Loading ...
Sorry, an error occurred while loading the content.

Unwanted signals in bandpass when Near Spur

Expand Messages
  • wythevillebob
    I am receiving unwanted reception of Signals that I am not tuned to. For example if I am listening to a CW signal at the lower end of the band, I am also
    Message 1 of 4 , Nov 18, 2012
    • 0 Attachment
      I am receiving unwanted reception of Signals that I am not tuned to. For example if I am listening
      to a CW signal at the lower end of the band, I am also hearing signals that are about 3-5 kcs away from the
      Zero center frequency, I.E. adjacent to the Spur any format (cw,ssb,digital). The unwanted signals are in the band regardless of where I tune (when the unwanted signals occur around the spur, I am not tuned anywhere near the spur). I can tune to an open freq, no signals present, and I still hear the offending signal that is near
      the spur.

      My setup is the following.

      Gigabyte GA-970A-UD3, 8gb memory, AMD quad core 965, speed about 3.1 ghz, and the Audio card on board the mobo is a RealTek ALC 889 codec set at line in, all other inputs muted, audio sample rate 16 bit 192kcs.

      I am using RF-Space Version 1.5 R1048 with the Softrock Ensemble II built by Tony Parks, purchased about 2 months ago.

      I have also built and installed line input isolation on both I and Q signals with 600/600 xformers. Spur sidebands decreased from the center spur( did have two constant signals, one on each side)
      signals with isolation are now gone, with just a single small spur. However, if I tune to a signal down or up the band and a signal appears close (1-5kcs within the spur) I hear that signal also with the tuned signal altho it is weaker, but very readable. Only way to
      get clear reception is to move the offending signal away from the center spur by moving the band selection up or down, till the spur no longer has a signal near it. Then the reception is extremely good. No echo's no unwanted offending signals.

      I have also tried installing bandpass filters that are very narrow in front of the rx, the W3NQN 20mtr and 40 mtr kits from Kits and Parts.
      They work however, the symptoms are the same with or without the filters. I had first thought that they were out of band signals but found out they are not.

      Thus I know where are the signals coming from, But not sure how to solve and correct. This appears to be a function of the Spur and beat freq with the signal near the spur and the Line-input audio processed of the I and Q signals (it becomes a broad band issue, no matter what or where I tune you can hear the signal near the spur).(have tried many different levels of line input Same results)

      As I indicated, I can tune the offending signal away from the center spur freq (keep in mind that I am tuned 20 kcs away for example)
      and the unwanted signal disappears. The way I remove the offending signal is by moving the center freq up or down to get the offending signal out of the nearby spur.

      I do not have the classic Images associated with the I and Q not being correct. The Image rejection in the RF Space is working very good.

      Not sure as to what the next step should be in solving the unwanted signals??

      Any suggestions welcome.

      Thanks to the party that suggested muting all of the other line inputs, which I have done, This did solve the issue with an echo that occurred at times, this now is no longer a issue.

      Thanks in Advance

      Bob WB3DEH

      This is a very good rx for introduction to SDR and I am in no way have any objections to the Ensemble II, just wondering
      if this above issue can be solved.
    • Alan
      ... Subject: [softrock40] Unwanted signals in bandpass when Near Spur ... This is a mixer setting. You have Line in enabled in your soundcard playback mixer.
      Message 2 of 4 , Nov 18, 2012
      • 0 Attachment
        ----- Original Message -----
        Subject: [softrock40] Unwanted signals in bandpass when Near Spur


        >I am receiving unwanted reception of Signals that I am not tuned to. For example if I am listening
        > to a CW signal at the lower end of the band, I am also hearing signals that are about 3-5 kcs away from the
        > Zero center frequency, I.E. adjacent to the Spur any format

        This is a mixer setting.

        You have "Line in" enabled in your soundcard playback mixer.
        You hear the signals straight through, as well as those processed by the SDR program.

        73 Alan G4ZFQ
      • wythevillebob
        I will check the line Input to make sure it is muted also. I have attached in the photos a screen shot of the item, under IMAGES II. Thanks for the response.
        Message 3 of 4 , Nov 18, 2012
        • 0 Attachment
          I will check the line Input to make sure it is muted also. I have attached in the photos a screen shot of the item, under IMAGES II.

          Thanks for the response. Bob

          --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
          >
          >
          > ----- Original Message -----
          > Subject: [softrock40] Unwanted signals in bandpass when Near Spur
          >
          >
          > >I am receiving unwanted reception of Signals that I am not tuned to. For example if I am listening
          > > to a CW signal at the lower end of the band, I am also hearing signals that are about 3-5 kcs away from the
          > > Zero center frequency, I.E. adjacent to the Spur any format
          >
          > This is a mixer setting.
          >
          > You have "Line in" enabled in your soundcard playback mixer.
          > You hear the signals straight through, as well as those processed by the SDR program.
          >
          > 73 Alan G4ZFQ
          >
        • wythevillebob
          Alan G4ZFQ: Thank you so much, after looking and looking for the correct place to disable the line in recording function, I finally found the menu and muted
          Message 4 of 4 , Nov 18, 2012
          • 0 Attachment
            Alan G4ZFQ: Thank you so much, after looking and looking for the correct place to disable the line in recording function, I finally found the menu and muted the input record on line input. This has plagued me since getting the softrock ensemble II and the RF-Space Version 1.5 r 1048 about two months ago. The SDR radio has sparked my interest in the technical developments.

            Again I thank you very much for the help.

            Makes it a completely different experience.

            Regards

            Bob WB3DEH

            --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
            >
            >
            > ----- Original Message -----
            > Subject: [softrock40] Unwanted signals in bandpass when Near Spur
            >
            >
            > >I am receiving unwanted reception of Signals that I am not tuned to. For example if I am listening
            > > to a CW signal at the lower end of the band, I am also hearing signals that are about 3-5 kcs away from the
            > > Zero center frequency, I.E. adjacent to the Spur any format
            >
            > This is a mixer setting.
            >
            > You have "Line in" enabled in your soundcard playback mixer.
            > You hear the signals straight through, as well as those processed by the SDR program.
            >
            > 73 Alan G4ZFQ
            >
          Your message has been successfully submitted and would be delivered to recipients shortly.