Given an AP with 100 mW of output power connected through a cable with 3 dB of loss to the antenna with a 10 dBi gain, what is the approximate EIRP level from the antenna in mW?

Given an AP with 100 mW of output power connected through a cable with 3 dB of loss to the antenna with a 10 dBi gain, what is the approximate EIRP level from the antenna in mW?

• A. 1000 mW
• B. 100 mW
• C. 500 mW
• D. 50 mW

Answer: (C)

EIRP is the effective power radiated by the antenna, found by taking the power delivered to the antenna and multiplying it by the antenna’s gain (in linear terms). First, account for the cable loss: a 3 dB loss halves the power, so the power reaching the antenna input is 100 mW × 0.5 = 50 mW. The antenna has a gain of 10 dBi, which is a linear factor of 10 (since 10 dB corresponds to 10×). Multiply 50 mW by 10 to get 500 mW. So the approximate EIRP is 500 mW. The other answers would require different handling of the loss or gain.

EIRP is the effective power radiated by the antenna, found by taking the power delivered to the antenna and multiplying it by the antenna’s gain (in linear terms).

First, account for the cable loss: a 3 dB loss halves the power, so the power reaching the antenna input is 100 mW × 0.5 = 50 mW. The antenna has a gain of 10 dBi, which is a linear factor of 10 (since 10 dB corresponds to 10×). Multiply 50 mW by 10 to get 500 mW.

So the approximate EIRP is 500 mW. The other answers would require different handling of the loss or gain.