[time-nuts] Frequencies used for GPS

Dave Martindale dave.martindale at gmail.com
Thu Oct 20 12:20:09 EDT 2011

On Thu, Oct 20, 2011 at 06:52, Chuck Harris <cfharris at erols.com> wrote:
> Here is the standard antenna for the T-Bolt.  Not a helix, but
> rather some sort of crossed dipole.
> The feed point is the corners of the two V shaped elements, forming
> a sort of bowtie  ><  With the ends capacitively coupled to the
> ground plane.

But notice that unlike a bowtie, the two visible arms are different lengths.

I would guess that the other side is similar, with the two long arms
in a straight line and the two short arms perpendicular to that.  So
you end up with one dipole that's too long for resonance, and another
dipole (at right angles to the first) that's too short for resonance.
The shifts away from resonance cause a phase shift of the current
relative to voltage, with one dipole leading and the other lagging.
And the phase shifts make it a circularly polarized antenna, instead
of linearly polarized.

(I'm not an antenna expert, but this explanation makes sense to me).

- Dave

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