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  • Originally posted by caius View Post
    abcd, what does your software suggest for the performance of that franklin/spider hybrid? It looks like it might be worth a try.
    MY NEW DESIGN:
    HYBRID OF FRANKLIN & SPIDER



    FRANKLIN-SPIDER
    Gain = 4.14 dBi
    SWR = 2.09


    Franklin Spider.PNG



    SPIDER
    Gain = 2.08 dBi
    SWR = 1.97


    Spider.PNG




    Based on my above design, an antenna was built by forum member xforce30164, and is on trial run now:

    http://forum.planefinder.net/threads...na.23/page-131

    IMG_20150407_202113_1428430883242.jpg
    Last edited by abcd567; 2015-04-08, 07:16.

    Comment


    • Interesting!
      The results of the thick/thin co-linear don't match the results I get with the real antenna, at least from an impedance stand point.
      Also the gain you find would be fantastic if it was true: 16 dBi at 90!
      I am afraid that for some reasons, 4nec2 does not do a good job here.

      In the other designs, with 2mm wires, you should use 65mm for 1/4 wave and 130mm for 1/2 wave.
      Using 69 and 138 probably give you an antenna with a resonance at 1040 Mhz.

      Comment


      • Originally posted by JLD View Post
        Interesting!
        The results of the thick/thin co-linear don't match the results I get with the real antenna, at least from an impedance stand point.
        Also the gain you find would be fantastic if it was true: 16 dBi at 90!
        I am afraid that for some reasons, 4nec2 does not do a good job here.
        ....snip...
        Yes, in some cases the 4nec2 software does give erroneous results, but we never know how it will behave in a particular case. In fact it has put me in an embarassing situation several times due to erroneous results.

        For this reason, after simulation, I always make a prototype and put it to trial run. Unfortunately I dont have access to VNA and other test equipment to conduct a laboratory test. I therefore put my prototype directly in operation and compare ttheir results with my benchmark antenna.

        Can you please post the photos of your antenna, and maximum range plot? I use VRS (virtual radar server) software or adsbScop software to plot maximum range over a period of at least 24 hrs.

        The ONLY piece of test equipment I have
        MJCA-211.JPG.jpeg
        Last edited by abcd567; 2015-04-08, 07:32.

        Comment


        • Originally posted by JLD View Post
          ...snip....
          In the other designs, with 2mm wires, you should use 65mm for 1/4 wave and 130mm for 1/2 wave.
          Using 69 and 138 probably give you an antenna with a resonance at 1040 Mhz.
          Thanks for key information about dimensions. I will keep these figures in mind when designing/simulating antennas

          Comment


          • Hi All,

            I ordered a batch last month for the same source as Nic ordered them and they just arrived.
            These are the specs:

            SPECS
            1090MHz antenna
            Gain: 9dBi
            Connector: N-Female
            Output power: 100W

            ELECTRICAL SPECIFICATIONS
            Frequency Range: 1090MHz
            Impedance: 50 Ohm
            VSWR: Less than 1.5
            Gain: 9dBi
            Radiation: Omni
            Max. Power Input-watts: 100W
            Lightning protection: DC ground
            Horizontal Beam Width: 360 degree
            Vertical Beam Width: 14 degree

            MECHANICAL SPECIFICATIONS
            Height: 221420 mm
            Termination: N-Female
            Radome Material: Fiberglass
            Hold pole diameter: 25-40mm

            PM me if you want one. I know sending them to England from NL is expensive and is best done in a batch of 3 or more.
            The rest of Europe is reasonable!

            Ta Frank

            Comment


            • @JLD and abcd, i will try to get the parts to make the antenna during the week but I am away with work for a week this coming Monday so it may be a two weeks before i can get access to a VNA.
              T-EGLF8

              Comment


              • wire size ratio.png

                This table gives a good idea of the actual length an antenna should be in function of its 1/2 wave to wire diameter ratio.
                For 2mm the ratio is close to 70 at 1090 Mhz and requires a 6% shortening compared to 1/2 wave size (intersection between the curves and the 1/2 wave resonance vertical line)
                JL

                Comment


                • @JLD:
                  Thank you for posting the length correction factor graph. Very useful & handy. What is the name of book from which this grapg is taken?

                  Comment


                  • RSGB radio communication handbook

                    Preview: http://www.rsgbshop.org/acatalog/PDF..._12_sample.pdf

                    Comment


                    • Originally posted by JLD View Post
                      RSGB radio communication handbook

                      Preview: http://www.rsgbshop.org/acatalog/PDF..._12_sample.pdf
                      Thank you very much.
                      Googled & found 38 pages of chapter 16 at another location as well:

                      http://lipcsey.gportal.hu/portal/lip...4047_02956.pdf

                      Comment


                      • with the spider franklin is this effectively what you are doing https://www.mikrocontroller.net/atta...2917/adsb2.gif by this i mean they are probably behaving in the same fashion

                        i've made something along these lines and it worked quite well. Again like a spider one very easy to make and get right.
                        Last edited by SpaxmoidJAm; 2015-04-11, 10:29.
                        T-EGLF8

                        Comment


                        • Originally posted by SpaxmoidJAm View Post
                          with the spider franklin is this effectively what you are doing https://www.mikrocontroller.net/atta...2917/adsb2.gif by this i mean they are probably behaving in the same fashion

                          i've made something along these lines and it worked quite well. Again like a spider one very easy to make and get right.
                          Yes, both are wire collinears, but the difference is in Phasing arrangement - Coil vs Stub.

                          Accuracy in both the design and construction are very important for collinear to give good performance.

                          Few mm error in design or few mm error in construction knocks down collinear from excellent to poor.

                          For both the design & the construction, it is much easier to be accurate with stub than with the coil.

                          Franklin Spider.PNG . adsb2.gif . ads-b-1.jpg . adsb-3.jpg . adsb-4-rev.JPG
                          Last edited by abcd567; 2015-04-12, 05:14.

                          Comment


                          • Has anyone used this?
                            http://sdr-kits.net/VNWA3_Description.html

                            VNWA3-2.jpg . VNWA3 Presentation.jpg

                            Comment


                            • which one is stub?

                              Comment


                              • Originally posted by kucengemok View Post
                                which one is stub?
                                The U shaped / hairpin shaped part in this one:

                                Franklin Spider.PNG
                                Last edited by abcd567; 2015-04-12, 18:09.

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