Message-ID: <000001c4ccaf$17505420$e21a86d4@erica>
From: "g3ldo" <g3ldo@ukonline.co.uk>
To: rsgb_lf_group@blacksheep.org
References: <5.1.0.14.0.20041117111955.020e7d70@u0019445.kuleuven.be>
Date: Wed, 17 Nov 2004 10:52:26 -0000
MIME-Version: 1.0
Subject: Re: LF: Loading Coils
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Hi Chris,
>
> >With this new arrangement I obtained my personal best Q of about 250..
> >
> >Placing the new coil in the aerial circuit made a slight improvement
> >to the aerial current - from about 1.2 A to 1.5 A
> >I would have thought that as most of the losses were in the coil a
> >bigger current improvement would have been achieved.
> The loss in the loading coil rarely exceeds 10 .. 20 Ohm, unless Q is very
low.
> Other losses (ground, greenery, buildings)  are typical 50 .. 100 Ohm,
> unless you live close to the sea
> So once you have the coil losses below 10 Ohm don't expect too much from
> further coil improvement.
> About your "slight improvement" : increasing the current from 1.2 to 1.5 A
> increases the ERP by 56 % (2 dB), that's not so "slight"
>
> >Unfortunately two neighbours' telephone wires pass over my garden
> >where the mast was to be situated.
> >Any suggestions - should I go over the wires or keep well clear of
> >them and cut a length off the aerial ?

> I wouldn't be too keen to get the antenna wire over the phone lines.
> In the event that the wire breaks and drops on the phone line during
> transmission  (can happen if you burn some ropes or isolators due to
> arcing)  you might put several kV on the phone line and cause a lot of
damage.
>
> 73, Rik  ON7YD


I have an inverted L cum Inverted V with the centre about 16m high and the
end just under 10m high.
The 10m high end passes over a telephone line that crosses the garden. The
concerns mentioned by Rik did occur to me.
I did have the antenna wire fall down due to a failure of an insulator
(before replaced by those excellent PA0SE insulators) during some early TA
tests. In the event the detuning of the antenna system shut down the power
so no damage (that I know of) occured.

Peter, G3LDO