At 12:09 PM -0700 10/7/02, Jim Shaw wrote:
>A 'vertical dipole' for 20M and above is possible to elevate to 1+
>WL or so..., so I hope you look at the higher elevations than just
>the 1/2 WL or lower ones.... What about a similar set results for a
>20 meter horizontal dipole? If you can generate the results in
>similar units of WL (not feet) then it should be easy to scale the
>results to any band other than 20M.
OK; here are NEC-4 results for two "half-wavelength" (actually 10.1-m
long) dipoles for f = 14 MHz: one vertical with its bottom one full
free-space wavelength, i.e., 21.414 meters above my New England
ground; and a horizontal dipole at 31.514 meters, equal to the height
of the top of the vertical dipole. Gains are at elevation angle =
7.5 degrees.
Antenna | Gain (dBi)
-------------+-----------
|
Vertical | 4.1
|
Horiz. dipole| 7.1 <-- better than the vertical by 3.0 dB.
(broadside) |
Note that if you multiply all dimensions by the same factor and
divide the frequency by that factor you will not get the same gains,
because the loss tangent of the ground varies with frequency.
I think we've beat this thread to death. In every case that we've
examined, a half-wave-resonant horizontal dipole at the same height
as the top of a vertical dipole (whether the vertical dipole is
naturally half-wave-resonant or shortened by center loading) has more
gain broadside at 7.5 deg elevation than the vertical dipole. Off
its end, a horizontal dipole is worse.
73 de Chuck, W1HIS
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