EIRP

This calculator will give you the effective power output from the transmitting antenna referenced against a hypothetical isotropic antenna, this is mostly useful for checking that you are within the relevant government regulated power limits.

Transmitter details

Transmitter Power Output(dBm)
Transmitter Cable Attenuation(dB)
Transmitter Antenna Gain(dBi)
EIRP(mW)

The formula used to derive the EIRP is where Pt is the power of the transmitter in dBm, Lc is the loss of the connectors and cable to connect the antenna in dB and Ga is the gain of the antenna in dBi.

In New Zealand, at the time of writing the current maximums for spread spectrum devices are as follows:

Frequency	Peak Power
2.4Ghz	4000mW
5.3Ghz	250mW
5.4Ghz	1000mW
5.8Ghz	4000mW