Dear all,
> With regard to UK VLF experimenters I don't think it is true that everyone
> 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 radiate in
certain ways - your intentions are irrelevant. Non-radio equipment which
radiates interference can be illegal, though obviously no-one intends it to
radiate.
As for propagation modes (earth conduction, near-field, far-field), the
distinction between these is legally awkward as the Law tends to view the
physics very simplistically. Yes, your loudspeaker and the mains wiring
probably 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
ridiculously 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 Einstein taught us
in 1905! It's the old Oscar Wilde line about the truth being 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
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