From: Chris Trayner <C.Trayner@leeds.ac.uk>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Date: Thu, 20 Jan 2011 08:15:04 +0000
Thread-Topic: LF: Re: VLF Earth Mode does NOT need an NoV - official at last
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Dear all,

> With regard to UK VLF experimenters I don't think it is true that everyo=
ne necessarily wants to radiate a far-field signal as far as possible.

> No NOV required for Earth Mode (conduction/induction) applicable to Cave=
 divers where it is not intended to propagate a signal into the ether, but=
 to communicate through the earth.

There has been a lot of talk about what people intend to do. Surely this=
 is irrelevant? The Law presumably says that that you may or may not radia=
te in certain ways - your intentions are irrelevant. Non-radio equipment=
 which radiates interference can be illegal, though obviously no-one inten=
ds it to radiate.

As for propagation modes (earth conduction, near-field, far-field), the di=
stinction between these is legally awkward as the Law tends to view the ph=
ysics very simplistically. Yes, your loudspeaker and the mains wiring prob=
ably do radiate a tiny amount of far-field radiation, but the Law was not=
 written by people who understood that. My guess is that the Law has ridic=
ulously wide-ranging powers which, fortunately, it tends not to use.

To add to the fun, if you think that near-field and far-field are distinct=
, try reading a good textbook on electromagnetic radiation. Indeed, if you=
 think that electric and magnetic fields are distinct, try reading what Ei=
nstein taught us in 1905! It's the old Oscar Wilde line about the truth be=
ing rarely pure and never simple.

It seems to me that there are four issues:
- The physics
- Ethics (e.g. not causing interference)
- Common sense and realism (e.g. you can't eliminate all interference)
- The Law
These are not necessarily tied in with each other!

73,
Chris G4OKW

-----------------------
Dr Chris Trayner
School of Electronic & Electrical Engineering,
The University of Leeds,
Leeds LS2 9JT, United Kingdom
Tel: +44 113 34 32053
Fax: +44 113 34 32032