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Fw: Re: [softrock40] Re: Bandpass filter smilter

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  • windy10605@juno.com
    OK, good point Art. They --do-- respond to harmonics and I can see how this would be a really serious problem for using it as an LF receiver design. 73 Kees
    Message 1 of 7 , Jan 30, 2006
      OK, good point Art. They --do-- respond to harmonics and I can see how this would be a really serious problem for using it as an LF receiver design.
       
      73 Kees K5BCQ
       
      ----- Forwarded Message -----
      From: KY1K <ky1k@...>
      Date: Wed, 01 Feb 2006 14:15:03 -0500
      Subject: Re: [softrock40] Re: Bandpass filter smilter
       
      Good observation Joe, you discovered the Achilles Heal of the
      softrock type detectors! Although it's not a serious problem, you
      have to be aware of it and limit front end filters response to
      appropriate values.

      The ratio between the lowest frequency passed by the front end filter
      and the highest frequency passed cannot be more than two to one-for
      exactly the reason you describe.

      It responds to harmonics.

      Several have thought of using the softrock for VLF and ULF receivers,
      say from 2 KHz to 80 KHz. And, of course they run into the same problem.

      2 KHz to 4 KHz is ok, 4 KHz to 8 KHz is ok.......but don't try 2 KHz
      to 8 KHz without separate filters for eash 'band'.

      GL to all.

      Art

      At 11:46 AM 2/1/2006, you wrote:

      >Kees,
      >
      >  When I first received my SR40 I
      replaced the input transformer
      >with a wide band transformer made by
      RELCOM. I was using a DDS board
      >to supply the Xtal input with the idea of
      just using bandpass or
      >lowpass filters ahead of rx. to cover a large
      frequency. It seened to
      >work ok at hf frequencies but when i tried it a
      LF 200-450khx I
      >received a lot of broadcast stations that i didn't have
      with my
      >superhet SD40 as sugested by wa6ufq. Further testing revealed
      the
      >following problems.
      >
      >Strong spurious response at odd
      multiples of the receive fqequency
      >3x,5x 7x as a example when tuned to
      300khz receiver would respond
      >to 900,1500,2100khz ect. now you can see
      why i was hearing strong
      >broadcast stations at LW.
      >
      >The
      input transformer I used i rated to 50khz, maybe my receiver has
      >a
      problem but phase and balance look good.
      >I also checked another SR40 at
      10mhz it also could hear 30mhz.
      >
      >Another problem the shows up is
      automatic phase and balance changes
      >when changing bands such as going
      from 40 to 20 mtrs. Not a concern
      >if this data can be stored for each
      band.
      >
      >Can you please verify the above on your
      receiver?
      >
      >Thanks Joe
      wa9cgz
      >
      >
      >
      >
      >
      >
      >
      >
      >
      >Yahoo!
      Groups Links
      >
      >
      >
      >

    • joe price
      ... I would expect that the SR40 would respond to even harmonics but mine responds ONLY to odd multiples of the rx frequency I don t understand why. Can
      Message 2 of 7 , Feb 1, 2006
        --- In softrock40@yahoogroups.com, windy10605@... wrote:>
        > OK, good point Art. They --do-- respond to harmonics and I can see how
        > this would be a really serious problem for using it as an LF receiver
        > design.
        >
        > 73 Kees K5BCQ
        >

        I would expect that the SR40 would respond to even harmonics but mine
        responds ONLY to odd multiples of the rx frequency I don't understand
        why. Can someone else check this? The v5 rx uses a different QSD scheme
        i'm not sure it's the same I will test and report result.

        Joe wa9cgz
      • joe price
        Disregard message below I cheched a 30mtr rx it responds to even and odd harmonics need more testing. ... scheme
        Message 3 of 7 , Feb 1, 2006
          Disregard message below I cheched a 30mtr rx it responds to even and
          odd harmonics need more testing.

          > I would expect that the SR40 would respond to even harmonics but mine
          > responds ONLY to odd multiples of the rx frequency I don't understand
          > why. Can someone else check this? The v5 rx uses a different QSD
          scheme
          > i'm not sure it's the same I will test and report result.
          >
          > Joe wa9cgz
          >
        • joe price
          Disregard message below I cheched a 30mtr rx it responds to even and odd harmonics need more testing. ... scheme
          Message 4 of 7 , Feb 1, 2006
            Disregard message below I cheched a 30mtr rx it responds to even and
            odd harmonics need more testing.

            > I would expect that the SR40 would respond to even harmonics but mine
            > responds ONLY to odd multiples of the rx frequency I don't understand
            > why. Can someone else check this? The v5 rx uses a different QSD
            scheme
            > i'm not sure it's the same I will test and report result.
            >
            > Joe wa9cgz
            >
          • KD5NWA
            Not just odd and even multiples, it can respond to fractions 5/8....to keep unwanted signals, increased dynamic range, and keep the noise down you need a front
            Message 5 of 7 , Feb 1, 2006
              Not just odd and even multiples, it can respond to fractions 5/8....to keep unwanted signals, increased dynamic range, and keep the noise down you need a front end filter as tight as possible. Saying that however, for playing around mobility might be more important issue.

              The best of both is if you can find a multi-band front end filter unit (specially the double tuned) from 20 to 50 years ago, you can tune from 100KHz to 30MHz in one small box so you have mobility and better discrimination.

              I have one in a box in the garage, I've been searching for it, but I have not found it.

              At 03:49 PM 2/1/2006, joe price wrote:
              Disregard message below I cheched a 30mtr rx it responds to even  and
              odd harmonics need more testing.

              > I would expect that the SR40 would respond to even harmonics but mine
              > responds ONLY to odd multiples of the rx frequency I don't understand
              > why. Can someone else check this? The v5 rx uses a different QSD
              scheme
              > i'm not sure it's the same I will test and report result.
              >
              > Joe wa9cgz
              >







               
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              Cecil Bayona
              KD5NWA
              www.qrpradio.com

              I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ...

            • Bob Bartel
              ... From: KD5NWA To: softrock40@yahoogroups.com Sent: Wednesday, February 01, 2006 5:37 PM Subject: Re: Fw: Re: [softrock40] Re: Bandpass filter smilter . I
              Message 6 of 7 , Feb 2, 2006
                 
                ----- Original Message -----
                From: KD5NWA
                Sent: Wednesday, February 01, 2006 5:37 PM
                Subject: Re: Fw: Re: [softrock40] Re: Bandpass filter smilter

                .

                I have one in a box in the garage, I've been searching for it, but I have not found it.
                 
                Joe wa9cgz
                That must be one big garage Joe.
                 
                Bob W2AWS










                 
                Yahoo! Groups Links

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                Cecil Bayona
                KD5NWA
                www.qrpradio.com

                I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ...

              • KD5NWA
                About 70 boxes full of parts, boards,etc. I have to go through all the boxes one at a time, then put them back, it s cold in the garage right now. ... Cecil
                Message 7 of 7 , Feb 2, 2006
                  About 70 boxes full of parts, boards,etc. I have to go through all the boxes one at a time, then put them back, it's cold in the garage right now.

                  At 11:04 AM 2/2/2006, you wrote:
                   
                  ----- Original Message -----
                  From: KD5NWA
                  To: softrock40@yahoogroups.com
                  Sent: Wednesday, February 01, 2006 5:37 PM
                  Subject: Re: Fw: Re: [softrock40] Re: Bandpass filter smilter

                  .

                  I have one in a box in the garage, I've been searching for it, but I have not found it.
                   
                  Joe wa9cgz

                  That must be one big garage Joe.
                   
                  Bob W2AWS










                   
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                  Cecil Bayona
                  KD5NWA
                  www.qrpradio.com

                  I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ...

                  YAHOO! GROUPS LINKS

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                  Cecil Bayona
                  KD5NWA
                  www.qrpradio.com

                  I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ...

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