Here's an interesting new nugget -
Note the mention of the "Clear Channel" frequencies, which established 1090 kHz as one of several clear channel designations.
March 29, 1941: Radio Stations Shuffle Frequencies on ‘Moving Day’
By Hugh Hart
March 29, 2011 |
7:00 am |
Categories: 20th century, Business and Industry, Communication
1941: Americans wake up on Saturday morning to discover that Jack Benny, Bob Hope and other radio stars of the day no longer occupy their familiar spots on the dial. In a massive shuffle, radio stations have engineered a game of musical chairs at 3 a.m. Eastern time, and 80 percent of North America’s AM frequencies are reassigned to new channels.
This so-called Moving Day resulted from the North American Radio Broadcasting Agreement, negotiated by the United States, Canada and Mexico. The pact extended the AM broadcast band from 1500 kHz to 1600 kHz (mostly called kilocycles rather than kilohertz in those days).
The reordering shifted most existing AM stations’ frequencies in order to create bandwidth for new clear-channel station allocations.
Designed to implement radio standardization throughout the Western Hemisphere, the agreement followed a futile 1939 attempt to squash Mexican “border blasters,” which for three decades would continue to overpower U.S. stations with extremely strong signals.
The agreement established clear-channel frequencies, which afford more protection from electromagnetic skywave interference at night, across the radio dial. The new broadcast order also reserved 1230, 1240, 1340, 1400, 1450 and 1490 kHz mainly for local stations.
Nations including the Bahamas, the Dominican Republic and Cuba later signed on to iterations of the NARBA plan.
The ponderously named “Regional Agreement for the Medium Frequency Broadcasting Service in Region 2″ superseded NARBA rules in 1981.