Subject: Re What does radar due to people? (fwd)
Date: Thu, 4 Jun 1998 044542 -0500 (CDT)
From: "Roy L. Beavers" <rbeavers@llion.org>
To: emfguru@hotmail.com
--------------------------------------------------
---------- Forwarded message ----------
Date: Wed, 03 Jun 1998 22:18:40 -0700
From: "Harrison A. G. Stone"
To: deb@carneylaw.net
Cc: rbeavers@mail.llion.org
Subject: Re: What does radar due to people? (fwd)
>
> Date: Wed, 03 Jun 1998 14:04:20 -0600
> From: Deb Carney
> Subject: What does radar due to people?
>
> We have discovered that among the many different kinds of antennaes up
> here on the Lookout Mountain Antenna Farm just West of Denver is
> radar.It may be the doppler radar used by the local news station. It
> looks like a covered white ball sitting an top of 1 of the towers and
> looks like it is at about the same altitude as my home which is about 1
> mile away. A local scientist used a machine on my deck and picked up a
> clear radar signal but said we were below the main power beam.
> Can you direct me to information on the effect of this kind of radar on
> people at this close range?
> Thank you,
> Deb-a worried mother
_________________________________________
Several thoughts as a result of your post. First: Doppler radars are
generally used for measurement of relative velocity - such as the radar
speed traps, measuring the speed of a baseball, or, in larger, more
elaborate installations, measuring how fast a guided missle is coming
toward you. It seems unlikely that a news organization would have
mounted a fixed unit to measure missle speed. A "large" white dome does
not really convey an idea of the size - or purpose - of the
installation. "Radomes" were originally developed to provide weather
protection for radar antennas - mostly the type that revolved in azimuth
and/or moved in elevation, for tracking missiles, planes and the like.
Size of the "dome" was generally based on the size, not the power level,
of the antenna. Usually, the size was determined by the frequency (or
wavelength) at which the equipment was operating, and the directionality
of the antenna (that is, how narrow an angle the set was intended to
"look" at at any one instant. Radomes were also used on certain radar
and radio positioning equipment on planes in flight. Not well liked by
piolets, in the early days, since they slowed the plane, and often made
it difficult to handle. "small" radomes ranged from 6 or 7 inches
across, up. A really "large" radome, on a fixed tower or building,
might reach 60 feet across and high. BUT - the size of the 'dome' does
not have anything do do with what the contained equipment does. Domes
are also used to house satellite receiving antennas for TV news video
and for electronic data processing links, particularly in geographical
locations where ice and snow are found.
Second: even pretty powerful radars - that is, military units with
power levels having peak pulses in the megawatt region, start to have
pretty weak radiated signal powers at a distance of a mile. Also, a
radar beam is, by design, intended to direct is energy, much like a
search-light, into a narrow, concentrated beam, in order to focus as
much power as possible in a single direction. In other words, it is
trying to "illuminate" a relatively small object - like a plane - at a
fairly long range. So the antenna is designed to put as much power as
possible into just that narrow beam, and not waste any on the rest of
the surroundings.
In general, good design tries to keep the out of beam power down around
one one-thousandth of the power in the beam. If this object is really a
radar, and not a communications set, it wouldn't want to waste energy
looking along the horizon anyway - it would be intended to look upward,
so the beam would not be aimed directly at anything on the same level.
Third: Being able to pick up a clear radar signal does not imply that
there is even enough energy present for there to be a "bounce" or retrun
which is strong enough for the very sensitive receiving apparatus in the
equipmant to datect. You have probably seen advertixements for "radar"
detectors for use in cars. These little receivers can pick up the
signal from a speed trap many times further away from the source than
the user of the speed trap can pick up the returned signal from your
car. This is why they are popular among some people. The ONLY way in
which you can evaluate the actual amount of energy reaching your place
is by measurement with a calibrated field strength meter. This is an
instrument which measures the actual amount of energy which is arriving
at your location. Without an actual reading of this tye, I would tend
not to worry about this installation, simply because the distance
involved provides a verysignificant reduction in any em wave. Remember,
with any radiated signal - any form of em radiation - the signal
strengeh decreases as the inverse square of the distance. for example:
if I have a certain field strength at 1 foot, at two feet the strength
is 1/2x2, or 1/4 the strength at 1 foot. at 4 feet, it is down to 1/16
th of the original strength, and so forth. In dealing with all forms of
radiated em energy, increasing distance always reduces the strength of
the signal - quite rapidly.
If you are really worried, see if you can locate someone who has access
to a field strength meter, and knows how to use it - and get them to
make a measurement. Until then, I wouldn't let myself worry to the point
where the emotional stress started to damage my onwn mental and
physical health. If you know any amateur radio operators, or
communications systems repair people, one of them might be able to
borrow a field strength meter long enough to make the measurements for
you.
Best of luck, and I hope that some of this is useful information. I'll
be happy to answer any questions for you if I can. Harrison Stone
Archive provided courtesy of WaveGuide, http://www.wave-guide.org
Reprinted with permission of Roy Beavers, http://www.feb.se/EMF-L/EMF-L.html