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  • Originally posted by Scroggie View Post
    Are you just using software to give those results or constructing the antenna and making measurements with a generator?
    I did make the one with 53mm long, 5mm dia, 16 turn coil, and did measure SWR. Please see this post:

    https://forum.flightradar24.com/foru...150#post184150

    However I did NOT make the one with your coil. You made it, and based on your measurements, I did computer simulation and posted results of simulation


    Originally posted by Scroggie View Post
    It would be interesting to see what's inside the commercial Flightaware antenna - must be something like this.
    This is Flightaware antenna with pvc pipe removed.

    image_10493.jpg

    Comment


    • Originally posted by abcd567 View Post

      I did make the one with 53mm long, 5mm dia, 16 turn coil, and did measure SWR. Please see this post:

      https://forum.flightradar24.com/foru...150#post184150

      However I did NOT make the one with your coil. You made it, and based on your measurements, I did computer simulation and posted results of simulation




      This is Flightaware antenna with pvc pipe removed.

      image_10493.jpg
      That is interesting - the top looks very similar to what we've been discussing but with a 4 or 5 turn coil. Could I please ask you to run your computer simulation using your measurements 60,53,137 mm but with 1.5 mm copper wire coil (1.54 mm with insulation) of 6.9 mm diameter (Wire centre to wire centre), 8.44 mm overall. It should be much worse than what you achieved but I'm curious as to how different it is to the 10 turn close wound.

      Scroggie

      Comment


      • Originally posted by Scroggie View Post
        Could I please ask you to run your computer simulation using your measurements 60,53,137 mm but with 1.5 mm copper wire coil (1.54 mm with insulation) of 6.9 mm diameter (Wire centre to wire centre), 8.44 mm overall. It should be much worse than what you achieved but I'm curious as to how different it is to the 10 turn close wound.

        Scroggie
        Will run simulation this weekend.

        Comment


        • Any one interested to run simulation himself/herself, can download modelling software 4nec2 (free of cost) fromhere:

          Download 4NEC2 Software (free of cost)


          Also, I have uploaded my following simulation model files to DropBox. Anyone can download these from Dropbox and run in software 4NEC2.

          Monopole with Coil and Ground Plane.nec

          Super J-Pole with Coil.nec

          .

          Comment


          • Originally posted by abcd567 View Post
            Any one interested to run simulation himself/herself, can download modelling software 4nec2 (free of cost) fromhere:

            Download 4NEC2 Software (free of cost)


            Also, I have uploaded my following simulation model files to DropBox. Anyone can download these from Dropbox and run in software 4NEC2.

            Monopole with Coil and Ground Plane.nec

            Super J-Pole with Coil.nec

            .
            That great - will have a look at that.
            Incidentally I've been experimenting today and cannot replicate the success I had at first with the close wound coil of 10 turns. Throughout today your design has been noticeably better albeit with 1 mm wire.(same dimensions 60,53,137)
            In the last hour I've modified an eBay purchased magnetic -mount identical to the one you show in an earlier post. I too found it to be very poor but it occurred to me that if the top section was 137mm it might be usable. So I exposed the metal at the top and soldered on some 1.5 mm copper to increase that section above the coil to 137 mm. Yesterday I had made six quarter-wave radials at 45 degrees mounted on an F - SMA adapter so it's now a simple matter to experiment with different elements by just plugging them in. So this modified eBay antenna (minus it's magnetic base) is installed waiting for tomorrows signals. I've added a short piece of wire at the bottom to compensate for length that was inside the base that I have removed. As soon as I connected it, even from the bedroom window a couple of aircraft were visible at 200nm. It certainty looks good but with only 8 aircraft over the UK at the moment I'll have to wait until tomorrow to see just how good.

            Scroggie

            Comment


            • Originally posted by Scroggie View Post

              So this modified eBay antenna (minus it's magnetic base) is installed waiting for tomorrows signals. I've added a short piece of wire at the bottom to compensate for length that was inside the base that I have removed. As soon as I connected it, even from the bedroom window a couple of aircraft were visible at 200nm. It certainty looks good but with only 8 aircraft over the UK at the moment I'll have to wait until tomorrow to see just how good.

              Scroggie
              1. Vertical length Inside magnetic base is about 10 to 15 mm depending on make of antenna.

              Optimized whip inside.jpg


              2. If you keep the magnetic base, and place it on a large metallic can, you get a good ground plane, and dont need to add radials. This is exactly what I have done. The Butter Cookies lid is providing a good ground plane, no need of radials.


              Coiled Collinear and Quarter Wave.jpg

              Comment


              • Originally posted by abcd567 View Post

                2. If you keep the magnetic base, and place it on a large metallic can, you get a good ground plane, and dont need to add radials. This is exactly what I have done. The Butter Cookies lid is providing a good ground plane, no need of radials.

                Do you suggest to keep the plastic bottom of these antennas or to remove it before putting it on a metal surface?

                Comment


                • Originally posted by Mephisto View Post

                  Do you suggest to keep the plastic bottom of these antennas or to remove it before putting it on a metal surface?
                  No need to remove plastic adhesive covering of the base. I have once removed the black plastic adhesive circle from base, but it did not give any improvement. Even with plastic in place, there is enough capacitive coupling between base metal and the food can.
                  Last edited by abcd567; 2020-04-21, 19:02.

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