[TriLUG] WiFi quality monitoring

[Alan Porter]

> Putting a 9dBi antenna is only making it more illegal

Just an aside -- The 9dBi antenna is not "boosting" the power.
It is FOCUSING it.

The "i" stands for "isotropic", and that refers to a
theoretical antenna that radiates the same energy in all
directions.  A 9dBi antenna squashes the radiation pattern
so it is less like a sphere and more like a donut.  It does
this squashing trick through the shape of the conductors.

Typically, you want the radio waves to go out sideways, and
you don't want to waste energy sending your signal into the
sky.  So a typical transmitter antenna is a metal pole,
sometimes with some little metal "aimers" to flatten that
pattern out into a donut aimed at the horizon all around.

When the cool kids in the 1990's used to lean their car phone
antennas over to look "swept back", that aimed their antenna
donuts sideways, and actually reduced their gain significantly
(I've heard 20dB, or 1/100th of normal signal strength), at
least in some directions, like ahead of and behind the car.

With a Pringles can antenna or a yagi or other directional
antenna, you might get more than 9dBi in gain in the "good"
direction, at the expense of the gain in the "bad" directions.
Dish antennas take this same concept to the extreme, bending
their radiation spheres into narrow beams.

And yes, the "legality" that Joe mentioned refers to the effective
radiated power in a particular direction, so focusing the 50mW
isotropic radiation into the equivalent of a 500mW beam violates
the letter of that law.

Not judging here... just spreading a little bit of radio knowledge
and terminology, hopefully in a very approachable way.

Alan