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Noisy Perseus - contact trouble?

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  • Bjarne Mjelde
    I ve noticed that the noise level of my Perseus is around 20-30dB higher than on my SDR-IQ. It appears that the USB port may be the problem. If I move the
    Message 1 of 4 , Aug 3, 2008
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      I've noticed that the noise level of my Perseus is around 20-30dB
      higher than on my SDR-IQ. It appears that the USB port may be the
      problem. If I move the cable around a bit, the noise
      changes/increases; if I press the contact tighter to the Perseus USB
      port it decreases with 5-10dB. I also tried a different USB cable but
      no luck.

      A common signal reference was Murmansk 657, -75dBm on both receivers,
      so it's a matter of noise, not sensitivity. The difference is clearly
      audible as well.

      Advice, anyone?

      Bjarne
    • Bjarne Mjelde
      I ve uploaded this audio file of my local Murmansk 657 kHz. First 15 seconds on the IQ, the rest on the Perseus. S-meter readings (peak) were identical.
      Message 2 of 4 , Aug 3, 2008
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        I've uploaded this audio file of my local Murmansk 657 kHz. First 15
        seconds on the IQ, the rest on the Perseus. S-meter readings (peak)
        were identical.

        http://www.box.net/shared/wvoyuw6wwk

        Bjarne
      • Nico iv3nwv
        ... Yes, it is matter of noise, but noise is matter of the demodulator bandwidth. The demodulator bandwidth of the first part of your record is around 2.4 Khz,
        Message 3 of 4 , Aug 3, 2008
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          > A common signal reference was Murmansk 657, -75dBm on both receivers,
          > so it's a matter of noise, not sensitivity. The difference is clearly
          > audible as well.

          > Advice, anyone?

          Yes, it is matter of noise, but noise is matter of the demodulator
          bandwidth.
          The demodulator bandwidth of the first part of your record is around
          2.4 Khz, while in the second the bandwidth has been set to 4 kHz.
          Being 1) an AM demodulator a non linear device and 2) the equal
          loudness contour of the human ear very sensitive in the 2-4 kHz
          frequency range, it would be much better that comparisons were made
          with the same settings (analyze your mp3 file with an audio
          spectrometer, i.e redirect its audio output to Winrad, and you will
          discover what I mean).

          Nico
        • Bjarne Mjelde
          Apparently I have been mislead by the difference in SDR-IQ and Perseus spectrogram displays. I measured the Perseus sensitivity today and it is -101 dBm on
          Message 4 of 4 , Aug 5, 2008
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            Apparently I have been "mislead" by the difference in SDR-IQ and
            Perseus spectrogram displays. I measured the Perseus sensitivity
            today and it is -101 dBm on one spot in MW, AM mode, as expected.

            Bjarne

            --- In perseus_SDR@yahoogroups.com, "Bjarne Mjelde"
            <bjarne.mjelde@...> wrote:
            >
            > I've noticed that the noise level of my Perseus is around 20-30dB
            > higher than on my SDR-IQ. It appears that the USB port may be the
            > problem. If I move the cable around a bit, the noise
            > changes/increases; if I press the contact tighter to the Perseus USB
            > port it decreases with 5-10dB. I also tried a different USB cable
            but
            > no luck.
            >
            > A common signal reference was Murmansk 657, -75dBm on both
            receivers,
            > so it's a matter of noise, not sensitivity. The difference is
            clearly
            > audible as well.
            >
            > Advice, anyone?
            >
            > Bjarne
            >
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