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Skimmer on VHF/UHF

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  • g0dja
    I ve only just joined the group, and started to use Skimmer, so apologies if this has been asked before. I m more into VHF and UHF than HF, so I have a
    Message 1 of 6 , Apr 28, 2008
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      I've only just joined the group, and started to use Skimmer, so
      apologies if this has been asked before.

      I'm more into VHF and UHF than HF, so I have a reasonable set up for
      23cm that is capable of hearing a CW beacon with the callsign GB3MHL
      about 50km away from me.

      Now, if I monitor on 20 or 30m I get decodes of callsigns, but not of
      signals on 23cm that are, to my ears and on the view screen, better
      signals than those on 20m...

      What's the issue with the VHF/UHF signals that doesn't affect the HF
      signals I wonder?

      Thanks - Dave (G0DJA0
    • David Ackrill
      ... I don t know why I wrote 50km, it s actually 217km away. I think I was thinking of the much closer one at Emley Moor (GB3MLE) which is about 47km and is a
      Message 2 of 6 , Apr 29, 2008
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        g0dja wrote:

        > I'm more into VHF and UHF than HF, so I have a reasonable set up for
        > 23cm that is capable of hearing a CW beacon with the callsign GB3MHL
        > about 50km away from me.
        >

        I don't know why I wrote 50km, it's actually 217km away. I think I was
        thinking of the much closer one at Emley Moor (GB3MLE) which is about
        47km and is a collosal signal here of course. In fact, the Skimmer does
        stuggle with that one, but there's a well known fault with the PSU on
        the beacon which makes the CW note very rough.

        Anyway, decoding on GB3MHL is much better today, so conditions may be a
        bit better and the Skimmer can now decode about 99% of the time.

        Dave (G0DJA)
      • Alex, VE3NEA
        Hi Dave, The bandwidth of the input signal in the 3-kHz mode must be 3 kHz. If it is less than that, the sensitivity of the decoder drops significantly. Your
        Message 3 of 6 , Apr 29, 2008
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          Hi Dave,

          The bandwidth of the input signal in the 3-kHz mode must be 3 kHz. If it is
          less than that, the sensitivity of the decoder drops significantly. Your
          signal has only about 1500 Hz BW - at this bandwidth, CW Skimmer can decode
          only very strong signals. Please see if you can use a wider filter in your
          radio.

          73 Alex VE3NEA




          > Alex, VE3NEA wrote:
          >> Hi Dave,
          >>
          >> Please send me a short I/Q recording of the 23 cm signal.
          >>
          >> 73 Alex VE3NEA
          >>
          >
          > Hi Alex,
          >
          > The Skimmer seems to be getting the callsign and locator 99% of the time
          > now, but I've attached a sample for you anyway.
          >
          > It got the call OK the second time, but thought the call was TI3MHL and
          > occasionally gets the 3 as a 4.
          >
          > Cheers - Dave (G0DJA)
          >
        • David Ackrill
          ... Thanks for the explanation Alex, I guess that s because I was using the CW setting on my TS2000X, the width setting was 2000Hz. I will try again using
          Message 4 of 6 , Apr 29, 2008
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            Alex, VE3NEA wrote:
            > Hi Dave,
            >
            > The bandwidth of the input signal in the 3-kHz mode must be 3 kHz. If it is
            > less than that, the sensitivity of the decoder drops significantly. Your
            > signal has only about 1500 Hz BW - at this bandwidth, CW Skimmer can decode
            > only very strong signals. Please see if you can use a wider filter in your
            > radio.
            >
            > 73 Alex VE3NEA

            Thanks for the explanation Alex,

            I guess that's because I was using the 'CW' setting on my TS2000X, the
            width setting was 2000Hz.

            I will try again using USB, as that allows me to go up to 50000Hz.
            Although your point about needing a stronger signal is born out by the
            fact that the stronger signal from the beacon today was being decoded.

            I've been using the SDR-IQ on 20M with CWSkimmer today, and have got the
            aggregator running now. However, I have noticed some errors coming up
            on the aggregator DOS window.

            One says "error:cannot send spot - http://skimmer.dxwatch.com/rx.php -
            500 server closed connection without sending any data back" and the
            other says "500 cant connect to skimmer.dxwatch.com:80 (connect: Unknown
            error)" then the next time it goes through OK for quite a long time
            until the next error message comes up.

            I thought I'd mention these errors in case they mean something to the
            operation of the aggregator.

            Cheers - Dave (G0DJA)
          • David Ackrill
            ... Ooops, that s a typo of course. The maximum width, with the TS2000X in USB, is 5000Hz. Dave (G0DJA)
            Message 5 of 6 , Apr 29, 2008
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              David Ackrill wrote:

              > I will try again using USB, as that allows me to go up to 50000Hz.

              Ooops, that's a typo of course. The maximum width, with the TS2000X in
              USB, is 5000Hz.

              Dave (G0DJA)
            • David Ackrill
              Thinking ahead a little... Is there a way to use the SDR-IQ/14 as a transverter IF, but have the Skimmer log the spots on a different frequency? For instance,
              Message 6 of 6 , Apr 29, 2008
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                Thinking ahead a little...

                Is there a way to use the SDR-IQ/14 as a transverter IF, but have the
                Skimmer log the spots on a different frequency?

                For instance, in Europe the 4M band (70MHz) is becoming available in
                more countries to Amateurs but many/most commercial radios don't cover
                the band. Or, even if they do the resultant signals and receivers are
                poor. Therefore, many people use a transverter for that band.

                Similarly, on the higher microwave bands it's not uncommon to use
                transverters from bands such as 10m/2m or even 70cm.

                Dave (G0DJA)
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