Call signs in the United States

By international agreement, all call signs starting with the letters K, N, and W, as well as AAA-ALZ, are reserved exclusively for use in the United States.

Although most transmitters regulated by the Federal Communications Commission (FCC) are issued call signs for their official identification, the general public is most familiar with the ones used by radio and TV broadcasting stations.

However, there is a wide variety in how much emphasis stations give to their call signs; for some it is the primary way they establish public identity, while others largely ignore their call signs, considering a moniker or slogan to be more easily remembered by listeners (and those filling in diaries for the Nielsen Audio ratings measurement).

A few AM stations have had the same call letters for 100 years or more: KDKA in Pittsburgh, Pennsylvania, has been in continuous use since 1920, while WBZ in Boston, KYW in Philadelphia, and KWG in Stockton, California, all date back to 1921.

Thousands of radio and TV stations have been established, with a wide variety of reasons for choosing particular call signs.

In early 1923 the boundary was moved to its present location, the Mississippi River, in order to balance the populations in the two regions.

These include WBAP (Fort Worth, Texas), and WDAF-FM and WDAF-TV (Kansas City, Missouri), which inherited their calls from the original WDAF (now KFNZ).

[5] Another is KYW, which was originally launched in Chicago by the Westinghouse corporation in 1921 and later moved to Philadelphia: the call sign was temporarily transferred to Cleveland, where it was used from 1956 to 1965.

Over the next few years a small number of additional three-letter calls were authorized, with the final grant made in 1930 to WIS in Columbia, South Carolina.

[7] CBS Radio most prominently took advantage of this rule: resurrecting WJZ and adding WJZ-FM in Baltimore, as well as WBZ-FM in Boston.

This happened most recently in 2000, when KKHJ in Los Angeles was allowed to change back to KHJ, fourteen years after it had last used the three-letter call.

Telegraph operators generally used Morse code, and it was standard practice to assign identifying letters to individual offices located along a line.

Early radio stations (originally called "wireless telegraphy") commonly employed former telegraph operators, who continued the practice.

While there was no need for telegraph stations to coordinate their assignments, the great distance that radio signals traveled required international standardization.

As early as 1906, the Service Regulations adopted by the Berlin International Wireless Telegraph Convention specified that "calls shall be distinguishable from one another and each must be formed of a group of three letters".

[23] Despite this pronouncement, the United States would be slow to adopt this standard, largely because radio stations were unregulated at this time.

[24] The lack of coordination and duplication of call signs used by merchant ships was eventually determined to be a threat to maritime navigation.

A November 1911 report by Commissioner of Navigation Eugene Tyler Chamberlain[25] noted the lack of standards in the latest compilation of ship call letters,[26] and decided to take measures to rectify the situation, invoking his authority given "by the act of July 5, 1884" to assign "signal letters to American merchant vessels".

[27] No reason was given for splitting the ships into two groups, and this differed from the practice followed for the assignment of the earlier flag signal letters, which had been sequentially issued with no differentiation between the two regions.

[28] This new statute placed the licensing authority, including issuing call letters to both ship and land stations, under the control of the Bureau of Navigation in the Department of Commerce.

At this time the United States also started to participate with international regulations, and one of the first acts was to be formally assigned call letter blocks.

In the east, beginning in April 1922 calls were issued in alphabetical order with "A" fixed as the third letter, i.e. WAAB, WAAC, WAAD... WBAB, WBAC... etc.

Surviving stations from this era include WBAP (Fort Worth, Texas), WHAS (Louisville, Kentucky) and WTAM (Cleveland).

In April 1923 the pattern switched to calls centered on "B", including WBBM (Chicago), WCBM (Baltimore) and WMBD (Peoria, Illinois).

In late 1983, the FCC adopted a number of changes that greatly reduced its role in call letter assignments and disputes, including:[33] Call sign information for U.S. stations are set out in chapter I of the FCC rules, Title 47 (Telecommunication) of the Code of Federal Regulations (C.F.R.

Example of a radio station that prominently promotes its call letters. ( WOR , New York City)
Other stations downplay their call letters, in favor of an easily remembered slogan. This is also the standard practice in most other countries.( KGMZ-FM , San Francisco)
Historically, the west (blue) has normally had K calls and the east (red) has normally had W. The middle area (yellow) received W calls from 1912 until January 1923, when a boundary shift to the Mississippi River transferred it to K territory.
Map showing the numeral codes for amateur radio call signs in the United States. The region in which the operator was licensed determines the numeral.