Jim Lux wrote:
They do make a nifty $100-200 or so WiFi spectrum analyzer which has a
calibrated receiver. And, if you have a wifi card with an exernal
antenna, you can do even better.


First of all, a $100 item in the US is $200-$300 here (or more, depending
upon the regulation required to get it in, the rarity, etc). For example,
cheap MP3 players are around 25% more expensive, an iPod is double.

Second, I have never seen a real meaningfull number from a computer. Whether it
is MacOS, Linux, or Windows XP, they all give some sort of relative number,
for signal strength.

In some cases it has been useful, for example using Kismac, I found that the
signal strength as measured by my WiFi card in my Mac, was in the mid 50's
with a bluetooth dongle on the computer, and in the 60's without one.

No matter what the number really is 50 is about where it gives up completely.

However, it does not really help me. What I need is to be able to place a
device at a specific distance from a 2.4 gHz antenna and read the EIRP.

I can assume that a 100mW signal into the little whip on the back of a router,
produces and EIRP of 100mW, which makes all gain antennas illegal. Or I can
make an attempt at measuring it. It does not have to be 100% accurate, 10%
or even 25% off would be good enough.

For example, I found that placing my meter at about 1 inch from a WiFi router
running "full tilt" produced a reading of .36mv/cm2 on the meter. However the
only real information I can get from that is yes, the router is transmitting
a signal, and yes, I can read it, but no, I have absolutely no clue as to
what it means.

I may be asking the impossible, but what I would like to get is a number
for example, if I hold the meter an inch from the antenna, 100mW EIRP is
1 mv/cm2. Then I can do something useful with it, as I already know how
to compensate for distance. :-)

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM