Perpendicular dipoles -- single feed line?

Discussion in 'The Okie Corral' started by InjuriousGeorge, Sep 14, 2007.

  1. InjuriousGeorge

    InjuriousGeorge

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    I was going to put this on QRZ but this forum needs some activity!!

    The leaves are going to start falling in a month, and I want to put up a pair of perpendicular home-brew 20M dipoles over the house. I have 60' oaks surrounding my modest domus and over the house will be the shortest feedline.

    What are my options for a single feedline? A remote switch? Are there any good low-noise 12V-induced impedance-neutral switches anyone can recommend?
     
  2. G23Adam

    G23Adam .- -.. .- --

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  3. martho

    martho

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    Are you looking to have gain in one direction?

    Many people that use a design like you are describing are looking for a directional antenna. In theory, you will have a 2 element beam, if correctly spaced and fed. Many people do this with delta loops on 40/80/160 or with inverted Vs.

    There is a design in the ARRL handbook for a way to do it with inverted Vs
     
  4. InjuriousGeorge

    InjuriousGeorge

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    Only one dipole will be TX/RX at any time.

    With a dipole most of the energy is radiated perpendicular to the element.

    With two perpendicular dipoles I could switch between a N-S favoring antenna and a E-W favoring antenna, get the best match for the station I'm trying to work and go from there.

    Make sense?

    The switch I'm looking for would actually be mounted up close to the feed points of the elements. That's why I was thinking low voltage would be a good idea :).
     
  5. G23Adam

    G23Adam .- -.. .- --

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    most dipoles tend to be hung too low.... gives them more of an omnidirectional pattern. Also, if you hang the dipole as an Inverted V, you'd get the omni pattern you're looking for. The Smith Charts are a little misleading for a dipole. just run your wire N/S and enjoy....

    Hang one, you'll be happy enough with it. It is after all a dipole. A dipole has no gain whatsoever, if you want something to pull in a station, get yourself a beam.


    Now if directional receive antennas are what you want, Google "Beverage antennas".
     
  6. myg30

    myg30

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    Both Martho and G23 have good suggestions, I've had beams and dipoles, V's and max of 100w output. I used to go crazy switching between them to get a sig out of the noise.
    I enjoy now,working DX with my 100w,my dipole 25ft off the ground and compete w/the big gun's on 20m AND get the same RST as them.
    Someone may drown you out from time to time,but I was always told that if you can hear them, they can hear you if they try.
    You want to be a contest winner, go fer the beams and tower.
    AMMO is getting expensive,my dipole is good enough fer me.

    Enjoy, the bands are getting better.

    Are most glockers hams and Brothers ? OR are most Brother's hams and glockers ? Im new here and just found the Ham page's.

    Hi to all and gud DXing.

    Mike
     
  7. InjuriousGeorge

    InjuriousGeorge

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    So I guess a set of dipoles for directivity is out... I may build a 2-el yagi instead and use a TV rotator.
     
  8. martho

    martho

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    You had talked about using one feedline with your setup. There is no way to only use one of the dipoles using a single feed. You mentioned a remote switch, which would accomplish what you wanted, but just adds insertion loss(small but measurable)

    What do you want to do on 20m? Are you looking to work stuff in the south pacific or are you just looking to play stateside?

    A 20m dipole at 60' will play decent. Dipoles have nulls of the end of the antennas, but have a nice pattern on each side. Now, if you get the dipole too low, you have lots of spikes/nulls in several directions.

    If you are looking for something directional, you can find an old A3 or other tribander, take the driven element and feed it. This will give you a 10 15 20 dipole which you can rotate. A3's are around for less than $100 and you can use the DE for your rotatable. They work great and will give you some directionality.

    It all depends on what you want to do
     
  9. Kerrville Dan

    Kerrville Dan

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    I have two W5GI wire antennas (similar to G5RV antenna) perpendicular with two feed lines, both about 25 feet high. I often can hear a station on one that I can't hear on the other.