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HB9CV antenna design

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by CT2FZI, Apr 6, 2010.

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  1. CT2FZI

    CT2FZI Ham Member QRZ Page

    Hello fellow hams,

    I am looking for a good (as in that I can understand) HB9CV antenna design.

    I will try to make in the same boom 2 HB9CV for 2M and 70CM band operation.

    Question: does the boom diameter have any influence on the design?
    Question: Is the length of the space between the gamma match and the boom critical?
    Question: will I be able to share the same boom with the 2 bands?

    Sorry for all of these questions... But I would like to try to build this antenna in the right path!

    And thanks in advanced!
     
  2. G0GQK

    G0GQK Ham Member QRZ Page

    My suggestion is that you do some Googling for this antenna. There are many sites on the internet with antenna designs, you should be able to find one somewhere, but it will take some time.

    G0GQK
     
  3. CT2FZI

    CT2FZI Ham Member QRZ Page

    Hello G0GQK,

    Thanks for your reply.

    And you know, "Google is my Bible, Astalavista is my sin" ;)

    I did search for it and I've found several designs and several formulas, but none would fit the answers to my questions posted here ;)

    Nevertheless I will analyse the docs better...
     
  4. KC8VWM

    KC8VWM Ham Member QRZ Page

    I will try to make in the same boom 2 HB9CV for 2M and 70CM band operation.

    Question: does the boom diameter have any influence on the design?

    It would have an influence on the design if the design involves elements mounted through the boom or when elements are mounted directly on the boom. If the antenna elements are mounted above the boom and are "insulated" from the boom, them boom diameter would have little to no effect.

    If the elements are mounted through the boom and you change the boom diameter then you would have to add a "correction factor" and modify the element lengths.

    Question: Is the length of the space between the gamma match and the boom critical?

    "Critical" isn't really the word I would use, but when you change or modify the original dimensions of a gamma design, it will change the desired results. A gamma match is really just a tuning capacitor. Changing the dimensions results in a different range of available tuning capacitance. When "changes" are made, the gamma match can be "retuned" to accommodate these changes made provided the tuning capacitor remains capable of tuning within the desired "range." If the changes made are drastic, then the tuning capacitor (gamma match) will no longer be capable of tuning in such a desired tuning range and it would need to be reconstructed using different dimensions to do so.

    Additionally a "gamma match" is not typically a good antenna tuning method when constructing antenna's for the UHF bands because losses become higher in that region. The external conjugate "T" match or "Hairpin" matching systems are often used instead. These matching systems are also better to use on VHF than Gamma matches would be. Gamma matches are acceptable to use on VHF but it's not considered as an optimal design. But yes it "works"

    Question: will I be able to share the same boom with the 2 bands?

    Yes you can, but typically you want to avoid designing elements that are harmonically related to one another because this might skew the pattern and have other undesirable effects. Antenna modeling software would be helpful to see the "effects" any additional elements would have on one another. This aspect of construction and design requires a more advanced in depth analysis and careful study.


    Sorry for all of these questions... But I would like to try to build this antenna in the right path!


    Sure, no problem. That's why these forums exist here. :)
     
    Last edited: Apr 7, 2010
  5. CT2FZI

    CT2FZI Ham Member QRZ Page

    Thank you so much!

    Your answers XIT(ed) my ideas (Yaesu uses clarifier)!

    I will post the results here when I finish the 2 antennas - yes I will keep them separated...
     
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