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SP-70 Transformer performance?

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  • Pete Smith
    I received and installed the two Triad SP-70 isolation transformers that I ordered from Gopher, and ran I/Q balance adjustments in both Rocky and CW Skimmer. I
    Message 1 of 11 , Jun 29, 2008
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      I received and installed the two Triad SP-70 isolation transformers that I
      ordered from Gopher, and ran I/Q balance adjustments in both Rocky and CW
      Skimmer.

      I was surprised to see that both the gain and phase results show a
      substantial difference between the two channels. The phase difference is
      7-8 degrees, while the gain of one channel is only .65 to .66 of the
      other. There is also a fairly substantial scattering of the data points,
      though this is a phenomenon I've grown to expect as the software collects
      real-world signals over time. The image suppression is working well, however.

      What I'm wondering is whether such differences are common? Are they a
      function of normal, to-be-expected variations in transformer manufacturing,
      or possibly differences in the two sound card channels? Or is it possible
      that I have a wiring error in my 8.3 receiver. I realize the gain
      imbalance is only ~2 dB, but I'm still wondering...


      73, Pete N4ZR
    • Jeff Kashinsky
      Have you tried spapping the channels to see it the variation follows the transformers. Mine will appear on Monday so I can t try yet? Jeff W2UA ... that I ...
      Message 2 of 11 , Jun 29, 2008
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        Have you tried spapping the channels to see it the variation follows
        the transformers. Mine will appear on Monday so I can't try yet?

        Jeff
        W2UA

        --- In softrock40@yahoogroups.com, Pete Smith <n4zr@...> wrote:
        >
        > I received and installed the two Triad SP-70 isolation transformers
        that I
        > ordered from Gopher, and ran I/Q balance adjustments in both Rocky
        and CW
        > Skimmer.
        >
        > I was surprised to see that both the gain and phase results show a
        > substantial difference between the two channels. The phase
        difference is
        > 7-8 degrees, while the gain of one channel is only .65 to .66 of
        the
        > other. There is also a fairly substantial scattering of the data
        points,
        > though this is a phenomenon I've grown to expect as the software
        collects
        > real-world signals over time. The image suppression is working
        well, however.
        >
        > What I'm wondering is whether such differences are common? Are
        they a
        > function of normal, to-be-expected variations in transformer
        manufacturing,
        > or possibly differences in the two sound card channels? Or is it
        possible
        > that I have a wiring error in my 8.3 receiver. I realize the gain
        > imbalance is only ~2 dB, but I'm still wondering...
        >
        >
        > 73, Pete N4ZR
        >
      • Pete Smith
        I did try swapping, and it did follow. Not sure that tells me anything, though hi 73, Pete
        Message 3 of 11 , Jun 29, 2008
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          I did try swapping, and it did follow. Not sure that tells me anything,
          though hi

          73, Pete

          At 11:48 AM 6/29/2008, you wrote:
          >Have you tried spapping the channels to see it the variation follows
          >the transformers. Mine will appear on Monday so I can't try yet?
          >
          >Jeff
          >W2UA
          >
          >--- In softrock40@yahoogroups.com, Pete Smith <n4zr@...> wrote:
          > >
          > > I received and installed the two Triad SP-70 isolation transformers
          >that I
          > > ordered from Gopher, and ran I/Q balance adjustments in both Rocky
          >and CW
          > > Skimmer.
          > >
          > > I was surprised to see that both the gain and phase results show a
          > > substantial difference between the two channels. The phase
          >difference is
          > > 7-8 degrees, while the gain of one channel is only .65 to .66 of
          >the
          > > other. There is also a fairly substantial scattering of the data
          >points,
          > > though this is a phenomenon I've grown to expect as the software
          >collects
          > > real-world signals over time. The image suppression is working
          >well, however.
          > >
          > > What I'm wondering is whether such differences are common? Are
          >they a
          > > function of normal, to-be-expected variations in transformer
          >manufacturing,
          > > or possibly differences in the two sound card channels? Or is it
          >possible
          > > that I have a wiring error in my 8.3 receiver. I realize the gain
          > > imbalance is only ~2 dB, but I'm still wondering...
          > >
          > >
          > > 73, Pete N4ZR
          > >
          >
          >
          >
          >------------------------------------
          >
          >Yahoo! Groups Links
          >
          >
          >
        • Jack Smith
          Pete: Although the transformers are spec ed at 600:600, in fact there is a small difference in the number of turns between the primary and secondary windings.
          Message 4 of 11 , Jun 29, 2008
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            Pete:

            Although the transformers are spec'ed at 600:600, in fact there is a
            small difference in the number of turns between the primary and
            secondary windings.

            Did you set the two transformers up with the same pin numbers on the
            Softrock side for both channels?

            I'll make a measurement or two later today, but you are not seeing
            normal operation, I believe.

            Jack

            Pete Smith wrote:
            >
            > I did try swapping, and it did follow. Not sure that tells me anything,
            > though hi
            >
            > 73, Pete
            >
            > At 11:48 AM 6/29/2008, you wrote:
            > >Have you tried spapping the channels to see it the variation follows
            > >the transformers. Mine will appear on Monday so I can't try yet?
            > >
            > >Jeff
            > >W2UA
            > >
            > >--- In softrock40@yahoogroups.com
            > <mailto:softrock40%40yahoogroups.com>, Pete Smith <n4zr@...> wrote:
            > > >
            > > > I received and installed the two Triad SP-70 isolation transformers
            > >that I
            > > > ordered from Gopher, and ran I/Q balance adjustments in both Rocky
            > >and CW
            > > > Skimmer.
            > > >
            > > > I was surprised to see that both the gain and phase results show a
            > > > substantial difference between the two channels. The phase
            > >difference is
            > > > 7-8 degrees, while the gain of one channel is only .65 to .66 of
            > >the
            > > > other. There is also a fairly substantial scattering of the data
            > >points,
            > > > though this is a phenomenon I've grown to expect as the software
            > >collects
            > > > real-world signals over time. The image suppression is working
            > >well, however.
            > > >
            > > > What I'm wondering is whether such differences are common? Are
            > >they a
            > > > function of normal, to-be-expected variations in transformer
            > >manufacturing,
            > > > or possibly differences in the two sound card channels? Or is it
            > >possible
            > > > that I have a wiring error in my 8.3 receiver. I realize the gain
            > > > imbalance is only ~2 dB, but I'm still wondering...
            > > >
            > > >
            > > > 73, Pete N4ZR
            > > >
            > >
            > >
            > >
            > >------------------------------------
            > >
            > >Yahoo! Groups Links
            > >
            > >
            > >
            >
            >
          • Pete Smith
            Yes, I did, Jack - I was very careful to make sure that the top of the windings (pins 1 and 3) went to the signal lines from the SoftRock and to the sound
            Message 5 of 11 , Jun 29, 2008
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              Yes, I did, Jack - I was very careful to make sure that the top of the
              windings (pins 1 and 3) went to the signal lines from the SoftRock and to
              the sound card, and that the bottoms (2 and 4) went to the common lead on
              their respective side of the transformer. I will double-check, because I
              have a history of this sort of mistake, but I don't think so.

              I did notice that the DC resistance of the primary and secondary are quite
              different - 72 vs 92 ohms.

              I am also seeing about the same dead-zone as with the radio-shack
              transformers - maybe slightly narrower - around the LO frequency.

              73, Pete N4ZR

              At 12:23 PM 6/29/2008, you wrote:
              >Pete:
              >
              >Although the transformers are spec'ed at 600:600, in fact there is a
              >small difference in the number of turns between the primary and
              >secondary windings.
              >
              >Did you set the two transformers up with the same pin numbers on the
              >Softrock side for both channels?
              >
              >I'll make a measurement or two later today, but you are not seeing
              >normal operation, I believe.
              >
              >Jack
              >
              >Pete Smith wrote:
              > >
              > > I did try swapping, and it did follow. Not sure that tells me anything,
              > > though hi
              > >
              > > 73, Pete
              > >
              > > At 11:48 AM 6/29/2008, you wrote:
              > > >Have you tried spapping the channels to see it the variation follows
              > > >the transformers. Mine will appear on Monday so I can't try yet?
              > > >
              > > >Jeff
              > > >W2UA
              > > >
              > > >--- In softrock40@yahoogroups.com
              > > <mailto:softrock40%40yahoogroups.com>, Pete Smith <n4zr@...> wrote:
              > > > >
              > > > > I received and installed the two Triad SP-70 isolation transformers
              > > >that I
              > > > > ordered from Gopher, and ran I/Q balance adjustments in both Rocky
              > > >and CW
              > > > > Skimmer.
              > > > >
              > > > > I was surprised to see that both the gain and phase results show a
              > > > > substantial difference between the two channels. The phase
              > > >difference is
              > > > > 7-8 degrees, while the gain of one channel is only .65 to .66 of
              > > >the
              > > > > other. There is also a fairly substantial scattering of the data
              > > >points,
              > > > > though this is a phenomenon I've grown to expect as the software
              > > >collects
              > > > > real-world signals over time. The image suppression is working
              > > >well, however.
              > > > >
              > > > > What I'm wondering is whether such differences are common? Are
              > > >they a
              > > > > function of normal, to-be-expected variations in transformer
              > > >manufacturing,
              > > > > or possibly differences in the two sound card channels? Or is it
              > > >possible
              > > > > that I have a wiring error in my 8.3 receiver. I realize the gain
              > > > > imbalance is only ~2 dB, but I'm still wondering...
              > > > >
              > > > >
              > > > > 73, Pete N4ZR
              > > > >
              > > >
              > > >
              > > >
              > > >------------------------------------
              > > >
              > > >Yahoo! Groups Links
              > > >
              > > >
              > > >
              > >
              > >
              >
              >------------------------------------
              >
              >Yahoo! Groups Links
              >
              >
              >
            • Jack Smith
              I ran quick check and see no evidence of serious phase or amplitude differences. I used the 8192 KHz Softrock Lite board with SP70 transformers on both
              Message 6 of 11 , Jun 29, 2008
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                I ran quick check and see no evidence of serious phase or amplitude
                differences.

                I used the 8192 KHz Softrock Lite board with SP70 transformers on both
                channels. Operating without a terminating resistor into the x10 probes
                of a Tektronix TDS430 digital oscilloscope. Set a signal generator on
                the input and swept from -100 KHz to +100 KHz of the 8192 KHz center
                frequency. Set the TDS430 to compute and display phase difference
                between the two channels as well as to compute and display the cycle RMS
                for each channel for amplitude differences.

                Stepped in 20 KHz increments from -100 to +100 KHz. Over this range, the
                amplitude difference between the two channels was around 1 or 2 percent
                except at the -100 KHz extreme where it was 5% or so. Phase shift over
                the entire 200 KHz range was less than 4 degrees. That is, at 0 KHz
                offset (centered) the phase shift was 90 degrees as close as I can
                measure it with the digital oscilloscope. At -100 KHz, it was -92
                degrees. At +100 KHz it was -88 degrees. This is actually the same phase
                shift of 2 degrees, but it shows up with an inverted sign depending on
                which way you are with respect to zero center frequency. I'll call it 4
                degrees phase error, but it might be more accurate to say it's 2 degrees
                error.

                So, at least with the setup I have the SP70 transformers seem to work well.

                Jack


                Pete Smith wrote:
                >
                > I did try swapping, and it did follow. Not sure that tells me anything,
                > though hi
                >
                > 73, Pete
                >
                > At 11:48 AM 6/29/2008, you wrote:
                > >Have you tried spapping the channels to see it the variation follows
                > >the transformers. Mine will appear on Monday so I can't try yet?
                > >
                > >Jeff
                > >W2UA
                > >
                > >--- In softrock40@yahoogroups.com
                > <mailto:softrock40%40yahoogroups.com>, Pete Smith <n4zr@...> wrote:
                > > >
                > > > I received and installed the two Triad SP-70 isolation transformers
                > >that I
                > > > ordered from Gopher, and ran I/Q balance adjustments in both Rocky
                > >and CW
                > > > Skimmer.
                > > >
                > > > I was surprised to see that both the gain and phase results show a
                > > > substantial difference between the two channels. The phase
                > >difference is
                > > > 7-8 degrees, while the gain of one channel is only .65 to .66 of
                > >the
                > > > other. There is also a fairly substantial scattering of the data
                > >points,
                > > > though this is a phenomenon I've grown to expect as the software
                > >collects
                > > > real-world signals over time. The image suppression is working
                > >well, however.
                > > >
                > > > What I'm wondering is whether such differences are common? Are
                > >they a
                > > > function of normal, to-be-expected variations in transformer
                > >manufacturing,
                > > > or possibly differences in the two sound card channels? Or is it
                > >possible
                > > > that I have a wiring error in my 8.3 receiver. I realize the gain
                > > > imbalance is only ~2 dB, but I'm still wondering...
                > > >
                > > >
                > > > 73, Pete N4ZR
                > > >
                > >
                > >
                > >
                > >------------------------------------
                > >
                > >Yahoo! Groups Links
                > >
                > >
                > >
                >
                >
              • Pete Smith
                OK, so I guess my next step is to take them out of the circuit and see what happens to the numbers. Thanks, Jack! 73, Pete
                Message 7 of 11 , Jun 29, 2008
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                  OK, so I guess my next step is to take them out of the circuit and see what
                  happens to the numbers. Thanks, Jack!

                  73, Pete

                  At 02:21 PM 6/29/2008, Jack Smith wrote:
                  >I ran quick check and see no evidence of serious phase or amplitude
                  >differences.
                  >
                  >I used the 8192 KHz Softrock Lite board with SP70 transformers on both
                  >channels. Operating without a terminating resistor into the x10 probes
                  >of a Tektronix TDS430 digital oscilloscope. Set a signal generator on
                  >the input and swept from -100 KHz to +100 KHz of the 8192 KHz center
                  >frequency. Set the TDS430 to compute and display phase difference
                  >between the two channels as well as to compute and display the cycle RMS
                  >for each channel for amplitude differences.
                  >
                  >Stepped in 20 KHz increments from -100 to +100 KHz. Over this range, the
                  >amplitude difference between the two channels was around 1 or 2 percent
                  >except at the -100 KHz extreme where it was 5% or so. Phase shift over
                  >the entire 200 KHz range was less than 4 degrees. That is, at 0 KHz
                  >offset (centered) the phase shift was 90 degrees as close as I can
                  >measure it with the digital oscilloscope. At -100 KHz, it was -92
                  >degrees. At +100 KHz it was -88 degrees. This is actually the same phase
                  >shift of 2 degrees, but it shows up with an inverted sign depending on
                  >which way you are with respect to zero center frequency. I'll call it 4
                  >degrees phase error, but it might be more accurate to say it's 2 degrees
                  >error.
                  >
                  >So, at least with the setup I have the SP70 transformers seem to work well.
                  >
                  >Jack
                  >
                  >
                  >Pete Smith wrote:
                  > >
                  > > I did try swapping, and it did follow. Not sure that tells me anything,
                  > > though hi
                  > >
                  > > 73, Pete
                  > >
                  > > At 11:48 AM 6/29/2008, you wrote:
                  > > >Have you tried spapping the channels to see it the variation follows
                  > > >the transformers. Mine will appear on Monday so I can't try yet?
                  > > >
                  > > >Jeff
                  > > >W2UA
                  > > >
                  > > >--- In softrock40@yahoogroups.com
                  > > <mailto:softrock40%40yahoogroups.com>, Pete Smith <n4zr@...> wrote:
                  > > > >
                  > > > > I received and installed the two Triad SP-70 isolation transformers
                  > > >that I
                  > > > > ordered from Gopher, and ran I/Q balance adjustments in both Rocky
                  > > >and CW
                  > > > > Skimmer.
                  > > > >
                  > > > > I was surprised to see that both the gain and phase results show a
                  > > > > substantial difference between the two channels. The phase
                  > > >difference is
                  > > > > 7-8 degrees, while the gain of one channel is only .65 to .66 of
                  > > >the
                  > > > > other. There is also a fairly substantial scattering of the data
                  > > >points,
                  > > > > though this is a phenomenon I've grown to expect as the software
                  > > >collects
                  > > > > real-world signals over time. The image suppression is working
                  > > >well, however.
                  > > > >
                  > > > > What I'm wondering is whether such differences are common? Are
                  > > >they a
                  > > > > function of normal, to-be-expected variations in transformer
                  > > >manufacturing,
                  > > > > or possibly differences in the two sound card channels? Or is it
                  > > >possible
                  > > > > that I have a wiring error in my 8.3 receiver. I realize the gain
                  > > > > imbalance is only ~2 dB, but I'm still wondering...
                  > > > >
                  > > > >
                  > > > > 73, Pete N4ZR
                  > > > >
                  > > >
                  > > >
                  > > >
                  > > >------------------------------------
                  > > >
                  > > >Yahoo! Groups Links
                  > > >
                  > > >
                  > > >
                  > >
                  > >
                  >
                  >------------------------------------
                  >
                  >Yahoo! Groups Links
                  >
                  >
                  >
                • Jack Smith
                  There s an argument that as long as the software corrects for the phase and amplitude differences, then forget about fixing it. Jack
                  Message 8 of 11 , Jun 29, 2008
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                    There's an argument that as long as the software corrects for the phase
                    and amplitude differences, then forget about fixing it.

                    Jack


                    Pete Smith wrote:
                    >
                    > OK, so I guess my next step is to take them out of the circuit and see
                    > what
                    > happens to the numbers. Thanks, Jack!
                    >
                    > 73, Pete
                    >
                    > At 02:21 PM 6/29/2008, Jack Smith wrote:
                    > >I ran quick check and see no evidence of serious phase or amplitude
                    > >differences.
                    > >
                    > >I used the 8192 KHz Softrock Lite board with SP70 transformers on both
                    > >channels. Operating without a terminating resistor into the x10 probes
                    > >of a Tektronix TDS430 digital oscilloscope. Set a signal generator on
                    > >the input and swept from -100 KHz to +100 KHz of the 8192 KHz center
                    > >frequency. Set the TDS430 to compute and display phase difference
                    > >between the two channels as well as to compute and display the cycle RMS
                    > >for each channel for amplitude differences.
                    > >
                    > >Stepped in 20 KHz increments from -100 to +100 KHz. Over this range, the
                    > >amplitude difference between the two channels was around 1 or 2 percent
                    > >except at the -100 KHz extreme where it was 5% or so. Phase shift over
                    > >the entire 200 KHz range was less than 4 degrees. That is, at 0 KHz
                    > >offset (centered) the phase shift was 90 degrees as close as I can
                    > >measure it with the digital oscilloscope. At -100 KHz, it was -92
                    > >degrees. At +100 KHz it was -88 degrees. This is actually the same phase
                    > >shift of 2 degrees, but it shows up with an inverted sign depending on
                    > >which way you are with respect to zero center frequency. I'll call it 4
                    > >degrees phase error, but it might be more accurate to say it's 2 degrees
                    > >error.
                    > >
                    > >So, at least with the setup I have the SP70 transformers seem to work
                    > well.
                    > >
                    > >Jack
                    > >
                    > >
                    > >Pete Smith wrote:
                    > > >
                    > > > I did try swapping, and it did follow. Not sure that tells me
                    > anything,
                    > > > though hi
                    > > >
                    > > > 73, Pete
                    > > >
                    > > > At 11:48 AM 6/29/2008, you wrote:
                    > > > >Have you tried spapping the channels to see it the variation follows
                    > > > >the transformers. Mine will appear on Monday so I can't try yet?
                    > > > >
                    > > > >Jeff
                    > > > >W2UA
                    > > > >
                    > > > >--- In softrock40@yahoogroups.com
                    > <mailto:softrock40%40yahoogroups.com>
                    > > > <mailto:softrock40%40yahoogroups.com>, Pete Smith <n4zr@...> wrote:
                    > > > > >
                    > > > > > I received and installed the two Triad SP-70 isolation
                    > transformers
                    > > > >that I
                    > > > > > ordered from Gopher, and ran I/Q balance adjustments in both Rocky
                    > > > >and CW
                    > > > > > Skimmer.
                    > > > > >
                    > > > > > I was surprised to see that both the gain and phase results show a
                    > > > > > substantial difference between the two channels. The phase
                    > > > >difference is
                    > > > > > 7-8 degrees, while the gain of one channel is only .65 to .66 of
                    > > > >the
                    > > > > > other. There is also a fairly substantial scattering of the data
                    > > > >points,
                    > > > > > though this is a phenomenon I've grown to expect as the software
                    > > > >collects
                    > > > > > real-world signals over time. The image suppression is working
                    > > > >well, however.
                    > > > > >
                    > > > > > What I'm wondering is whether such differences are common? Are
                    > > > >they a
                    > > > > > function of normal, to-be-expected variations in transformer
                    > > > >manufacturing,
                    > > > > > or possibly differences in the two sound card channels? Or is it
                    > > > >possible
                    > > > > > that I have a wiring error in my 8.3 receiver. I realize the gain
                    > > > > > imbalance is only ~2 dB, but I'm still wondering...
                    > > > > >
                    > > > > >
                    > > > > > 73, Pete N4ZR
                    > > > > >
                    > > > >
                    > > > >
                    > > > >
                    > > > >------------------------------------
                    > > > >
                    > > > >Yahoo! Groups Links
                    > > > >
                    > > > >
                    > > > >
                    > > >
                    > > >
                    > >
                    > >------------------------------------
                    > >
                    > >Yahoo! Groups Links
                    > >
                    > >
                    > >
                    >
                    >
                  • Pete Smith
                    ... OK, I removed the transformers from the circuit temporarily - which I should have done before I started this thread - and both the phase and amplitude
                    Message 9 of 11 , Jun 29, 2008
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                      At 02:21 PM 6/29/2008, Jack Smith wrote:
                      >I ran quick check and see no evidence of serious phase or amplitude
                      >differences.

                      OK, I removed the transformers from the circuit temporarily - which I
                      should have done before I started this thread - and both the phase and
                      amplitude difference curves remained about the same, which confirms Jack's
                      measurements. So then I switched to a different sound card (again, I
                      should've done this before) and again, the phase and amplitude numbers are
                      broadly comparable. So unless someone points out something I've
                      misunderstood, it appears that both the level and phase differences are in
                      the output of the SoftRock 8.3. That is, the phase difference is 7-8
                      degrees and one channel's gain seems to be about .65 of the other.

                      Any idea if what sort of assembly error or component failure could be
                      responsible? The radio otherwise seems to operate very well on all bands
                      80-10 meters. Or is this possibly just due to component variations in a
                      correctly wired receiver? Since the I/Q balance circuitry seems to have no
                      problem managing it, maybe I should just leave it alone?

                      73, Pete N4ZR
                    • Jack Smith
                      Pete: That seems odd to me. My experience is with only the Softrock Lite 6.2 boards, but that won t stop me from making comments ... At least with the Lite
                      Message 10 of 11 , Jun 29, 2008
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                        Pete:

                        That seems odd to me. My experience is with only the Softrock Lite 6.2
                        boards, but that won't stop me from making comments ...

                        At least with the Lite boards, the I and Q channels have identical
                        component values and circuit design. Hence, the response (amplitude and
                        phase) should track rather closely, certainly within the component
                        tolerances. Your values are way outside normal component tolerances. For
                        this purpose, the op amp can be considered a perfect device; it's
                        performance is governed by the external RC parts in the feedback
                        network, absent a faulty op amp.

                        Hence, I would take a look around the op-amp output stages and see if
                        perhaps you put a wrong resistor in one side or accidentally swapped two
                        similar appearing resistors. Or, capacitors. Another possibility would
                        be a bad mixer switching IC, where one of the channels has greater
                        resistance than the other channels.

                        And, as I said before, as long as the software automatically compensates
                        for it, whether this gets fixed or ignored depends on how interested you
                        are in troubleshooting and whether you have the necessary test gear to
                        sort it out. Something like the "Click and Clack" automobile experts
                        policy for the "check engine" light. Cover it up with black tape if it
                        gets too distracting.

                        Jack

                        Pete Smith wrote:
                        >
                        > At 02:21 PM 6/29/2008, Jack Smith wrote:
                        > >I ran quick check and see no evidence of serious phase or amplitude
                        > >differences.
                        >
                        > OK, I removed the transformers from the circuit temporarily - which I
                        > should have done before I started this thread - and both the phase and
                        > amplitude difference curves remained about the same, which confirms
                        > Jack's
                        > measurements. So then I switched to a different sound card (again, I
                        > should've done this before) and again, the phase and amplitude numbers
                        > are
                        > broadly comparable. So unless someone points out something I've
                        > misunderstood, it appears that both the level and phase differences
                        > are in
                        > the output of the SoftRock 8.3. That is, the phase difference is 7-8
                        > degrees and one channel's gain seems to be about .65 of the other.
                        >
                        > Any idea if what sort of assembly error or component failure could be
                        > responsible? The radio otherwise seems to operate very well on all bands
                        > 80-10 meters. Or is this possibly just due to component variations in a
                        > correctly wired receiver? Since the I/Q balance circuitry seems to
                        > have no
                        > problem managing it, maybe I should just leave it alone?
                        >
                        > 73, Pete N4ZR
                        >
                        >
                      • Brad Thompson
                        ... Hello, Pete and the group-- I m not surprised that he resistance windings are different. The primary winding goes on closest to the core, and the secondary
                        Message 11 of 11 , Jun 29, 2008
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                          At 12:36 PM 6/29/2008, Pete Smith wrote:

                          >Yes, I did, Jack - I was very careful to make sure that the top of the
                          >windings (pins 1 and 3) went to the signal lines from the SoftRock and to
                          >the sound card, and that the bottoms (2 and 4) went to the common lead on
                          >their respective side of the transformer. I will double-check, because I
                          >have a history of this sort of mistake, but I don't think so.
                          >
                          >I did notice that the DC resistance of the primary and secondary are quite
                          >different - 72 vs 92 ohms. <snip>

                          Hello, Pete and the group--

                          I'm not surprised that he resistance windings are different. The
                          primary winding goes on closest to the core, and the secondary winding
                          gets applied next. However, the length of turn increases because the
                          secondary is physically further away from the core. Thus, the
                          primary might require 100 feet of wire while the secondary requires
                          140 feet for the same number of turns.

                          The manufacturer can use a larger-diameter wire for the secondary
                          winding, but the larger wire takes up more space and makes
                          it more difficult to get the required number of turns onto the core.

                          73--

                          Brad AA1IP
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