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Home Brew Hair pin & balun

Discussion in 'CB Antennas' started by GunSlinger338, Nov 12, 2009.

  1. GunSlinger338

    GunSlinger338 Active Member

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    anyone ever try a split driven element , hair pin match and balun on a Maco beam ???
    I have gathered all the parts to insulate , split and support the driven element
    I also have coming a Balun with side lugs by Balun designs.... should be hear in a few days


    i will post up some pics when i get it all done .. in the next few weeks



    any input would be appreciated
     

  2. Jay in the Mojave

    Jay in the Mojave Active Member

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    Hello Gen Slinger 338:

    Yes it can be done. I have converted a few of them into a Crusader 10K Beams.

    But get ready for opening a can of worms if you don't document your work correctly. That is the antenna will no dough need a few adjustments along the way. You will need to document the antenna lengths and SWR, and any changes you make to the antenna, or you will be lost in space in a heart beat. I have gotten lost many times forgetting just were I was on the beams adjustments.

    This project is best done with a crank up and tilt over tower allowing the antenna guy easy and safe access to the antenna.

    Scaling the Yagi Beam Antennas shown in the ARRL Antenna Book for your frequency and lengths is a good place for a new beam design. There are lots of beam web sites and such out there.

    Once the beam is dialed in it will be well worth the effort to have a really efficient matching design.

    Good luck!

    Jay in the Mojave


     
  3. W5LZ

    W5LZ Crotchety Old Bastard

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    As Jay said, yes it can be done. The one question I have is why you'd want to do that, other than just wanting to do that? I can't say I've ever heard of any huge differences in performance using a 'hair-pin' match, but then I really haven't paid that much attention.
    You can 'optimize' anything to some extent. That optimization means lots of work for very little improvement in most cases, sort of. But if you enjoy doing this kind'a stuff, then who cares, do it!
    - 'Doc
     
  4. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    I just put a three element up yesterday at two wave lengths in height for 10/11 meters.

    Used an old mosley beam as a starter, split element driver with a 1:1 balun at the feed point.

    Used the standard dipole formula for the driven element and then 10% bigger for the reflector and 10% smaller for the director.

    the three element went together very well and gives a broad bandwidth according to the mfj analyzer, 2:1 at 26.300 to 28.800.

    The F/B Seems to be roughly 24 DB and forward gain is better than expected.

    Used .15 WL spacing from driven to reflector and .12 from driven to first director, standard 65" and 56" respectively.

    Build the beam with all elements in place then tune the driven for lowest SWR at desired freq, then re adjust the reflector and director for the 10% diference in lenght then re-check VSWR.

    This is old school practice and as stated before it does take patience to get it correct.

    Once correct you will be amazed at the side null of the beam as no lousy matching gamma to deter the beam pattern.

    Side nulls fall off the chart when at a 90 degree angle from recieving station.

    The balun, reccomend a CURRENT type to force equal amounts of currnet into each leg of the dipole/driven element for equal distribution of current.

    Also keep into consideration the balun current rating, I used a 2KW but it is rated in SSB, if you are an AM user suggest you go four times the rating on the balun as to the amount of watts you intend to use so there will not be any heat problems at the feed point balun.

    Use some type of sealant on the conections at the dipole, I use liquid electrical tape as it seals everything.

    I have not found any baluns that are 100% weather proof no matter what they are advertised as so pay attention to water proofing the balun also.

    Antennas are alot of fun to build and experiment with, good luck with your yagi experiment and let us know how it turns out.

    73's
     
  5. Captain Kilowatt

    Captain Kilowatt Professional Amateur
    Staff Member

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    I built a six element beam for 6m and used a hairpin match. It was super easy to match once I realized that the driver element has to be a bit shorter than the standard formula would dictate due to the length of the hairpin.I used a 1/2 wave coaxial 4:1 balun at the feedpoint and the SWR was perfect at the design frequency of 50.125 MHz.

    Waverider,I suspect you are seeing such a broad bandwidth with your antenna because of the 10% differance in lengths of the reflector and director. The standard to follow is 5% not 10. This will result in slightly more gain but slightly narrower bandwidth.
     
  6. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Yes you are correct on standard being 5% verses the 10% I used in the yagi I built.

    The goal was bandwidth with directivity.

    Cover the lower portion of 10 meters as my Mosley PRO67B is not a good vswr lower portion of 10 meters, and also to get into 26 mhz to cover the Australian and New Zealand portions of the 11 meter bands
    .

    Compromise? Yes but will the lost gain due to 10% length of elements ever be missed? Doubt it.

    thanks for reply and have a great day,,73's
     
  7. GunSlinger338

    GunSlinger338 Active Member

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    Thanks Jay and Wavrider ...
    This is a M107 set to factory specs with a 10k gamma
    should be fun experimenting any way.. My tower is a crank up fold over so that's not an issue..

    I have extra parts to put it back to Maco specs if it doesn't turn out better or at least as good as it is now

    Thanks
     
  8. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Gunslinger.

    Good luck on the experimentation, forgot to mention the diameter of the tubing you are using ( spelling incorrect ? still working on first cup of coffee).

    The larger the diameter of the driven element the broader bandwidth the antenna will have so take this into consideration also.
     
  9. GunSlinger338

    GunSlinger338 Active Member

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    Thanks ...

    Wavrider / Jay .... any advise on the diameter of tubing for the match itself ???

    i have available all sizes both stainless and aluminium ... just wondering if it will make an difference.
    I'm sure it will play a role in the final tuned dimensions of the antenna


    thanks again
     
  10. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Gunslinger,

    I use this style beta match, 1/2" tubing 18 to 24 " length.

    It is over kill on the size but I have never had one fail due to weather or watts.

    I have used this same beta match on 20 and 40 meter mono banders and works well with full legal power:D
     

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  11. GunSlinger338

    GunSlinger338 Active Member

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    Yup.. thats it.. same style I plan to use.
    i have some 3/8 aluminum tubing i want to use for the match.... because i have the little black rubber end caps for it !!!

    i'm all about the details... some say its OCD
     
  12. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Maybe be ocd but until they have started to remove a beam on a tower and find some nice stinging flying insects have decided to make a home in the hollow tube. They have a tendacy to get very irate when you disturb there home, and very hard to escape when strapped to the tower in a climbing harness. I take a small can of wasp and hornet spray in the climbing tool pouch since that happened to me a few years back.

    3/8" will be just fine and will work wonderfully.

    I am still feeling out the three element I made using the balun and beta, so far results seem great. I will leave it up for this winter season and if I like it well enough a six element will be up on the tower next spring.
     
  13. Jay in the Mojave

    Jay in the Mojave Active Member

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    Hello Gunslinger 338: Get the 7 element beam working first with the existing elements all the same diameters first, I suggest.

    Then try a larger diameter driven element, it will have to be a few inches shorter than the stock element. But when tuning the yagi beam, leave the elements along, but its ok to adjust the driven elements lengths and the Hairpin for min SWR. You maynot see a hole lot of bandwidth increase.

    Jay in the Mojave



     
  14. HiDef

    HiDef Active Member

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    Real world stuff that works.

    Cptn kw is right about having to make the driven element shorter than one used with a gamma match.

    A properly executed gamma match will not ruin the 90 degree null. I have a 5 element vertical here that used to get alomst 40 dB rejection off the sides with a gamma match until I did some extra loading with other antennas that tweeks the boom.

    The straightness of the boom is very important to those rejection nulls which are so useful for direction finding;)

    Last junk antenna I made for a friend used a split feed, coil of RG-213 for a balun and a hairpin shape piece of 1/2" CATV Foamflex hardline. Works great but a P.I.A. to tune.
     
  15. straight razor

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    lol gun slinger i made one just like that for a one element i made for my apartment and
    the only problem i had was the swr where ok but the imp was off like crazy, so i read
    that i need to have a balun with it also.. so thats my next step but the hairpin does
    work and trust me even with the imp off i was whoopin a lot of stations on the 27.025
    and its mounted on my terrence.. am not talking now since my amps are down, just got
    bored with radio so i left everything blowed up in a pile on the floor, now am on the bench again trying to get my tetrode back up and running..
    http://str8razorny.multiply.com/photos/album/21/one_element_direct_feed_with_a_hairpin_match_straight_razor_built#photo=1
     

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