Transmission power in aviation is measured in watts. The power output of an aircraft radio is typically in the range of 8 to 30 watts, depending on the aircraft and radio model. Larger aircraft with more robust electrical systems may have higher-powered radios. Light aircraft usually have radios in the 10–20 watt range.

Power output is not the same as the effective radiated power (ERP) or equivalent isotropic radiated power (EIRP) that actually reaches the receiver. ERP and EIRP take into account the antenna gain and directional characteristics. A well-designed antenna can double or triple the effective radiated power compared to a poorly matched antenna.

From a regulatory perspective, maximum transmitter power is controlled by law. ICAO Annex 10 specifies maximum power limits to prevent harmful interference. Ground stations also operate within strict power limits. These power limits are coordinated internationally so that adjacent nations' frequencies do not cause mutual interference.

As a pilot, you do not adjust transmitter power in flight. The power output is fixed at the factory or during maintenance. Your role is to ensure that:

These factors ensure that your transmitted signal reaches the receiver with good clarity and at appropriate strength.