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Re: LF: Amp metres

To: [email protected]
Subject: Re: LF: Amp metres
From: "Mike Dennison" <[email protected]>
Date: Thu, 30 Mar 2000 14:10:13 +0100
In-reply-to: <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
> Didn't Dud Charman's indoor antenna circus demonstrate the truth of the
> axiom that a small antenna has the same radiation pattern as a very
> small antenna?

I also believe that all short verticals have the same basic radiation
pattern (the upper hemishere of a doughnut, with low angle suckin if
ground loss is significant).
I was privileged to see Dud Charman's aerial circus in the 1960s as
a schoolboy. For those who do not know, he had a large copper
tray with a coax socket in the centre. He would then feed miniature
antennas with UHF or microwaves and demonstrate their radiation
pattern with a hand-held RF detector driving a lightbulb. Seeing a
text book radiation pattern demonstrated in such a practical way
was really amazing.
The flaw in this demonstration, however, is that it assumes little or
no ground loss. I am sure that with practical levels of ground loss,
the lowest angles are attenuated more on very short verticals than
on taller ones.

Mike, G3XDV (IO91VT)

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