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Re: ISCAT and JT6M

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  • 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 1 of 7 , Apr 6, 2011
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      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 2 of 7 , Apr 6, 2011
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        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 3 of 7 , Apr 6, 2011
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          "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 4 of 7 , Apr 6, 2011
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            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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