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From: "Peter Martinez" <peter.martinez@btinternet.com>
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Date: Sat, 24 Jun 2006 09:30:37 -0000
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Subject: LF: Re: Top-fed LF antenna idea
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Status: O

>From G3PLX:

Brian said:
>Why struggle with a short whip when on flat roof of many buildings is space
>for a 70 foot  horizontal ?

The important thing is to maximise the RF current flowing 'into the sky' and 
minimise the RF current which is just flowing back round behind you into the 
earthy side of your transmitter.  So whatever it is you are using as a way 
of generating an RF current in the top of the tower, it needs to be 'out 
there' rather than 'in here', otherwise the current just flows in a small 
loop at the top of the tower, with no associated radiation resistance.

I think there's a law of physics which says that the effectiveness of an 
antenna is a function of how much of the sky you can fill with wire. It must 
ultimately derive from Murphy's law, which is best stated as "If something 
is going to be really worth doing then it's not going to be easy".

73
Peter