Saturday, March 29, 1941, was a big day in broadcasting in the North America. At 3:00 AM Eastern Time, most of the broadcast stations in the United States had to change frequency, due to the North American Radio Broadcasting Agreement (NARBA).  The agreement was signed in Havana in 1937 and ratified by the U.S. Senate in 1938. The ratification stipulated that it should take effect a year after the treaty was ratified by four of the participating countries, Canada, Cuba, Mexico, and the United States.

The treaty was necessitated mostly by the powerful Mexican “border blaster” stations which operated on the same frequencies as U.S. stations and caused considerable interference. For example, an earlier post details how Chicago’s WCFL suffered interference from XEAW in Reynosa, Mexico.

Mexico had no incentive to deal with the situation, since it had never been assigned any “clear channel” stations on which these powerful stations could operate. The interference was Uncle Sam’s problem, and Mexico had no reason to fix it. As an incentive, NARBA gave Mexico its own clear channels on 800, 900, 1050, 1220, 1550, and 1570 kilocycles. The rest of North America agreed to keep these channels clear for Mexico. And in return, Mexico would limit its superpower stations to those channels.

The make room for the new channels, the broadcast band was expanded. It had previously run from 550 to 1500 kHz. The new band would extend from 540 to 1600 kHz, where it remained until 1990 when the top of the band was expanded to 1700 kHz.

As a result of the change, 777 of the country’s 862 standard broadcast stations got their orders to move. In most cases, the stations moved up the dial. Near the bottom of the dial, the move was generally up 10 kHz. Toward the top of the dial, most stations moved up 40 kHz. For example, WCCO in Minneapolis moved from 810 kHz to its present spot on the dial at 830.

Over the next few months, there was a great deal of activity. Transmitters would need some tuning during the early morning hours of March 29. But the most pressing matter was new crystals, and the change put a strain on the country’s crystal manufacturers. Since most stations had a spare, stations were encouraged to buy the spare from an existing station on their new frequency and to sell their own spare to a station moving in. For broadcast engineers, the night of March 28, 1941, would be a busy one.

Radio dealers could also take advantage of an opportunity for some business. It was estimated that there were ten million sets in use with pushbutton tuning. The September 15, 1940, issue of Broadcasting
pointed out that a service call to reset the buttons should cost about $2, although any listener “who can read and handle a screw-driver” should be able to do the job. As the months went on, many radio dealers sought to capitalize on the opportunity to visit customers’ homes, and perhaps sell a new set while they were there.

On this day 75 years ago, September 11, 1945, the FCC announced the new channels. The headline shown above is from the September 15, 1940, issue of Broadcasting.  It marked the start of a six-month frenzy to make the necessary changes.

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