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Message-ID: <55F29B964A0142EE93CCD0BCFD084EDF@JimPC>
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <4D25EC9A.6030201@iup.uni-heidelberg.de>
In-Reply-To: <4D25EC9A.6030201@iup.uni-heidelberg.de>
Date: Thu, 6 Jan 2011 21:33:28 -0000
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Subject: LF: Re: adding a L into a 300m LF vertical?
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Dear Stefan, LF Group,

> _Questions:_ Is my calculation reasonably useful? Would YOU add that
> coil in a height of 100m above GND?

I have found with NEC simulations that they give you a reasonable idea of 
the impedance, but not a precise value. Especially for the resistance, where 
there are many unknowns - NEC really only sets a lower limit.

On the basis of the calculations, I would first try without the coil, then 
if results are as expected, I would try it with the coil. Otherwise there 
are too many variables to make sense of the experiment - if the coil goes up 
and the impedance is totally different from the calculation, is it because 
of the coil, the antenna, or the calculation?

>
> I tend to let it be since the improvement isn't that much and the effort
> is high. Furthermore the coil losses could be higher since i have to use
> a thin wire to keep the weight small...

Yes - the 136k coils I have made with Q > 300 have been rather big, either 
with RF Litz wire or thick solid wire.

Hope to see some signals at the weekend,

Cheers, Jim Moritz
73 de M0BMU