Inverted V vs a Flat-top dipole?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N3TD, Mar 25, 2009.

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  1. N3TD

    N3TD Ham Member QRZ Page

    Inverted V vs Dipole??????

    My primary interests are in DX and contesting.

    Land is not an issue for wire antennas (almost 2 acres to play with). My property in the back is surrounded by pine trees 40-50ft tall. So 1/2 wave lengths and longer are an option.

    Right now I have a off-center fed dipole at 28ft. I am looking at changing it from a flat top to an inverted V.

    I also want to get something up on 160m while I am considering a tower and beams.
     
  2. KA4DPO

    KA4DPO Premium Subscriber QRZ Page

    The only big differenc between an inverted Vee and a flat top is that the inverted Vee is virtually omni-directional while the flat top will be somewhat directional to it's broadside and low signal off the ends.
     
    VE7JBT likes this.
  3. K5RCD

    K5RCD XML Subscriber QRZ Page

    Eric:

    With the real estate you have to work with, a horizontal loop, full wave, for 160 meters would be ideal.

    Get some ladder line, a good roller inductor tuner, a roll of 12 gauge insulated wire (THHN) from Home Depot and go for it.

    Most hams would KILL for such a setup.

    Let me know if I can help.

    You might find This helpful.
     
  4. KA4DPO

    KA4DPO Premium Subscriber QRZ Page

    I forgot one thing Eric. The ends of an inverted Vee are usually mounted close to the ground so the takeoff angle is high. A dipole mounted 50 or 60 feet high will have a lower radiation angle and would probably be a better DX antenna. I say probably because it would be in most but not all casses. Propagation is a funny thing.
     
    VE7JBT likes this.
  5. NA0AA

    NA0AA Ham Member QRZ Page

    IIRC, there's a formula for the comparison - I believe the center of an inverted V has to be higher than the center of a flattop diple for equal effectiveness.

    As the dipole is raised higher above the ground, the radiation become more and more 'ideal' that is to say, nulls off the ends of the wires begin to become increasingly obvious and the classic 'pinched balloon' shape starts to evolve.

    And yes, that also means lower angles of radiation also result.

    IIRC, you have to get more than 1/2 WL above ground for this to happen.
     
  6. K4SAV

    K4SAV Ham Member QRZ Page

    If you compare a flat top 80 meter dipole at 50 feet with an inverted vee with top at 50 ft and ends at 10 feet, the flat top dipole will be 2 to 3 dB better at all elevation angles, broadside to the antennas. Close proximity to ground causes significant loss. However off the ends of the antennas and at very low elevation angles, the inverted vee will have more gain than the flat top.

    So I would recommend the flat top dipole unless your favorite DX direction happens to be off the ends of the antenna.

    For 160 it will be difficult to beat an inverted L, maybe 50 ft vertical to one of those pine trees and a horizontal wire to another tree. If you want to build a 160 inverted L, then it is very little extra effort to include another vertical element for 80 using the same radial system. For DX, the inverted L for 80 should be as good, or maybe a little better, than either the dipole at 50 ft or the inverted vee.

    Jerry, K4SAV
     
  7. G0GQK

    G0GQK Ham Member QRZ Page

    High and flat every time

    G0GQK
     
  8. K8JD

    K8JD Ham Member QRZ Page

    I work as far or even farther off the ends of my 160 and 80 M dipoles, than the broadside directions.. :eek:! Not much null off the ends unless the dipole is close to a wavelength up in the air.
    The inverted V dipoles have a lower resonant freq for a given length of wire ! Not much else.
    Getting the feedpoint of a dipole (the maximum radiation here) to the highest possible place is one advantage I can think of when you go inv V.
     
  9. KB5URQ

    KB5URQ Ham Member QRZ Page

    Would it not also be easier to implement a flat-dipole at height (say, 50 feet) than to use a loop?

    For a flat-dipole you'd need 2 structures to tie off to; whereas, for a loop, you'd probably need 3 or 4 structures to maintain the circular-type shape?

    Jason
    KB5URQ
     
  10. W4HAY

    W4HAY Ham Member QRZ Page

    I've used both the horizontal dipole and the inverted V. So many other variables come into play that I haven't been able to tell any difference.

    My present trap dipole is kind of in between. It's not flat, but the included angle is too large to be classified as a V. 50-100 Watts give me access to the world when Ol' Sol cooperates.
     
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