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WSJT questions

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  • Jose M. Valdes R. YV5LIX
    Hello All, I m new to the group and to WSJT. Name is Jose (Joe) and call YV5LIX I have a couple of question. 1.- What is the best mode for terrestrial weak
    Message 1 of 6 , May 2, 2005
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      Hello All,

      I'm new to the group and to WSJT.

      Name is Jose (Joe) and call YV5LIX

      I have a couple of question.

      1.- What is the best mode for terrestrial weak signals in 144 using WSJT
      4.9.7?

      All references in the manual are to EME, meteor scatter and tropo in 6
      meters, but nothing regarding 144 MHz terrestrial/tropo/esporadic-E weak
      signals.

      2.- Is there a FSK441 page similar to the JT65 Terrestrial Link, JT65 EME
      Link and Ping Jockey Central pages?

      73/DX Jose M. Valdes R. (Joe) YV5LIX
      eQSL.cc Advisory Board Member
      QSL manager EA7FTR
      SYSOP YV5LIX DX Cluster
      telnet://yv5lix.org.ve:7300
      VHF Packed: 145.430 YV5LIX
      http://www.yv5lix.org.ve
    • Rex Moncur
      Hello Jose For 144 MHz terrestrial the mode to use depends on whether you want to work via troposcatter or meteor scatter. In general troposcatter is used for
      Message 2 of 6 , May 2, 2005
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        Hello Jose

         

        For 144 MHz terrestrial the mode to use depends on whether you want to work via troposcatter or meteor scatter.

         

        In general troposcatter is used for up to about 800 km and meteor scatter from about 800 km to 2000 km.

         

        For troposcatter the mode to use is JT65 and the sub-mode JT65b is generally preferred for 144 although you can pick up an extra 1 dB by using JT65a if both stations have good frequency stability – less than 1 Hz drift per TX cycle.

         

        For meteor scatter on 144 MHz the best mode is FSK441 and generally people around the World use the sub-mode  FSK441a.  FSK441b has forward error correction that reduces the errors and false information and while this does slow it down it works deeper into the noise and this means there is little difference in performance between the two modes.  Testing shows that on two meters FSK441a has a slight advantage for distances below 1000 km and FSK441b has a small advantage for distances above 1000 km, but there is not much in it.

         

        73 Rex VK7MO

         




      • Philip
        Hello Jose, Apparently better than JT65, for Terrestrial use, is the old JT44 (JT65 is now optimised for EME working). The last version of WSJT, which has JT44
        Message 3 of 6 , May 3, 2005
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          Hello Jose,

          Apparently better than JT65, for Terrestrial use, is the old JT44
          (JT65 is now optimised for EME working).

          The last version of WSJT, which has JT44 is version 3.8.1, which is
          still available for download (for this reason) from the main WSJT
          site.

          In practice this means that you keep both versions of WSJT on your
          computer (in different folders) and keep version 3.8.1 for JT44 use
          only.

          There was some time ago a message on the group all about this.

          73 de Philip G0ISW

          http://www.qsl.net/g0isw



          --- In wsjtgroup@yahoogroups.com, "Jose M. Valdes R. YV5LIX"
          <yv5lix@c...> wrote:
          > Hello All,
          >
          > I'm new to the group and to WSJT.
          >
          > Name is Jose (Joe) and call YV5LIX
          >
          > I have a couple of question.
          >
          > 1.- What is the best mode for terrestrial weak signals in 144 using
          WSJT
          > 4.9.7?
          >
          > All references in the manual are to EME, meteor scatter and tropo
          in 6
          > meters, but nothing regarding 144 MHz terrestrial/tropo/esporadic-E
          weak
          > signals.
          >
          > 2.- Is there a FSK441 page similar to the JT65 Terrestrial Link,
          JT65 EME
          > Link and Ping Jockey Central pages?
          >
          > 73/DX Jose M. Valdes R. (Joe) YV5LIX
          > eQSL.cc Advisory Board Member
          > QSL manager EA7FTR
          > SYSOP YV5LIX DX Cluster
          > telnet://yv5lix.org.ve:7300
          > VHF Packed: 145.430 YV5LIX
          > http://www.yv5lix.org.ve
        • Rex Moncur
          Hello Philip and Jose The question as to whether JT44 or JT65 is better for tropo-scatter is an interesting issue. The reasons why JT44 can be better are: 1.
          Message 4 of 6 , May 3, 2005
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            Hello Philip and Jose

             

            The question as to whether JT44 or JT65 is better for tropo-scatter is an interesting issue.

             

            The reasons why JT44 can be better are:

             

            1. It has a 1 minute TX+RX cycle cf 2 mins for JT65 and thus one can complete more quickly when signals are strong enough for it to work.
            2. Because of the shorter RX period there is also a lower probability of loosing a decode due to meteor bursts which are the major problem on any long tropo-scatter path on two meters.  Meteor bursts usually have a Doppler shift that can be up to a few 10s of Hz on two meters and both JT44 and JT65 have difficulty in coping with any strong bursts near the reference tone (ie that cannot be removed by lowering the tolerance).

             

            Against those advantages JT65 will typically decode signals at -28 dB in WSJT units compared to around -19 dB for JT44.  Thus as a general rule one would find JT65 better on the weakest signals and JT44 to be preferred on stronger signals.

             

            However, the nature of tropo-scatter signals is that they have very heavy QSB, typically 10 to 15 dB range of variations on 144 MHz,  over a half hour test period (rising to 20 dB on 432MHz).  Thus if you wait long enough a weak signal will always decode on JT44, but by this time you will have probably already decoded it on JT65.  It is therefore very difficult to quantify which is best other than by experience.  My experience is that on two meters where meteors are prevalent JT65 is to be preferred if the median signal level is less than about -20 dB, but JT44 can be of advantage for median signal levels stronger than -20 dB.  On 432 MHz, where the loss of a decode due to meteors almost never occurs JT65 is a clear winner for tropo-scatter.

             

            73 Rex VK7MO

             

          • Philip
            Rex/Jose, What Rex says sounds good to me and makes sense too of our experiences here in Europe. Have fun and enjoy WSJT as much as I have, it transformed
            Message 5 of 6 , May 3, 2005
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              Rex/Jose,

              What Rex says sounds good to me and makes sense too of our
              experiences here in Europe. Have fun and enjoy WSJT as much as I
              have, it transformed 144MHz working for me, particularly with FSK441
              and Meteor Scatter.

              http://www.qsl.net/g0isw

              73 de Philip G0ISW


              --- In wsjtgroup@yahoogroups.com, "Rex Moncur" <rmoncur@b...> wrote:
              > Hello Philip and Jose
              >
              >
              >
              > The question as to whether JT44 or JT65 is better for tropo-scatter
              is an
              > interesting issue.
              >
              >
              >
              > The reasons why JT44 can be better are:
              >
              >
              >
              > 1. It has a 1 minute TX+RX cycle cf 2 mins for JT65 and thus one
              can
              > complete more quickly when signals are strong enough for it to work.
              > 2. Because of the shorter RX period there is also a lower
              probability
              > of loosing a decode due to meteor bursts which are the major
              problem on any
              > long tropo-scatter path on two meters. Meteor bursts usually have
              a Doppler
              > shift that can be up to a few 10s of Hz on two meters and both JT44
              and JT65
              > have difficulty in coping with any strong bursts near the reference
              tone (ie
              > that cannot be removed by lowering the tolerance).
              >
              >
              >
              > Against those advantages JT65 will typically decode signals at -28
              dB in
              > WSJT units compared to around -19 dB for JT44. Thus as a general
              rule one
              > would find JT65 better on the weakest signals and JT44 to be
              preferred on
              > stronger signals.
              >
              >
              >
              > However, the nature of tropo-scatter signals is that they have very
              heavy
              > QSB, typically 10 to 15 dB range of variations on 144 MHz, over a
              half hour
              > test period (rising to 20 dB on 432MHz). Thus if you wait long
              enough a
              > weak signal will always decode on JT44, but by this time you will
              have
              > probably already decoded it on JT65. It is therefore very
              difficult to
              > quantify which is best other than by experience. My experience is
              that on
              > two meters where meteors are prevalent JT65 is to be preferred if
              the median
              > signal level is less than about -20 dB, but JT44 can be of
              advantage for
              > median signal levels stronger than -20 dB. On 432 MHz, where the
              loss of a
              > decode due to meteors almost never occurs JT65 is a clear winner for
              > tropo-scatter.
              >
              >
              >
              > 73 Rex VK7MO
            • Jose M. Valdes R. YV5LIX
              Hello, Boy what a great group. Thanks for all the answer to my question, all where very nice and very clear, I now have much better idea of how to use WSJT to
              Message 6 of 6 , May 3, 2005
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                Hello,

                Boy what a great group.

                Thanks for all the answer to my question, all where very nice and very
                clear, I now have much better idea of how to use WSJT to its full capacity.

                It is always nice to belong to a group with such a nice collection of
                members.

                73/DX Jose (Joe), YV5LIX
                http://www.yv5lix.org.ve
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