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  • Improving my coco antenna

    I have just finished and fine tuned my 16 element coco antenna, it is currently on a dodgy rigged mast and is about 3 metres of the ground at the base of the array. As the landlord lives upstairs putting it on the roof is not an option.
    My idea is to fill a drum with concrete with a pipe in the middle and 3 tie points then slide another 7 metre pipe into it with a guy plate to tie back just below the top of the same pipe and also support the riser for the array. Then there are three options

    1. A 15 metre run of cable to the pi and dongle.

    2 Put the dongle up there and run an active USB cable to it.

    3 Build an enclosure and put all the parts up there and just run the power to it.

    My current array is made of RG 6 quad 75 ohm which is connected to a 5 metre run of the same RG6, it is then strip tied into 30 centimetres of RG 58 50 ohm that has an MCX on the end of it going into the dongle from jetvision. The reception is far superior to the internal antenna supplied with the dongle with many more hits per day. There was only one place in Brisbane that I could find MCX connectors a specialist Antenna shop and he suggested I make the array and feeder cable from from RG 58. I also wondered what you are all using to amplify and filter your signals.

    Thanks and I know this is one of those questions that probably crops up all the time, but it is a good opportunity to listen to the words of wisdom from all of you.
    T-YBBN167 PiRad108

  • #2
    Just an FYI, RG58 isn't very good for what we are receiving at long length.

    @ 1090Mhz (approximations)

    15m of RG 58 = 8dB loss

    RG213 = 4dB

    LMR400 = 2dB

    Check the rest of this area, there are a number of DIY antenna tests and suggestions
    Last edited by Oblivian; 2018-02-27, 09:57.
    Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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    • #3
      Originally posted by Oblivian View Post
      Just an FYI, RG58 isn't very good for what we are receiving at long length.

      @ 1090Mhz (approximations)

      15m of RG 58 = 8dB loss

      RG213 = 4dB

      LMR400 = 2dB

      Check the rest of this area, there are a number of DIY antenna tests and suggestions
      Thanks, the one catalog I have with cable in it has limited info on db loss. I am going through what is here already, and taking all the replies on board as well
      T-YBBN167 PiRad108

      Comment


      • #4
        Couple of online ones about.
        http://www.qsl.net/co8tw/Coax_Calculator.htm

        ADSB is of course 1090Mhz (hence the multiple x1090 names)
        Posts not to be taken as official support representation - Just a helpful uploader who tinkers

        Comment


        • #5
          I am only using a 1' run of RG58 as a feed into the MCX connector, the main feed and the array is RG6/U, it was just impossible to get the MCX male connector onto the RG6 hence the short length of RG58. I have a better dongle on order that has an SMA connector.
          T-YBBN167 PiRad108

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          • #6
            Originally posted by PiRad108 View Post
            I am only using a 1' run of RG58 as a feed into the MCX connector, the main feed and the array is RG6/U, it was just impossible to get the MCX male connector onto the RG6 hence the short length of RG58. I have a better dongle on order that has an SMA connector.
            Or order a ready-made pigtail with SMA-f to mcx. And one from F-female to SMA-male. Put F-connectors on the RG6 cable, for which it was intended. Now it will work for all dongles with either SMA or mcx.

            /M
            F-ESDF1, F-ESGG1, F-ESGP1, F-ESNK1, F-ESNV2, F-ESNV3 F-ESSL4, F-LFMN3
            P-ESGR, P-ESIA, P-ESIB, P-ESGF
            mrmac (a) fastest.cc

            Comment


            • #7
              F-female to SMA-male pigtail
              F-female to SMA-male Pigtail.jpg . . F-female to SMA-male RG316 pigtail.jpg


              F-female to MCX-male pigtail
              F-male to MCX-male Pigtail.jpg . . F-female to MCX-male RG316 pigtail.jpg
              Last edited by abcd567; 2018-02-28, 00:01.

              Comment


              • #8
                How good or bad is a DIY antenna cannot be measured as majority of the hobbyists lack necessary costly test equipment.

                However a DIY antenna can be evaluated by COMPARING its performance with a reference antenna, i.e. another DIY antenna of known performance.

                This comparioson should be done by swaping the antennas ONLY, keeping all other parameters same (i.e. same antenna location and height, same coax, connectors/pigtails for connecting antenna to DVB-T dongle, same Dongle, same Pi and same Software).

                A good choice for reference DIY antenna is a 1/4 wavelength ground plane, also known as Spider. It is easy to make, is naturally tuned, and has a stable performance.

                A good CoCo should give better plane count and better maximum range compared to Spider. If the CoCo performs equal or less than Spider than the CoCo is not well made.

                Click the link below to see how to make an easy DIY 1/4 wavelength ground plane antenna:

                EASY ANTENNA # 3 : QUICK SPIDER

                .
                Last edited by abcd567; 2018-02-28, 03:46.

                Comment


                • #9
                  Originally posted by abcd567 View Post
                  How good or bad is a DIY antenna cannot be measured as majority of the hobbyists lack necessary costly test equipment.

                  However a DIY antenna can be evaluated by COMPARING its performance with a reference antenna, i.e. another DIY antenna of known performance.

                  This comparioson should be done by swaping the antennas ONLY, keeping all other parameters same (i.e. same antenna location and height, same coax, connectors/pigtails for connecting antenna to DVB-T dongle, same Dongle, same Pi and same Software).

                  A good choice for reference DIY antenna is a 1/4 wavelength ground plane, also known as Spider. It is easy to make, is naturally tuned, and has a stable performance.

                  A good CoCo should give better plane count and better maximum range compared to Spider. If the CoCo performs equal or less than Spider than the CoCo is not well made.

                  Click the link below to see how to make an easy DIY 1/4 wavelength ground plane antenna:

                  EASY ANTENNA # 3 : QUICK SPIDER

                  .
                  Thank You for that
                  T-YBBN167 PiRad108

                  Comment


                  • #10
                    I have been having fun building and learning about antennas the last few days. A few disappointments along the way as well, my first antenna 16 element coco array failed on examination I found it was the severe heat we have been having the joins had expanded and got slippery and several had separated, lesson use heatshrink instead of electrical tape. I am awaiting the better dongle from jetvision so my two new antennas have been built with SMA connectors and are yet to be tested one is a simple spider thanks to abcd567. The other after making a decision to switch to 50 ohm cable is an 8 element coco made from RG8 this presented a few challenges due to the thickness of the cable it is very rigid, it also has a 2 mm solid copper core. I cut groves in the outer sheath at each end of the elements then pushed the central core in to the incisions, crimped it with pliers then zip tied, tested, heat shrinked and zip tied the heat shrink with another round of zip ties. I then enclosed it in a PVC tube and popped a connector on the tail.
                    T-YBBN167 PiRad108

                    Comment


                    • #11
                      Originally posted by PiRad108 View Post
                      I have been having fun building and learning about antennas the last few days. A few disappointments along the way as well, my first antenna 16 element coco array failed on examination I found it was the severe heat we have been having the joins had expanded and got slippery and several had separated, lesson use heatshrink instead of electrical tape. I am awaiting the better dongle from jetvision so my two new antennas have been built with SMA connectors and are yet to be tested one is a simple spider thanks to abcd567. The other after making a decision to switch to 50 ohm cable is an 8 element coco made from RG8 this presented a few challenges due to the thickness of the cable it is very rigid, it also has a 2 mm solid copper core. I cut groves in the outer sheath at each end of the elements then pushed the central core in to the incisions, crimped it with pliers then zip tied, tested, heat shrinked and zip tied the heat shrink with another round of zip ties. I then enclosed it in a PVC tube and popped a connector on the tail.
                      Just exercise a little caution when using PVC conduit to enclose your coco. Some, but by no means all, PVC conduit can degrade the signal you're attempting to receive. There is plenty of advice on the net re testing of these conduits but I've found the safest (buggered if I'm sticking it in the microwave oven) is to try it inside the property with and without it for comparison before hoisting it up the mast.

                      Some also require painting as they aren't UV protected and that too can be problematic depending on the paint used.

                      Sounds like you've got everything else pretty well covered. It is indeed fun isn't it?

                      Regards,
                      Gregg
                      Last edited by fungus; 2018-03-04, 01:36.
                      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


                      • #12
                        Originally posted by PiRad108 View Post
                        ... my first antenna 16 element coco array failed on examination...
                        Jeez, even with a full RF lab it's almost impossible to get a collinear with that many elements in phase. IF you are building "blind", try 3-4 elements. If you have a good SWR meter, maybe 5-6.

                        /M
                        F-ESDF1, F-ESGG1, F-ESGP1, F-ESNK1, F-ESNV2, F-ESNV3 F-ESSL4, F-LFMN3
                        P-ESGR, P-ESIA, P-ESIB, P-ESGF
                        mrmac (a) fastest.cc

                        Comment


                        • #13
                          Originally posted by MrMac View Post
                          Jeez, even with a full RF lab it's almost impossible to get a collinear with that many elements in phase. IF you are building "blind", try 3-4 elements. If you have a good SWR meter, maybe 5-6.

                          /M
                          I am just starting to learn what I does and does not work as you know there is lots of misleading info out there. On that note my 8 element RG8 coco which is on its first day test in the carport because it is raining at the moment is getting the best results so far for that location having used the supplied short whip antenna, and a Spider in that location which only has decent Northern line of sight and getting 40 NM max, this one has already given me 62 NM.
                          T-YBBN167 PiRad108

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                          • #14
                            It's better to start with something easier!


                            The problem is, even if you DO have an SWR meter, the small phase differences messes with the radiation pattern so that all that theoretical gain will never materialize. This is not visible on SWR, it can be perfectly resonant but still not give the expected gain in any direction.

                            I have seen this well demonstrated, worked for a major antenna manufacturer and we made a 10dB collinear. It was a b*tch to assemble correctly and we had a fully automated compact range (anechoic chamber) with an ABB robot that made automated over-night 360x360 gain measurements that we invested 3 million USD in. Unless you have access to that kind of equipment that can actually measure gain in different directions, it WILL be sub-optimal.

                            There is a reason both FR24 and Flightaware decided that the best performance comes from 5-6 dB collinear antennas. I know for a fact that FR24 tested a lot of different ones before they made that choice.


                            BR /M
                            F-ESDF1, F-ESGG1, F-ESGP1, F-ESNK1, F-ESNV2, F-ESNV3 F-ESSL4, F-LFMN3
                            P-ESGR, P-ESIA, P-ESIB, P-ESGF
                            mrmac (a) fastest.cc

                            Comment


                            • #15
                              @MrMac:
                              Fully agree.

                              Flightaware 26 inch Antenna: Wire Collinear, with Decoupling Sleeve.

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