FW: [FoxHunt] Turnstile antennas for 2M

[Kuon & Dale Hunt]

> From: bob <wolfbob@csnsys.com>
>
> ...The Yagi and most directional antennas are directional
> in both planes about the same...


   Actually not.  The half-power beamwidth is different for
   the E and H planes, especially for shorter beams as would
   be typical of ARDF.  This is clear if you consider a 1-element
   antenna - the dipole.  When vertical it is omnidirectional,
   but when horizontal it has directivity with nulls off the
   ends.  Extended to 2- or 3-element yagis there is still a
   significant improvement in directivity when used horizontally,
   and the front/side ratio is greatly reduced due to the
   null off the ends of the elements.  This difference is not
   as noticable for long yagis, but is still visible in the
   free-space patterns.


> It does rule out using a lot of direction finding
> techniques such as dopplers and LPers as they are most difficult to get
> going H-Pol.


    Actually not that hard, as long as you have omnidirectional
    horizontally polarized antennas to use instead of the
    usual whips.  This could be a turnstyle, halo, or small
    horizontal loop of some sort.  Two of the latter would make
    a small TDOA rig, or, with a phasing line, would allow a
    L'Per to be used.  If you really want to be creative you can
    extend either principle to 80m antennas!  The theory is all
    there in Jasik, Kraus et. al.  Just requires someone crazy
    enough to try it, and not worry how practical it really is.


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