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  • I'm glad you guys are having fun. I opted out of this and bought a tuned antenna.

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    • I also bought a professionally made, tuned one.... which was, well, shall we say a dead dodo!

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      • Originally posted by peterhr View Post
        I'm glad you guys are having fun. I opted out of this and bought a tuned antenna.
        I can afford to purchase a professional antenna, but I will loose the enjoyment & satisfaction I get by achieving & discovering things.

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        • SUCCESS!!!! - 450 kms+ : The result of 23 hrs trial run of 4-elements, 124 mm element-length, open top CoCo
          Cable used: RG6, Foamed Polyethylene (FPE) insulation, VF=82%
          Element length = wavelength x VF/(1+VF) = 275 mm x 0.82/(1+0.82) = 124 mm

          VRS Range Plot Screen Grab
          coco-4element-124mm-23hr run-23July2014-R.png


          SETUP PHOTOGRAPHS
          DSC03200RR.JPG

          DSC03198RR.jpg

          DSC03199RR.jpg
          Last edited by abcd567; 2014-07-23, 18:11.

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          • Congratulations on a very successful experiment, with superb range!
            Wish I could say the same from my experiment running over here. Getting rather meager range from a 4 element, added another 2 elements and it gave reasonable coverage, yet nothing to get excited about. Not sure what is wrong with mine, as previous experiments yielded better coverage.

            PS: What is the lenght of your top element's centre, as can be seen on the photo?
            Last edited by HermanZA; 2014-07-23, 19:19.

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            • Originally posted by HermanZA View Post
              Congratulations on a very successful experiment, with superb range!
              Wish I could say the same from my experiment running over here. Getting rather meager range from a 4 element, added another 2 elements and it gave reasonable coverage, yet nothing to get excited about. Not sure what is wrong with mine, as previous experiments yielded better coverage.

              PS: What is the lenght of your top element's centre, as can be seen on the photo?
              The center wire projecting over top element is 20mm, but is not an element. I left it there just in case I need to add few more elements above, or solder a whip to it.
              What is the insulation material of cable you used to make coco? Is it polethylene, or teflon, or foamed polyethylene.. Your element length will not be 124mm if the VF is not 82%.
              Polyethylene (RG58) has a VF of 0.69, element length =112mm
              Teflon has a VF of .66 (if i remember correctly), element length =109mm
              and foamed polyethylene has a VF of 0.82, element length = 124mm
              Last edited by abcd567; 2014-07-23, 20:51.

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              • Inner is made of Foam PE. Same RG6 cable that we discussed via email some time ago. Only difference is that the top stub is about 8mm long, where yours are 20mm. So when I added elements to it, I removed the top one, and added 3 more similar dimension elements.

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                • Originally posted by HermanZA View Post
                  .......Getting rather meager range from a 4 element, added another 2 elements and it gave reasonable coverage, yet nothing to get excited about. Not sure what is wrong with mine, as previous experiments yielded better coverage. . . . .
                  Now this is a conflicting situation. I get excellent results, while HermanZA gets not very good results. We need few more volunteers to run the test to be sure. Any volunteers?

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                  • Originally posted by SBSer View Post
                    .........-- Is it not perhaps the type of coax used to make the antenna that makes the difference?
                    The outer conductor could , because of the shape in this case, present a longer path for the signal than for instance a braid as in RG6 and thereby confirming the theory by abcd567 that the outer conductor should be longer than the inner.
                    Knowing the "black art" of antenna making, it could just work out to the correct length........
                    Your argument seems very powerful & logical.

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                    • I built one tonight to test out.. but it is not working at all.. I am afraid that I may have damaged the tiny connector on the RTL dongle while plugging it in... Dark out now .. so will have to look at it again tomorrow.
                      Prvious to this I have been using only a 1/2 dipole, so the comparison should have been a big improvement.
                      Built to abcd567 instructions, 4 elements 124mm using foam RG6. Tested with an ohm meter.. no shorts and continuity to the top section both shield and center.
                      So it not working at all means I must have broken the connector :-(


                      EDIT:
                      Ok.. so I lied... It is dark but I went and took the thing down anyway..
                      Connections to the dongle are fine... tested with an ohm meter from the dongle circuit board all the way to the top of the antenna.. continuity but no shorts... fired it all back up.. still nothing..
                      rechecked my measurements and everything looks fine...
                      I have tried different co-co designs and have not gotten one to work better than a 1/2 dipole.. I must be doing something wrong.
                      Last edited by tvengineer; 2014-07-24, 02:29.

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                      • Originally posted by tvengineer View Post
                        I built one tonight to test out.. but it is not working at all.. I am afraid that I may have damaged the tiny connector on the RTL dongle while plugging it in... Dark out now .. so will have to look at it again tomorrow.
                        Prvious to this I have been using only a 1/2 dipole, so the comparison should have been a big improvement.
                        Built to abcd567 instructions, 4 elements 124mm using foam RG6. Tested with an ohm meter.. no shorts and continuity to the top section both shield and center.
                        So it not working at all means I must have broken the connector :-(
                        Thanks for your contribution to the efforts of antenna community.

                        My very first DIYantenna was a 1/2 wave dipole.

                        All the CoCos I have previously built (3.5, 4, 8 elements), performed much inferior to the tiny 1/2 wave dipole.

                        The 4 element Franklin proved to be much superior to the 1/2 wave dipole.

                        The Pepsi-can sleeved dipole somewhat superior to 1/2 wave dipole.

                        New Coco 4-element 124mm has also proved superior to the 1/2 wave dipole.

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                        • Originally posted by SBSer View Post
                          ........BTW my carefully made LMR 400 coco and tested open works perfectly without an amplifier but with amp only 50 or so miles on SBS-1eR, Radarbox and dongle.
                          Does your amplifier work OK with other antenna? Maybe the amplifier is defective. A bad amplifier acts as attenuator.

                          One more strange thing which I have experienced is that when I used an amplifier with frequency range starting at 47 MHz (47 - 2500 MHz), the amplifier, for some queer reason, did not amplify 1090 MHz signal. When I used an amplifier with frequency range starting high at 950 MHz (950 - 2300 MHz), the amplifier worked perfectly well for 1090 MHz. This was also experienced by another person trying to use amplifier.

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                          • Originally posted by tvengineer View Post
                            I built one tonight to test out.. but it is not working at all.. I am afraid that I may have damaged the tiny connector on the RTL dongle while plugging it in... Dark out now .. so will have to look at it again tomorrow.
                            Prvious to this I have been using only a 1/2 dipole, so the comparison should have been a big improvement.
                            Built to abcd567 instructions, 4 elements 124mm using foam RG6. Tested with an ohm meter.. no shorts and continuity to the top section both shield and center.
                            So it not working at all means I must have broken the connector :-(


                            EDIT:
                            Ok.. so I lied... It is dark but I went and took the thing down anyway..
                            Connections to the dongle are fine... tested with an ohm meter from the dongle circuit board all the way to the top of the antenna.. continuity but no shorts... fired it all back up.. still nothing..
                            rechecked my measurements and everything looks fine...
                            I have tried different co-co designs and have not gotten one to work better than a 1/2 dipole.. I must be doing something wrong.
                            just a thought - short circuit the top of the antenna temporarily and check it is low resistance from the other end - to make sure all connections are good.

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                            • Originally posted by HermanZA View Post
                              .......Getting rather meager range from a 4 element, added another 2 elements and it gave reasonable coverage, yet nothing to get excited about..........
                              Add 2 more elements and make it 8-element coco. I have noted most amateurs are making CoCo with 8 or more elements.

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                              • Originally posted by abcd567 View Post
                                Add 2 more elements and make it 8-element coco. I have noted most amateurs are making CoCo with 8 or more elements.
                                Like the one I built... 8 and a half elements was based on a HAM 70cm band antenna design.
                                http://ads-b.ca/antenna-collinear-F-CYYZ2/img_9712.htm
                                www.ADS-B.ca

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