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Old May 17th 07, 08:09 PM posted to alt.internet.wireless,rec.radio.amateur.antenna
Jeff Liebermann Jeff Liebermann is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 15
Default Wireless Internet service antenna, radiation

Richard Clark hath wroth:

There is probably more radiation from your microwave leaking out than
you will find coming from any wireless ISP.


Ummmm... shall we do the math?

Microwave evens are required to be below 5 mw/sq-cm at a distance of 5
cm. Food and Drug Administration/Center for Devices and Radiological
Health (FDA/CDRH) performance requirements in Title 21, CFR, Part
1030.10. Ugh.

I'll assume the typical 50mw wireless access point, with the usual
2dBi rubber ducky antenna. It's easy to calculate if you assume that
the radiation pattern from the rubber ducky is a sphere and you ignore
near field effects.
The surface area of the sphere is:
4*Pi* radius^2 = 4 * 3.14 * 5cm ^2 = 314 sq-cm.
The 50 mw of RF is spread equally over the surface so the power
density is:
50 mw / 314 sq-cm = 0.16 mw/sq-cm
which is MUCH less than the 5mw/sq-cm limit for used microwave ovens,
or the 1mw/sq-cm required for new microwave ovens.

The actual power density is slightly higher because the pattern is
really a torus and NOT a sphere, but it's not going to change very
much. My guess(tm) is double but I'm too lazy to grind the numbers
exactly. Anyway, at 5cm test distance, you're safer with a wi-fi
access point than with a microwave oven.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558