Message-ID: <003f01c0eec5$8bbd9780$90b21bca@xtr743187>
From: "Vernall" <vernall@xtra.co.nz>
To: rsgb_lf_group@blacksheep.org
References: <775449.991848311278.JavaMail.computernetworks@gomailjtp01>
Subject: Re: LF: Wire in the Air etc
Date: Thu, 7 Jun 2001 08:15:21 +1200
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John G4CNN,

> Dick PA0SE mentioned recently that radiation from the loading coil is
approximately equivalent to the radiation from a piece of wire of the same
length. This must surely mean that the reduction in the size of the loading
coil, when one can put more wire in the sky, does not just reduce loading
coil losses resulting from the reduced RF resistance of the coil, but
perhaps more importantly by moving radiated energy up and away from the
earth, where it has some chance of not being absorbed by the immediate
environment.

You are over-complicating the claim.  All that is being said is that if the
coil is x metres high, then irrespective of the coils of wire, it is
reasonable to include x metres in the consideration of antenna effective
height.

> If this is so then elevating the loading coil, either by putting it high
up the vertical element or simply by raising it as high above the ground as
possible must contribute to an improved signal. Presumably as usual this
will appear as a reduction in the resistance at resonance. This I think will
be my next experiment. Alternatively a longer coil should raise the high
voltage part of the coil and also reduce losses. Comments?

Lower system resistance allows more current to circulate, for a given
applied power.  So doing things that lowers system resistance is always "a
winner".  The height above ground for the loading coil is mainly a matter of
impacting on CURRENT DISTRIBUTION and that is reflected in a moderately
higher value of radiation resistance.  The radiation resistance is very
difficult to test, as it is of the order of milliohms versus tens of ohms
for other losses.

Mechanical support of a low loss LF loading coil is challenge, as is
weatherproofing (for high voltage).

73, Bob