Date: 16 Sep 99 16:42:47
From: Don Stauffer <stauffer@gte.net>
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I have paid a lot of attention in recent years to stories of health
hazards of low frequency EMF, and have not exactly been overwhelmed by
the evidence. I am not sure whether, in your case, you are talking
about low frequency fields or RF fields. Which IS the concern? It is
well known that sufficient field intensities of RF fields DO create
health hazards. However, I was under the impression that certification
rules addressed this.
Low frequency fields is something else. Epidemiological studies on this
have been full of flaws. For instance, they deal with the VOLTAGE of
power lines in the vicinity, whereas the fields are a function of the
CURRENT in the line, and for the same power transmission, a higher
voltage line will actually be carrying LESS current, and hence produce
less magnetic field.
The researchers frequently do not really understand the rapid falloff in
field intensity if there are multiple wires involved, in which case the
exposure to appliances in the house may be a greater cause of exposure
than neighborhood power lines.
Now, as for avionics. About two or three years ago I did some research
on low frequency fields in the avionics bay of a high end business jet.
The idea was to see if we could build a magnetic compass right into an
INS box. The idea was to see if by measuring the power consumption of
the avionics, could we add a correction factor to the actual magnetic
compass reading.
I used an extremely sensitive magnetometer as a compass. Yes, I did see
some compass errors depending on the amount of current being drawn on
various buses. BUT, that still represents a very small magnetic field.
If these small values of field were of significance, the general
population is exposed to similar changing fields every time they turn
around in the Earth's magnetic field.
--
Don Stauffer in Minneapolis
stauffer@gte.net
http://home1.gte.net/stauffer/
