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Thread: Homebrew dual band yagi for 17m and 12m - Open Sleeve

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  1. #1

    Default Homebrew dual band yagi for 17m and 12m - Open Sleeve

    Hello! I am interested in building a dual band 17m and 12m yagi. I am thinking of a reflector and driven element on 17m and would like to try and put a driven element and director in front for 12m. I want to use one feed to the 17m driven element and use open sleeve coupling to excite the 12m driven element. I would be using full size, lightweight telescopic aluminium elements and would like to know the following....
    1. How to calculate the close spacing between the driven elements? Is it trial and error?
    2. Would the 12m driven element have to be in 2 parts and isolated from the boom?
    3. What the charcteristic feed imedance would be for the 17m driven element?
    4. Could I use one hairpin (beta type match) for both bands?

    Any help and suggestions regarding building this type of antenna would be appreciated. I have never used this type of coupling system before but am interested in trying to build it.
    Thanks in advance! Cheers Jess

  2. #2
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  3. #3
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    Default

    The force 12 warc 2/2 is also very similiar. get a hold of the manual and build it, its a little shorter then dk7zb's.

  4. #4

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    Thanks for the link and replies so far - Does anyone have the dimensions or manual for the above Force 12 warc 2/2? Cheers Jess

  5. #5
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    Quote Originally Posted by G8IYE View Post
    Thanks for the link and replies so far - Does anyone have the dimensions or manual for the above Force 12 warc 2/2? Cheers Jess

    will email you.

  6. #6

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    HI,
    i have some experience about opensleeve antenna ( tribands in my case) calculated by software, set and fix by me with Mini vna analyzer for best impedance for all 3 bands.
    you found my experience here:
    http://forums.qrz.com/showthread.php...ve-feed-system

    Quote Originally Posted by G8IYE View Post
    Hello! I am interested in building a dual band 17m and 12m yagi. I am thinking of a reflector and driven element on 17m and would like to try and put a driven element and director in front for 12m. I want to use one feed to the 17m driven element and use open sleeve coupling to excite the 12m driven element. I would be using full size, lightweight telescopic aluminium elements and would like to know the following....
    spacing of12m drive depends on the impedance of the 12-meter antenna.The spacing tune the impedance near 50 ohms, you have to move it to found best impedance.
    2. Would the 12m driven element have to be in 2 parts and isolated from the boom?
    the opensleeve element have to be in one part, and in my opinion, insulated by boom, Itried both cases,the isolated element provides an easier and better adaptation resonance.

    3. What the charcteristic feed imedance would be for the 17m driven element?
    I can' t answer, becouse my feed band element was a moxon element and the impedance was exatly 50 ohms, i feed it by choke 1:1 balun.
    You have to transform any impedance to 50 ohm by transformer, hairpin or others,is not important to the characteristic impedance of the feed drive element in relation to opensleeve operation.


    4. Could I use one hairpin (beta type match) for both bands?
    yes, you can use hairpin match for feed 17 mt element, to get rigth resonance on 17, then move off or close the opensleeve drive for best resonance on 12 m.

    Any help and suggestions regarding building this type of antenna would be appreciated. I have never used this type of coupling system before but am interested in trying to build it.
    Thanks in advance! Cheers Jess
    This is my 2 cents,
    I hope that' s help you, and apologize me about my english.. :-)

  7. #7

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    Hi Marco! Thanks for your help and congratulations on building your interesting antenna. I hope to make this dual bander 17m and 12m when the weather gets better here. I'll keep you posted :-) Cheers Jess

  8. #8

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    Quote Originally Posted by G8IYE View Post
    Hi Marco! Thanks for your help and congratulations on building your interesting antenna. I hope to make this dual bander 17m and 12m when the weather gets better here. I'll keep you posted :-) Cheers Jess
    Jess, it is my pleausure , open sleeve feed syistem gives me surprise and positive feedback, beacouse solves a lot of sort match problems in multiband antennas.

    Tell me about yours future steps.

    Best 73, Marco

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