North American Radio Broadcasting Agreement

The North American Radio 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 kHz to 1500 kHz to its 1941 limits of 540 kHz to 1600 kHz to its present limits of 540 kHz 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.

The agreement eventually governed AM band use in the United States, Canada, Mexico, Cuba, the Dominican Republic, and Haiti. 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 kHz local channels (formerly 1200, 1210, 1310, 1370, 1420, and 1500 kHz) 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 kHz to 40 kHz, although Mexico elected to enforce a 30 kHz "same market" channel spacing, unless such reduced spacing was in conflict with an abutting nation's "border zone" allocations, in which case 40 kHz 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 dial positions.

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 kHz, an 80 kHz spacing, as the new "same market" spacing of 40 kHz accommodated this case (these moved stations would be allocated to 1450 and 1490 kHz, a 40 kHz spacing).

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

Agreement

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.

In the United States, the new frequencies took effect at 3:00 a.m. Eastern on March 29, 1941.

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.

Frequency changes

See also: Canadian allocations changes under NARBA

Among the most significant changes were:

Old Freq. (kHz)	Station(s)	Moved (kHz)	New Freq. (kHz)	Notes
—	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
980	KDKA	up 40	1020
990	WBZ	up 40	1030
1000	WHO	up 40	1040
1010	KQW (now KCBS)		740	KQW did not move until 1947
—	new Mexican clear		1050
1020	KYW	up 40	1060
1030	CFCN (now CBR)	down 20	1010
	CKLW		800
1040	WTIC KRLD KWJJ (now KFXX)	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 WJSV (now WFED)	up 40	1500
1470	KGA WLAC WMEX	up 40	1510
1480	KOMA WKBW (now WWKB)	up 40	1520
1490	KFBK WCKY	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 move.
	W9XBY to KITE (now dark)	up 20	1550
1550	W2XR to WQXR (now WFME)	up 10	1560
	W6XAI to KPMC (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

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. However, NARBA still officially remains in effect between the Bahamas, Dominican Republic, and United States because those countries have not formally abrogated NARBA. 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).

See also

• Canadian allocations changes under NARBA
• Clear-channel station — which includes a listing of present North American clear-channel stations
• Geneva Frequency Plan of 1975 — a similar agreement concerning the rest of the world

External links

• More on clear, regional and local AM Channels in Canada Mexico and USA
• FCC information on AM station classes
• "Building the Broadcast Band" the development of the 520–1700 kHz Medium wave (AM) band
• "Behind the Clear-Channel Matter" history of clear-channel AM radio stations