[TowerTalk] Stacks (optimizing gain at takeoff angle)

[EUGENE SMAR]

TT:

     Let's not confuse the multiple-WL-above-earth operation of
V/UHF/mwave antenna arrays, such as cellular and PCS antennas, with the
fractional-WL-above-earth operation of typical HF Yagis.  The far-field
radiation pattern of the former is enitrely formed in free space (let's not
argue about reflections from the tower, etc.) while the pattern of the
latter exploits the reflection of the wave off the nearby ground in forming
its FF pattern.

     Mechanical down-tilt is a technique used to fill in coverage
holes near the tower in modern "wireless" networks, but mainly to minimize
interference from and to areas outside the prime coverage area of the site.
Downtilt is possible because one can, in effect, take the entire environment
of the antennas' radiation pattern and "point" it where it is needed.  To
"aim" the max gain lobe of a HF array at the desired elevation angle as
suggested would require that the earth surface also be tilted to the same
angle.

73 de
Gene Smar  AD3F
-----Original Message-----
From: w3svj@juno.com <w3svj@juno.com>
To: towertalk@contesting.com <towertalk@contesting.com>
Date: Sunday, August 20, 2000 2:37 PM
Subject: Re: [TowerTalk] Stacks (optimizing gain at takeoff angle)


>
>The freq is greatly different so I suppose the results will also be
>different but for what it's worth I pass along this info.
>The cell site at our radio club location has a three faced mounting
>platform with three vertical antennas per side. All of the antennas have
>physically downward tilt of about 20/30 degrees, it's hard to tell when
>they are 120 feet up in the air. I don't know what electrical
>characteristics they have.
>
>73 de Nate, W3SVJ, in Pittsburgh where it's not so smokey anymore.
>
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