Date: Sat, 5 Feb 2011 12:05:30 +0100 (CET)
From: Jacek Lipkowski <sq5bpf@lipkowski.org>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
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On Sat, 5 Feb 2011, Roger Lapthorn wrote:

> Gas pipes are non-metallic I think?

i think the high pressure pipelines are metallic.

> Not sure I like the idea of connecting many watts of VLF power into high 
> voltage pylons or gas pipes. In the UK we would be locked up as 
> suspected terrorists!

hey, no risk - no fun :)

> Having a few watts VLF piggyback a water pipe connected to my central 
> heating radiators sounds as if it should be more legitimate. After all, 
> we use such connections often as the ground systems for verticals.

it's probably not any more or less legal coupling vlf or hf to them.

btw. try a phone line. if you have an old wire infrastructure the wire 
will be grounded at the phone exchange far away. you can couple a few mA 
of VLF current to the grounded wire. 1km of wire really works wonders as a 
transmit antenna, but i'm sure that this is illegal (at least here the 
phone line is property of the phone company, and only accepted equipment 
can be connected to it).

> This raises the question about the legality of putting VLF signals along 
> utilities - is this actually permitted? After all, there are intercoms 
> and data systems that intentionally use the mains electricity wiring. 
> Anyone know what IS permitted?

if it isn't forbidden, then it's permitted. unless you ask for permission, 
of course, then legislation might be added to take the posibillity away 
from you.

if you don't conenct to the utilies directly, but couple to them, then i 
think it is legal. there are specific laws that describe the permitted 
electromagnetic field strength. these laws are carefully written, so that 
the power infrastructure is exempt from these laws (or otherwise they 
would fail), this is achieved by defining the lowest frequency. in Poland, 
and probably elsewhere too, these laws work from 30kHz up, so <9kHz is 
exempt. making a direct connection might still be illegal, but not due to 
electromagnetic emission, but due to tresspassing laws etc. but i'm not 
sure they work, since i haven't seen any signs saying that you can't get 
near the pylons. btw it will be very hard for you to generate a bigger 
field strength than the power line is already generating.

jacek