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  • Originally posted by peterhr View Post
    ....T-EGBB19 : RTL2832U / R820T+ Raspberry Pi + Dump1090 with home brew collinear 7m above ground level....
    @peterhr:
    Do you like to share the details of your home-brew antenna, so that others can also built & try it?
    If yes, it will be nice if you post some pictures (or sketches) of your home-brew antenna showing it's elements & element sizes.

    Comment


    • Originally posted by abcd567 View Post
      @peterhr:
      Do you like to share the details of your home-brew antenna, so that others can also built & try it?
      If yes, it will be nice if you post some pictures (or sketches) of your home-brew antenna showing it's elements & element sizes.
      it's this one http://www.balarad.net/ made up out some sky dish / direct TV dish satellite down lead I had in the shed.

      Youtube ... http://www.youtube.com/watch?v=TkUYdCPFXXs

      it's open at the top - no resister - I should have left a 1/4 wave whip at the top

      The sections have duct tape over the joints to hold them together better than vinyl tape.

      the whole thing is in a 22mm PVC overflow pipe held in place top and bottom with a plug of hot melt glue - like this the whole thing stirred around a lot in the wind - so I took it to the local plumbers merchant and found a second PVC tube that would tight-fit slide over the whole thing to stiffen it up.

      For people just trying it - make up the coco antenna, then tape it to a bamboo cane to hold it straight - you can put it into sealed tube later if it works for you.

      Comment


      • Originally posted by peterhr View Post
        .......

        it's open at the top - no resister - I should have left a 1/4 wave whip at the top

        The sections have duct tape over the joints to hold them together better than vinyl tape..........

        ........For people just trying it - make up the coco antenna, then tape it to a bamboo cane to hold it straight - you can put it into sealed tube later if it works for you.....
        Thanks. I have noted 3 flavours of top element
        (1) Same length as other elements, but core & braid shorted at top throuh 75/50 ohm resistor.
        (2) half length (i.e. 1/4 wavelength), core& braid shorted directly at top.
        (3) Same length as other elements, but half of it (1/4 wavelength) with braid, & upper half (1/4 wavelength) core only as whip. No shorting of core & braid.

        Since my antenna is indoor, bamboo can be left as a permanent feature

        Sent from my N762 using Tapatalk 2
        Last edited by abcd567; 2013-11-25, 22:30.

        Comment


        • Originally posted by abcd567 View Post
          Thanks. I have noted 3 flavours of top element
          (1) Same length as other elements, but core & braid shorted at top throuh 75/50 ohm resistor.
          (2) half length (i.e. 1/4 wavelength), core& braid shorted directly at top.
          (3) Same length as other elements, but hal of it (1/4 wavelength) with braid, & upper half (1/4 wavelength) core only as whip. No shorting of core & braid.

          Since my antenna is indoor, bamboo can be left as a permanent feature

          Sent from my N762 using Tapatalk 2
          Tried no2, useless.
          I'm in favour of no 3 since it needs no special arrangement for an amplifier later

          Sent from my Casio fx-82c using Tapatalk
          Last edited by peterhr; 2013-11-26, 08:45.

          Comment


          • Originally posted by peterhr View Post
            it's this one http://www.balarad.net/ made up out some sky dish / direct TV dish satellite down lead I had in the shed.

            Youtube ... http://www.youtube.com/watch?v=TkUYdCPFXXs

            it's open at the top - no resister - I should have left a 1/4 wave whip at the top

            The sections have duct tape over the joints to hold them together better than vinyl tape.

            the whole thing is in a 22mm PVC overflow pipe held in place top and bottom with a plug of hot melt glue - like this the whole thing stirred around a lot in the wind - so I took it to the local plumbers merchant and found a second PVC tube that would tight-fit slide over the whole thing to stiffen it up.

            For people just trying it - make up the coco antenna, then tape it to a bamboo cane to hold it straight - you can put it into sealed tube later if it works for you.
            As I mentioned in a previous post... I tested PVC and Fiberglass tubes to hold this same antenna and Fiberglass tube gave me 25-50 km better reception in some directions. There is a youtube video showing the test results I can't find now of course. It was based on a HAM radio antenna both receiving and transmitting. PVC seems to detune the incoming signal.
            Andy T-KTIK1

            RPI - http://Temporarily off Line due to t...98.37.214:8080

            Comment


            • I didn't read through the whole msg tread... sorry... but if you short the top element (braid to center wire) or add a resistor you can't use an amp with power injection as it will cause a short and amp is useless and actual not work at all. Am sure you already know that by now...
              Andy T-KTIK1

              RPI - http://Temporarily off Line due to t...98.37.214:8080

              Comment


              • Yes, num 3 also here. no shorting. Sorry forgot to use quote and won't let me edit it now.
                Last edited by andyk1; 2013-11-26, 18:23.
                Andy T-KTIK1

                RPI - http://Temporarily off Line due to t...98.37.214:8080

                Comment


                • Originally posted by andyk1 View Post
                  I didn't read through the whole msg tread... sorry... but if you short the top element (braid to center wire) or add a resistor you can't use an amp with power injection as it will cause a short and amp is useless and actual not work at all. Am sure you already know that by now...
                  @andyk1: I have built & run the Coco with top element shorted+amplifier+power injector. I blocked DC to reach antenna by inserting a capacitor. Please see my previous post of last week with photos.


                  Sent from my N762 using Tapatalk 2

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                  • Originally posted by andyk1 View Post
                    I didn't read through the whole msg tread... sorry... but if you short the top element (braid to center wire) or add a resistor you can't use an amp with power injection as it will cause a short and amp is useless and actual not work at all. Am sure you already know that by now...
                    ... unless you use a capacitor on the antenna side of the amp to block the dc voltage ... a second power injector (with no power to inject) would do the same thing - would be a nice module with screw on connectors...

                    using the whip is just nicer, if looking to support the antenna in a tube without mangling the whip at the top - attach a thick mono filament plastic line fishing line, strimmer nylon to the coco a little further down and attach that to the tube.

                    Comment


                    • Originally posted by peterhr View Post
                      .....using the whip is just nicer, if looking to support the antenna in a tube without mangling the whip at the top - attach a thick mono filament plastic line fishing line, strimmer nylon to the coco a little further down and attach that to the tube.
                      I will replace the top shorted element of my Coco with whip type and give it 2 trial run, one without amplifier, other with amplifier.

                      Sent from my N762 using Tapatalk 2

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                      • Built my 10 element today, and tried the 3 top configurations... The 1/4 top whip wins hands down, with almost 2db gain over the shorted top...
                        Not bothering with an amp at this stage.
                        What are you guys using for live plots?
                        I did my tests with a signal generator + antenna analyser...

                        Sent using Tapatalk from my ZX81

                        Comment


                        • Originally posted by andyk1 View Post
                          As I mentioned in a previous post... I tested PVC and Fiberglass tubes to hold this same antenna and Fiberglass tube gave me 25-50 km better reception in some directions. There is a youtube video showing the test results I can't find now of course. It was based on a HAM radio antenna both receiving and transmitting. PVC seems to detune the incoming signal.
                          Fair enough, I used what was easily available.

                          For a really good coco people need to use a high quality coaxial cable with a known velocity factor (and calculate the segment lengths) - I just used what was in the garden shed.

                          Comment


                          • Originally posted by peterhr View Post
                            Fair enough, I used what was easily available.

                            For a really good coco people need to use a high quality coaxial cable with a known velocity factor (and calculate the segment lengths) - I just used what was in the garden shed.
                            That's me too. I generally first try the stuff readily available, and go for specialized stuff if results are not good, or later use specialized stuff, just for comparision of results obtaied with the common stuff & specialized stuff.

                            Sent from my N762 using Tapatalk 2
                            Last edited by abcd567; 2013-11-26, 20:26.

                            Comment


                            • Originally posted by abcd567 View Post
                              That's me too. I generally first try the stuff readily available, and go for specialized stuff if results are not good, or later use specialized stuff, just for comparision of results obtaied with the common stuff & specialized stuff.

                              Sent from my N762 using Tapatalk 2
                              Yep, Same here. Started using what I had laying around and went from there. Couldn't find a fiberglass tube locally to save my life. Driving home, in my driveway saw the reflector tube and just happened to be just the right length...
                              Andy T-KTIK1

                              RPI - http://Temporarily off Line due to t...98.37.214:8080

                              Comment


                              • PVC tubing = unnaturally coloured. And can often contain the likes of lead based dye.. which as you know stops signals dead Hence the often difference in reception to other materials
                                Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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