hello! experience with 802.11x and extreme humidity?

[Simon Byrnand]

At 13:57 14/10/02 +1000, Darryl Smith wrote:

>Microwave ovens use a power output of maybe 800W to excite the water.
>Wireless cards operate on something like 1-10 mWatt. There is a bit of a
>difference here...

:)

>Basically MicroWave ovens use BRUTE FORCE to heat the food. They don't
>use the most efficient frequency... But building a microwave oven for 22
>GHz is a problem - not because of the cost of generating the signal, but
>the cost of keeping the signal enclosed. The door needs to seal much
>better in order for energy not to escape...

Actually the reason 2.45Ghz was chosen was a compromise between two
different things -

Too low in frequency and the effeciency drops - too much of the Microwave
engergy passes through the food without being absorbed, (doesn't cook very
well) too high in frequency and the Microwaves can't penetrate far enough
into the food. (cooks near the outside) 2.45Ghz was the nearest ISM band
that gives this compromise.

>People bitch about cellphone towers and the energy they emit... Well, a
>microwave with a door that does not work properly is much worse... MUCH
>worse.
>
>Increasing frequency is one of the best ways to decrese range...
>Lowering power works too, but lower frequencies are not as attenuated by
>walls...

The real reason for using higher and higher frequencies, is that IF you are
willing to accept the reduced range, then the payoff is there is much more
bandwidth available the higher in frequency you go. More bandwidth = either
more channels, or more throughput per channel, or both.

>Even in 100% humidity, most of the air is empty.... Therefore the odds
>for attenuation of a signal is poor, since not much signal will hit the
>water. 100% water is different since it is a solid, and in a
>structure...

I've found 2.4Ghz is *MUCH* more robust than people give it credit for. On
a 6km link we have even the worst possible rain and storms that we've had
hardly affect the signal by more than about 2dB. Unless the antenna gets
blown over that is ;-)

Regards,
Simon