[time-nuts] Frequencies used for GPS
cfharris at erols.com
Thu Oct 20 17:46:54 UTC 2011
For what it is worth, the short dipole is made up of 3.5cm long halves,
and the long dipole is made up of 4cm long halves.
Dave Martindale wrote:
> 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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