Tom and all,
If I am reading the question correctly, aren't we talking about something that
is done at VHF/UHF with great regularity? Stacked vertical elements, stacked
vertically polarized beams and all manner of stacked vertical "anything" are
done there all of the time to avoid cross polarization loss when the other
stations (especially mobile) are the main users.
So understanding that it is done at those frequencies, the answer to the
original question of "can it be done," so to speak, is a resounding YES. I
just don't have any idea how you could extrapolate that to MF (160
meters)...... It would be a monstrously tall structure..... he he he.
Actually, I have a set of stacked vertical beams that I use for a
point-to-point link with a marginal repeater from my cabin up in the high
country on the Mogollon Rim in AZ...... It is an incredibly effective antenna
that was much less so with a single vertical beam..... Hopefully I didn't just
waste everyone's time by misinterpreting the question..... :) :)
Mike AB7ZU
Kuhi no ka lima, hele no ka maka
On Sep 6, 2013, at 2:46, "Tom W8JI" <w8ji@w8ji.com> wrote:
>> Isn't this a "Vertical dipole"? Two quarter wave radiating elements? And
>> tower behind it will be some kind of reflector/director depending on height.
>> The radials seem unimportant if thought of this way.
>
> Antennas radiate because of the current flow.
>
> So you would have two current maximums, one maximum near the earth for the
> lower element, and another maximum higher up about 1/4 wave away from earth.
>
> The end result would be earth conductivity dependent, but somewhere between a
> little better or a little worse than a 1/2 wave vertical. The spacing of
> current maximums would be a little wider than a vertical dipole or half wave
> vertical, but still too close for any real significant gain. Because a
> current maximum would be at earth level, ground losses might eat up any very
> small gain.
>
> Maximum stacking gain with 1/4 wave between current maximums is about 0.5 dB.
> This is reduced because the bottom element is against earth, and could even
> go negative. Most of any gain, if it had gain, would come from the top
> element and the earth reflection.
> _________________
> Topband Reflector
_________________
Topband Reflector
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