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Re: [Q15X25] Status of Q15X25?

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  • dubose@texas.net
    ... Rick, There is just so much you can do/get from a mode that is restricted to a 3 KHz or less bandwidth. Higher throughputs and robustness where signals
    Message 1 of 33 , Nov 16, 2004
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      Quoting Rick Williams <mrfarm@...>:


      > There was a comment made on on of the groups, by the person who is
      > working on the SCAMP data transfer protocol. He apparently had tried
      > it on HF circuits but found it was not that good.
      >
      > The majority of unconnected modes appear to be very slow and would be
      > even slower with an ARQ wrapper, so maybe a new mode that uses
      > multitones may work well?
      >
      > Comments?
      >
      > Sincerely,
      >
      > Rick, KV9U

      Rick,

      There is just so much you can do/get from a mode that is restricted to a 3 KHz
      or less bandwidth. Higher throughputs and robustness where signals are usable
      at a -5 dB SNR on a poor CCIR channel will require signal bandwidths from 8-10
      Khz.

      If the ARRL adopts a position that data modes will be less and 3 Khz, then
      200-300 WPM at the above referenced signal level is about the best possible.

      Walt/K5YFW
    • Stewart
      GE, Rick - I guess all I can say is that the proof is in the the pudding and my comments are based on experience, which after should be the ultimate test.
      Message 33 of 33 , Nov 17, 2004
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        GE, Rick -

        I guess all I can say is that the proof is in the the pudding and my
        comments are based on experience, which after should be the ultimate
        test. Incidentally, I would add that we do re-review programs that
        had been looked at previously.

        What has to be remembered is that MARS stations are not concerned
        with going around the world point-to-point. Our nets generally
        involve distances of 200 to 300 miles, give or take, although there
        are nets that do cover a much larger area and can require the use of
        relays to get some stations checked in. Additionally, we are
        essentially using clear channels and formal net procedures, hence we
        are generally not bogged down with QRM, deliberate or otherwise.
        Additionally, we have a number of channels available such that for
        part of the year we will use one frequency for a given net, and move
        2 or 3 or 4 MHz for the rest of the year, recognizing the seasonal
        changes in propagation.

        I have no particular quarrel with your comments about PACTOR.
        However, because it is an ARQ mode, when conditions go south, the
        ACKing and NAKing can really stretch out the time to send a message.
        Taking 20 minutes or more to send one message, even though it will be
        complete, seems to me not to make much sense and certainly ties up a
        frequency unnecessarily.

        I can sympathize, and agree, with your plaint about so many modes and
        finding someone to talk with. Fortunately, for me. if a new mode
        comes along we will take the opportunity to look at it on one of our
        digital nets, and then whatever happens will happen as far as what we
        do with it. If some of us want to look at it further, we will simply
        set up a sked and do so at a time of our convenience.

        With respect to FNpsk, I only know was is found on the referenced web
        site. I personally am not aware of any dedicated reflectors at this
        point in time, although that is not to say one doesn't exist.

        Finally, with respect to "lab" testing, it is essential for the
        development of software. However, as long as one does not disregard
        new advances, the old axiom about "not fixing something that works"
        is still valid.

        73,

        Stewart NNN0STE W1UVE


        --- In Q15X25@yahoogroups.com, "Rick Williams" <mrfarm@m...> wrote:
        >
        > Stewart wrote:
        >
        > >>>>> To encapsulate our thoughts on MT63, based on consistant use
        over two
        > years, there is nothing that has touched it when conditions have
        > deteriorated to the point that other modes have dropped out of
        sight.
        > It is not unusual to be receiving solid copy on the screen and not
        > see anything on the waterfall or hear anything from the speaker. P-
        > III, let alone any other mode, as good as it is, does not appear to
        > match MT63 down in the trenches.
        >
        > =====
        >
        > I wonder why your experiences are so different from the actual
        tests done
        > with measuring how deep into the noise MFSK16 and other modes are
        able to do
        > compared with MT63?
        >
        > Of all the modes MT63 is about the worst in terms of weak signals!
        >
        > Pactor is really very good and my understanding is that it works
        well below
        > what some have claimed at only -5 db S/N.
        >
        > But I think the largest factor for MARS is that MT63 is able to TX
        much
        > faster data rates due to the huge BW. Many times larger than most
        of the
        > other digital modes. This works OK on a voice channel but not so
        good for
        > spectrum conservation.
        >
        > One thing that MT63 does extremely well is handle multipath and if
        you are
        > often using NVIS, you will encounter this phenomenon to a greater
        degree
        > than longer distance TX. Is it possible that this may be another
        reason for
        > the apparent success of MT63?
        >
        > >>>> Incidentally, if you are interested, there is an excellent
        > implementation of an ARQ application of QPSK63 to be found at:
        > http://www.w1fn.org FNpsk, a freeware program, effectively
        > automates the conduct of a digital net to a very high degree.
        >
        > ======
        >
        > This is completely new to me and have not seen this before. Any
        others here
        > finding this to work well?
        >
        > Is there a list or group that discusses this mode?
        >
        >
        > What is happening though is that there are so many modes, and so
        few digital
        > operators of these modes, that you rarely find anyone else to
        connect with.
        > For example, I have tried MT63 on 30 and 40 meters with no luck
        finding
        > anyone else. With a more commonly used mode, such as PSK31, it is
        much
        > easier to find someone.
        >
        > 73,
        >
        > Rick, KV9U
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