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spurs found at 1 and 2 MHz

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  • Jurgen Bartels
    Recently while DXing the 1600-1700 kHz band I noticed a weak carrier and then discovered it was a spur caused by Perseus, because Winradio did not show it, and
    Message 1 of 4 , Oct 1, 2008
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      Recently while DXing the 1600-1700 kHz band I noticed a weak carrier and then
      discovered it was a spur caused by Perseus, because Winradio did not show it,
      and once Perseus was connected back to the antenna, Winradio showed it also.

      I just tried to do it again and connected only a 50 Ohm termination resistor to
      the input (no antenna), but don't see it in that range anymore. But I do see
      weak spurs at 1 and 2 Mhz and those I see also on Winradio when I connect it to
      Perseus input. Thus the spurs are actually leaving Perseus.

      For 1Ms/s mode
      The spur level is -105 dBm,
      the noise floor for the other frequencies is -113 dBm

      Lowering the sample rate also reduces the spur level that I monitored with
      winradio. The higher the rate the higher the spur levels become

      Setting the attenuation higher reduces the level seen by Winradio,
      but Perseus s-meter shows them stronger and stronger

      with 30dB the meter shows -75dBm, with 0dB only -107 dB

      Do others see that also?



      Jurgen Bartels Suellwarden, N. Germany
      http://dx.3sdesign.de/tv_logs_2008.htm

      http://fewo.3sdesign.de - Holidays at Northsea coast
    • Mauno Ritola
      I have spurs at 1 and 2 MHz when antenna disconnected adn using 1000 kS/s sampling rate, not with others. Much clearer if Presector clicked. ... From: Jurgen
      Message 2 of 4 , Oct 1, 2008
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        I have spurs at 1 and 2 MHz when antenna disconnected adn using 1000 kS/s sampling rate, not with others. Much clearer if Presector clicked.
         
        ----- Original Message -----
        Sent: Wednesday, October 01, 2008 4:46 PM
        Subject: [perseus_SDR] spurs found at 1 and 2 MHz

        Recently while DXing the 1600-1700 kHz band I noticed a weak carrier and then
        discovered it was a spur caused by Perseus, because Winradio did not show it,
        and once Perseus was connected back to the antenna, Winradio showed it also.

        I just tried to do it again and connected only a 50 Ohm termination resistor to
        the input (no antenna), but don't see it in that range anymore. But I do see
        weak spurs at 1 and 2 Mhz and those I see also on Winradio when I connect it to
        Perseus input. Thus the spurs are actually leaving Perseus.

        For 1Ms/s mode
        The spur level is -105 dBm,
        the noise floor for the other frequencies is -113 dBm

        Lowering the sample rate also reduces the spur level that I monitored with
        winradio. The higher the rate the higher the spur levels become

        Setting the attenuation higher reduces the level seen by Winradio,
        but Perseus s-meter shows them stronger and stronger

        with 30dB the meter shows -75dBm, with 0dB only -107 dB

        Do others see that also?

        Jurgen Bartels Suellwarden, N. Germany
        http://dx.3sdesign. de/tv_logs_ 2008.htm

        http://fewo. 3sdesign. de - Holidays at Northsea coast

      • Willi Passmann
        ... I can confirm spurs without antenna on 1 MHz 125 sampling rate: -117 dBm (none with preselector off ) 500 sampling rate -127 dBm (-124 with preselector
        Message 3 of 4 , Oct 1, 2008
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          Mauno Ritola schrieb:
          I have spurs at 1 and 2 MHz when antenna disconnected adn using 1000 kS/s sampling rate, not with others. Much clearer if Presector clicked.

          I can confirm spurs without antenna on
          1 MHz
          125 sampling rate: -117 dBm (none with preselector 'off')
          500 sampling rate -127 dBm (-124 with preselector 'off')
          1000 sampling rate -123 dBm (-122 with preselector 'off')
          2000 sampling rate -115 dBm (-114 with preselector 'off')

          2 MHz
          1000 sampling rate -118 dBm (-117 with preselector 'off')
          2000 sampling rate -119 dBm (-118 with preselector 'off')

          The signal strength may differ by about 5 dBm when hitting the same sampling rate a second time.
          Another FPGA matter?

          vy 73,
          Willi

          http://www.radio-portal.org/sdr.html
          SDR-Special

        • Jurgen Bartels
          ... Just tried it again after upgrading to 1.1c Now the spurs don t show up in the spectrum, but instead a phantom spur is continously shown at center
          Message 4 of 4 , Oct 1, 2008
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            > I can confirm spurs without antenna on
            > 1 MHz
            > 125 sampling rate: -117 dBm (none with preselector 'off')
            > 500 sampling rate -127 dBm (-124 with preselector 'off')
            > 1000 sampling rate -123 dBm (-122 with preselector 'off')
            > 2000 sampling rate -115 dBm (-114 with preselector 'off')
            >
            > 2 MHz
            > 1000 sampling rate -118 dBm (-117 with preselector 'off')
            > 2000 sampling rate -119 dBm (-118 with preselector 'off')
            >
            > The signal strength may differ by about 5 dBm when hitting the same
            > sampling rate a second time.

            Just tried it again after upgrading to 1.1c
            Now the spurs don't show up in the spectrum, but instead a phantom spur is
            continously shown at center frequency, no matter what frequency is chosen.
            S-meter shows -101 dBm. After switching s-rate serveral times the spurs
            at 1 & 2 Mhz appeared again. Only in 2000 mode it disappears.

            Winradio sees the 1 MHz spurs at maximum in 1000-mode, in 2000-mode it is much
            weaker

            My minimal level does not get lower than -114 (in 1000-mode) on other
            frequencies, probably caused by the sticking phantom spur. It seems your level
            can go much lower




            Jurgen Bartels Suellwarden, N. Germany
            http://dx.3sdesign.de/tv_logs_2008.htm

            http://fewo.3sdesign.de - Holidays at Northsea coast
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