[MLB-WIRELESS] Wireless press.

[Jason Hecker]

EIRP means Effective (or was it Emitted) Isotropic Radiated Power.  Using 
EIRP gives you an absolute reference.

An Isotropic radiator can be considered to be a point source.  If it were 
to radiate it would emit an ever growing perfect sphere shaped envelope of 
RF energy.

Anyway, if your 30mW card (which converts to 14dBm) is hooked up to a 24dBi 
antenna (for now assume lossless cable) then 14dBm+24dBi is 38dBm or 
6.3Watts EIRP.   4W is 36dBm.

Now, the point of all this is that if you have a point source and a 24dBi 
antenna and you are looking at them head on, using the numbers above you 
will need to put 38dBm (6.3 Watts) into the point source for it to 
irradiate you with the same amount of energy your 24dBi antenna illuminates 
you with from 30mW (14dBm) of power going into it.

A better analogy is a lighthouse light.  It has something akin to a point 
source being the bulb.  If you look at the bare bulb from a distance, it's 
not so bright.  Put in the lenses and mirrors and collect all the light 
that would go everywhere into one direction and then look at it, you'll be 
blinded.  It'll be equivalent to looking into a _bare_ lightbulb that is 
much, much brighter.

So an antenna is basically a device for focusing RF energy like a 
lighthouse's mirrors and lenses.

I hope this helps.

Oh, dBi (which all antennas are or should be specified in) is a logarithmic 
quantitative measurement of the antennas focusing (gain) abilities with 
reference to the point source.


 > So something like 4mW is still 4mW (or less) regardless of if it comes out
> > of a high gain antenna or not?
> >
> > Am I on the right track here?


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