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My first collinear antenna

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  • @FR24-BB8
    Looks good. Waiting for results.

    It is 5 and 1/2 element, with top 1/2 element shorted at top.

    Seems you have used 20 mm dia (nominal) copper water pipe for sleeve. I also used copper water pipe, but closed it at one end by an end cap. It seems instead of end cap, you have used a coin.

    The lowermost element is not a radiating element, it is balun. That is why I counted 5 , and not 6 full elements.

    Generally people use even number of full elements. Any specific reason to choose odd number?
    Last edited by abcd567; 2016-07-04, 21:52.

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    • Originally posted by SpaxmoidJAm View Post
      looking good, now to see if it works.

      Have you checked to see if the PVC is blocking RF, you can stick a small piece in the microwave for a minute if gets warm its hurting performance.
      Tried it now, it's ok.

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      • My first collinear antenna

        Originally posted by abcd567 View Post
        @FR24-BB8
        Looks good. Waiting for results.

        It is 5 and 1/2 element, with top 1/2 element shorted at top.

        The lowermost element is not a radiating element, it is balun. That is why I counted 5 , and not 6 full elements.

        Generally people use even number of full elements. Any specific reason to choose odd number?
        Nope, just followed @SpaxmoidJAm guide. Perhaps i misunderstood something?

        Edit: I didn't use a coin, I soldered a washer at the end and mounted a female/female f-connector through the washer.
        Last edited by FR24-BB8; 2016-07-04, 21:57.

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        • @FR24-BB8
          No you did not miss anything, i was just curious, as mostly people use even number of full elements.

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          • My first collinear antenna

            The initial result with my coco seems quite disappointing, but I'll let it sit at least until tonight (24 hrs) and then post a range plot.

            Meanwhile I have adjusted this spider and removed the horizontal radials, cause the best results I've had is with spiders and radials directly bent 45° (both coax only and bare copper).

            Last edited by FR24-BB8; 2016-07-05, 08:18.

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            • @FR24-BB8
              If after 24 hrs trial, results are still disappointing, try following :
              (1) Add or remove one 1/2 wave piece, making it even number of pieces.. Try it for 24 hrs
              (2) Remove copper sleeve balun. Try it for 24 hrs.
              Last edited by abcd567; 2016-07-05, 09:55.

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              • My first collinear antenna

                @abcd567

                Yeah. I probably try doing it in a couple of hours already. I can see that aircrafts in the same flight path I picked up at 125+nm earlier is picked up at 50-70 now. So I feel like doing something.
                Last edited by FR24-BB8; 2016-07-05, 11:15.

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                • Here is the range plot from 17 hours with the 5 1/2 element coco with balun:

                  coco_with_balun_halfattop.PNG

                  I have now taken the half length away from the top. Letīs see how that performs.

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                  • Try also this, its just worked for me way better..


                    Sent from my iPad using Tapatalk

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                    • My first collinear antenna

                      @abcd567
                      I already get better readings (up to 170-175 nm) with the top half element removed. For some reason I can't post an image right now but I post it tomorrow. I will then also remove the balun and compare the results.

                      Edit:
                      I did not remove 1 1/2 element. Just the top shorted half. So it's now a 5 element coco with a copper sleeve balun, performing better than with 5 1/2. It's easy to try other variants, so before removing the balun, I'll take of 1 element to make it an even number, and do some tests. I'll post range plots with all variants later.

                      @skyspotter
                      Thx for the tip.
                      Last edited by FR24-BB8; 2016-07-05, 18:38.

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                      • it was from a design on here somewhere in the 280 pages of the best antenna design, if you going for a even number you dont need the shorted stub, it was something to do with the odd number.
                        T-EGLF8

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                        • Originally posted by FR24-BB8 View Post
                          @abcd567
                          I already get better readings (up to 170-175 nm) with the top half element removed. For some reason I can't post an image right now but I post it tomorrow. I will then also remove the balun and compare the results.

                          Edit:
                          I did not remove 1 1/2 element. Just the top shorted half. So it's now a 5 element coco with a copper sleeve balun, performing better than with 5 1/2. It's easy to try other variants, so before removing the balun, I'll take of 1 element to make it an even number, and do some tests. I'll post range plots with all variants later.

                          @skyspotter
                          Thx for the tip.
                          This is the way to find a better antenna. It is a hard way, and needs lots of patience, but as the sayings go, "fruit of patience is sweet" & "hard work pays".

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                          • @abcd567

                            Yeah, that's right. I really enjoy building and testing these antennas. Would for sure not be as fun just to buy a commercial one. Half or even more of the fun is these technical matters.

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                            • Hi again.

                              Here is the first comparison 5 segments with and without balun over aprox the same amount of time:

                              With balun:

                              coco_with_balun_5_segments.PNG

                              Without balun:

                              coco_without_balun_5_segments.PNG

                              I really donīt know what to say about this result, they are just about the same, maybe a bit better range with the one without the balun... But from FR24 point of view i got a max range of 177 nm with the one without balun, and the max range iīve got from them are 179 with bare copper spider so..

                              I will continue my tests with only 4 segments, with and without copper sleeve balun, but first i will try out my bare copper with no horizontal radials.

                              image1.JPG
                              Last edited by FR24-BB8; 2016-07-06, 20:54.

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                              • @FR24-BB8
                                1) In your map:
                                a) how many km or nm is outermost ring (red)
                                OR
                                b) how many km or nm between adjuscent rings

                                2) Now try with one element removd (i.e. 4 element coco) and then add 2 elements (i.e. 6 element coco), and try again.

                                Please note that 2 consecutive full elements balance each other, hence even number of full elements make a balanced coco, and is expected to give better results than one with odd number of full elements.

                                ** full element = 1/2 wavelength x Velocity Factor of coax

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