Re: [IRCA] Tower height vs power

[Charles A Taylor <MWDXer@xxxxxxx>]

Patrick,

What Mike wrote was partially correct, but a full wavelength tower would be 
efficient.

The problem with towers over 0.5 wavelength is that the tower radiates more 
and more of the power at higher angles.
That power is refracted by the ionosphere back into the groundwave zone, 
where it causes selective addition and
subtraction to the ground wave. During subtractive interference, the 
carrier cancels more or less, causing the sidebands
to be too intense for proper demodulation with the carrier on ordinary AM 
sets, and so distortion sets in.

In fact, I do think some low-power AMs use a co-owned TV tower as a 
radiator. The rationale here is that the reflected
skywave returns at a distance that is already QRMed by co-channel interference.

73 de Charlie



At 11:31 PM 2/2/2007 -0800, you wrote:
>Mike,
>
>Thanks. I fiqured there must be a reason no one uses anything over 5/8
>on a tower. In some areas, I am sure a fullwave tower could be used.
>
>73,
>
>Patrick
>
>Patrick Martin
>KAVT Reception Manager
>
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        -----
Charles A Taylor, WD4INP
Greenville, North Carolina 

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