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From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <BAY124-F3900F6885CA03CA4608264CF250@phx.gbl> <000901c7aa26$ecfaff60$82147ad5@w4o8m9> <000d01c7aa8c$6d692860$7c0d7ad5@w4o8m9> <466AB1CB.2060907@telia.com> <001301c7acd6$14f492e0$15337ad5@w4o8m9> <003401c7acdd$ec08ad50$1f03210a@Hugh>
Date: Tue, 12 Jun 2007 13:40:43 +0100
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Subject: LF: Re: Re: Tree current
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Dear Hugh, Dave, LF Group,

Certainly in principle it is reversible - I suppose in principle you could
use a Rogowski coil as a coupling device, but due to the small mutual
inductance between the coil and the "antenna element", it would be extremely
inefficient, even before the losses in the wood were taken into account. On
the other hand, the conventional cored current transformer would be a
reasonable way to match to a very low inpedance antenna - I saw an HF loop
design somewhere that used this kind of arrangement.

I did check to see if the current was zero when the coil was not around a
tree - initially it wasn't, which is why I added the screen, which improved
things a lot. It didn't entirely eliminate the residual reading, but reduced
it to only a small fraction of the measured current levels. It isn't easy to
measure millivolts when you are in a kV/m field!

Cheers, Jim Moritz
73 de M0BMU