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  • Originally posted by lutorm View Post
    That's dedication! Did you find that the calculated results agreed with the experimental ones?
    No, I did not simulate for open stub when I got the 4nec2 software. I did simulate for shorted stub, and calculated tap position is sufficiently close to experimenatal tap position.

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    • Originally posted by lutorm View Post
      That's dedication! Did you find that the calculated results agreed with the experimental ones?
      Here is simulation for shorted one with 3/16 inch copper pipe (post #940).
      Coax Cable Tap 25mm from shorted end.
      http://forum.flightradar24.com/threa...ll=1#post51076
      Last edited by abcd567; 2014-05-07, 07:02.

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      • Originally posted by lutorm View Post
        ..........Did you find that the calculated results agreed with the experimental ones?
        I am using a 4-element Franklin made up of core of RG6.

        Wire size: 1 mm dia / 14 AWG (indoor installation; no wind; 1 mm dia copper clad steel wire is mechanically strong enough for indoor conditions).
        The 4 vertical limbs are each 138 mm.
        The upper & lower phasing stubs are each 67mm-4mm-67mm.
        The impedance matching stub is 69mm-5mm-69mm.
        For shorted stub, the optimum cable tap position is 18 mm from shorted end.
        For open stub, the optimum cable tap position is 11 mm from open end.


        Here are simulation results for open & shorted stub types with above noted dimensions:

        SHORTED STUB

        franklin - 4 element - 5mm SHORTED stub - swr gain pattern.png . franklin - 4 element - 5mm SHORTED stub - tap sweep.png




        OPEN STUB

        franklin - 4 element - 5mm OPEN stub - swr gain pattern.png . franklin - 4 element - 5mm OPEN stub - tap sweep.png

        Conclusion:
        Simulation results show that open stub has better SWR (1.1) compred to shorted stub (1.6).
        Also, open stub has the advantage that it does not require DC blocking.

        The advantage of shorted stub type is that entire antenna is in one piece, so alignment of upper & lower halves, as well as fixing to support is easier. Also one-piece antenna should be mechanically more stable than two-piece antenna.
        Last edited by abcd567; 2014-05-07, 14:29.

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        • .
          Interesting Antennas:

          1) Collinear: http://qsl.net/py4zbz/adsb.htm#b

          2) Full wave: http://qsl.net/py4zbz/adsb.htm#e

          .

          Comment


          • Excellent idea to use welding rod!

            Come one - we need one of you antenna guys to create a new hardware thread 'Practical Antenna Designs' - put in place holder posts at the start of the thread for different design types (coco, franklin, dipoles, etc) then edit those posts to populate them and keep them updated ... so the relevant stuff stays at the start of the thread. The emphasis on the thread would be building effective antennas, maybe with links to theory / calculation posts further down the thread.

            Comment


            • I couldn't agree more.
              Maybe make the thread sticky and add a prefix like [How to].
              Many of us were lost in all of these pages, and I'm sure that if all the info would be in one place lots of people could find the relevant info faster. This will rise the quality and coverage of the feeder stations.

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              • .
                Antenna .. antenna ... antenna everywhere...














                .
                Last edited by abcd567; 2014-06-14, 06:34.

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                • abcd567,

                  Thanks for those antenna pics. The missus now feels a lot better about the 5 antennas (plus 2 that are no longer in use) on our roof. I wouldn't want to be the poor bloke trying to find the faulty one amongst the top two.... talk about rats nests. Brilliant.

                  I'm staggered that some of those can pick up any signal. Wouldn't those in front block the signal to those at the rear? Also, they obviously don't like 'sharing.'

                  Regards,
                  Gregg
                  Last edited by fungus; 2014-05-12, 08:30.
                  YSSY2/T-YSSY4 [SBS-1 Basestation w/- SSE-1090 SJ Mk2 Antenna (Thanks Delcomp) ] [Uniden UBCD996T w/- 16 element Wideband Discone VHF/UHF Antenna, and tuned 108MHz-137MHz Airband Antenna] [Trialing a home-brew 1090MHz collinear antenna]

                  Comment


                  • Would be interesting to know what some of those arrays are used for, specially those chernobyl/chornobyl systems, also those dipoles with the yellow guy ropes.

                    EDIT: After some in-depth Googl'ing, seems its part of the Duga Over-the-horizon radar system http://chornobyl.in.ua/en/chernobyl-2-2.html Imagine if those could be taken down and re-built (as ADS-B antenna masts!)
                    Last edited by HermanZA; 2014-05-12, 08:56.

                    Comment


                    • .
                      What a car...



                      Last edited by abcd567; 2014-06-14, 06:28.

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                      • What software are you guys using to plot your coverage ?

                        Im using RTL dongle + rtl1090 + feeder software, but would like to produce a plot !

                        Thanks

                        Comment


                        • Rooster,
                          On the newer versions of Virtual Radar Server ( http://www.virtualradarserver.co.uk/ ) it has the capability to do range plotting.
                          I prefer ADSBScope ( http://www.sprut.de/electronic/pic/p...b/adsb_en.html) ... bit trickier to get working, but small footprint on your PC's resources. This helped me a lot in working out whats going on (or should come down) with my antenna's

                          VRS has a nice clean look, my personal 'keep it open all day long' app. Range is not active here.
                          ADSBScope keep track of my range - been neglecting that one a bit the past few weeks, specially after the update, to my range there is rather incomplete.

                          img-scope_resize.jpgimg-vrs_resize.jpg
                          Last edited by HermanZA; 2014-05-12, 15:52.

                          Comment


                          • SBSplotter:
                            http://jetvision.de/sbs.shtml
                            Liviu
                            A.net JetPhotos.Net PlaneSpotters.net
                            RTL USB/dump1090/FreeBSD + Franklin antenna + PlanePlotter

                            Comment


                            • Originally posted by HermanZA View Post
                              Would be interesting to know what some of those arrays are used for, specially those chernobyl/chornobyl systems, also those dipoles with the yellow guy ropes.

                              EDIT: After some in-depth Googl'ing, seems its part of the Duga Over-the-horizon radar system http://chornobyl.in.ua/en/chernobyl-2-2.html Imagine if those could be taken down and re-built (as ADS-B antenna masts!)

                              (1) The site of antennas with yellow guy ropes is for collecting weather information called a "HF Radar" or "WERA Radar" System.
                              Please see
                              http://ifmaxp1.ifm.uni-hamburg.de/info.shtml

                              http://www.aslenv.com/WERA.html


                              (2) The giant steel structure at Chernobyl is Soviet era Russian Military's Over-the-Horizon Radar antenna Duga-3 also known as "Russian Woodpecker". This site is reportedly no more active. It is commonly believed that Russians used to pump in tens of Mega Watts of RF power into this "cage dipole"** antenna array.

                              Please see http://en.wikipedia.org/wiki/Duga-3

                              ** A cage dipole is basically an attempt to achieve a broader bandwidth by using a thicker radiator. Building a dipole out of, say, a large-diameter aluminum tube isn’t very practical, but you can create almost the same thing, electrically speaking, by using a number of individual wires properly spaced to create a antenna that looks like a round bird-cage (as in the "Russian Woodpecker" picture). That’s the principle behind the cage dipole. A typical HF cage dipole can exhibit a bandwidth almost 2 times broader than a single-wire dipole. There are other means of creating an electrically “thick” antenna. The bow tie, for example, makes use of the same principle
                              Last edited by abcd567; 2014-05-12, 17:52.

                              Comment


                              • Originally posted by Rooster View Post
                                What software are you guys using to plot your coverage ?

                                Im using RTL dongle + rtl1090 + feeder software, but would like to produce a plot !

                                Thanks
                                Hi Rooster,
                                I use SBSPlotter and adsbScope together.
                                SBSPlotter settings are Port = 30003 and IP = 127.0.0.1

                                adsbScope - from the menu go to other, Network, Network setup, and at the bottom choose preset RTL1090. This should give you port 31001 and IP 127.0.0.1. To start adsbScope running choose the icon Start RAW-data client.

                                At the botton of the RTL1090 screen you should get BS highlighted cyan and IP highlighted green if both connections have been made properly.

                                You can't run VRS and adsbScope simultaneously
                                T-EGUB1

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