Jeff Liebermann wrote:
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.


Nice analysis! One point: the wireless signal is constant, but the
household microwave signal is semi-discreet in time.

If the microwave is in use one hour per day [ the 1 hour per day use of
a microwave oven is in my experience far greater than most people use
for the cup of tea, soup, etc.], the equivalent energy exposure of the
two sources of radiation are (using your numbers):

Household microwave oven: 1 hour * 5 mw/sq cm = 3600sec * 5mw/sq cm =
1800 mw-sec/sq cm.

Wireless transmitter: 24 hr * 0.16 mw/sq cm = 24 * 3600 sec/hr * 0.16
mw/sq cm = 13,825 mw-sec/sq cm.

The total energy exposure from the wireless is 7.68 times the microwave
exposure on an integrated basis. This is admittedly a quick estimate,
since almost no one is located directly to either source in practice.
Yet, it is not conclusive that the wireless is trivial compared to the
microwave.

Q