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LF: A question of calibration

To: <[email protected]>
Subject: LF: A question of calibration
From: "Malcolm Harman" <[email protected]>
Date: Thu, 27 Sep 2007 19:17:28 +0100
Reply-to: [email protected]
Sender: [email protected]
Hi. Can anyone reassure me.
 
I am in the process of using PA0SE's most helpful article http://www.veron.nl/tech/lf/fsm/pa0se.htm to assist in calibrating my 'Eton E5' as a field strength receiver for 500 kHz .
 
He says:  "Most field strength meters do not measure the electric but the magnetic component of the electromagnetic field. But this is no problem because in the far field of the antenna (where we measure) there is a fixed relation between the electric and the magnetic field components: E/H=120*pi ohm=377 ohm"

Then in the final paragraph of the 'Calibration' section he uses this same equation to convert A/m to V/m in a near field.

Not that I would want to question an expert, but I guess the far field issue is something to do with the distance it takes for a plain wave to form from an antenna and presumably the equation remains valid, even between the "Helmholtz coils" with the 377ohm relationship still applicable?

73 Malcolm (G3NZP, near Gatwick)

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