

          -- 73, Joe, K1JT
        • Steve Norris
          It [WSJT] has lost some modes when they were superseded by something better. Joe summed it up there. I was always partial to JT44 in the old days. Heck,
          Message 4 of 7 , Apr 6, 2011
            "It [WSJT] has lost some modes when they were superseded by something better." 
             
            Joe summed it up there.  I was always partial to JT44 in the old days.  Heck, living only 30 miles from Princeton 10 years ago, I even helped a time or two with test transmissions of JT44.  When it was superceded, I kept that old version on my computers for "years".  Never used it [JT44] again.  Now it's gone from my computer.
             
            Today, I keep a copy of WSJT7 with JT6M here.  Because last year's Es season needed it.  But I suspect that come May-July 2011, I will find most folks using ISCAT for those "marginal prop" attempts at US to DX QSOs.  Might never use it [JT6M] again.  And then it will be gone from my computer.
             
            And so it goes.   ;>)  Thanks for the continued work, Joe.
             
            Steve, W5KI
             
             
             
             
            ----- Original Message -----
            Sent: Wednesday, April 06, 2011 10:11 AM
            Subject: [wsjtgroup] Re: [wsjt-eu] ISCAT and JT6M
             
            ...
            During its 10 years, WSJT has gained a number of new modes. It has lost
            some modes when they were superseded by something better. "Survival of
            the fittest," you might say.
            ...
            JT44 was a good mode, but JT65 is certainly better. ...
            ...
            The same thing is happening now with ISCAT. JT6M was dropped because
            ISCAT is clearly better ...
          • 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 5 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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