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Homebrew 2m coaxial collinear vertical

Discussion in 'Amateur Radio Antennas' started by HomerBB, Mar 31, 2018.

  1. HomerBB

    HomerBB Sr. Member

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    About 6 months ago I thought I'd try one of these - 2m coaxial collinear vertical.
    I used 75 Ohm coax seeing I had tons of it. I adjusted the half wave and quarter wave sections for Velocity Factor and started cutting and assembling. I only had room in the crappie pole for the 1/4^ stinger, 1/4^ bottom section, and either 4 or 6 1/2^ sections. Then I abandoned the project because I wasn't sure where to go with it next. I pretty much forgot about it until my ham neighbor asked me when I was going to tackle a collinear. I showed him what I'd started. He told me to put the analyzer on it. Well, it ranged 1.1 to 1.5:1 SWR across! Boy was I surprised. :)
    I need to add a set of GP radials and I think I'll be happy ('til the next time).
    Got a signal check to a reliable station 15 miles south of me. Signal improved on his IC 746 from 5 to 10+ over my 2m j-pole.



    20180331_145402-01.jpeg
     
    Riverman71 likes this.

  2. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Proves how a J pole antenna is not all that.
     
    midnight special likes this.
  3. HomerBB

    HomerBB Sr. Member

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    Perhaps. It does show how much improvement several 1/2^ elements aligned get more gain than a single 1/2^. Both mounted at 20' to the coax connection
     
  4. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    from a 5s unit reading to a 10 +???
    gain of over 5 S units or 30 DB??

    Not doubting the numbers of the receive station just saying if there is actually 30 db of gain on that coaxial collinear antenna then that J pole had -gain or greatly attenuated your transmitted signal.

    So if the receive station noticed 5 S units on your transmission, did your receive increase by 5 s units??

    Homer you know what you are doing, you a home brewer of antennas and have in-depth knowledge of antenna theory.

    Just saying I do not see how a coaxial collinear can have 30 db of gain, my cushcraft 13 element yagi only has 15.8 dbi gain. Convert to DBD and that is not even 3 S units.
     
    Road Squawker likes this.
  5. HomerBB

    HomerBB Sr. Member

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    Well, clearly the best one I've ever made. :D

    Just repeating what he said. I did not see it on my end. He relies on his radio to "speak" to him. He doesn't actually see his meter. So, I'll ask some others.
    I feel a bit silly. I hadn't even thought about what he said. I do know he came up on me some.
    I only expect 3 or so db of gain if I have enough sections inside the fishing pole. . . I have no way of knowing what his meter says, or his radio speaks. Nor if it is way off. Maybe his "Siri" is as bad as my spell checker.
    It's posted, so I'll leave it.
    I will get some more folks to give me their impressions.
    Thanks.
     
    #5 HomerBB, Mar 31, 2018
    Last edited: Apr 1, 2018
  6. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Forget any type of S-meter calibration on FM radios. For whatever reason they are nothing like AM/SSB mode rigs. I have seen what appears to be TREMENDOUS gain on FM mode when really it is just the ALC responding differently in that mode. It does not matter the band either. I have seen similar effects on 70cm, 2m, 6m and even 10m FM. In FM mode actual signal strength is not important at all. It's the level of quieting you get and very little signal can result in full quieting.
     
    sunbulls and HomerBB like this.
  7. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    I have a blind ham friend that I installed the "talking board" in his kenwood ts450, so when he was asked for RS he always replied I hear you Lima Charlie but I can not see the S meter.

    What matters most is that it works for what you want it to do and is an improvement over the J pole.

    Happy Easter
     
    HomerBB likes this.
  8. HomerBB

    HomerBB Sr. Member

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    Whew!
    I thought I had finally cracked, gone over the edge. And I thought CB would do that to me, got my ticket, and went antenna gain bonkers. . .
     

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