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Bare bones WSPR

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  • md1clv
    Hi all, I ve just joined the group and thought you might be interested in the bare bones WSPR transmitter I ve been working on. It uses the technique from
    Message 1 of 9 , Feb 22, 2013
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      Hi all,
      I've just joined the group and thought you might be interested in the "bare bones" WSPR transmitter I've been working on.

      It uses the technique from http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter to produce a WSPR signal directly on either the 2200m band or the 630m band (frequencies over 1MHz won't work.)

      The output is a square wave so it must be filtered before going to an antenna. I've also not put code in to turn off the transmitter if Ctrl-C is pressed yet.

      If anyone's interested, the code is at https://github.com/DanAnkers/WsprryPi

      Dan MD1CLV
    • bob_g3wkw
      Very interesting. I compiled the code and spotted myself straight away! Perhaps 10Hz off target but who knows really! I didn t bother with an antenna yet. It
      Message 2 of 9 , Feb 23, 2013
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        Very interesting. I compiled the code and spotted myself straight away! Perhaps 10Hz off target but who knows really! I didn't bother with an antenna yet. It makes me wonder if a transverter is needed at all for digital modes on the LF bands. Can they all be generated directly on final frequency? Worth further exploration. Off to build an LPF and connect an antenna.

        Bob
        G3WKW
      • bob_g3wkw
        Actually I must have been very lucky to have that work first time as I had not realised that there was no timing built in. I did note my spot was about +4 on
        Message 3 of 9 , Feb 23, 2013
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          Actually I must have been very lucky to have that work first time as I had not realised that there was no timing built in. I did note my spot was about +4 on DT. So I made a bash script to kick it off at the right time and for simplicity of programming set it off at 59 seconds. No decode. A few more lines got it to 00 seconds and it decodes but with a timing error of -1.8. Read the spec and set it to 01 seconds and now I have -0.8 which I put down to calibration of the two machines. my script below if anyone wants it. I am sure it can be done more elegantly. "test" was a simple script to call wspr-pi with my call and locator but it could/should be done directly at this point, had I started from here! Next a random repeat loop:

          #! /bin/bash
          rem=0
          echo "waiting for next odd minute"
          while [ $rem = 0 ]; do
          m=$(date +"%M")
          let "rem = m % 2"
          echo -ne "\r" $(date)
          done
          echo -ne "\n\n odd minute started, waiting for 50th second\n"

          while [ $(date +"%S") != 50 ]; do
          echo -ne "\r" $(date)
          done
          echo -ne "\n Starting in 10 seconds\n\n"
          while [ $(date +"%S") != 01 ]; do
          echo -ne "\r" $(date)
          done
          echo -ne "\n Ready to Start\n\n"
          sudo ./test
          exit






          --- In Raspberry_Pi_4-Ham_RADIO@yahoogroups.com, "bob_g3wkw" <bob.thornton@...> wrote:
          >
          >
          >
          > Very interesting. I compiled the code and spotted myself straight away! Perhaps 10Hz off target but who knows really! I didn't bother with an antenna yet. It makes me wonder if a transverter is needed at all for digital modes on the LF bands. Can they all be generated directly on final frequency? Worth further exploration. Off to build an LPF and connect an antenna.
          >
          > Bob
          > G3WKW
          >
        • Daniel Ankers
          ... Hi Bob, I did the timing in my testing by running the program from the crontab with */2 in the minutes column, which worked well enough to get decodes.
          Message 4 of 9 , Feb 24, 2013
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            On 24 February 2013 01:14, bob_g3wkw <bob.thornton@...> wrote:
             

            Actually I must have been very lucky to have that work first time as I had not realised that there was no timing built in. I did note my spot was about +4 on DT. So I made a bash script to kick it off at the right time and for simplicity of programming set it off at 59 seconds. No decode. A few more lines got it to 00 seconds and it decodes but with a timing error of -1.8. Read the spec and set it to 01 seconds and now I have -0.8 which I put down to calibration of the two machines. 

            Hi Bob,

            I did the timing in my testing by running the program from the crontab with "*/2" in the minutes column, which worked well enough to get decodes.

            You asked earlier about other digital modes.  We couldn't do all modes (I assume PSK31 is impossible, for example, because we can't control the output phase) but we can do any that are frequency shift keyed (like RTTY) or on-off keyed (like CW or OPERA.)   A lot of these modes would not suffer from the frequency restriction we have with WSPR, which comes from the 1.46Hz tone separation used in WSPR - it would be possible to generate CW at up to 2m.  To do more complicated modes it's better to get one of the cheap DDS modules off ebay and control that from the Pi.

            Dan MD1CLV
          • Paul M
            Nice Project. Many thanks for your work and for making it available. Paul 5B8BA/G7SPV Number: 312953 (on the new on Linux counter)  
            Message 5 of 9 , Feb 24, 2013
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              Nice Project.

              Many thanks for your work and for making it available.

              Paul 5B8BA/G7SPV
              Number: 312953
              (on the new on Linux counter)

               
              ___________________________________________________________________________________

              Disclaimers: I have entered into no agreements regarding mails erroneously sent to this address, and reserve the right to do as I wish with any such emails.
            • bob_g3wkw
              This much shorter script will start wspr-pi at 1 second into the even minute. Bob G3WKW =========================================================== #!
              Message 6 of 9 , Feb 24, 2013
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                This much shorter script will start wspr-pi at 1 second into the even minute.

                Bob
                G3WKW
                ===========================================================

                #! /bin/bash
                # this script will execute wspr-pi at 1 second into even minute
                rem=999
                echo -e "waiting to start at 120+1\n "
                while [ $rem != 1 ]; do # looking for one second
                let "m = "$(date +%s)"" # total seconds since 1970
                let "rem = m % 120" # remainder after /120
                echo -ne "\r" $rem " " # display the count
                done
                echo -ne "\reven minute + " $rem " seconds.\n"
                sudo ./wspr-pi G3WKW IO91 00 475700
                exit

                ===============================================================
              • mathisono
                Hot shit FM radio works! I bought a computer didn t think i just put another transmitter on the shelf! Am i correct in thinking that a TNC could be eliminated,
                Message 7 of 9 , Feb 24, 2013
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                  Hot shit FM radio works! I bought a computer didn't think i just put another transmitter on the shelf!

                  Am i correct in thinking that a TNC could be eliminated, and the Rpi just generate and send its own aprs packet?


                  Maybe the first raspberry pi to transmit CW on the Ham radio bands!
                  http://youtu.be/50VhnBKLiQc
                • bob_g3wkw
                  I haven t worked out how the modulation is done. WSPR is fine because that is pure FSK but APRS would be AFSK on FM. But you can do APRS on a Pi using
                  Message 8 of 9 , Feb 25, 2013
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                    I haven't worked out how the modulation is done. WSPR is fine because that is pure FSK but APRS would be AFSK on FM.

                    But you can do APRS on a Pi using 'soundmodem' and 'xastir'. I ran it together with bluetooth and my GPS puck, but can't really think why I would want anyone else to know where I am!

                    Bob

                    G3WKW
                  • Mathison Ott
                    APRS works best when you can receive and transmit signals. Can anyone confirm/comment on the power output, its got to be low! LPF are must I knock out my DTV
                    Message 9 of 9 , Feb 25, 2013
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                      APRS works best when you can receive and transmit signals. 

                      Can anyone confirm/comment on the power output, its got to be low! 

                      LPF are must I knock out my DTV when transmitting on a 2m jpole! 

                      Thanks again

                      Mathison kj6dzb





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