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  • Hi abcd567,
    Thanks for that, would explain a few things, I've grabbed the software, will see if it runs under wine or crossover later today when I get a chance to have a play.

    Comment


    • FOR NEWBIES: ANTENNA CONCEPTS BY WATER ANALOGY
      Please see sketch below.
      water to antenna analogy.png

      .

      Comment


      • Originally posted by Rooster View Post
        true, but I honestly think all this techno mumbo jumbo is massive overkill... I suspect most users just want to build a working antenna.. the maths just complicates folk to the point of giving up before they start.

        Sent using Tapatalk from my ZX81
        Math, assuming it is correct, never complicates anything! It reveals the truth.

        Comment


        • Originally posted by Exadios View Post
          Math, assuming it is correct, never complicates anything! It reveals the truth.
          unless you are talking about theoretical science... Then it's a smoke screen for "we don't know"! lol

          Sent using Tapatalk from my ZX81

          Comment


          • All the technical stuff to me is unneccesary

            For my own antenna construction I use the simple formula
            300 divide by freq = full wave
            300 divided by 1090 = 275 mm

            so 1 wave = 275mm

            3/4 wave = 206.5 mm
            1/2 wave =137.5mm
            1/4 wave = 68.75 mm


            These are all the measurements you need

            Bottom of antenna -------/////--------------/////--------------/////--------------/////-------------- Top of antenna

            1st element = 68.75mm
            coil = 206.5mm of wire, wound into coil 68mm long
            2nd element = 137.5mm
            coil
            3rd element = 137.5mm
            coil
            4th element = 137.5mm

            Add as many elements / coils as you want




            Above antenna requires 1/4 w ground plane radials

            ADSB ANTENNA.jpg
            Last edited by YWYY; 2014-04-14, 12:40.

            Comment


            • Originally posted by abcd567 View Post


              SCREENSHOT 4 of 4 - Three-and-Half (3.5) Element CoCo - SHORTED TOP
              Gain = 6.7 dBi, SWR = 6.42 (mismatch loss = 3.3 dB)
              Net Gain Seen by Receiver = Antenna Gain - Mismatch Loss = 6.7 - 3.3 = 3.4 dBi
              [ATTACH=CONFIG]3873[/ATTACH]
              Looks just like the antenna used by FR24

              Now we know why the top is shorted !

              http://ads-b.ca/radar-cape-apart.htm
              www.ADS-B.ca

              Comment


              • Originally posted by Exadios View Post
                Math, assuming it is correct, never complicates anything! It reveals the truth.
                Originally posted by Rooster View Post
                unless you are talking about theoretical science... Then it's a smoke screen for "we don't know"! lol

                Sent using Tapatalk from my ZX81
                For persons interested in getting things done, some amount of maths is manageable, but too much of maths is like smoke screen.
                It varies from person to person how much maths is 'too much maths'.

                Mathematics is in fact the set of rules which govern everything in this universe.
                It is the foundation of all sciences, including apparently unrelated sciences like biology.

                Comment


                • Originally posted by 1090 MHz View Post
                  Looks just like the antenna used by FR24

                  Now we know why the top is shorted !

                  http://ads-b.ca/radar-cape-apart.htm
                  Yes, this is the conclusion drawn by me also, which I have mentioned in the begining of the post #826, and quote it below:

                  "Reading yesterday's results (post # 824) and this post's results clearly show that:

                  (1) For antennas having even number of full elements, adding an open or shorted half element (1/4 wave element) worsens it's performance.

                  (2) For antennas having odd number of full elements, adding an open half element (1/4 wave element) worsens it's performance, but adding a shorted half element (1/4 wave element) improves it's performance."

                  Comment


                  • .
                    FOR NEWBIES: ANTENNA CONCEPTS BY WATER ANALOGY

                    Please see sketch below.

                    water to antenna analogy.png



                    .

                    Comment


                    • Originally posted by 1090 MHz View Post
                      Looks just like the antenna used by FR24

                      Now we know why the top is shorted !

                      http://ads-b.ca/radar-cape-apart.htm
                      Thanks @1090MHz.
                      The 3.5 element CoCo I built, tried, and posted in this forum last year, was based on design provided by you through photos in above link to your web page http://ads-b.ca/radar-cape-apart.htm.
                      Thanks for sharing. You deserve to share the credit in the work done by me.

                      Comment


                      • Originally posted by peterhr View Post
                        Have a look at http://adsb.alle.bg/filter/ for designs of antenna filters. [this doesn't look easy!]
                        Originally posted by charan View Post
                        the filter is too complicated
                        This filter requires knowledge of Wave Guides & Cavity Resonators, which are realm of microwave & radar engineers. For an ADS-B hobbyist, this subject is too complicated.

                        Comment


                        • Originally posted by abcd567 View Post
                          This filter requires knowledge of Wave Guides & Cavity Resonators, which are realm of microwave & radar engineers. For an ADS-B hobbyist, this subject is too complicated.
                          Affirm ; i agree with you.!!! but a small doubt what resonator coil (home made) does for the better reception?
                          RTL SDR : T-VEVZ1

                          Comment


                          • Originally posted by abcd567 View Post
                            Yes, this is the conclusion drawn by me also, which I have mentioned in the begining of the post #826, and quote it below:

                            "Reading yesterday's results (post # 824) and this post's results clearly show that:

                            (1) For antennas having even number of full elements, adding an open or shorted half element (1/4 wave element) worsens it's performance.

                            (2) For antennas having odd number of full elements, adding an open half element (1/4 wave element) worsens it's performance, but adding a shorted half element (1/4 wave element) improves it's performance."
                            So what is the final recommendation on making a coco - 7 elements with a shorted 1/2 element at the top ... or do an open topped 8 element?

                            Is there any recommendation for what to do at the bottom for impedance matching if required...?

                            Comment


                            • Originally posted by peterhr View Post
                              So what is the final recommendation on making a coco - 7 elements with a shorted 1/2 element at the top ... or do an open topped 8 element?

                              Is there any recommendation for what to do at the bottom for impedance matching if required...?
                              Tomorrow I will model a 7.5 element CoCo, and post its simulation result. By comparing results of 8 element open top ( post # 824) & 7.5 element shorted top, we can decide.

                              .j
                              Last edited by abcd567; 2014-04-15, 20:12.

                              Comment


                              • Originally posted by peterhr View Post
                                So what is the final recommendation on making a coco - 7 elements with a shorted 1/2 element at the top ... or do an open topped 8 element?

                                Is there any recommendation for what to do at the bottom for impedance matching if required...?
                                Comparison of simulation results shows that 7.5 element shorted top is slightly better than 8 element open top. Please see screenshots below.

                                SCREENSHOT 1 of 2 - Seven-and-Half (7.5) Element CoCo - SHORTED TOP
                                Gain = 9.23 dBi, SWR = 3.87 (mismatch loss = 1.85 dB)
                                Net Gain Seen by Receiver = Antenna Gain - Mismatch Loss = 9.23 - 1.85 = 7.38 dBi

                                coco 7.5 element shorted at top simulation output.png


                                SCREENSHOT 2 of 2 - Eight (8) Element CoCo - Open Top
                                Gain = 9.52 dBi, SWR = 4.63 (mismatch loss = 2.33 dB)
                                Net Gain Seen by Receiver = Antenna Gain - Mismatch Loss = 9.52 - 2.33 = 7.19 dBi

                                coco 8 element simulation output.png


                                .
                                Last edited by abcd567; 2014-04-16, 07:25.

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