Message-ID: <002801c1f027$c5711d80$05e9fea9@g3aqc>
From: "Laurie Mayhead" <laurie@g3aqc.freeserve.co.uk>
To: rsgb_lf_group@blacksheep.org
Subject: LF: Re. Its up-no its down etc.
Date: Tue, 30 Apr 2002 10:15:20 +0100
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Hi John,
I think the results you describe are reasonably consistant with the facts as
you describe them,although the increase in signal as reported by Dave and I
is perhaps a bit ambitious. Increasing the height of the antenna from 20 to
55 feet
would mean an increase in Rres of x7.6 and hence a similar increase in Pwr
radiated.(r prop.to h squared.). However the fact that only part of the
ant.is at
55feet means that the inc.in height is not 2.75 times but rather less say
times 2 (guess.but based on some experiments carried out here). This would
result in an increase of 4 in pwr.radiated if it were not for the effect of
the close proximity of the trees to the new wire, which will absorb power
(The increase in R loss confirms the effect of the trees.which are a lossy
capacitor.) So I guess that our reports were a bit ambitious, but it does
look like there is a very good trade off between inreased height ( R prop.
to h squared) and loss. So keep on trying!.
Regarding the loading coil capacitance try putting a grounded screen between
the coil and ground(but not too close to the coil) this certainly works for
me.
Elevated coils will work where the vert wire. is close to the trees but in
your case this is not so likely to be effective. Hope this helps. 73s
Laurie.