[MLB-WIRELESS] Question about some Wireless cards

Tony Langdon tlangdon at atctraining.com.au
Fri Jun 14 13:02:27 EST 2002


> the antenna gain is *added* to the card's gain.

If the power is in dBm and the gain is in dB, yes, you add those numbers to
get the EIRP (effective isotropic radiated power, for those who've recently
arrived).  Also, don't forget to subtract cable and connector losses (these
can be significant at 2.4 GHz).

EIRP basically means that the field strength in the main beam of the antenna
is the same as it would be if the EIRP power was fed into an antenna that
radiated equally in all directions (otherwise known as an "isotropic
antenna).

And before anyone asks, no, you can't build an isotropic antenna, it's a
useful theoretical construct only, but (AFAIK) impossible to build. :)

> I'm not sure if that literally means you just add the two numbers 
> together or not, but the card gain is a measure of the power coming 
> out of the card, and the antenna gain a measure of how much the 
> antenna concentrates that power.

That's basically it.

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