The Federal Communications Commission (FCC) rules regarding power output for frequency-hopping spread spectrum (FHSS) state that a maximum output to the intentional radiator (IR) with 5 megahertz (MHz) of carrier frequency bandwidth must be which one of the following?

• A. 5 watts.
• B. 0.5 watts.
• C. 0.1 watts.
• D. 1 watt.

Answer: (D)

FHSS power rules are about matching the emission method to the allowed energy you can send. When a device uses frequency-hopping spread spectrum and the hopping bandwidth is 5 MHz or more, the FCC allows up to 1 watt of power to the antenna. This 1-watt limit (30 dBm) balances giving enough signal to function over distance while keeping interference to other devices in the band reasonably low. If the bandwidth were smaller, the allowed power would be restricted accordingly, so for a 5 MHz hopping spread, 1 watt is the maximum you can use.