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  • Originally posted by F-EGLF1 View Post
    1000 would only get you one of the cheap hand held Chinese ones that they sell on e-bay, I don't think you would be very pleased with the results you got for the money, 'proper' antennae analysers will set you back 5000+ even second hand, however they would give you the results you wanted.
    Ben.
    Thanks every one for your advices. Due to high price, I have dropped the idea of setting up a test bench. For now I will survive with my $10 analogue (moving needle type) multimeter, 20kOhm/V DC, 9kOhm/V AC. , till I win a lottery or hit a jackpot in a casino .

    Comment


    • Hi Rooster
      I have gone through the paper. What I conclude is that:

      The statement in document is applicable to individual elements of CoCo, where one conductor is small dia (core), and second conductor is large dia (braid).

      If two elements are connected with core & braid cross-connected, the PAIR of element has two similar conductors. Each conductor comprising of half of it's length small dia (core), and other half a large dia (braid). Hence in PAIR of elements, two conductors are identical making the PAIR balanced.

      The CoCo as a whole is balanced, if it has even number of elements, say n, giving n/2 number of pairs. The CoCo will be unbalanced if n is odd, giving (n-1)/2 pairs + 1 single element, causing imbalance.

      Well, above is my understanding from the article. If any one has gone through it and has different opinion, I welcome him/her to post his/her opinion.
      Last edited by abcd567; 2014-05-25, 19:14.

      Comment


      • Transmission Lines (Twin Lead, Coaxial Cable, Waveguides etc) DO NOT RADIATE RF Energy.

        Reason:
        The entire electromagnetic field is confined in the narrow space between two conductors.
        For twin lead, it is confined in the space between the two parallel wires.
        For Coaxial cable it is confined in the space between shield and core.
        For Waveguides, it is confined in the internal volume of the waveguide.

        Then why & how the CoCo, which is made up of pieces of non-radiating coaxial cable, radiates so effectively?
        Last edited by abcd567; 2014-06-14, 06:11.

        Comment


        • Originally posted by abcd567 View Post
          Transmission Lines (Twin Lead, Coaxial Cable, Waveguides etc) DO NOT RADIATE RF Energy.

          Then why & how the CoCo, which is made up of pieces of non-radiating coaxial cable, radiates so effectively?
          I think you answered this yourself with your excellent drawing a few posts back
          Ben.
          FR24 F-EGLF1, Blitzortung station 878, OGN Aldersht2, PilotAware PWAldersht, PlanePlotter M7.

          Comment


          • Originally posted by abcd567 View Post

            The cable "Andrew Heliax" will make a very sturdy CoCo



            Outer Conductor: Copper
            Inner Conductor: Copper-Clad Aluminum
            Diameter over Jacket, 0.63 inch /16 mm
            Diameter over Copper Outer Conductor: 0.55 inch / 14 mm
            Diameter Inner Conductor: 0.189 inch / 4.6 mm

            Impedance: 50 1 ohms
            Maximum Frequency: 8.8 GHz
            Foam Dielectric
            Velocity Factor: 88%
            Yes it sure will... I was just given six 65 foot lengths of used but in excellent shape LDF1-50 which is the 1/4 inch hardline. Believe it or not it's from CYYZ runway 15L ILS Glidepath antenna system that was just replaced as part of a Nav Canada upgrade. They don't reuse any coax so this stuff was to be tossed in the trash. I was lucky enough to have a connection at CYYZ that got it for me. I'm going to be running 3 of these lines up my tower to new antennas. LDF1-50 is smaller in size then LMR-400 but has less loss then LMR-400. You need a pipe cutter to work with LDF1-50 but it's actually very easy to work with and the cuts are precise thanks to its corrugated shield.

            Some photos,
            http://ads-b.ca/LDF1-50/

            I do plan to build a nice collinear with this stuff.

            Specs
            http://www.repeater-builder.com/andr...spec-sheet.pdf

            abcd567, since you're local to me if you'd like some LDF1-50 you're more then welcome... I have more then I'll ever need
            www.ADS-B.ca

            Comment


            • Originally posted by 1090 MHz View Post
              .......abcd567, since you're local to me if you'd like some LDF1-50 you're more then welcome... I have more then I'll ever need
              Thank you for your offer. I will contact you by email.

              Comment


              • Originally posted by 1090 MHz View Post
                ........Some photos,
                http://ads-b.ca/LDF1-50/

                I do plan to build a nice collinear with this stuff.
                Some of your pictures indicate that you have already started to make the CoCo from LDF1-50

                .

                Comment


                • Originally posted by abcd567 View Post
                  Some of your pictures indicate that you have already started to make the CoCo from LDF1-50

                  .
                  Yes I made one element however it's the wrong length. The VF of LDF1-50 is 86% so if I'm correct the 1/2 wave elements should be 11.83 cm.
                  www.ADS-B.ca

                  Comment


                  • Originally posted by 1090 MHz View Post
                    Yes I made one element however it's the wrong length. The VF of LDF1-50 is 86% so if I'm correct the 1/2 wave elements should be 11.83 cm.
                    Waiting for completion & field test results of your diy Andrew Heliax LDF1-50 CoCo.

                    Comment


                    • Originally posted by abcd567 View Post
                      Waiting for completion & field test results of your diy Andrew Heliax LDF1-50 CoCo.
                      I was going to cut the elements to 11.83 cm but after looking at this site he says to cut shorter to take into account the connection spacing... see here:
                      http://wireless.gumph.org/content/3/...r_antenna.html

                      solder_element_diagram.jpg
                      www.ADS-B.ca

                      Comment


                      • Originally posted by 1090 MHz View Post
                        I was going to cut the elements to 11.83 cm but after looking at this site he says to cut shorter to take into account the connection spacing... see here:
                        http://wireless.gumph.org/content/3/...r_antenna.html

                        [ATTACH=CONFIG]4165[/ATTACH]
                        It is good to be as precise as practically possible. However CoCo has shown to be reasonably tolerent to element length error. Please see my post #1209 below
                        In simulation, I have kept a gap of 1 mm between shields of the adjuscent elements
                        Last edited by abcd567; 2014-05-27, 07:05.

                        Comment


                        • @1090MHz
                          Effect of error in the length of CoCo element on Gain, SWR, Pattern.
                          Simulation for air-insulated CoCo, VF=1, 1/2 wavelength=137.5mm.





                          .
                          Last edited by abcd567; 2014-05-27, 04:25.

                          Comment


                          • Originally posted by abcd567 View Post
                            Transmission Lines (Twin Lead, Coaxial Cable, Waveguides etc) DO NOT RADIATE RF Energy.

                            Reason:
                            The entire electromagnetic field is confined in the narrow space between two conductors.
                            For twin lead, it is confined in the space between the two parallel wires.
                            For Coaxial cable it is confined in the space between shield and core.
                            For Waveguides, it is confined in the internal volume of the waveguide.

                            Then why & how the CoCo, which is made up of pieces of non-radiating coaxial cable, radiates so effectively?

                            I found that the above statement "Transmission Lines DO NOT RADIATE RF Energy"

                            is true only if the currents in two conductors of transmission line are equal and opposite.

                            If the currents in two conductors are not equal & opposite, the transmission line will radiate.

                            Examle:
                            If a CoCo element's core is carrying 5 amps, and shield is carrying 7 amps in opposite direction, then 5 amps of core current will balance 5 amps of shield current, and remaining 7-5=2 amps of shield current will be utilized in radiating RF Energy in space.

                            The same unbalanced 2 amp will also flow through the shield of feeding coaxial cable, and make feed line shield to radiate. This is highly undesirable, and is prevented by various techniques like 1/2 λ coax balun, ferrite rings, ferrite beads, ferrite cored transformer, choke balun, and 1/4 λ sleeve (as in RadarCape CoCo), etc.

                            .
                            Last edited by abcd567; 2014-05-28, 23:07.

                            Comment


                            • .
                              FLAVOURS OF CoCo




                              .
                              Last edited by abcd567; 2014-05-29, 17:11.

                              Comment


                              • On internet, a huge variety of CoCo designs for 1090 Mhz and 2.4 Ghz are available. It is difficult to say which one is better unless all are made & tried under same conditions (i.e. Antenna Location, cable run, receiver etc to be same). Trial runs without amplifier are better as amplifier's AGC will dim the real difference. Also trial runs with antenna at window level or similar easy accessable position are practical, as it is tedious to install & uninstall trial antennas on roof.

                                The differences are basically in top element. Only one stem with odd number of elements can be made, and one piece each of different top elements made & installed/ tested one by one.

                                This is huge work. Any volunteers?

                                .
                                Last edited by abcd567; 2014-05-29, 16:10.

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