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

Re: image rejection help

Expand Messages
  • warrenallgyer
    Chris In the HDSDR menu there is a selection for RX Channel Mode. Make sure you have a known signal (I like to use my MFJ Antenna analyzer because it puts a
    Message 1 of 3 , Mar 24, 2013
    • 0 Attachment
      Chris

      In the HDSDR menu there is a selection for RX Channel Mode. Make sure you have a known signal (I like to use my MFJ Antenna analyzer because it puts a strong enough signal that can be measured easily at every stage in the receiver) on the screen, then go to Options/Channel Mode for RX and check each of the four options. It should normally be on I/Q but by running through Left Only, Right Only, and Left/Right combined, and observing the screen you will be able to see if either of your channels is missing and the relative level. Watch the noise level as you select Left/Right Combined.... it should rise by about 3 dB.

      I find this the quickest and surest way to confirm that the audio connections, cables, and levels are correct.

      A difference in levels between the left and right channel can usually be offset by PC and Software gain adjustments but it is not normal. The T5 transformer soldering is the first suspect here and then checking values in the components from the QSD mixer to the output jacks. There are two distinct paths here, accessible at key points on resistor hairpins and they should be almost identical throughout.

      Good luck!

      Warren Allgyer - W8TOD

      --- In softrock40@yahoogroups.com, "millerchris75" <millerchris75@...> wrote:
      >
      > I can use some help. I am finishing up the rx ensemble II. I am getting a mirror image on HDSRD. I have carefully gone through the image reduction help link at end of the build. Here is what I am confident on:
      > 1 T1 and T2 have been wired for correct phasing per updates.
      > 2. Sound card, xonar ds is set to line in and I can get two separate inputs. tested inputs. monitoring is off.
      > 3. The left channel I has a lower input than the right side Q when both are set to the same input level. But op amp tests out.
      > 5. When performing the testing of the op amp.
      > 6. I have gone and checked all of the components, I am not seeing anything wrong.
      >
      > I have been working on this for a while and need ideas.
      >
    • Alan
      ... Subject: [softrock40] image rejection help ... Are signals exactly the same each side? Is there absolutely no difference? I d think there would either have
      Message 2 of 3 , Mar 25, 2013
      • 0 Attachment
        ----- Original Message -----
        Subject: [softrock40] image rejection help


        >I can use some help. I am finishing up the rx ensemble II. I am getting a mirror image on HDSRD. I have carefully gone through
        >the image reduction help link at end of the build. Here is what I am confident on:
        > 1 T1 and T2 have been wired for correct phasing per updates.
        > 2. Sound card, xonar ds is set to line in and I can get two separate inputs. tested inputs. monitoring is off.
        > 3. The left channel I has a lower input than the right side Q when both are set to the same input level. But op amp tests out.
        > 5. When performing the testing of the op amp.
        > 6. I have gone and checked all of the components, I am not seeing anything wrong.
        >

        Are signals exactly the same each side?
        Is there absolutely no difference?
        I'd think there would either have to be a very big difference in the IQ signal levels for no difference to be seen.
        Or that the signals were exactly the same because they were shorted together.
        If there is a big difference between each signal then component differences (R25/26?) or bad soldering around the mixer might cause
        it.
        As Warren says a good stable signal is useful for this kind of investigation.
        An alternative is to run a transceiver at low power into a dummy load.

        73 Alan G4ZFQ
      Your message has been successfully submitted and would be delivered to recipients shortly.