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  • Originally posted by SpaxmoidJAm View Post

    i also trimmed up the j-pole to see if it would maje any difference.
    [ATTACH=CONFIG]3987[/ATTACH]
    which software is this i want to check mine also
    RTL SDR : T-VEVZ1

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    • Originally posted by charan View Post
      which software is this i want to check mine also
      Not quite that simple you need one of these to go with it LA19-13-02
      http://www.latechniques.net/products.asp

      they are rather expensive but luckily i can borrow one.
      T-EGLF8

      Comment


      • Originally posted by SpaxmoidJAm View Post
        Not quite that simple you need one of these to go with it LA19-13-02
        http://www.latechniques.net/products.asp

        they are rather expensive but luckily i can borrow one.
        is there any way to check which frequency is our antenna tuned to with equipment ??
        RTL SDR : T-VEVZ1

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        • Originally posted by charan View Post
          is there any way to check which frequency is our antenna tuned to with equipment ??
          https://www.youtube.com/watch?v=k2VVtKaysLo

          Good video
          www.ADS-B.ca

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          • Originally posted by 1090 MHz View Post
            will check thanks
            RTL SDR : T-VEVZ1

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            • you need a spectrum analyser, function generator and a directional coupler. If you have access to the first two buying a coupler will get you a set up where you can check stuff.

              for the j-pole i tweaked.
              original
              j_pole.jpg
              tweaked
              j-pole tweaked.jpg

              Hopefully over the weekend i will get a good run of F-EGLF1's copy of a radarcape aerial. We have been playing with it but neglected to take screenshots.
              Last edited by SpaxmoidJAm; 2014-05-01, 22:25.
              T-EGLF8

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              • My modded 12 element collinear antenna after looking at the FR24 antenna i made a quarter wavelength element on the top.. but it has 8 element and a quarter element so shall i keep it as it is or shall i remove 1 element for better reception? DSCN1295.jpg
                UPDATE im getting 50NMI in all directions and 110nmi in one direction and 70,60, etc will post a picture from ADScope if you want
                Last edited by charan; 2014-05-02, 04:15.
                RTL SDR : T-VEVZ1

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                • Originally posted by 1090 MHz View Post
                  The Guenter antenna is a 3.5 element Collinear. http://ads-b.ca/00-00.htm

                  I was planning on making a 14 element Collinear, but after discussing this idea with a radio engineer this is what his thoughts were.

                  The issue of having so much gain is the actual beamwidth and elevation of
                  the main lobe. More gain = lower elevation and narrower lobe which is great
                  for reception at ground level, but how will it fare at aircraft overhead?
                  Are we going to experience a wider cone of silence at that point?


                  So the antenna will have lots of gain and look downward... great if it's being used as a WiFi antenna, but not for seeing aircraft in the sky.

                  So my plan now is to make a slightly longer Guenter antenna of 5.5 elements that should give me about 2.5dB gain more and still have good range too... I hope.

                  The only way to know for sure will be to build it and test it up on the tower.
                  Why Does An Antenna of Higher Gain Not Always Yield Higher Signal Levels?

                  The gain of an antenna is the first specification considered in antenna selection.

                  Generally it is believed that an antenna with higher gain yields higher signal levels.
                  Unfortunately, it is not always the case.
                  Antennas, unlike signal amplifiers (where net increase in signal power occurs), are passive device and do not generate any net gain in total signal power. Instead, the antenna gain is from a concentration of the radiation power in certain directions.

                  The gain of a specific antenna can be calculated from its radiation pattern.
                  An antenna with higher gain simply means its radiation pattern is more concentrated in a narrower region.
                  In other words, when compared with an antenna of lower gain, the high gain antenna in principle yields higher signal levels only in certain specific directions, and actually yields lower signal levels in other directions.

                  Moral of the story/Lesson learned: Don't waste your time & energy in trying to make a super-high-gain antenna and then getting frustrated by the results. Make a moderate gain antenna & add an active element (signal amplifier) which actually gives a net increase in signal power.
                  Last edited by abcd567; 2014-05-02, 06:52.

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                  • I always use a torch as an analogy for antenna gain... A bare bulb throws light in all directions and looks the same brightness from any direction.... Now add a reflector, or a lens and the light looks a lot brighter, but only from one direction!
                    The bulb hasn't got any brighter, so what's happening?
                    The light has been "folded" so that it all moves in one direction...
                    It's the same with antennae - you never get something for nothing, so improving gain is always at the expense of at least one direction...

                    Sent from my ZX81

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                    • Here is my Range. with 8 1/4 antenna.. please advice me should i keep 8 1/4 or shall i remove 1 element for 7 1/4 ??
                      TEST.jpg
                      RTL SDR : T-VEVZ1

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                      • Originally posted by charan View Post
                        Here is my Range. with 8 1/4 antenna.. please advice me should i keep 8 1/4 or shall i remove 1 element for 7 1/4 ??
                        [ATTACH=CONFIG]4000[/ATTACH]
                        The surest way is to remove one full element (i.e. make it 7 1/4 ) and put it to trial run. Then compare results with 8 1/4.
                        P.S. The full elements are each 1/2 wavelength. The last 1/4 wavelength is therefore 1/2 element. The proper way to write is 8 1/2 and 7 1/2 (or 8.5 & 7.5)

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                        • I would keep adding or subtracting and trying it - 8 elements open ended to the dongle + rpi was giving me about 300km. I now have a shorter commercial antenna (3 1/2 elements?) that gives more range.

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                          • My first coco

                            Some photos of my first coco build and the results of the spectrum analyser, (I had to remove the background on the photo showing the analyser setup as it is in an area at work where they do prototyping and development work), unfortunately our usual analyser was not available as it was being used elsewhere.
                            This is a 3-1/2 element build using RG402.
                            If it is successful then I will be building a second one and fully documenting it with precise measurements and sources for the materials.
                            Currently it is with T-EGLF8 (SpaxmoidJAm) for live testing as he is already set up to try out different antennas, hopefully he will report his findings later this weekend.
                            Ben.
                            Attached Files
                            Last edited by F-EGLF1; 2014-05-02, 19:19.
                            FR24 F-EGLF1, Blitzortung station 878, OGN Aldersht2, PilotAware PWAldersht, PlanePlotter M7.

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                            • Originally posted by F-EGLF1 View Post
                              Some photos of my first coco build and the results of the spectrum analyser, (I had to remove the background on the photo showing the analyser setup as it is in an area at work where they do prototyping and development work), unfortunately our usual analyser was not available as it was being used elsewhere.
                              This is a 3-1/2 element build using RG402.
                              If it is successful then I will be building a second one and fully documenting it with precise measurements and sources for the materials.
                              Currently it is with T-EGLF8 (SpaxmoidJAm) for live testing as he is already set up to try out different antennas, hopefully he will report his findings later this weekend.
                              Ben.
                              Awww awesome im going to build it now ill wait for you results (Y)
                              RTL SDR : T-VEVZ1

                              Comment


                              • Originally posted by F-EGLF1 View Post
                                Some photos of my first coco build and the results of the spectrum analyser, (I had to remove the background on the photo showing the analyser setup as it is in an area at work where they do prototyping and development work), unfortunately our usual analyser was not available as it was being used elsewhere.
                                This is a 3-1/2 element build using RG402.
                                If it is successful then I will be building a second one and fully documenting it with precise measurements and sources for the materials.
                                Currently it is with T-EGLF8 (SpaxmoidJAm) for live testing as he is already set up to try out different antennas, hopefully he will report his findings later this weekend.
                                Ben.
                                Great!! You have made the coco in a very nice, tidy and professional way.
                                If the results are explained, it will be great for those members who are not familiar with the use of Network Analyzer.
                                Waiting for SpaxmoidJAm's feedback.
                                Great work. Thanks for sharing.

                                P.S. There is a coin sized circular copper plate with 4 copper-wire legs, which I understand is a Balun. Am I right? What is the other bigger dia copper tube at the right hand end?
                                Last edited by abcd567; 2014-05-03, 15:40.

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