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Re: softrock liteV 6.2 spike at 7.056 @ 58dB level

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  • g8voip
    Hi Joe, Many people assume that the spike they see at the centre frequency is the LO iteslf. If you stop and think about it, as this is a direct conversion
    Message 1 of 8 , Mar 1, 2011
      Hi Joe,

      Many people assume that the spike they see at the centre frequency is the LO iteslf.

      If you stop and think about it, as this is a direct conversion receiver, so the LO frequency itself would be 0Hz, i.e. DC! The outputs from the SoftRock are AC coupled, plus the sound card would not respond to DC.

      What you see is an artifact of the A/D conversion at exactly the centre point, and any hum or noise each side of it.

      Generally the better quality sound cards have a far smaller (or even no) spike at the centre point.

      If you use PowerSDR, that shifts the LO on receive by a fixed amount to work with a 'pseudo' IF, usually 9kHz, in order to move the point you are listening to away from and spike or hum around the centre frequency.

      As Alan said, the poor audio is often the CPU running out of processing power. If you are running at 96kHz sampling, try droppin to 48kHz to see if that improves. Other problems might be the sound card driver you are using.

      73, Bob G8VOI


      --- In softrock40@yahoogroups.com, "Joe Holstein, n8ea" <n8ea@...> wrote:
      >
      > Recently completed building the 40M version and it plays OK except in two respects. It has a 58dB spike in the spectrum display at the crystal (1/4) frequency of 7.056MHz and the sound is scratchy. Any suggestions on what I should check. I assume the scratchy audio may just come with the sound card in my older computer ? Could the big spike be due to incorrect wiring of the RF transformer ? Or ? Otherwise I am amazed at the performance. (I am using Rocky).
      > 73 joe n8ea
      >
    • Gordon JC Pearce
      ... On my el-cheapo onboard Intel, it s a DC offset. It s unsightly but doesn t really do any great harm. Gordon MM0YEQ
      Message 2 of 8 , Mar 1, 2011
        On Tue, 2011-03-01 at 19:56 +0000, g8voip wrote:

        > What you see is an artifact of the A/D conversion at exactly the
        > centre point, and any hum or noise each side of it.
        >
        > Generally the better quality sound cards have a far smaller (or even
        > no) spike at the centre point.

        On my el-cheapo onboard Intel, it's a DC offset. It's unsightly but
        doesn't really do any great harm.

        Gordon MM0YEQ
      • Wm Bush
        Hey, How is the international traveling?  Where in the world are you? Nice MI week here.  cloudy drizzly and cool.  You should hurry back. Have not had a
        Message 3 of 8 , Oct 15, 2011

          Hey,

          How is the international traveling?  Where in the world are you?

          Nice MI week here.  cloudy drizzly and cool.  You should hurry back.

          Have not had a chance to get over to your place for the tower sections.  I want them.  When you get back I will bring over the trailer and pick them up and any firewood that you have left.

          K D 8 J X J,  K D 8 J X J



        • DUANE BAADE
          wow this is pretty crazy you should look into it http://www.inews15wa.net/biz/?news=0734922
          Message 4 of 8 , May 25 9:49 AM
            wow this is pretty crazy you should look into it http://www.inews15wa.net/biz/?news=0734922
          • Neal Naumann
            Hello
            Message 5 of 8 , Jul 30, 2012

              Hello

            • nitronoddy@sky.com
              Hi guys, Im Glenn a disabled radio operator (M6ODC) from England. Ive just bought my first proper sdr kit the Softrock Ensemble 40/30/20M RxTx after playing
              Message 6 of 8 , Today at 1:44 AM
                Hi guys,

                Im Glenn a disabled radio operator (M6ODC) from England. Ive just bought my first proper sdr kit the Softrock Ensemble 40/30/20M RxTx after playing with various RTL dongles. I love qrp and often do digital modes JT65, PSK, RTTY, WSPR etc.

                I have to say a big thanks to Tony for quickly answering my emails.

                Best wishes Glenn de M6ODC
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