Every licensed radio station carries an identifier called a call sign — a short string of letters that legally identifies the broadcaster. To most listeners, call signs are background noise. To regulators, engineers, and radio enthusiasts, they encode a surprisingly large amount of information about a station’s history and location.
The International Convention
Call sign prefixes are allocated internationally by the International Telecommunication Union (ITU). The first one or two letters indicate which country the licence was issued in. The United States uses K, W, N, and A. Canada uses CF, CJ, and VE ranges. The United Kingdom uses callsigns starting with G, M, and 2E for amateur licences, while broadcast stations have historically been identified differently — by their frequency and service name rather than a formal call sign in the American sense.
The US East-West Split
In the United States, a geographical rule dates back to the early days of regulated broadcasting. Stations east of the Mississippi River were generally assigned call signs beginning with W, while stations west of it received K-prefixed signs. There are notable exceptions — KDKA in Pittsburgh and KYW in Philadelphia predate the rule — but the pattern holds for most of the country’s thousands of licensed stations.
How Stations Choose Their Call Signs
After the prefix, broadcasters can often apply for specific letter combinations, subject to availability. Many stations choose combinations that reflect their brand, city, or format. A station calling itself “Rock 105” might apply for KROK. A station in Fort Worth might go for KFTW. Broadcasters sometimes pay significant sums to acquire the call signs of defunct stations when they carry strong brand recognition with audiences.
Frequency Modifiers
In the US, stations add an FM or AM suffix to their call sign, or LP (low power) for restricted licence holders. A station might be known on-air as WXYZ-FM to distinguish it from an AM station with the same base letters operating in the same market.
Other Countries
The UK, Australia, and most of Europe use different systems. British local radio stations were historically numbered rather than lettered — Radio 1, Radio Leicester — and commercial stations often operate under brand names that have no formal call sign equivalent. Australia assigns prefixes based on state and licence type. In practice, each regulator builds its own naming logic on top of the ITU framework.
Why It Still Matters
Call signs matter most to engineers filing technical reports, to the FCC and equivalent regulators maintaining licence databases, and to DXers who log distant station receptions. For everyday listeners, the call sign has largely been replaced by the brand name — but behind every radio brand is a licence number and a call sign that gives it legal standing to broadcast.