North American Regional Broadcasting Agreement

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The North American Regional Broadcasting Agreement, usually referred to as NARBA, is a treaty that took effect in March 1941 and set out an international bandplan and interference rules for mediumwave AM broadcasting in North America. NARBA accommodated much of the U.S. bandplan of 1928, with accommodation to Canada and Mexico.

Although mostly replaced by other agreements in the 1980s, the basic bandplan of NARBA has remained to the present day. Among its major features were the extension of the broadcast band from its former limits of 550 to 1500 kc. to its 1941 limits of 540 to 1600 kc. to its present limits of 540 to 1700 kHz and the shift of most existing AM stations' frequencies to make room for additional clear-channel station allocations for Canada and Mexico.[1]

The agreement eventually governed AM band use in the United States, Canada, Mexico, Cuba, the Dominican Republic, and Haiti.[citation needed] In accordance with the treaty, clear channel frequencies were set aside across, roughly, the lower half of the radio dial (with a few regional channels thrown in), and regional channels across, roughly, the upper half of the radio dial (with a few clear channels thrown in).

The replacement 1230, 1240, 1340, 1400, 1450, and 1490 kc. local channels (formerly 1200, 1210, 1310, 1370, 1420, and 1500 kc.) were reserved for local channel stations (these are regional channels if located outside the North American continent, in which case regional channel stations could be allocated to those channels).

The agreement also officially reduced the "same market" minimum channel spacing from 50 to 40 kc., although Mexico elected to enforce a 30 kc. "same market" channel spacing, unless such reduced spacing was in conflict with an abutting nation's "border zone" allocations, in which case 40 kc. was enforced.

It required that most existing AM stations change frequencies according to a well-defined "table", which attempted to conserve the electrical height of the extant vertical radiator(s) and thereby controlling possible interference, while resulting in a wholesale yet predictable shuffling of radio station frequencies.

There were about 100 stations which were not changed according to the "table" and in these cases every attempt was made to move an existing clear channel station to a possibly distant clear channel (and not to a regional channel) and to move an existing regional channel station to a possibly distant regional channel (and not to a clear channel); local channel stations were not moved outside of the "table" as the "table" accommodated every eventuality, including even the cases of stations on the two highest local channels, 1420 and 1500 kc., an 80 kc. spacing, as the new "same market" spacing of 40 kc. accommodated this case (these moved stations would be allocated to 1450 and 1490 kc., a 40 kc. spacing).

At the same time, this spacing protected the international medium-wave distress frequency, 500 kc., which must be protected by all stations everywhere.


Although a 1933 conference on the subject failed, a 1937 North American Radio Conference in Havana agreed on the principles for frequency allocations. In late 1937, the Inter-American Radio Conference agreed to protect U.S. AM stations by eliminating Mexican border blasters. In mid-1938, the United States Senate ratified the Havana treaty and asked for it to take effect a year after the treaty was ratified by three of the four participating countries of Canada, Cuba, Mexico, and the U.S. At first, the Mexican Senate refused to ratify. Nevertheless, the U.S. and Canada completed a frequency agreement in 1939, based on the Havana Treaty, and Mexico ratified the NARBA treaty at the end of the year.[2]

In the United States, the new frequencies took effect at 3A.M. Eastern[1] on March 29, 1941.[2]

A three-year NARBA agreement in 1946 gave Cuba five U.S. clear channel allocations. A November 1950 NARBA agreement, signed by the Bahamas, Canada, Cuba, the Dominican Republic, Jamaica and the U.S., gave Cuba the right to use six, and Jamaica two, U.S. clear channel allocations.[2]

Frequency changes[edit]

Among the most significant changes were:

Old Freq.
Station(s) Moved
New Freq.
new Canadian clear 540 allocated to CBK later shared with Mexico
550-680 all unchanged 550-680
690 all, except CFRB unchanged 690 Canadian clear
CFRB 860
700-720 all unchanged 700-720
730 all, except CFPL unchanged 730
CFPL 1570
new Canadian clear 740 allocated to CBL which moved from 840
740-780 all up 10 750-790
new Mexican clear 800 allocated to XELO
790-830 all up 20 810-850
840 CBL 740
new Canadian clear 860 allocated to CFRB
850-870 all up 20 870-890
new Mexican clear 900
880-970 all up 30 910-1000
new Canadian clear 1010 allocated to CFCN (now CBR) which moved from 1030
980 KDKA up 40 1020
990 WBZ up 40 1030
1000 WHO up 40 1040
1010 WHN (now WEPN) up 40 1050
KQW (now KCBS) 740
WNAD (now KWPN) 640
WNOX (now WNML) 990
new Mexican clear 1050
1020 KYW up 40 1060
1030 CFCN (now CBR) down 20 1010
CKLW 800
1040 WTIC
up 40 1080
1050 KNX up 20 1070 shared with CBA (now silent)
1060 WBAL up 30 1090
WJAG up 40 1110 this was later traded for 780 with KFAB
1070–1150 all up 30 1100–1180
1160 WOWO up 30 1190
WWVA up 10 1170
1170 WCAU (now WPHT) up 40 1210
1180 KEX up 10 1190
KOB (now KKOB) 770
WDGY (now KFAN) down 50 1130
WINS 1010
1190 WOAI up 10 1200
WSAZ (now WRVC) 930
WATR 1320
new Mexican clear 1220
1200–1450 all up 30 1230–1480
1460 KSTP
up 40 1500
1470 KGA
up 40 1510
1480 KOMA
up 40 1520
1490 KFBK
up 40 1530
1500 all down 10 1490
1510 CKCR (later CHYM) down 20 1490
new Bahamian clear 1540 allocated to ZNS-1 shared with KXEL
new Canadian/Mexican clear 1550 allocated to CBE (now CBEF) and XERUV, both stations "grandfathered" at 10 kW
1530 W1XBS to WBRY
(later WTBY, then WQQW; now dark)
up 60 1590 Since 1934 U.S. frequencies above 1500 had been
allocated only to four experimental stations that
broadcast with a signal 20 kHz wide for "high fidelity."
The stations were converted to regular broadcasting
(and regular call signs) with the NARBA frequency
(now dark)
up 20 1550
1550 W2XR to WQXR
(now WFME)
up 10 1560
(now KNZR)
up 10 1560
new Mexican clear 1570 allocated to XERF
new Canadian clear 1580 allocated to CBJ
new regional channels 1590-1600 1590-1700 after "Rio"

Current status[edit]

NARBA has been substantially superseded by the Regional Agreement for the Medium Frequency Broadcasting Service in Region 2 (which was signed in Rio de Janeiro in 1981 and took effect on 1 July 1983 at 08:00 UTC). The interference protection criteria in the Rio Agreement are significantly different from NARBA, particularly in that the concept of clear-channel stations is eliminated. NARBA countries the Bahamas, Canada, Mexico and the United States are also signatories of the Rio Agreement. In that agreement, the Bahamas and Canada also declared their intent to denounce NARBA.[3] However, NARBA still officially remains in effect between the Bahamas, Dominican Republic, and United States[4] because those countries have not formally abrogated NARBA.[5] The United States also has bilaterial agreements with Canada and with Mexico: the Agreement Between the Government of the United States of America and the Government of Canada Relating to the AM Broadcasting Service in the Medium Frequency Band (1984) and the Agreement Between the Government of the United States of America and the Government of the United Mexican States Relating to the AM Broadcasting Service in the Medium Frequency Band (1986).[5]

See also[edit]

External links[edit]


  1. ^ a b Miller, Jeff (2010-05-01). "A Chronology of AM Radio Broadcasting 1900-1960". Retrieved 2010-05-11. 
  2. ^ a b c "Broadcasting Special Issue". Broadcasting. 1970-11-02. Retrieved 2010-05-11. 
  3. ^ Regional Administrative MF Broadcasting Conference (Region 2), Rio de Janeiro, 1981 (PDF). ISBN 92-61-01311-2. Retrieved 2010-05-11.  Bahamas and Canada announce their intent to renounce NARBA in Final Protocol statement No. 4 on page 88.
  4. ^ 47 C.F.R. 73.1650. Retrieved 2010-05-11.
  5. ^ a b "1997 Report on International Negotiations and Notifications Concerning Radio Services". Washington, D.C.: Federal Communications Commission (Planning & Negotiations Division, International Bureau). July 1997. Retrieved 2010-05-11.