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RE: [digsstv] How does it work?

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  • Bud Haynes
    From: digsstv@yahoogroups.com [mailto:digsstv@yahoogroups.com] On Behalf Of on5ex Sent: Sunday, August 07, 2011 4:41 PM To: digsstv@yahoogroups.com Subject:
    Message 1 of 5 , Aug 8, 2011
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      From: digsstv@yahoogroups.com [mailto:digsstv@yahoogroups.com] On Behalf Of on5ex
      Sent: Sunday, August 07, 2011 4:41 PM
      To: digsstv@yahoogroups.com
      Subject: [digsstv] How does it work?

       

       

      Hi Gents,

      I don't know about you, guys, but I'd like to know how EasyPal works. Not how to handle the program, but how a picture is divided into segments, which modulation techniques are involved, error correcting methods etc. I tried to get 'the picture' by googling around, but the puzzle remains. If someone would be willing to publish a 'EasyPal for Dummies', I'd be much obliged. This group dissuates from contacting VK4AES, but who else is capable of explaining the mode?

      73,

      Johan on5ex

      Same here, I have been using easypal for a couple of years with my signalink usb, in the past I have gotten lots of pics, but with every new update I copy fewer pics.

      The only place I can hear them with my antenna is on 14.233, I hear them talking back and forth and tell there are pics being sent but I can rarely copy them.

      Usually on Sunday I will leave it run for 8 hours or so and on a good day will get 1 picture.

      Bud – KV7G

       

       

       

       

       

    • Bob N3PPH
      I am not sure the problem is with the program. There are a couple of ops who seem to think they own that frequency and just make it hard to send a picture. Why
      Message 2 of 5 , Aug 8, 2011
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        I am not sure the problem is with the program. There are a couple of ops who seem to think they own that frequency and just make it hard to send a picture. Why try when people will just talk over the pic. I have not bothered to go to 14.233 for a while because of this. I have more than once heard "someones trying to send a picture" and instead of waiting as a gentleman would they continue to talk, sometimes I notice an increase in signal strength too. Now it is even worse with JASTA killing all SSTV fun.
        73,
        Bob N3PPH

        On 8/8/2011 8:22 AM, Bud Haynes wrote:  

         

         

        From: digsstv@yahoogroups.com [mailto:digsstv@yahoogroups.com] On Behalf Of on5ex
        Sent: Sunday, August 07, 2011 4:41 PM
        To: digsstv@yahoogroups.com
        Subject: [digsstv] How does it work?

         

         

        Hi Gents,

        I don't know about you, guys, but I'd like to know how EasyPal works. Not how to handle the program, but how a picture is divided into segments, which modulation techniques are involved, error correcting methods etc. I tried to get 'the picture' by googling around, but the puzzle remains. If someone would be willing to publish a 'EasyPal for Dummies', I'd be much obliged. This group dissuates from contacting VK4AES, but who else is capable of explaining the mode?

        73,

        Johan on5ex

        Same here, I have been using easypal for a couple of years with my signalink usb, in the past I have gotten lots of pics, but with every new update I copy fewer pics.

        The only place I can hear them with my antenna is on 14.233, I hear them talking back and forth and tell there are pics being sent but I can rarely copy them.

        Usually on Sunday I will leave it run for 8 hours or so and on a good day will get 1 picture.

        Bud – KV7G

         

         

         

         

         

      • Andy Eskelson
        I have seen some basic info regarding the transmission method, I ll see if I can locate the source, It may have been a magazine article somewhere. Basically
        Message 3 of 5 , Aug 8, 2011
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          I have seen some basic info regarding the transmission method, I'll see
          if I can locate the source, It may have been a magazine article somewhere.

          Basically the process is:

          All images are simple files, so what is done is to transmit the file
          rather than an analogue image.

          The transmission bandwidth is split up into a large number of very narrow
          bandwidth channels, you can see these as the stripes in the waterfall.

          Each channel is used to carry some of the binary information.

          At the remote end these channel are decoded to recreate the binary file.

          The clever bit, is the built in error correction. HF is a poor medium for
          transmitting data of any sort, so it needs all the help it can get. I
          think the error correction is based on reed-solomon but I'm going from
          memory so I could be wrong. What happens is that extra data is added to
          the file (which is transmitted in blocks of data) which can help
          reconstruct the correct block even if there are multiple reception
          errors in it. Obviously it can't correct everything, but it helps a lot.


          The basic problem with DSSTV is that it is NOT really a listeners mode,
          as you may not get all of the blocks correctly, and while you can
          display partial decodes to some extent you still need to have received
          a large number of the blocks correctly before the image can
          be decoded.

          If you are in active communication with the other station, you can
          request resends and so on, which overcomes most of the problems. As a
          listener you can't do this and you are relying on the good reception of
          the blocks. You might pick up some blocks you missed from any requested
          retransmits that you hear, but it's very hit-or-miss

          One or two images from just monitoring is about the norm here as well.
          I find better luck on 80m here in europe. 40m is a dead loss due to the
          commercial stations in the evening.



          later...

          I found the reference:

          http://gi0dvu.co.uk/technical.aspx

          click on the DSSTV link This is a artical by Ralph Taggart WB8DQT

          What I cannot find is the more in-depth description of the protocol.

          Andy


          On Mon, 8 Aug 2011 06:22:50 -0600
          "Bud Haynes" <kv7g@...> wrote:

          >
          >
          >
          >
          > From: digsstv@yahoogroups.com [mailto:digsstv@yahoogroups.com] On Behalf Of
          > on5ex
          > Sent: Sunday, August 07, 2011 4:41 PM
          > To: digsstv@yahoogroups.com
          > Subject: [digsstv] How does it work?
          >
          >
          >
          >
          >
          > Hi Gents,
          >
          > I don't know about you, guys, but I'd like to know how EasyPal works. Not
          > how to handle the program, but how a picture is divided into segments, which
          > modulation techniques are involved, error correcting methods etc. I tried to
          > get 'the picture' by googling around, but the puzzle remains. If someone
          > would be willing to publish a 'EasyPal for Dummies', I'd be much obliged.
          > This group dissuates from contacting VK4AES, but who else is capable of
          > explaining the mode?
          >
          > 73,
          >
          > Johan on5ex
          >
          > Same here, I have been using easypal for a couple of years with my signalink
          > usb, in the past I have gotten lots of pics, but with every new update I
          > copy fewer pics.
          >
          > The only place I can hear them with my antenna is on 14.233, I hear them
          > talking back and forth and tell there are pics being sent but I can rarely
          > copy them.
          >
          > Usually on Sunday I will leave it run for 8 hours or so and on a good day
          > will get 1 picture.
          >
          > Bud - KV7G
          >
          >
          >
          >
          >
          >
          >
          >
          >
          >
          >
        • CT1QK
          You can find some information on the site of PY4ZBZ http://www.qsl.net/py4zbz/hdsstv/HamDRM.htm The protocol of the good old DIGTRX is the same when it uses
          Message 4 of 5 , Aug 8, 2011
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            You can find some information on the site of PY4ZBZ
            http://www.qsl.net/py4zbz/hdsstv/HamDRM.htm
            The protocol of the good old DIGTRX is the same when it uses the
            Hamdrm mode and it has a good explanation of the system used.
            I think it has also a page in English but I don't know where.
            Find the English help for the program on the end of the page.

            73
            CT1QK
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