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G0FTD > WANTED 24.09.04 01:36l 43 Lines 1788 Bytes #999 (0) @ WW
BID : FE7064G0FTD
Read: GUEST
Subj: Re: 70MHz Horizontal Mobile Ant?
Path: DB0FHN<DB0THA<DB0ERF<DB0FBB<DB0BI<DB0PRA<DB0LJ<DB0RES<ON0AR<VK6HGR<
GB7YFS<GB7CIP<GB7SXE
Sent: 040923/2126Z @:GB7SXE.#38.GBR.EU #:6193 [Hastings] FBB7.00i $:FE7064G0FTD
From: G0FTD@GB7SXE.#38.GBR.EU
To : WANTED@WW
PA2RHB wrote:-
> Mind you, _I_ did not say you get a lot of low angle radiation from an
> antenna at 30cm over the car top. I would place it far higher, but the
> question was, Can we go to 20cm. So I say No, even at 30cm, -3dB is as
> high as 45 degs, so do not go under 30cm.
Well I think we pretty well agree there then, which is good ;-)
I will remove my "stupid head" and say that I've been fortunate enough
to have done so many experiments that radio amateurs can only read about
when it comes to antenna design, propagation and angles of radiation etc.
Although I must admit I have never been very interested æwave stuff
except some experiments at 1.8GHz showing wavefront defraction around
a square conducting body (Sorry that's not much but I have THE actual
measure plots here).
The low angle radiation out in the plains of ZS will no doubt be essential,
45ø is a waste of time unless you want Sporadic E ;-)
-3db @ 45ø according to my experience and calculations is more like 1m above
the car body - but RF is RF, and there are many inconsistencies that can
be encountered so calculations may not be absolute.
So in *my* opinion, max radiation at 90ø and tailing off by 3db at 45ø
is acheived with an antenna about 1 metre above the car body, 30cm is even
worse and certainly NOT recommended.
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ 73 - Andy ³
³ G0FTD ³
³ Whitstable, Kent ³
³22:24 on 2004-Sep-23³
³ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³
³ ³ Û ³ ³
ÀÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÙ
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