The Great Frequency Change of 1941
At 3AM EST on March 29, 1941, something amazing happened as AM radio stations
all over America changed frequency. It was planned months in advance, and was
referred to as “Moving Day.”
Not one or two at a time. Most all of them. On one day. In fact, 802 of the 893 AM
stations in the USA changed on that night from one spot on the dial to another.
What was the reason for this? It was the NARBA (North American Radio Broadcast
Agreement). Negotiated among the US, Canada, Mexico, Cuba, the Dominican
Republic and Haiti, this agreement was the result of four years of negotiations, from
1937 to 1941
At that time, with the increase in broadcasting stations in the US and other countries,
more and more signals were beginning to interfere. One of the big problems in the
1930s had been the growth of high power stations in Mexico that were aimed at the USA
(such “bootleg” stations were outlawed under NARBA).
The goal of the NARBA was to coordinate the assignment of radio frequencies and
minimize interference, especially between countries.
Wherever it was possible, stations were left where they were, or moved to adjacent
channels. This minimized the financial burden on the stations, who wouldn’t have
to make major adjustments to transmitters, tuning networks and antennae.
However, the new assignment of “Clear Channels” to Canada, Mexico, and Cuba
required some moves as far as 40 kHz up the dial.
A big “win” for broadcasters was the extension of the Broadcast Band to 540 kHz on
the low side to an extra 100 kHz, the top was now 1600 kHz. Channels set aside for
local stations were 1230, 1240, 1340, 1400, 1450, and 1490 kHz.
In general, here is how the negotiators designed the moves:
91 stations from 550 kHz to 720 kHz were left unchanged.
21 stations from 740 kHz to 780 kHz were moved up 10 kHz.
22 stations from 790 kHz to 870 kHz were moved up 20 kHz.
633 stations from 880 kHz to 1450 kHz were moved up 30 kHz.
11 stations from 880 kHz to 1450 kHz were moved up 40 kHz.
11 stations from 1460 kHz to 1490 kHz were moved up 40 kHz.
63 stations on 1500 kHz were moved down 10 kHz.
41 stations were moved in other ways.
Here are some examples of the moves made by noted United States stations:
WWL 850 (870)
WLS 870 (890)
WJZ 760 (770) (now: WABC)
WABC 860 (880) (now: WCBS)
WFLA 940 (970)
WINS 1180 (1000) (later to 1010)
WQXR 1550 (1560) (now: WQEW)
NARBA was the controlling agreement between nations in the Western Hemisphere until
1981 when a Regional Agreement for the Medium Frequency Broadcasting Service in Region 2 was put into operation.