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  • I have now started 2nd round of comparision trial run of 66mm & 100mm cantennas.

    Today I have put 100mm cantenna on 12 hrs trial run (mid day to mid night - maximum traffic).
    Tomorrow I will put 66mm cantenna on trial from mi day to mid night.

    This will give me another set of range comparasion.

    I am planning to run a third set of similar trial runs next week. Three sets spread in time will give a better insight.

    Comment


    • Yes I agree, I have built many colinear antennas with lots of failures. The one I use now is built to the formulas for wave-length and there is no guessing on the measurements as its not detuned by pvc pipe

      http://forum.flightradar24.com/attac...0&d=1406435713

      Comment


      • Originally posted by YWYY View Post
        Yes I agree, I have built many colinear antennas with lots of failures. The one I use now is built to the formulas for wave-length and there is no guessing on the measurements as its not detuned by pvc pipe

        http://forum.flightradar24.com/attac...0&d=1406435713
        Wow! Looks great and very simple! That's what we need for DIY antenna.

        Antennas requiring phasing/tuning/matching are sensetive to dimensional accuracy and a nightmare for DIY hobbyist.

        Any error in multi element antennas is multiplied by the number of elements. Collinears (coaxial collinear & franklin collinear) are example of this.

        Antennas using tuning/phasing/matching/loading coils also present similar problem. Any error in diameter of coil , inter-turn spacing/length of coil creates an error in inductance & self capacitance of coil and affects performance.

        What I am struggling for is to find a simple, repeatable design, whose performance does not appreciably deteriorate with dimensional errors common in DIY hobby situation.
        Last edited by abcd567; 2014-08-21, 23:23.

        Comment


        • @YWYY:
          Is your CB band whip fed through loading coil?

          Your antenna pucture shows a small cylinder between whip & coax (below circular ground plane plate), which looks like an enclosure for a loading coil.

          Comment


          • Originally posted by abcd567 View Post
            Wow! Looks great and very simple! That's what we need for DIY antenna.

            Antennas requiring phasing/tuning/matching are sensetive to dimensional accuracy and a nightmare for DIY hobbyist.

            Any error in multi element antennas is multiplied by the number of elements. Collinears (coaxial collinear & franklin collinear) are example of this.

            Antennas using tuning/phasing/matching/loading coils also present similar problem. Any error in diameter of coil , inter-turn spacing/length of coil creates an error in inductance & self capacitance of coil and affects performance.

            What I am struggling for is to find a simple, repeatable design, whose performance does not appreciably deteriorate with dimensional errors common in DIY hobby situation.
            I'm coming back to your original design of amplified dipole ... but with waterproofing for outside use.

            Comment


            • Originally posted by peterhr View Post
              I'm coming back to your original design of amplified dipole ... but with waterproofing for outside use.
              You mean this one?




              Last edited by abcd567; 2014-08-22, 09:49.

              Comment


              • Originally posted by abcd567 View Post
                @YWYY:
                Is your CB band whip fed through loading coil?

                Your antenna pucture shows a small cylinder between whip & coax (below circular ground plane plate), which looks like an enclosure for a loading coil.
                Hi no, I use a uhf elevated feed for the whip, the disk is the groundplane.



                With this antenna it can be built to the formulas with no adjusting for velocity and no loading effect from pvc radome. Its just wound around a fibreglass whip
                Attached Files
                Last edited by YWYY; 2014-08-22, 11:14.

                Comment


                • Originally posted by abcd567 View Post
                  You mean this one?




                  Absolutely - but with the amplifier wrapped against the weather and a small bead of silicone caulk where the wires go into the coax to stop water ingress

                  Comment


                  • Originally posted by YWYY View Post
                    Hi no, I use a uhf elevated feed for the whip, the disk is the groundplane.





                    With this antenna it can be built to the formulas with no adjusting for velocity and no loading effect from pvc radome. Its just wound around a fibreglass whip
                    Great. Thanks for the detailed dimensioned pictures which make it easy to build one.

                    I want to make this antenna and need following additional information:

                    (1) What is the diameter of fiberglass whip?

                    (2) Is 206 mm length of coil or length of wire in the coil?

                    Length of coil = distance between two ends of coil, measured in a straight line along the axis of whip.

                    Length of wire in coil = pi x dia of coil x number of turns
                    .
                    .
                    Last edited by abcd567; 2014-08-23, 01:05.

                    Comment


                    • Hi
                      1. the diametar of the whip is not important, its just a 27mhz cb whip. Make sure though that the fg whip is CLEAR fibreglass - Coloured will not work
                      2. 206.5 mm is the length of wire used to wind the coil. Th coil once wound, takes up 65 mm on the f/g

                      I used 2mm copper wire

                      I also made a shorter antenna with the same dimensions, only 4 elements,. I took a days plotting to get the range, then I covered it with heatshrink, leaving a couple of inches protruding out the top for trimming. I trimmed 1 mm at a time ...tested, then trimmed until it received the same as before I put the heatshrink on. It still receives exactly the same , I had to trim the top 137.5 mm (1/2 w ) down to 73 mm

                      I tried the same process on the longer antenna with 10 elements ( 1800mm) and couldnt get it to tune down. So I guess with a higher gain antenna, the detuning is much more severe. I use this antenna without a covering and it works fantastic, I get 270nm without a preamp, and I use 10 mtrs of LDF50 heliax coax
                      Last edited by YWYY; 2014-08-24, 05:30.

                      Comment


                      • @YWYY:
                        Great! Thank you very much for such detailed information. I will build one, but not very tall, only few elements. I feel that other forum members will also take advantage of your experience and try this antenna.

                        Comment


                        • Originally posted by peterhr View Post
                          Absolutely - but with the amplifier wrapped against the weather and a small bead of silicone caulk where the wires go into the coax to stop water ingress
                          Comparision of Half wavelength dipole & Cantenna - Both with No Amplifier, short feeder (Coax 12 ft/3.5 meters)

                          1 of 4 - Half-wavelength Dipole - No Amplifier



                          2 of 4 - Range of Half-wavelength Dipole - No Amplifier - 2 hrs run



                          3 of 4 - Cantenna - No Amplifier



                          4 of 4 - Range of Cantenna - No Amplifier - 45 minutes run



                          WITH AMPLIFIER, THE DIFFERENCE BETWEEN TWO ANTENNAS WILL BE MUCH LESS DUE TO ADDED GAIN & AGC (Automatic Gain Control) OF AMPLIFIER.

                          Range Rings are 50 nautical miles apart
                          .
                          Last edited by abcd567; 2014-08-24, 06:30.

                          Comment


                          • .
                            I have done several trial runs of Cantenna with 66mm dia Coke Can & 100mm dia Hot Chocolate can, but did not notice any improvement in range by using 100mm dia can.

                            The extra-ordinary range of 350+ nautical miles obtained few days ago did not occur again, and seems to be due to a very rare & favorable weather & atmospheric condition.
                            Last edited by abcd567; 2014-08-24, 04:22.

                            Comment


                            • This is the shorter one
                              Attached Files

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                              • COMPARISON OF CANTENNA & HALF WAVELENGTH DIPOLE BY SIMULATION

                                1 of 2 - Simulation of Cantenna
                                Cylinder: 66mm dia x 69 high
                                Whip:69mm high

                                Please see the radiation pattern. Lobes are pulled down slightly.
                                The maximum gain of 5.5dBi is at 110 degrees i.e. 20 degrees below horizon.
                                Will get more of low flying & on the ground planes.

                                The horizontal (90 degrees) gain is 4.8 dBi
                                SWR is 2.28





                                ================================================== ========================================


                                2 of 2 - Simulation of Half Wavelength Dipole
                                Upper & Lower Legs:68mm each
                                Please note the radiation pattern is symmetrical with maximum gain of 2.17 dBi in Horizontal direction.
                                SWR is 1.33

                                Last edited by abcd567; 2014-08-24, 07:23.

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