In accordance with the provisions of the agreement, its implementation is expected to take place within one year of its adoption by the four main signatories of the Covenant, the United States, Canada, Cuba and Mexico. On December 22, 1937, Cuba was the first country to be ratified and followed by the United States on June 15, 1938 and Canada on November 29, 1938. Meanwhile Mexico, the United States and Canada entered into a frequency agreement in 1939 on the basis of contractual standards. Mexico finally approved the treaty on December 29, 1939, and began work on its broad provisions. The NARBA agreements were significantly replaced by the Regional Agreement for the Medium Frequency Broadcasting Service in Region 2, which covers the entire Western Hemisphere, and signed in 1981 in Rio de Janeiro, Brazil, which came into force on 1 July 1983 at 08:00 UTC. The criteria for protection against interference in the Rio agreement are very different from those of NARBA and the concept of clear channel stations is eliminated. In adopting this agreement, the Bahamas and Canada have indicated that they intend to renounce compliance with NARBA.  However, much of the structure introduced by this treaty has remained intact. The interim agreement expired on 29 March 1949 and there were great difficulties in agreeing on a replacement, in part because of Mexican objections that resulted in two failed conferences. A new narba agreement, to enter into force for five years after ratification, was finally signed on November 15, 1950 in Washington, D.C.
for the Bahamas, Canada, Cuba, the Dominican Republic, Jamaica and the United States.  Mexico, which had withdrawn from the conference, and Haiti, which was not participating, had to have the opportunity to participate. (The United States and Mexico reached a bilateral agreement in 1957)  This agreement officially added 540 kHz as a clear channel frequency and also provided that Cuba could share six and Jamaica two of the allocations of Us clear channels.  Some provisions remained controversial and this version of the treaty was not ratified by the United States until early 1960. In 1980, Cuba announced a year of withdrawal from the NARBA treaty.  The 1950 NARBA provisions are still in effect for the Bahamas, the Dominican Republic and the United States as these countries have not officially repealed NARBA.  The United States also has active bilateral agreements with Canada (“Agreement between the Government of the United States of America and the Government of Canada through the AM Broadcasting Service in the Medium Frequency Band” (1984)” and Mexico (“Agreement between the Government of the United States of America and the Government of the United States of Mexico through the am Broadcasting Service in the Medium Frequency Band (1986).  Due to the existence of an improved radio design, the agreement also reduced the minimum separation of the “same type of frequencies. Market” from 50 to 40 kHz.