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Re: Loop questions?

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  • John Stumm
    ... greater ... Steve A spiral wound loop will inherently produce better nulls. I m surpised that nobody has mentioned this.
    Message 1 of 16 , Dec 21, 2006
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      --- In loopantennas@yahoogroups.com, "Steve B." <mcqueen_34@...> wrote:
      >
      > I would like to build a loop to optimize the nulling effects but I'm
      > not sure what produces a greater null. Will a loop with a larger
      > diameter create greater nulls; will a loop with higher Q create
      greater
      > nulls? Does any one have any experience with this?
      >
      Steve
      A spiral wound loop will inherently produce better nulls. I'm surpised
      that nobody has mentioned this.
      http://f1.grp.yahoofs.com/v1/oMuKRa5H8wSSm2qH8L7eeNVGXtyE374L2XNxhIOp69g
      PSNy2SQgw-PRMI_oUA_OKWmNktnn_7cJU-
      cdolPoCaVCNLKCexiOBuYQ/JohnsLoopDaJour/Spiraloop.JPG

      john
    • Andy
      ...
      Message 2 of 16 , Dec 23, 2006
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      • Marc
        ... Sorry, even when I copy paste the complete link, it does not work ... Isn t there a shorter version?? In wich discussion group can I find the picture ??
        Message 3 of 16 , Dec 27, 2006
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          John Stumm wrote:
          > --- In loopantennas@yahoogroups.com, "Steve B." <mcqueen_34@...> wrote:
          >
          >> I would like to build a loop to optimize the nulling effects but I'm
          >> not sure what produces a greater null. Will a loop with a larger
          >> diameter create greater nulls; will a loop with higher Q create
          >>
          > greater
          >
          >> nulls? Does any one have any experience with this?
          >>
          >>
          > Steve
          > A spiral wound loop will inherently produce better nulls. I'm surpised
          > that nobody has mentioned this.
          > http://f1.grp.yahoofs.com/v1/oMuKRa5H8wSSm2qH8L7eeNVGXtyE374L2XNxhIOp69g
          > PSNy2SQgw-PRMI_oUA_OKWmNktnn_7cJU-
          > cdolPoCaVCNLKCexiOBuYQ/JohnsLoopDaJour/Spiraloop.JPG
          >


          Sorry, even when I copy paste the complete link, it does not work ...
          Isn't there a shorter version?? In wich discussion group can I find
          the picture ??

          Marc

          --
          --
          Apres l'emission "faux" par la RTBF, le Premier Ministre Flamand Yves Leterme s'est exprime contre le journal "Liberation":
          "Le peuple Belge n'a pas les capacites intellectuelles pour discuter sur le sujet de la scission".
        • Andy
          ... Andy
          Message 4 of 16 , Dec 27, 2006
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            > Sorry, even when I copy paste the complete link, it does not work ...
            > Isn't there a shorter version?? In wich discussion group can I find
            > the picture ??

            See my reply that came a few days ago:

            > http://groups.yahoo.com/group/loopantennas/files/JohnsLoopDaJour/
            >
            > and scroll down to Spiraloop.JPG

            Andy
          • Steve
            That is because Yahoogroups doesn t allow linking directly to any files or photos, they do it by using dynamic links. Click on a file or photo, wait 30 minutes
            Message 5 of 16 , Dec 27, 2006
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              That is because Yahoogroups doesn't allow linking directly to any
              files or photos, they do it by using dynamic links. Click on a file or
              photo, wait 30 minutes and hit "Reload" on your browser and it'll say
              it doesn't exist. Hit "Back" on your browser so you are back in the
              folder, hit "Reload", then click on the file or photo again and it
              works again.

              You can get tricky about it, but the simplest way is to only link to
              the folder and then give that link.

              Tricky:
              http://groups.yahoo.com/group/loopantennas/files/JohnsLoopDaJour/Spiraloop.JPG

              Copy the complete URL to the folder, then manually type in the file
              name. That link will work, but after you click on it the Location
              listed in your browser will look like the long incomprehensible
              temporary link below.

              Steve Greenfield
              listowner loopantennas

              --- In loopantennas@yahoogroups.com, Andy <Andy.groups@...> wrote:
              >
              > >
              >
              http://f1.grp.yahoofs.com/v1/oMuKRa5H8wSSm2qH8L7eeNVGXtyE374L2XNxhIOp69gPSNy2SQgw-PRMI_oUA_OKWmNktnn_7cJU-cdolPoCaVCNLKCexiOBuYQ/JohnsLoopDaJour/Spiraloop.JPG
              >
              > This link (patched to fix the line-wrapping) didn't work for me.
              >
              > Go to:
              >
              > http://groups.yahoo.com/group/loopantennas/files/JohnsLoopDaJour/
              >
              > and scroll down to Spiraloop.JPG
              >
              > Andy
              >
            • Richards
              WOW -- Not THAT is quite a loop antenna. I am making one, but it is not that big. Cool. /// Richards ////
              Message 6 of 16 , Dec 28, 2006
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                WOW -- Not THAT is quite a loop antenna. I am making one, but it
                is not that big.

                Cool. /// Richards ////
                =========================================================

                Steve wrote:

                > http://groups.yahoo.com/group/loopantennas/files/JohnsLoopDaJour/Spiraloop.JPG
              • aimo ruoho
                the ADCOCK ARRAY???????????? ... Have you considered using the Adcock array? It has the best nulls that i have encountered in models and in practice. Another
                Message 7 of 16 , Dec 31, 2006
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                  the ADCOCK ARRAY????????????

                  CR <vk3he@...> wrote: --- In loopantennas@yahoogroups.com, "Steve B." <mcqueen_34@...> wrote:
                  >
                  > I would like to build a loop to optimize the nulling effects but I'm
                  > not sure what produces a greater null. Will a loop with a larger
                  > diameter create greater nulls; will a loop with higher Q create greater
                  > nulls? Does any one have any experience with this?

                  Have you considered using the Adcock array? It has the best nulls that
                  i have encountered in models and in practice.

                  Another antenna that models very well with a very deep null off the
                  back is the FLAG antenna. The 1 meter high by 2 meter wide flag has a
                  superb pattern from 1 to 30mhz. The gain is very low at the lower
                  frequencies however you can scale it for the frequency range you seek
                  for better gain. After looking at all the patterns i thought i had
                  constructed the model incorrectly, however after contacting K6SE
                  about it he did confirmed that the pattern indeed was excellent. The
                  flag makes a great compact rotable DF antenna using the null.

                  I have been experimenting with super resolution direction finding
                  antennas both loops and active. However the learning curve is very
                  steep since the mathematics and theory is very complex. Also the lack
                  of availability of phase locked receivers makes the job just about
                  impossible.

                  I personally think that rather than creating an electrically perfect
                  antenna that will only hold its pattern over a narrow frequency range
                  you would be far better off investing your eggs in some kind of
                  beamforming array using DSP methods. Even a accurate phasing system
                  would work.

                  This link below is a great introduction to a simple beam stearing
                  system for noise reduction. As the author demonstrates phase
                  selectivity with DSP is very effective. Using the same techniques DSP
                  direction finders can pin point a signal with 1 degree accuracy using
                  small aperture loops. They can also filter out noise and multiple
                  signals on the same frequencies by phase filterng and processing.

                  I have been trying to build a copy of the Watkins Johnson WJ8976 HF DF
                  system using similar techniques. However progress has been slow
                  because of the sheer lack of information and suitable phase coherent
                  receivers.

                  http://www.pa0sim.nl/index.htm

                  The discussion on the Alford Loop might be of interest to you as well.
                  The nulls look superb from 2 to 30 mhz. I use 4 Alford loops at the
                  moment with a MFJ 1026 phase controller and the results are very
                  impressive. Adding DSP phase comparisons and evaluations to all 4
                  antennas will be the next step. Unfortunately all this science is
                  locked behind a great wall of secrecy, commercial confidentiality and
                  deep research by the leading maths experts of the world. I could
                  just well imagine how well systems like the Rohde and Schwartz works
                  based on my limited experiments with phase selectivity and post
                  processing on HF.

                  Craig





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