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Re: Re : is there a computer doctor in the house ?

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  • Robert Allbright
    Hi Daithi thanks for mentioning use of lock and RIT - must remember these. By the way, when I worked you a few days ago and mentioned your visible sidebands I
    Message 1 of 7 , Jun 4, 2008
      Hi Daithi
      thanks for mentioning use of lock
      and RIT - must remember these.
      By the way, when I worked you a few
      days ago and mentioned your visible sidebands
      I probably had too much rf gain.
      I've been doing lots of experimenting
      measuring my IMD etc etc + reading up on psk31
      lots yet to learn.
      This is a brill mode and 30m rules ok hi!
      73 Rob G3RCE 30MDG#0852
    • Mel
      Hello Ed and Andy, Thankyou for your responses. Andy,your query is the net control on ? Well I have Digipan, and what the equivilant name is I can t remember,
      Message 2 of 7 , Jun 5, 2008
        Hello Ed and Andy,

        Thankyou for your responses. Andy,your query "is the net control on"?
        Well I have Digipan, and what the equivilant name is I can't
        remember, but it used to be on, so I'll do a check tomorrow. The
        reason I say this is because strange things happen, for example
        sometimes the signal indicator in the right corner of the screen
        appears, and sometimes it doesn't ! Why, simple answer, I dunno !

        Also I have another little problem which I could never solve on this
        computer. A couple of years ago I had a fuse blow in the rig PSU
        which caused all sorts of problems for me and among them was strange
        happenings on Digipan, it opened on PSK63, but would not decode it. I
        decided to download a new copy, deleted all I could find of the
        unwanted software and downloaded a new copy and bless my soul if the
        new copy didn't have the same problem, I couldn't believe it !

        So I downloaded again, and again, and the third copy still had the
        same problem,so I have to squirt a bit of RF on the waterfall to get
        it to change from fat lines to thin lines and decode PSK 31. Again
        why does it do this, I dunno ! The PC which doesn't seem to be able
        to TX/RX on the same frequency has an otherwise perfect Digipan copy
        which opens as it should. I've since been told that there is
        something amiss in the registry and to find "something" (I've since
        forgotten)but when I checked the registry I couldn't find it anyway.

        Hello Ed, now about this sound card calibration. I know nothing about
        this, so how do I go about adjusting the RX sampling frequency to
        compensate ? Would you be kind and give me some instructions, if you
        wish to do it off here post it to Mel gzerogqk@...

        OK, that seems to be it for the moment, as the BBC used to tell us
        when the TV service went belly up, Normal service will resume as soon
        as possible.

        Kind regards to all, Mel G0GQK
      • Dáithí
        To be absolutely honest, I found that calibrating the sound card wound up being a waste of time. The reason is simple - your Tx and Rx frequencies are slightly
        Message 3 of 7 , Jun 5, 2008
          To be absolutely honest, I found that calibrating the sound card wound up being a waste of time.
           
          The reason is simple - your Tx and Rx frequencies are slightly offset, so you spend ages aligning them.
           
          Then you go on the air, send a CQ - and lo and behold - the incoming signal can be anything up to 25 Hz or more away from your carefully aligned frequencies - because the other guy isn't quite matching your exact spot.
           
          remember - the average rig can be anything up to 4 parts per million inaccurate - and on 30 metres, that works out at 40 Hz (which is almost the width of your signal)
           
          73 de Daithi GI7OMY
           
          On 05/06/2008 22:07:43, Mel (gzerogqk@...) wrote:
          > Hello Ed and Andy,
          >
          > Thankyou for your responses.
          Andy,your query "is the net control on"?
          > Well I have Digipan, and what
          the equivilant name is I
          > can't
          > remember, but it used to be on,
          so I'll do a check tomorrow. The
          > reason I say this is because strange
          things happen, for example
          > sometimes the signal indicator in the right
          corner of the screen
          > appears, and sometimes it
          > doesn't ! Why,
          simple answer, I dunno !
          >
          > Also I have another little problem
          which I could never solve on this
          > computer. A couple of years ago I had
          a fuse blow in the rig PSU
          > which caused all sorts of problems for me and
          among them was strange
          > happenings on Digipan, it opened on PSK63, but
          would not decode it. I
          > decided to download a new copy, deleted all I
          could find of the
          > unwanted software and downloaded a new copy and bless
          my soul if the
          > new copy didn't
          > have the same problem, I
          >
          couldn't believe it !
          >
          > So I downloaded again, and again, and the
          third copy still had the
          > same problem,so I have to squirt a bit of RF on
          the waterfall to get
          > it to change from fat lines to thin lines and
          decode PSK 31. Again
          > why does it do this, I dunno !
        • Ed Hekman
          ... on ? ... [...] ... about ... you ... soon ... Mel, The term net control is used in MultiPSK only I think. On other programs such as Digipan the term Tx
          Message 4 of 7 , Jun 6, 2008
            --- In 30meterPSKGroup@yahoogroups.com, "Mel" <Gzerogqk@...> wrote:
            >
            > Hello Ed and Andy,
            >
            > Thankyou for your responses. Andy,your query "is the net control
            on"?
            > Well I have Digipan, and what the equivilant name is I can't
            > remember, but it used to be on, so I'll do a check tomorrow. The
            > reason I say this is because strange things happen, for example
            > sometimes the signal indicator in the right corner of the screen
            > appears, and sometimes it doesn't ! Why, simple answer, I dunno !
            [...]
            > Hello Ed, now about this sound card calibration. I know nothing
            about
            > this, so how do I go about adjusting the RX sampling frequency to
            > compensate ? Would you be kind and give me some instructions, if
            you
            > wish to do it off here post it to Mel gzerogqk@...
            >
            > OK, that seems to be it for the moment, as the BBC used to tell us
            > when the TV service went belly up, Normal service will resume as
            soon
            > as possible.
            >
            > Kind regards to all, Mel G0GQK

            Mel,

            The term 'net' control is used in MultiPSK only I think. On other
            programs such as Digipan the term 'Tx lock' is used. As long as the
            Tx frequency is not locked it should track the Rx frequency.

            MultiPSK has a built-in calibration procedure that determines the
            correct Rx and Tx sampling frequencies. With other programs you can
            estimate the offset between Rx and Tx by locking the Tx frequency and
            noting the difference between Tx and Rx frequencies. Make sure that
            the other station does not have not have the Tx frequency locked.
            Since each station may have some offset error, the data should be
            collected for many QSOs so these errors would be averaged out.

            If you collect this data for many QSOs at different frequencies
            across the audio spectrum and plot the pairs of frequencies, you
            should be able to determine if there is a fixed offset independent of
            the audio frequency or if the offset is proportional to the audio
            frequency.

            A fixed offset would indicate an offset in the radio. An offset
            proportional to the audio frequency would indicate a difference in
            the Rx and Tx sampling frequencies. If you find that there is a
            difference in the Rx/Tx sampling frequencies, compute the ratio of
            the sampling frequencies and apply this correction to one of the
            frequencies. Digipan and MixW both have options for applying
            corrections to each sampling frequency.

            If you are confident that the station your are working has no offset
            between Rx and Tx frequencies, you can perform this test by tuning
            your radio and checking the offset across the audio spectrum. If the
            other station does have an offset, you will still be able to
            determine if you have an offset that is proportional to the audio
            frequency.

            I hope this helps. If you would like to collect some data and send
            it to me, I would be happy to analyze it.

            Ed
            WB6YTE
          • Mel
            Hello everyone, Thanks to everyone who have replied and especially Ed. All I can say is Phew !!! I hadn t realised it was going to be so complicated ! I have
            Message 5 of 7 , Jun 6, 2008
              Hello everyone,

              Thanks to everyone who have replied and especially Ed. All I can say
              is Phew !!! I hadn't realised it was going to be so complicated ! I
              have made notes on the descriptive information you sent and I'll go
              down the shack tomorrow and see what transpires. You mentioned that
              Digipan has options for applying corrections to each sampling
              frequency. I spent some time having a good look at Digipan but I was
              unable to see anything like this.

              Something I have observed is that the AFC " pulling power" on the one
              version of Digipan on computer A, my normal one, seems to be better
              than on computer B, which is the one which seems not to be tracking
              signals as well and is off with RX/TX. Going back to 2001, at that
              time I was using a TS430 for my first attempts with PSK, and I
              believed at the time that it was perhaps the 430 which was the
              problem which a station told me about the RX/TX being off.

              I will try Daithi's suggestion by locking the TX frequency and see
              how well the AFC will pull into the signal, but as mentioned earlier
              it doesn't seem to react as well as computer A.

              I did think about Jean's idea of using the RIT on the rig but as
              there is no way to measure an offset it was a bit "iffy", perhaps I
              should say, impossible to calibrate.

              Referring to Daithi's comment about the AFC I put out a CQ call the
              other day and a station replied parallel to my frequency. Thinking
              he's a bit close I'll move a bit,I put out another CQ, and it
              happened again, so I thought he must be responding to me. So to check
              it out I sent a message "please reply on my frequency" He called
              again off frequency and then went QRT. The next contact responded
              exactly on my frequency, its a mystery. The only way to find out is
              to have a local contact but there's nobody local who is using PSK.

              Anyway,where are my pills ? I think I'll go and have a lie down in a
              darkened room !

              Kind regards to all, Mel G0GQK
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