Border blaster

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A border blaster is a broadcast station that, though not licensed as an external service, is, in practice, used to target another country. The term "border blaster" is of North American origin, and usually associated with Mexican AM stations whose broadcast areas cover large parts of the United States, and United States border AM stations covering large parts of Canada. Conceptually similar European broadcasting included some pre-World War II broadcasting towards the United Kingdom, "radio périphérique" around France and the U.S. government-funded station Radio Free Europe, targeting European countries behind the Iron Curtain.

With broadcasting signals far more powerful than those of U.S. stations, the Mexican border blasters could be heard over large areas of the U.S. from the 1940s to the 1970s, often to the great irritation of American radio stations, whose signals could be overpowered by their Mexican counterparts. These are also sometimes referred to as X stations for their call letters: Mexico assigns callsigns beginning with XE or XH to broadcast stations.

On November 9, 1972, in Washington, D.C., the United States and Mexico signed an "Agreement Concerning Frequency Modulation Broadcasting in the 87.5 to 108 MHz Band". Since then, in the FM band power levels and frequency assignments have been set by mutual agreement between the two countries. AM radio border blasters still exist, though they are largely ignored due to the decline of AM radio in the U.S. and in Mexico. There are several such stations licensed by Mexico's Secretariat of Communications and Transportation using transmitters with an effective radiated power similar to those of major licensed commercial stations located within the U.S.