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Fast Facts:
Fast Facts:
Radio stations are assigned a call sign beginning with "K", if they are west of the Mississippi River, and beginning with "W" if they lie to the east. (Except for KDKA)
Radio stations are assigned a call sign beginning with "K", if they are west of the Mississippi River, and beginning with "W" if they lie to the east. (Except for KDKA)
However, there are some stations with only a 3-letter call sign, or stations with a "K" east of the Mississippi, or "W" on the west side.
These stations have been "grandfathered" meaning they are allowed to keep their current sign until the station's ownership changes hands.
Before 1922, three-letter call signs were arbitrary. In the 1920's, the FCC issued three-letter call signs based on slogans, such as WGN, which is owned by the Chicago Tribune, the "World's Greatest Newspaper", and WLS, then owned by Sears, Roebuck, the "World's Largest Store".
Hear the recreated audio of the first commercial radio broadcast, the Harding Cox Election results, voiced by Leo Rosenberg, radio’s first announcer: This is KDKA.
Plans were finalized with the Pittsburgh Post morning newspaper to acquire election returns by telephone. The election night broadcast, which began at 6 p.m. on Tuesday, Nov. 2, 1920, originated in a tiny, makeshift shack, atop one of the Westinghouse Electric buildings in East Pittsburgh.
The U.S. Department of Commerce, Bureau of Navigation, which served as the radio licensing agency of the day, issued the first radio license ever to KDKA, on Oct. 27, 1920. Many people ask if “KDKA” stands for anything — and the simple answer is: no. The call letters “KDKA” were assigned from a roster maintained to provide identification for ships and marine shore stations, these being the only regular services then in operation under formal license by the Federal Government. “KDKA” was simply the next set of call letters available on the roster.
FM radio works the same way that AM radio works. The difference is in how the carrier wave is modulated, or altered. With AM radio, the amplitude, or overall strength, of the signal is varied to incorporate the sound information. With FM, the frequency (the number of times each second that the current changes direction) of the carrier signal is varied.
FM signals have a great advantage over AM signals. Both signals are susceptible to slight changes in amplitude. With an AM broadcast, these changes result in static. With an FM broadcast, slight changes in amplitude don't matter -- since the audio signal is conveyed through changes in frequency, the FM receiver can just ignore changes in amplitude. The result: no static at all.
This is a lesson that demonstrates that AM radio signals can travel many 100's of miles at night. The student will listen to as many radio stations as possible obtaining the call signs and places of origin during the evening (after sunset) hours.
Use the AM and FM radio stations in Pittsburgh as a resource for this lesson. Click here.
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