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3 ele with Beta match home made....

Discussion in 'CB Antennas' started by zp9mce, Nov 29, 2010.

  1. zp9mce

    zp9mce Member

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    Hi all, best regards from Paraguay
    I wish them all a question I am building a 3 element yagi for cb, is a reform of an old antenna, using a beta match I had to make since it was broken.
    Not adjust for the band, I leave the steps I am using for frequency 27555, 5.46 m reflector, driven director 5.25 and 5.02, the space between the reflector and driven is 1.50 m and between the director driven and 1.57 mts.
    All measurements are in meters, the question is whether the measures seem right and how to make my beta match for this antenna.
    Thanks for your help friends.(y)


     
    #1
  2. Robb

    Robb Yup

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    One of the forum members ("Henry HPSD" from the Netherlands) has a great info page for what you seek:

    11 meter DX sytems

    Hope this helps!
     
    #2
  3. zp9mce

    zp9mce Member

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    Thank you for your prompt reply regarding the action of hairpin or beta match like me can help me, I read something in ARRL antenna book but still can not get the hainpin measures, if please some one designed for 11mts I appreciate your help.
    73.
     
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  4. TonyV225

    TonyV225 Supporting Member

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    This really takes some time to experiment and do a homebrew antenna build. I get way to frustrated but when there is great resources to reference to it sure makes things move a bit smoother.

    I kinow we have som antenna gurus here on the forum that may also beable to help if they happen to chime in.
     
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  5. Henry HPSD

    Henry HPSD Well-Known Member

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    Hi There,

    If you provide the element thickness and lengths of the sections ill be more than happy to put the antenna in enzec and see what it does.

    almost forgot...what is the maximum boomlength you can handle on that 3el ?

    Henry
    11 meter Dx antenna systemx

    ps. tnx for the compliment, together with a m8, were working on a new site).
     
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    Last edited: Nov 30, 2010
  6. Marconi

    Marconi Supporting Member

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    zp9mce, I can't give you measurements. A lot depends of the diameters you are using. I would guess you might be a bit short in the # noted, but that will likely have to be trial and error. You might find some close approximations on the dimensions and the beta for 11 meter at:

    http://www.cbtricks.com/ant_manuals/hygain/model_411/graphics/hy-gain_411_five_element_beam.pdf

    This is for an old HyGain 5 element, but it may get you close. Take a look at the details in their manual.

    Good luck and be careful.
     
    #6
  7. W5LZ

    W5LZ Crotchety Old Bastard

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    Manuel,
    I think the offer made by Henry is a good one.
    There are several methods of 'feeding' an antenna, the Beta match is just one of them. I can't say if there would be any advantage to it, or not, I haven't dealt with them. Beta matches are not very common, probably because others are 'easier' ones to make and use.
    Good luck!
    - 'Doc
     
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  8. zp9mce

    zp9mce Member

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    Hi to all. thanks fot the reponces.
    I mention that the boom is 3 meters x 5 cm in diameter, the elements have a diameter of 2.5 cm and 2 cm at the ends.
    The driven is cut and isolated from the rest of the antenna, just need to take measurements.
    I have also prepared a coaxial choke with 1.22 meters of RG-58, 7 laps sore a pvc pipe unbalance the antenna.
    I appreciate your help my friend, I commented that I have made a match of aluminum beta too but even I have no measurements.
    73 from Paraguay.
    (y)
     
    #8
  9. Henry HPSD

    Henry HPSD Well-Known Member

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    Hi There,

    Attached you can find three different antennas:

    1st : On the same boom a 50 ohm impedance yagi (direct feed 1:1 balun prefered.)
    2nd :eek:n the same boom a 28ohm impedance yagi (easy to make 50ohms through 75ohm cable).
    3rd : is yours it has 14ohms impedance and a calculation of a hairpin match.


    They all have there individual aspects.
    The yagi (option 3) with the lowest impedance has the heighst gain but very narrow bandwidth.
    THe yagi (option1) with the highest impedance has the lowest gain but best bandwidth
    Option 2 is a overall good performing yagi.

    Now, there are a few things to keep in mind...the lower the impedance of your Yagi the more critical the antenna will become. There are also other disadvanteges like more pickup of noises..

    And although there are many antenna manufacturers who work with the hairpin-match...
    It has some plus and down sides to my believe.
    The best reason why one should use it cause it is easy...a person may always be able to adjust the SWR.
    A small error in fabrication wont hurt..cause the hairpin can fix things ande still shows a 1on1 swr.
    And if we took a honest look there i guess there are not that many who really try calculate FB or gain... Nor can anyone tell the difference between 7 or 7,5dBI...(by ear).
    So its a bit forgiving with faults i guess..

    Secondly and that is something no one will tell you is that most manufacturers calculate there antennas without matching a device.
    IF they did, and some have.. there are true stories of gain dropping from 0,1 to 0,5 dB and
    some have proven that on a 70cm yagi the FB dropped with 10dB!
    now that is intresting isnt it :)

    Ending with a plus of the hairpin...it can make the antenna DC-grounded.

    You can also copy the hairpin-match from hygain,as Marconi mentioned, as long as you are using the same diameters and distances.


    Hope it helped,

    Kind regards,

    Henry
     

    Attached Files:

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    Last edited: Nov 30, 2010
  10. zp9mce

    zp9mce Member

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    Henry, and all, thanks for your help.
    I've bought all the materials to begin the project, choose option 2 to match the DK7ZB, I think the best option and easier to build without a doubt the hairpin match is difficult and we must respect the diameters and here is very difficult to get the proper materials.
    The calculation of the coax for the bout 2.23mts I get, I expect this out well.
    In a few days I will tenes news and photos to see as there remained the antenna.
    Henry my friend thanks for your time and patience, I will communicate the progress and difficulties, wish we had more people like you on the radio amateur.
    73-51 all.:blink:
     
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  11. Henry HPSD

    Henry HPSD Well-Known Member

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    Hello There,

    No worries, more than welcome..

    The length of the coax cable is depending on the type of75 ohm coax your planning on using.

    For example:
    frequency: 27,555 Mhz
    Cable H43...75ohm (that 75ohm is important!!!!)
    Velocity factor: 0,85

    Full wavelength =300/27,555= 10,887 Meter
    1/4 wavelength = 2,7212 meter
    1/4 wavelength x velocity factor =2,31 meters

    So that would be your total length if you were using H43 75 ohm Cable.

    ofcourse you must be precise in this, although there is some "uncertaincy" since the velocityfactor from the factoryn is not always as specified. Ive used to be using H43 cable wich has a velocity factor of 0,842..0,843..(measured).



    Kind regards,

    Henry
    www.19SD348.nl
     
    #11
  12. zp9mce

    zp9mce Member

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    Henry thanks for your help,
    I mention that I've finished the antenna, I have found that so I opted coxial RG 59, the VF is 0.82 to calculation gives me a value of 2.23 meters, and that is what they produced.
    The ROE of the antenna is 1.01 in 27555, but I have not been able to prove very bad weather here today, no voices heard nothing but petite.
    In few days we will say that this is all.
    A big hug morning I pictures.:LOL:
     
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  13. Henry HPSD

    Henry HPSD Well-Known Member

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    Hello!

    Very good to hear you SWR is oke!
    Just hoping for some propagation now...well done!

    Enjoy the weekend,

    Henry
    11 meter Dx antenna systemx
     
    #13
  14. zp9mce

    zp9mce Member

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    Yesterday in the last part of the night I could contact with Suriname and French Polynesia, with the latter my first contact, I gave a report of 5/7/9 was very impressive, I think the antenna is working fine.
    Thanks for everything my friend, soon remarked some experience and get photos.
    73-51.:whistle:
     
    #14
  15. tecnicoloco

    tecnicoloco Active Member

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    Fotos,Fotos,Fotos,Fotos de tu Nueva Antenna :pop:

    Felicidades por tu nueva antena
    73 de Andy/Tecnicoloco
     
    #15

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