RF power limits for 2.4ghz Wifi gear

The ACA has set a limit Between the ranges of 2400 MHz to 2483.5 MHz, the limit is a maximum of 4 W (watts) EIRP.

EIRP calculation
EIRP = Tx (dBm) + Antenna Gain (dB) - Feedline Loss (dB)

e.g. 30 mW WLAN card into a 24 dBi dish with 3dB coax and connector loss
30 mW = 15 dBm (see math below)
EIRP = 15dBm + 24dBi - 3dB = 36 dBm This system is right on the legal limit of +36dBm (4W) EIRP.

 

mwatts to DBM (where input is 100mw)
100 Log X 10 = 20 dbm

20

DBM to mwatts (where 20 is 20dbm
10 x^y ((20 - 30)/10 ) = 100mw