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Tx Problem

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  • bty230314
    First let me add my thanks to Tony and others who have supported him in the SoftRock project. I know its been said before, but the program has allowed me an
    Message 1 of 8 , Mar 2, 2007
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      First let me add my thanks to Tony and others who have supported him
      in the SoftRock project. I know its been said before, but the
      program has allowed me an insight into SDR technology, including the
      satisfaction of having built working Rxs.

      Now to the problem, --where my limited knowledge is letting me down.

      I have built the Rev6 Tx/Rx 40/80 M option, and the Rx is playing
      fine with Rocky and WinRad software, I have a good quiet baseline
      and can pick out CW and SSB signals easily. Not so good with M0KGK
      software, as the baseline is very noisy, and the signals quite
      difficult to pick out. However with care, I can pick up CW sigs. I
      suspect a set up problem.

      I have set up the Tx by adjusting R29 to give approx 50mV at R30 and
      R31. I expected that if I apply 12V to PTR input, the Tx should be
      transmitting into my dummy load, but I see no rf sig at the ant on
      my scope. I thought this would simulate a CW sig., which is my
      intended mode of operation.

      Probably I have the theory wrong. As my next question would have
      been, Why not have the CW keyer at the PTT input, rather than the
      COMM port ???

      I also have a hardware problem as COMM1 port does not function. Is
      there a way to change the set up to use COMM2 port for the key???

      Any comments would be appreciated

      Colin M3WCK
    • Dave
      ... You also need the Tx I and Q signals supplied from the sound card to get an RF output. Just applying 12V to the PTT input puts the rig in Tx mode with no
      Message 2 of 8 , Mar 2, 2007
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        --- In softrock40@yahoogroups.com, "bty230314" <cweaving@...> wrote:
        > I expected that if I apply 12V to PTR input, the Tx should be
        > transmitting into my dummy load, but I see no rf sig at the ant on
        > my scope.

        You also need the Tx I and Q signals supplied from the sound card
        to get an RF output. Just applying 12V to the PTT input puts the
        rig in Tx mode with no drive.

        > Why not have the CW keyer at the PTT input, rather than the
        > COMM port ???

        Because, as mentioned above, the software needs to know that it is
        to output the Tx I and Q signals appropriate for your operating mode
        and frequency.

        > I also have a hardware problem as COMM1 port does not function. Is
        > there a way to change the set up to use COMM2 port for the key???

        Although I have not tried it, I believe KGKSDR allows setting the
        port to COM2 on the Transceiver Options->Hardware tab (in the Ports
        block). Winrad and the current version of Rocky do not support Tx
        operation.

        Dave, WA3OFF
      • Dave
        ... Also, the software doesn t simply put out continuous Tx I and Q signals in CW mode. Keying waveform shaping is done on the I and Q, while PTT remains
        Message 3 of 8 , Mar 2, 2007
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          --- In softrock40@yahoogroups.com, "Dave" <dmertz@...> wrote:
          > the software needs to know that it is
          > to output the Tx I and Q signals appropriate for your operating mode
          > and frequency.

          Also, the software doesn't simply put out continuous Tx I and Q
          signals in CW mode. Keying waveform shaping is done on the I and Q,
          while PTT remains active until keying stops for long enough and the
          system returns to Rx.

          Dave, WA3OFF
        • Tony Parks
          Hi Colin, With an SDR type transmitter as in the RXTX all modes of tranmission, including CW, require quadrature audio signals from the soundcard line-out.
          Message 4 of 8 , Mar 2, 2007
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            Hi Colin,
             
            With an SDR type transmitter as in the RXTX all modes of tranmission, including CW, require quadrature audio signals from the soundcard line-out.  For CW two fixed frequency keyed quadrature sine waves are required where the frequency of the sine waves is equal to the frequency offset from the center frequency and the phase between the two sinewaves is + or - 90 degrees depending on if the RF output is to be above or below the center frequency.
             
            Thus the software needs to respond to key inputs to generate the quadrature sinewaves and a serial port input is a high speed way of connecting the key to the PC. 
             
            73,
            Tony KB9YIG
             
            ----- Original Message -----
            From: bty230314
            Sent: Friday, March 02, 2007 10:40 AM
            Subject: [softrock40] Tx Problem

            First let me add my thanks to Tony and others who have supported him
            in the SoftRock project. I know its been said before, but the
            program has allowed me an insight into SDR technology, including the
            satisfaction of having built working Rxs.

            Now to the problem, --where my limited knowledge is letting me down.

            I have built the Rev6 Tx/Rx 40/80 M option, and the Rx is playing
            fine with Rocky and WinRad software, I have a good quiet baseline
            and can pick out CW and SSB signals easily. Not so good with M0KGK
            software, as the baseline is very noisy, and the signals quite
            difficult to pick out. However with care, I can pick up CW sigs. I
            suspect a set up problem.

            I have set up the Tx by adjusting R29 to give approx 50mV at R30 and
            R31. I expected that if I apply 12V to PTR input, the Tx should be
            transmitting into my dummy load, but I see no rf sig at the ant on
            my scope. I thought this would simulate a CW sig., which is my
            intended mode of operation.

            Probably I have the theory wrong. As my next question would have
            been, Why not have the CW keyer at the PTT input, rather than the
            COMM port ???

            I also have a hardware problem as COMM1 port does not function. Is
            there a way to change the set up to use COMM2 port for the key???

            Any comments would be appreciated

            Colin M3WCK

          • cesco12342000
            ... I wonder if this is a good concept. There are numerous problems with the low-latency required for this type of keying. This low-latency stuff is
            Message 5 of 8 , Mar 2, 2007
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              > Keying waveform shaping is done on the I and Q,
              > while PTT remains active until keying stops

              I wonder if this is a good concept. There are numerous problems with
              the low-latency required for this type of keying. This low-latency
              stuff is responsible for quite some hiccups on the software side.

              A better thing would be to FORGET the shaping and key the tx
              directly, I and Q signals always on. The rx soundcard could be active
              while transmitting, allowing to listen in between the dits. I think
              this would work much better than to route those signals trough a PC
              with a lame non-realtime OS.
            • Lyle Koehler, K0LR
              My computer is a couple of years old and has an AMD Athlon 3200 processor. The sound card I use for I/Q input and output is an Audigy 2 NX USB card, and I run
              Message 6 of 8 , Mar 2, 2007
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                My computer is a couple of years old and has an AMD Athlon 3200
                processor. The sound card I use for I/Q input and output is an Audigy
                2 NX USB card, and I run everything at 96 kHz, supposedly 24 bits. If
                anything, I would expect the USB connection on my card to impose an
                additional speed penalty on the system. To test the system, I loaded
                up the memory in a K1EL K10+ keyer with a test message and played it
                back into the RXTXv6.1 at various speeds. The speed is "software"
                selected by entering it with the paddles. Although I didn't check it
                with a scope, the keying sounded fine in another receiver at 35 wpm
                and even at 50 wpm (to the extent that I can copy at that speed!).

                The whole point of software defined radio is to perform as many of the
                radio's analog functions as possible in software, to minimize the
                complexity of the hardware. "Soft" keying is one of those functions,
                and I think it would be difficult to come up with a simple hardware
                implementation that works as well as the CW shaping in KGKSDR.

                Lyle, K0LR

                --- In softrock40@yahoogroups.com, "cesco12342000" <cesco1@...> wrote:
                >
                >
                > A better thing would be to FORGET the shaping and key the tx
                > directly, I and Q signals always on.
              • Ford Peterson
                Colin wrote: ...snip... I have set up the Tx by adjusting R29 to give approx 50mV at R30 and R31. I expected that if I apply 12V to PTR input, the Tx should be
                Message 7 of 8 , Mar 2, 2007
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                  Colin wrote:

                  ...snip...


                  I have set up the Tx by adjusting R29 to give approx 50mV at R30 and R31. I
                  expected that if I apply 12V to PTR input, the Tx should be transmitting
                  into my dummy load, but I see no rf sig at the ant on my scope. I thought
                  this would simulate a CW sig., which is my intended mode of operation.

                  Probably I have the theory wrong. As my next question would have been, Why
                  not have the CW keyer at the PTT input, rather than the COMM port ???

                  I also have a hardware problem as COMM1 port does not function. Is there a
                  way to change the set up to use COMM2 port for the key???

                  Any comments would be appreciated

                  Colin M3WCK

                  ************************

                  Colin, and others...

                  I cannot help with the software issues as I have an issue of my own. I
                  dislike involving the comm port in the first place as the PC has always had
                  problematic serial port issues. Now with the ubiquitous USB ports, using
                  serial port ops is a virtual no-no. I did make an observation regarding the
                  R30/R31 measurements and setting R29 that was interesting to me.

                  When I set R29 according to the instructions, it took some fussing with the
                  pot to get them just right. What I did notice is that I could hear the
                  opposite side band.

                  For example, set to USB and listen to the transmitter using another
                  receiver. If you tune down to zero beat, and go past zero to the opposite
                  sideband, I could hear it just fine. Setting R29 according to the manual
                  does not produce as good a null as when you tune for minimum distortion of
                  the sidebands. In fact, it was very easy to set R29 to almost null out the
                  opposite sideband. What was interesting is that the setting of R29 using my
                  method did not result in the same setting as per the instructions.

                  I can only speculate as to why this is so. Perhaps the two transistors are
                  not well matched? Differences in the balance of the transformers? I don't
                  know for certain. I set mine for minimum spurious response instead of using
                  the volt meter on R30/R31.

                  Ford-N0FP
                  ford@...
                • bty230314
                  ... on ... mode ... Is
                  Message 8 of 8 , Mar 4, 2007
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                    --- In softrock40@yahoogroups.com, "Dave" <dmertz@...> wrote:
                    >
                    > --- In softrock40@yahoogroups.com, "bty230314" <cweaving@> wrote:
                    > > I expected that if I apply 12V to PTR input, the Tx should be
                    > > transmitting into my dummy load, but I see no rf sig at the ant
                    on
                    > > my scope.
                    >
                    > You also need the Tx I and Q signals supplied from the sound card
                    > to get an RF output. Just applying 12V to the PTT input puts the
                    > rig in Tx mode with no drive.
                    >
                    > > Why not have the CW keyer at the PTT input, rather than the
                    > > COMM port ???
                    >
                    > Because, as mentioned above, the software needs to know that it is
                    > to output the Tx I and Q signals appropriate for your operating
                    mode
                    > and frequency.
                    >
                    > > I also have a hardware problem as COMM1 port does not function.
                    Is
                    > > there a way to change the set up to use COMM2 port for the key???
                    >
                    > Although I have not tried it, I believe KGKSDR allows setting the
                    > port to COM2 on the Transceiver Options->Hardware tab (in the Ports
                    > block). Winrad and the current version of Rocky do not support Tx
                    > operation.
                    >
                    > Dave, WA3OFF
                    >
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