[FoxHunt] gamma-matched quad antennas

[Dale Hunt, WB6BYU]

Homingin at aol.com wrote:
> 
> Dale wrote a bunch of interesting stuff, including:
> >two different quads showed skew polarization
> 
> This is interesting.  I haven't looked for this.  If I get a chance this
> weekend, I'll check a couple of my quads to see what kind of polarization skew is
> present.
> 
> Dale, I assume you mounted the MicroHunt right at the feedpoint, with no feed
> line at all.  Of course, there can still be some radiation from the
> transmitter itself at indeterminate polarization.


    Joe -

       The only feedline was a double BNC male adaptor.  But I may
    try repeating the experiment with the transmitter mounted parallel
    to the boom to remove the effect of any radiation from it.  The
    measured results agreed pretty well with what EZNEC predicted.

       Certainly the effect on the pattern and the amount of rotation
    appear to be less for a 4-element quad than the 2-element ones I
    was testing.


> 
> Was there any azimuth skew on the main lobe in addition to the polarization
> skew?


        I've never measured any squint or azimuth skew with the antennas.
     In this case the quad was fixed and I was rotating a yagi to measure
     the polarization, but I should check for that the next time I get
     a chance as well.  I suspect that any squint would be more likely
     with horizontal polarization.  However if the transmitter is at, say,
     a 30 degree vertical angle from the antenna, the pattern may be shifted
     due to the difference in half power beamwidths between the two
     polarizations.  (It would shift one way above the quad and the other
     way if it is below the quad.)

> 
> When mobile hunting, I mechanically adjust the polarization of my RDF quad
> for max signal while taking bearings at a high spot that is least likely to be
> in multipath....


         I always tell people to do this when I'm giving a talk, but
      rarely remember to actually do it when hunting!  However, the local
      hunters are still in the "learning" stage so we try not to confuse
      them too much, and the antennas are almost always vertical (except
      when one falls over...)


         I often recommend the quads for general ham use, especially
      portable operation for ARES and for simplex.  I've also used them
      as reference antennas when we set up an antenna test range, and this
      may account for some of the interesting measurements we have seen
      there on occasion.  While this polarization rotation doesn't change
      the usefulness of the antennas for hunting, it still nags at me to
      see if I can come with a similarly simple feed system that gives the
      polarization that one might expect.  Certainly the T and Delta match
      systems seem to work - in fact, my first quad used a Delta match
      to eliminate any connection between the feedline and the aluminum
      wire elements.


         I'll be interested to hear what you discover!

            - Dale WB6BYU