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Message-ID: <7E66CE16BFD54F25AA1727BAA9AF3500@JimPC>
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <4C694CC6.3010609@o2.ie> <006401cb3d5a$e4ebca00$4001a8c0@lark> <4C696537.6090107@o2.ie>
In-Reply-To: <4C696537.6090107@o2.ie>
Date: Mon, 16 Aug 2010 18:44:47 +0100
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Subject: Re: LF: Re: Earth electrode antenna tests
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Dear Tony, LF Group,

EI8JK wrote:
> Last week I hooked up my sig genny to the loop and the maximum signal was 
> at right angles to the wire, so I was expecting receive to be the same.
> Seems not.

...But there is a difference in field strength and direction between near 
field and far field for the loop. For distant signals, the maximum 
radiation, and response to received signal, is in the plane of the loop, i.e 
along the line of the wire, if we assume the earth antenna behaves as a 
loop. But close to the loop, the maximum magnetic flux is along the axis of 
the loop, i.e. at right angles to the wire. so when two loops are a small 
fraction of a wavelength apart, maximum response should occur when they are 
side-by-side and parallel (more or less - the field lines curve round as you 
move off the loop axis). Think in terms of an air-cored transformer with 
single turn primary and secondary. Therefore, the "directional pattern" of a 
loop is different if you are doing experiments over short distances.

Cheers, Jim Moritz
73 de M0BMU