5/8 wave per side dipole as driver for a yagi?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by M0AGP, Jun 20, 2020.

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  1. M0AGP

    M0AGP Ham Member QRZ Page

    Assuming there is a little bit of gain on a 5/8 wave vertical, one could presumably use two of these to make a slightly better dipole, and going further, how about using it as the driver element for a yagi? Would the best directors and reflector by also roughly of 5/8 wave length or would it be better to have standard length reflector and directors?

    Apologies if this has been asked before - I couldn't find it on the forum or elsewhere. But of course it has been thought of before... Maybe the answer is "you could do it but it would be dumb" because all that extra metal could be put to better use as additional directors?

    I wonder if a quad that is 5/8 wave on a side has more gain than a standard quad? Oops, two questions - feel free to ignore the 2nd one!
     
  2. K7JEM

    K7JEM Ham Member QRZ Page

    A dipole with two 5/8 sides to it is called an "extended double zepp" and it has around 3 dB of gain compared to a dipole. If you put a reflector behind it, you can pick up close to another 3 dB of gain. I don't think it works well with directors, but someone maybe has done that.
     
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  3. M0AGP

    M0AGP Ham Member QRZ Page

    Interesting! And is the best reflector a half-ish wave one or a 1.25-ish wave one?
     
  4. K7JEM

    K7JEM Ham Member QRZ Page

    The reflector can be somewhat longer than the antenna, and spaced behind it around a quarter wavelength. About 20 years ago I used a pair of 10M EDZ antennas vertically polarized, and hung about 8 feet off of a 50ft tower. They worked very well for field day that year.
     
  5. WA7ARK

    WA7ARK Ham Member QRZ Page

    Hate to burst your bubble, but a 0.625wl dipole has only a tiny gain over a resonant 0.487wl one. You have to go to EDZ territory (1.2wl to see an appreciable change. The following is for a dipole height of 0.5wl:

    upload_2020-6-20_10-21-46.png
     
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  6. WB3BEL

    WB3BEL Ham Member QRZ Page

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  7. M0AGP

    M0AGP Ham Member QRZ Page

    Actually using two 5/8 waves (so 1.25 wave) was what I was suggesting - thanks for the plot!
     
  8. M0AGP

    M0AGP Ham Member QRZ Page

    That article is really interesting - unsurprisingly back in the late 1930s they had already thought of the EDZ beams, plus some configurations with quite narrow beamwidths.
     
  9. K8JD

    K8JD Ham Member QRZ Page

    EDZ is a Good Idea
    I put up a 20 M EDZ some years ago, fed it with 450 Ohm Balanced feedline thru the MFJ974 balanced line tuner. . YES, it really does work better on 20 M than a halfwave dipole , I noticed the directional gain even at 35 Ft up !
    One Plus is that it is ALSO a halfwave on 60 M, two halfwaves ceterfed (a Double Zepp) on 30 M, tunes up fine as a 3/4 wave dipole on 40 M. Something over 2 wavelengths on 17 and 15 M.
    On the higher bands 17 and 15 is would have a lot of peaks and nulls around the compass.
    I never tried to add a director or reflector due to the haphazard arrangement nature had to grow the forest.
     
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  10. WA4SIX

    WA4SIX Ham Member QRZ Page

    I believe you can crossfire EDZs, too.

    Ed
     

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