Regional Agreement for the Medium Frequency Broadcasting Service in Region 2

The Regional Agreement for the Medium Frequency Broadcasting Service in Region 2, commonly known as the Rio Agreement, is an international treaty that defines standards for AM band (mediumwave) radio stations in the western hemisphere. Covering North America, South America, and the Caribbean, it was signed in Rio de Janeiro, Brazil on 19 December 1981 and took effect on 1 July 1983 at 08:00 UTC.

A major feature of the Agreement was the division of stations into three main classifications: Class A, normally limited to 100 kilowatts (kW) daytime and 50 kW at night; Class B, limited to 50 kW, and Class C, limited to a nighttime power of 1 kW. Individual nations can make further refinements for their particular circumstances.

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