[TowerTalk] Stacks (optimizing gain at takeoff angle)

[z.pitman@libertel.nl]

It could not be said any better ! Thanks Gene!

Also Tom W8JI gave a very clear and understandable explanation of the very
same issue some months ago on the Antennas reflector. 

Tilting shortwave antennas is an other myth of ham radio, which should have
been discarded by now. 

73 de Zoli HA1AG





 
> 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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