[clug] Microwave/Wireless

[Alex Satrapa]

On 2 Feb 2005, at 20:58, John Fletcher wrote:

> That's probably because they both run on the same frequency.  Which 
> kind of
> makes non-scientists like me wonder why I am shooting these microwave
> oven-like waves through my house... or the effect of shooting them 
> through
> our neighbourhoods.

The reason WiFi is affected my microwave ovens is that they are on 
similar frequencies, but especially that WiFi is limited to something 
like 100mW maximum power (I'm not sure what arcane measurement they use 
for "maximum power"), which is well within the limits that a microwave 
oven is allowed to leak. Consider that a microwave oven is generating 
600W of microwave energy, and that the shielding is only 99% efficient 
- that's still a significant microwave emission that the WiFi is trying 
to compete with, even if the oven is highly tuned to one frequency 
(yeah, right!). From the brochure available at 
http://www.arpansa.gov.au/is_mwave.htm:

> ...Generally, the required design of oven doors should restrict this 
> leakage to a level well below that recommended by the Australian/New 
> Zealand Standard AS/NZS60335.2.25:2002 Household and similar 
> electrical appliances – Safety Part 2.25: Particular requirements - 
> Microwave ovens.
>
> The Standard specifies a test to assess the level of microwave leakage 
> and states that 'The microwave leakage at any point 50 millimetres or 
> more from the external surface of the appliance shall not exceed 50 
> watts per square metre'. ...

I'm not a communications engineer, so I don't know how to convert from 
flux (Watt/square metre) into the equivalent source power of an 
omnidirectional transmitter - but I would expect that those numbers 
translate to something more powerful than 100mW. I expect the leakage 
allowed is fairly high since the microwave oven isn't expected to be 
used 24x7 - so your body will have time to repair damage caused by the 
leaked radiation. Still, I don't sit in front of the microwave waiting 
for the food to cook (well, anymore - the first time I saw a microwave 
oven cooking food it was like aliens had visited planet Earth, so of 
course I watched).

As a general rule - don't use the microwave oven or a cordless phone 
while you're playing CounterStrike. Only cook your popcorn between 
games ;)

Alex