[TowerTalk] altitude

[Joe Giacobello]

I had asked a similar question several years ago.  I had read that the 
real height and ground effects of a horizontal antenna were really 
determined by the ground and terrain 2-1/2 - 3 wavelengths from the 
antenna.  A ham, EE grad student and antenna specialist from Va Tech had 
also commented that height combined with terrain that slopes off fairly 
rapidly does a lot to enhance low angle reinforcement, if I remember 
what he said correctly.  Frankly, I was a little skeptical.

However, since i live on a hilltop that's about 400' above the 
surrounding land and slopes off, more or less, at a 45 degree angle, I 
asked a contributor to this reflector who has expertise in the use of 
terrain analysis programs, to compare a horizontal antenna 450' above 
flat ground to the same antenna on a 50' tower on a hilltop like mine.  
He reported that the radiation patterns were virtually identical.  So if 
the terrain is contoured properly vs the wavelength of operation, higher 
elevations can be the equivalent of very high antennas over flat terrain.

73, Joe
K2XX

Jim Jarvis wrote:
> Jim,
>
> I've never seen any quantitative site studies supporting altitude as a
> dominant variable, unto itself.  The answer probably depends more on
> other variables than just altitude.  Like...does the terrain for 1-2 miles
> gently slope down from the antenna site?   Is the 3500' high site
> a wetlands?
>
> I had a simple 80m halfwave up about 85', adjacent to the
> Chesepeake Bay.  20' above sealevel.  Played great.
>
> On the other hand, when K2BMI bought his place in NJ's
> Sourland Mountains, he used to say "there's rf
> up there, that never gets down to the flatlands".  And,
> in fact, I heard openings from there I'd never heard before.
>
> So, unfortunately, your mileage may vary.  I'd be interested
> to know if anyone is aware of such a study.
>
> n2ea
>
> Message: 5
> Date: Fri, 10 Nov 2006 09:22:23 -0600
> From: "Jim Miller" <JimMiller at STL-OnLine.Net>
> Subject: [TowerTalk] Altitude
>
> If this is too far off topic, one flame will do.
> OK,  I understand the effects of and on
> 1. height of the antenna
> 2. angle of radiation
> 3. layout of the terrain in the near field
> 4. location surrounded by salt water vs. desert sand
> 5. etc.
> BUT: IS THERE A DIFFERENCE (if the same above conditions exist) whether the
> site is located
> at 300 ft or at 800 ft or at 1500 ft or 3500 ft? WHY?  Tnx es 73, de Jim
> KG0KP
>
>
>
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