From: "Tom Rauch" <email@example.com>
> > Actually, the commonly published gain figure you see for
> the EDZ is on the
> > order of 3 dB. (.64 wavelength each side of center.)
> You only see that gain when the antenna is in freespace or
> at a very high height.
> At 35-70 ft height on 80m, gain over a dipole is in the
> order of 2dB. You give up lower angles to get that gain, and
> it may not be worth it.
> Remember gain only comes at the price of signal strength in
> some other angle or direction. You have to give up a great
> deal of signal in some directions or angles to get 3dB gain.
> What matters most is maximum average gain at the desired
> angles and directions, not peak gain.
> 73 Tom
These posting have been very interesting because I have
been considering to shorten my 320' double extended zepp (80M)
to a 122' half wave dipole. I have had the zepp for 6 years up
around 90 feet. Although it has performed well, Eznec tells me
that the dipole may suit my operating interest more favorably.
Eznec plots the 90' high zepp with a 3 db gain at max lobe
for elevation angles of 15, 30, 45, and 60 degrees. However, the
dipole catches up with the zepp at 17, 18, 23, and 35 degrees
off center from the max lobe.
Further off center (around 35 degrees for the 15, 30, 45 degree
elevation) the zepp is down about 15 db!
As Tom says, "...it may not be worh it."
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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