What does the IEEE specify as the maximum allowable power output into the intentional radiator for IEEE 802.11a-, 802.11n-, and 802.11ac-compliant devices operating on the lower U-NII band?

• A. 10 mW
• B. 100 mW
• C. 400 mW
• D. 40 mW

Answer: (D)

The main idea is that radios sharing the 5 GHz spectrum are restricted in how much power they can put into the antenna to keep interference in check. For devices using 802.11a, 802.11n, or 802.11ac in the lower U‑NII band, the IEEE specifies a maximum conducted power at the transmitter output of 40 milliwatts. This value is the power at the radio port before any antenna gain is applied, so the actual radiated power depends on the antenna you connect. The goal of this limit is to minimize interference with other users and services in the same band while still allowing Wi‑Fi to work effectively indoors. Using more power would increase the risk of disrupting neighboring devices, whereas less power would hinder performance.