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Progress - Ensemble II RX Dead band cleanup

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  • Dave Sublette
    Good morning, After making the transformer secondary wiring mods, I still had 5 to 10 khz of a dead band around the LO frequency at the center of the
    Message 1 of 8 , Jul 24 5:41 AM
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      Good morning,

      After making the transformer secondary wiring mods, I still had 5 to 10
      khz of a "dead band" around the LO frequency at the center of the
      display, making it necessary to retune the LO often in order to see weak
      signals.

      Something wasn't right. I did report measuring case to BNC shield as a
      short, even with the optional strap left open. Upon further
      investigation I saw that the mounting nut for the pc board next to the
      BNC connector was making contact with the ground pad for the BNC. A
      brief touch of the dremel tool and I ground off the pad just enough to
      clear the nut. The BNC shield is now open to the case.

      There was still a 3 to 5 khz dead band at the LO point on the display.
      I removed the 12 v wall transformer supply and replaced it with a 12v
      lead acid battery supply. Viola! There is now only the faintest trace
      at the LO frequency in the center of the display. I can copy the weakest
      of signals right through it.

      Now I am considering building a "brute force" filter, using an Iron core
      toroid with bifilar winding and large filter caps in both the plus and
      minus leads of the supply. Before I do that, has anyone done it and was
      it effective? The filter, if I build it, will be bigger than the wall
      transformer supply :-)

      73,

      Dave, K4TO
    • Alan
      ... Subject: [softrock40] Progress - Ensemble II RX Dead band cleanup ... Dave, Was the 12 v wall transformer supply grounded? This sounds just like a ground
      Message 2 of 8 , Jul 24 6:12 AM
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        ----- Original Message -----
        Subject: [softrock40] Progress - Ensemble II RX Dead band cleanup



        > I removed the 12 v wall transformer supply and replaced it with a 12v
        > lead acid battery supply. Viola! There is now only the faintest trace
        > at the LO frequency in the center of the display. I can copy the weakest
        > of signals right through it.
        >
        > Now I am considering building a "brute force" filter, using an Iron core
        > toroid with bifilar winding and large filter caps in both the plus and
        > minus leads of the supply. Before I do that, has anyone done it and was
        > it effective? The filter, if I build it, will be bigger than the wall
        > transformer supply :-)
        >

        Dave,

        Was the 12 v wall transformer supply grounded?
        This sounds just like a ground loop. The actual smoothing of the supply is not very critical because it is smoothed by the 5V
        regulator.

        And you do not actually see the LO. This is at zero Hz at the soundcard. If you see a single spike then it is probably due to the
        soundcard ADC. What you see each side is usually powerline frequency and harmonics.

        73 Alan G4ZFQ
      • vbifyz
        Agree with Alan, this was a ground loop. The third pin (ground) on the power supply is not good. Even the parasitic capacitance between the wall wart
        Message 3 of 8 , Jul 24 9:59 AM
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          Agree with Alan, this was a ground loop.
          The third pin (ground) on the power supply is not good.
          Even the parasitic capacitance between the wall wart transformer windings is enough to create some current in the power wiring (a kind of ground loop). I tried several wall warts until I found one that gave me no central hump.
          Another "mod" that reduced it even further was 4.7k resistor in place of the antenna ground jumper. But this is probably effective for my antenna only.

          73, Mike

          --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
          >
          >
          > ----- Original Message -----
          > Subject: [softrock40] Progress - Ensemble II RX Dead band cleanup
          >
          >
          >
          > > I removed the 12 v wall transformer supply and replaced it with a 12v
          > > lead acid battery supply. Viola! There is now only the faintest trace
          > > at the LO frequency in the center of the display. I can copy the weakest
          > > of signals right through it.
          > >
          > > Now I am considering building a "brute force" filter, using an Iron core
          > > toroid with bifilar winding and large filter caps in both the plus and
          > > minus leads of the supply. Before I do that, has anyone done it and was
          > > it effective? The filter, if I build it, will be bigger than the wall
          > > transformer supply :-)
          > >
          >
          > Dave,
          >
          > Was the 12 v wall transformer supply grounded?
          > This sounds just like a ground loop. The actual smoothing of the supply is not very critical because it is smoothed by the 5V
          > regulator.
          >
          > And you do not actually see the LO. This is at zero Hz at the soundcard. If you see a single spike then it is probably due to the
          > soundcard ADC. What you see each side is usually powerline frequency and harmonics.
          >
          > 73 Alan G4ZFQ
          >
        • K2DMS
          Speaking of wall-warts, I was wondering why the Ensemble II RX DC input jack is not the 2.1mm, what I perceived to be more or less a recent standard in the
          Message 4 of 8 , Jul 24 10:28 AM
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            Speaking of wall-warts, I was wondering why the Ensemble II RX DC input jack is not the 2.1mm, what I perceived to be more or less a recent standard in the realm of ham radio.

            Just about everything else I have in the shack, Linksys routers, Kantronics KPC3+, and even an LCD TV use the 2.1mm plug for power.

            Did I get the wrong jack with my kit, or is this by design?

            --- In softrock40@yahoogroups.com, "vbifyz" <3ym3ym@...> wrote:
            >
            > Agree with Alan, this was a ground loop.
            > The third pin (ground) on the power supply is not good.
            > Even the parasitic capacitance between the wall wart transformer windings is enough to create some current in the power wiring (a kind of ground loop). I tried several wall warts until I found one that gave me no central hump.
            > Another "mod" that reduced it even further was 4.7k resistor in place of the antenna ground jumper. But this is probably effective for my antenna only.
            >
            > 73, Mike
            >
            > --- In softrock40@yahoogroups.com, "Alan" <alan4alan@> wrote:
            > >
            > >
            > > ----- Original Message -----
            > > Subject: [softrock40] Progress - Ensemble II RX Dead band cleanup
            > >
            > >
            > >
            > > > I removed the 12 v wall transformer supply and replaced it with a 12v
            > > > lead acid battery supply. Viola! There is now only the faintest trace
            > > > at the LO frequency in the center of the display. I can copy the weakest
            > > > of signals right through it.
            > > >
            > > > Now I am considering building a "brute force" filter, using an Iron core
            > > > toroid with bifilar winding and large filter caps in both the plus and
            > > > minus leads of the supply. Before I do that, has anyone done it and was
            > > > it effective? The filter, if I build it, will be bigger than the wall
            > > > transformer supply :-)
            > > >
            > >
            > > Dave,
            > >
            > > Was the 12 v wall transformer supply grounded?
            > > This sounds just like a ground loop. The actual smoothing of the supply is not very critical because it is smoothed by the 5V
            > > regulator.
            > >
            > > And you do not actually see the LO. This is at zero Hz at the soundcard. If you see a single spike then it is probably due to the
            > > soundcard ADC. What you see each side is usually powerline frequency and harmonics.
            > >
            > > 73 Alan G4ZFQ
            > >
            >
          • KQ8M
            In all of the Ensembles I have built I have not used the 4.7k resistor or the shorting ground. I have left it open to allow for isolation. Or, am I wrong? I
            Message 5 of 8 , Jul 24 10:30 AM
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              In all of the Ensembles I have built I have not used the 4.7k resistor or the shorting ground. I have left it open to allow for isolation. Or, am I wrong?

               

              I believe there was a discussion on this a while ago but not sure how it ended.

               

              73,

              Tim Herrick, KQ8M

              Charter Member North Coast Contesters

              kq8m@...

               

              AR-Cluster V6 kq8m.no-ip.org

              User Ports: 23, 7373  with local skimmer, 7374 without local skimmer

              Server Ports: V6 3607, V4 Active 3605, V4 Passive 3606

               

              From: softrock40@yahoogroups.com [mailto:softrock40@yahoogroups.com] On Behalf Of vbifyz
              Sent: Tuesday, July 24, 2012 12:59 PM
              To: softrock40@yahoogroups.com
              Subject: [softrock40] Re: Progress - Ensemble II RX Dead band cleanup

               

               

              Agree with Alan, this was a ground loop.
              The third pin (ground) on the power supply is not good.
              Even the parasitic capacitance between the wall wart transformer windings is enough to create some current in the power wiring (a kind of ground loop). I tried several wall warts until I found one that gave me no central hump.
              Another "mod" that reduced it even further was 4.7k resistor in place of the antenna ground jumper. But this is probably effective for my antenna only.

              73, Mike

              --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
              >
              >
              > ----- Original Message -----
              > Subject: [softrock40] Progress - Ensemble II RX Dead band cleanup
              >
              >
              >
              > > I removed the 12 v wall transformer supply and replaced it with a 12v
              > > lead acid battery supply. Viola! There is now only the faintest trace
              > > at the LO frequency in the center of the display. I can copy the weakest
              > > of signals right through it.
              > >
              > > Now I am considering building a "brute force" filter, using an Iron core
              > > toroid with bifilar winding and large filter caps in both the plus and
              > > minus leads of the supply. Before I do that, has anyone done it and was
              > > it effective? The filter, if I build it, will be bigger than the wall
              > > transformer supply :-)
              > >
              >
              > Dave,
              >
              > Was the 12 v wall transformer supply grounded?
              > This sounds just like a ground loop. The actual smoothing of the supply is not very critical because it is smoothed by the 5V
              > regulator.
              >
              > And you do not actually see the LO. This is at zero Hz at the soundcard. If you see a single spike then it is probably due to the
              > soundcard ADC. What you see each side is usually powerline frequency and harmonics.
              >
              > 73 Alan G4ZFQ
              >

            • Alan
              ... Subject: RE: [softrock40] Re: Progress - Ensemble II RX Dead band cleanup ... Mike, I often leave the ground between a PSU and the Softrock disconnected.
              Message 6 of 8 , Jul 24 11:10 AM
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                ----- Original Message -----
                Subject: RE: [softrock40] Re: Progress - Ensemble II RX Dead band cleanup


                > In all of the Ensembles I have built I have not used the 4.7k resistor or the shorting ground. I have left it open to allow for
                > isolation.

                Mike,

                I often leave the ground between a PSU and the Softrock disconnected. Just the positive. The return will then go back through the
                PSU ground, no loop. But it is probably best not to use the audio ground for the only Softrock ground. Doubling up on the Softrock
                computer ground, to a place near the soundcard, does not usually cause problems.

                Tim,

                That's how I do it, just leave open, no connection.
                Something like 4K7, or maybe much higher should do no harm and possibly discharge static. But the antenna coax shield itself should
                be grounded.
                The only time a link is required is if an end-fed is used.

                73 Alan G4ZFQ
              • Jerry Kaidor
                ... *** Also agree. And WRT modern wall warts - I think the transformers have been cost-reduced out of them, and they re using capacitive voltage dividers or
                Message 7 of 8 , Jul 24 12:05 PM
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                  > Agree with Alan, this was a ground loop.
                  ...I tried several wall warts until I found one that gave me no
                  > central hump....

                  *** Also agree. And WRT modern wall warts - I think the transformers have
                  been cost-reduced out of them, and they're using capacitive voltage dividers
                  or buck inductors. None of which gives you any ground isolation. Even if
                  there is no third pin on the wall wart, the neutral goes right back to the
                  ground at the other end.

                  Maybe a little DC-DC converter or isolator with an oscillator and
                  a toroid transformer?

                  Once upon a time, I had a Ten-Tec PM1 ( Power-mite 1 ), which was
                  actually Ten-tec's very first product. It was a direct conversion
                  receiver and a matching QRP transmitter, distributed as modules. I seem
                  to remember I could never get any hum reduction except with batteries.

                  I'm going to try removing the negative-ground link on my lab supply
                  and see if that makes any difference for my Ensemble RXTX.

                  - Jerry Kaidor
                • KQ8M
                  Hi Alan and thank you for your answer. By the way on the answer to Mike I am not sure I understand. You are saying you don t use the ground from the PSU only
                  Message 8 of 8 , Jul 24 9:49 PM
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                    Hi Alan and thank you for your answer.

                     

                    By the way on the answer to Mike I am not sure I understand. You are saying you don't use the ground from the PSU only the positive lead but then you say the return will go back through the PSU ground. You lost me there. Are you using the computers PSU to power the SoftRock? I have a couple of ancient Radio Shack 12v power supplies which are non switching and they seem to work great.

                     

                    73,

                    Tim Herrick, KQ8M

                    Charter Member North Coast Contesters

                    kq8m@...

                     

                    AR-Cluster V6 kq8m.no-ip.org

                    User Ports: 23, 7373  with local skimmer, 7374 without local skimmer

                    Server Ports: V6 3607, V4 Active 3605, V4 Passive 3606

                     

                    From: softrock40@yahoogroups.com [mailto:softrock40@yahoogroups.com] On Behalf Of Alan
                    Sent: Tuesday, July 24, 2012 2:11 PM
                    To: softrock40@yahoogroups.com
                    Subject: Re: [softrock40] Re: Progress - Ensemble II RX Dead band cleanup

                     

                     


                    ----- Original Message -----
                    Subject: RE: [softrock40] Re: Progress - Ensemble II RX Dead band cleanup

                    > In all of the Ensembles I have built I have not used the 4.7k resistor or the shorting ground. I have left it open to allow for
                    > isolation.

                    Mike,

                    I often leave the ground between a PSU and the Softrock disconnected. Just the positive. The return will then go back through the
                    PSU ground, no loop. But it is probably best not to use the audio ground for the only Softrock ground. Doubling up on the Softrock
                    computer ground, to a place near the soundcard, does not usually cause problems.

                    Tim,

                    That's how I do it, just leave open, no connection.
                    Something like 4K7, or maybe much higher should do no harm and possibly discharge static. But the antenna coax shield itself should
                    be grounded.
                    The only time a link is required is if an end-fed is used.

                    73 Alan G4ZFQ

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