Message-ID: <004f01c08187$5bfdc660$d6a174d5@w8k3f0>
From: "Dick Rollema" <d.w.rollema@freeler.nl>
To: rsgb_lf_group@blacksheep.org
References: <3.0.1.16.20010118142719.33cf5a3e@mail.cc.kuleuven.ac.be>
Subject: Re: LF: Caged Coils
Date: Thu, 18 Jan 2001 20:45:40 +0100
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To All from PA0SE

Rik, ON7YD wrote:

> The radiation resistance of a multiturn loop is :
>
> Rs = 31200 x (n x F / L^2)^2
> where Rs = radiation resistance, n = number of turns, F = loop area, L =
> wavelength.
>
> For my loadingcoil n = 120 and F = 0.04m^2, so at a wavelength of 2200m
the
> radiation resistance will be about 30 nano-Ohm. Estimated radiation
> resistance of my inverted-L antenna is about 40 milli-Ohm.
>
> Shielding the coil (done properly - avoiding short circuit turns) would
> make my signal 0.000003dB weaker.

I am not shure whether this calculation is applicable to a loading coil. The
coil in a mobile antenna for the HF bands is considered to radiate as a
linear conductor with a length equal to the length of the coil. I think this
could also be the case for a loading coil at LF. So if the coil is 1 metre
long (high) with its axis vertical it acts as a 1 m long vertical antenna
and when at the bottom of a vertical antenna it makes the radiator 1 m
longer.

73, Dick, PA0SE