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From: Mike Poulton
Subject: Re: Any ideas on measuring radiation in the home ?
Date: 4 Oct 2002 05:39:00 GMT
Organization: MTP Technologies
On 03 Oct 2002, email@example.com (milne_v) said:
> Radiated E-Field in volts/meter (or near field) is a verifiable and
> measurable quantity. Why do linemwn wear those suits when they're
> working near 400kv transmission lines?
That has nothing to do with radiated EM, it is to prevent electrocution.
They work hot, and capacitive coupling between their platform and the
line causes significant current to flow when they touch it. Thus,
without an equipotential suit, they would receive a severe (possibly
> There are also endless
> guidelines for E-Field exposure limits both in residential, indistrial
> and commercial environments posted by hydro companies for decades now.
> What are the guidelines for? You get close enough to a large E-Field
> and you'll get more than just thermal effects. Microwaves are also a
> large source of directed E-Field which is from time to time envisioned
> as a source for wireless power transmission, again more than thermal
> effects. The power receiving apparatus is often called a rectenna.
That seems rather irrelevant to the discussion at hand. Of course you
can transmit power with EM radiation. That's how radio works! The
issue is whether or not absorption of this radiation by humans causes
anything but heating. I have yet to see a reliable study indicating
otherwise. The only exception I know of is where the energy density is
high enough to cause nearly instant vaporization of stuff and subsequent
heating to very high temperatures, with enough of an E-field to then
ionize the gases. This is still primarily thermal, but involves some
magnetic and electrical interactions as well. At that power level, it
really doesn't matter what's happening. This is what you see when you
get a fireball in a microwave oven.
> Try holding a pop can up in front of a powerfull radar horn while the
> radar is operating. Use a long stick for the can. Must be something
> blowing that can apart.
Heat! Steam power!
> High power broad band micowave sources using
> sophisticated high power spark discharge devices such as marx
> generators integrated into a tuned transmission line are being tested
> for possible weaponization. Check out some of the US navel test ranges
> or use a search engine for the term "transient electromagnetic
Again, they are thermal devices when used against people. When used for
destroying electronics, they do so by being rectified by junctions
therein and by producing thermal damage inside sensitive parts.
> A number of home brew TED's are also on the net as well as
> coin and can crushers. A similar technique is used in medicine to
> produce powerfull, focused and directed acoustic shock waves, see
> "lithotripter". All have one thing in common, they use a very
> powerfull and high speed spark discharge. The first experiments in the
> production of milli-meter wave radiation also used a spark discharge
> system more than a hundred years ago.
You are mixing three distinctly different technologies here. Can and
coin crushers rely on the eddy currents created in metal loops due to
rapidly changing magnetic fields. They do not use microwave or
millimeter wave radiation and, in fact, do not use anything close to
that frequency range. It is a single huge pulse of current. Any
ringing that may occur after that pulse is simply coincidental, and
would likely be in the low megahertz range. Most of these devices DO
NOT use spark discharges. They use vacuum relays or simple shorting
bars. I have seen one design that uses a triggered spark gap, but only
a small fraction of the total energy is dissipated in the gap -- it just
acts like a switch.
Lithotripters are very different. They use a huge capacitor discharge
underwater to create a mechanical shockwave that is focused to pulverize
stones. Again, any ringing or EM radiation is coincidental and
Spark gap transmitters are totally different from both of the
aforementioned devices. They include a resonant circuit (L-C) to
intentionally produce high frequency EM radiation.
Not only do I speak for my company, I AM my company!
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