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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

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    • 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

      Comment


      • Originally posted by charan View Post
        is there any way to check which frequency is our antenna tuned to with equipment ??
        ***STOP PRESS** newest Rigol 7.5GHz DSA815-variant clip here: http://youtu.be/jKcf7VzU5NM ***See real-time effects on a homebrew antenna... tune it to 2m Am...


        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

                    Comment


                    • 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.

                          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.
                            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.

                              Comment


                              • Originally posted by abcd567 View Post
                                SNIP
                                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?
                                If you look at the photos of the commercial one you wil see that it has a similar arangement on the outside of the tube,
                                I thought that it was just to re-inforce the tube for the clamp, however it made a big difference to the result (it is 1/4-wavelength long) I have seen other plans with a similar arrangement but without the internal balun, (the coin sized plate is in fact a UK penny as it was all I had to hand at the time!).
                                I will try the next one without the upper internal balun and see what effect it has.
                                My build was based on the earlier photos, but with all the lengths re-calculated and the 1/4 stub tweaked on the analyser.
                                There is still much learning to do as so many people and sites have their own way of building these things, my hope is to provide a tested working design that anyone can copy with basic tools and get good results.
                                Using RG402 is far better than mucking about with ordinary coax as it can be pre cut to the exact length and solders easily so it should be more repeatable, in a future post I will detail the tools and methods I used on the MK2 build as I am photographing it stage by stage.
                                Ben.
                                FR24 F-EGLF1, Blitzortung station 878, OGN Aldersht2, PilotAware PWAldersht, PlanePlotter M7.

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