Washington, D.C.

Washington, D.C., formally the District of Columbia and commonly referred to as "Washington", "the District", or simply "D.C.", is the capital of the United States. The signing of the Residence Act on July 16, 1790, approved the creation of a capital district located along the Potomac River on the country's East Coast. The U.S. Constitution provided for a federal district under the exclusive jurisdiction of the Congress and the District is therefore not a part of any U.S. state.

The states of Maryland and Virginia each donated land to form the federal district, which included the pre-existing settlements of Georgetown and Alexandria. Named in honor of George Washington, the City of Washington was founded in 1791 to serve as the new national capital. In 1846, Congress returned the land originally ceded by Virginia; in 1871, it created a single municipal government for the remaining portion of the District.

Washington had an estimated population of 672,228 as of July 2015. Commuters from the surrounding Maryland and Virginia suburbs raise the city's population to more than one million during the workweek. The Washington metropolitan area, of which the District is a part, has a population of over 6 million, the seventh-largest metropolitan statistical area in the country.

Radio

Radio is the use of radio waves is to carry information, such as sound, by systematically modulating some property of electromagnetic energy waves transmitted through space, such as their amplitude, frequency, phase, or pulse width. When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form.

Radio systems need a transmitter to modulate (change) some property of the energy produced to impress a signal on it, for example using amplitude modulation or angle modulation (which can be frequency modulation or phase modulation). Radio systems also need an antenna to convert electric currents into radio waves, and vice versa. An antenna can be used for both transmitting and receiving. The electrical resonance of tuned circuits in radios allow individual stations to be selected. The electromagnetic wave is intercepted by a tuned receiving antenna. A radio receiver receives its input from an antenna and converts it into a form usable for the consumer, such as sound, pictures, digital data, measurement values, navigational positions, etc. Radio frequencies occupy the range from a 3 kHz to 300 GHz, although commercially important uses of radio use only a small part of this spectrum.

Washington

Washington commonly refers to:

Washington may also refer to:

Geography

United States

Cities and communities

Other features

Outside the United States

Music hall

Music hall is a type of British theatrical entertainment that was popular from the early Victorian era circa 1850 and lasting until 1960. It involved a mixture of popular songs, comedy, speciality acts and variety entertainment. The term is derived from a type of theatre or venue in which such entertainment took place. British music hall was similar to American vaudeville, featuring rousing songs and comic acts, while in the United Kingdom the term "vaudeville"' referred to more working-class types of entertainment that would have been termed "burlesque" in America.

Originating in saloon bars within public houses during the 1830s, music hall entertainment became increasingly popular with audiences, so much so, that during the 1850s, the public houses were demolished and specialized music hall theatres developed in their place. These theatres were designed chiefly so people could consume food and alcohol and smoke tobacco in the auditorium while the entertainment took place. This differed somewhat from the conventional type of theatre, which until then seated the audience in stalls with a separate bar-room. Major music halls, were based around London and included Early music halls like the Canterbury Music Hall in Lambeth, Wilton's Music Hall in Tower Hamlets and The Middlesex, in Drury Lane, otherwise known as the Old Mo.

Radio broadcasting

Radio broadcasting is a unidirectional wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both. Audio broadcasting also can be done via cable radio, local wire television networks, satellite radio, and internet radio via streaming media on the Internet. The signal types can be either analog audio or digital audio.

In 2009, there were 3,494 radio broadcasting stations in the United States.

History

The earliest radio stations were simply radiotelegraphy systems and did not carry audio. For audio broadcasts to be possible electronic detection and amplification devices had to be incorporated.

The thermionic valve was invented in 1904 by the English physicist John Ambrose Fleming. He developed a device he called an "oscillation valve" (because it passes current in only one direction). The heated filament, or cathode, was capable of thermionic emission of electrons that would flow to the plate (or anode) when it was at a higher voltage. Electrons, however, could not pass in the reverse direction because the plate was not heated and thus not capable of thermionic emission of electrons. Later known as the Fleming valve, it could be used as a rectifier of alternating current and as a radio wave detector. This greatly improved the crystal set which rectified the radio signal using an early solid-state diode based on a crystal and a so-called cat's whisker. However, what was still required was an amplifier.