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MTR 20m receiver performance

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  • warren_3byd
    Hi All, I have an MTR from the first build and I have had plenty of contacts on 40m but always found stations hard to hear on 20m. I have now done some testing
    Message 1 of 4 , Aug 3, 2013
      Hi All,

      I have an MTR from the first build and I have had plenty of contacts on 40m but always found stations hard to hear on 20m.

      I have now done some testing of the performance on both 40 and 20, and found that it needed about 6db more from the signal generator to achieve the same audio level out of the receiver on 20 compared to 40.

      I have gone over the receiver front end and I am happy that the correct components and turns have been used and the trimmers are tuned for best performance.

      I measured the injection level from the DDS at the top of R18, I had -21dBm on 40 and -33dBm on 20.

      All tests were done with a commercial radio generator / analyser.

      So the question is, is this difference in receiver performance a feature or a fault?

      73
      Warren
      VK3BYD
    • Yannick
      Hi Warren, First my MTR is built for 30m/20m and I mostly use it on 20m. I have not noticed this behavior on my MTR and here is my experience with the MTR
      Message 2 of 4 , Aug 4, 2013
        Hi Warren,

        First my MTR is built for 30m/20m and I mostly use it on 20m.
        I have not noticed this behavior on my MTR and here is my experience with the MTR sensitivity.

        When on a quiet band (20m in the mid-afternoon), if I hear on my TS-590s a signal who is just 1S point above the noise but clearly copiable, it will still be copiable on the MTR but deeper in the noise. I guess that means the MDS of the MTR is within 6-9dB of that of the TS-590s.
        When the band is noisy it's another story of course, but with its narrow filter and quiet receiver chain, the MTR is never deceiving.
        One difference is that being without AGC, on the MTR the signals are just three levels :
        - weak (and if there is QSB or noise, too weak)
        - good copy
        - strong
        On a modern receiver with a good AGC circuit, you can usually guess where the S-meter needle will be just listening to the signal.

        If have not done A/B comparison on 30m between a commercial receiver and the MTR, but I have never had the feeling it was much less sensitive. The same between 30m and 20m on the MTR.

        73,
        Yan - XV4Y.
        ---
        http://costa.radioclub.asia/ (Project COSTA : Online contest statistics)

        --- In AT_Sprint@yahoogroups.com, "warren_3byd" <vk3byd@...> wrote:
        >
        > Hi All,
        >
        > I have an MTR from the first build and I have had plenty of contacts on 40m but always found stations hard to hear on 20m.
        >
        > I have now done some testing of the performance on both 40 and 20, and found that it needed about 6db more from the signal generator to achieve the same audio level out of the receiver on 20 compared to 40.
        >
        > I have gone over the receiver front end and I am happy that the correct components and turns have been used and the trimmers are tuned for best performance.
        >
        > I measured the injection level from the DDS at the top of R18, I had -21dBm on 40 and -33dBm on 20.
        >
        > All tests were done with a commercial radio generator / analyser.
        >
        > So the question is, is this difference in receiver performance a feature or a fault?
        >
        > 73
        > Warren
        > VK3BYD
        >
      • Tom
        Hi Warren, With an uncalibrated HP8640B I can clearly hear a signal at -130dbm on both 40 and 20 meters. I have the MTR2. I would start looking for broken smt
        Message 3 of 4 , Aug 5, 2013
          Hi Warren,

          With an uncalibrated HP8640B I can clearly hear a signal at -130dbm on both 40 and 20 meters. I have the MTR2.
          I would start looking for broken smt caps in the 20M LPF/BPF by unsoldering them from the board. They sometimes are impossible to spot unless you remove them one by one.

          Tom, ak2b
          >
          > So the question is, is this difference in receiver performance a feature or a fault?
          >
          > 73
          > Warren
          > VK3BYD
          >
        • warren_3byd
          Thanks Yan and Tom, I felt the performance of the MTR on both bands should be similar but without another receiver it was difficult to confirm. I can hear
          Message 4 of 4 , Aug 5, 2013
            Thanks Yan and Tom,

            I felt the performance of the MTR on both bands should be similar but without another receiver it was difficult to confirm.

            I can hear signals on 20, but it was not until I fed a known signal in and measure the resultant audio output that I realised I had a problem.

            I will continue to work on it.
            Thanks,
            Warren.
            VK3BYD


            --- In AT_Sprint@yahoogroups.com, "warren_3byd" <vk3byd@...> wrote:
            >
            > Hi All,
            >
            > I have an MTR from the first build and I have had plenty of contacts on 40m but always found stations hard to hear on 20m.
            >
            > I have now done some testing of the performance on both 40 and 20, and found that it needed about 6db more from the signal generator to achieve the same audio level out of the receiver on 20 compared to 40.
            >
            > I have gone over the receiver front end and I am happy that the correct components and turns have been used and the trimmers are tuned for best performance.
            >
            > I measured the injection level from the DDS at the top of R18, I had -21dBm on 40 and -33dBm on 20.
            >
            > All tests were done with a commercial radio generator / analyser.
            >
            > So the question is, is this difference in receiver performance a feature or a fault?
            >
            > 73
            > Warren
            > VK3BYD
            >
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