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38-525: The Liberty Broadcasting System (commonly referred to simply as Liberty ; sometimes referred to as LBS , Liberty Radio or the Liberty Radio Network ) was a U.S. radio network of the late 1940s and early 1950s founded by Gordon McLendon , which mainly broadcast live recreations of Major League Baseball games, by following the action via Western Union ticker reports. The sound effects were very realistic, and many listeners were not aware

76-460: A broadcast transmitter , a transmitter used in broadcasting , as in FM radio transmitter or television transmitter . This usage typically includes both the transmitter proper, the antenna, and often the building it is housed in. A transmitter can be a separate piece of electronic equipment, or an electrical circuit within another electronic device. A transmitter and a receiver combined in one unit

114-472: A frequency modulation (FM) transmitter, it is added by varying the radio signal's frequency slightly. Many other types of modulation are also used. The radio signal from the transmitter is applied to the antenna , which radiates the energy as radio waves. The antenna may be enclosed inside the case or attached to the outside of the transmitter, as in portable devices such as cell phones, walkie-talkies, and garage door openers . In more powerful transmitters,

152-429: A radio frequency signal which when applied to the antenna produces the radio waves, called the carrier signal . It combines the carrier with the modulation signal, a process called modulation . The information can be added to the carrier in several different ways, in different types of transmitters. In an amplitude modulation (AM) transmitter, the information is added to the radio signal by varying its amplitude . In

190-823: A radio transmitter or just transmitter (often abbreviated as XMTR or TX in technical documents) is an electronic device which produces radio waves with an antenna with the purpose of signal transmission up to a radio receiver . The transmitter itself generates a radio frequency alternating current , which is applied to the antenna . When excited by this alternating current, the antenna radiates radio waves. Transmitters are necessary component parts of all electronic devices that communicate by radio , such as radio (audio) and television broadcasting stations, cell phones , walkie-talkies , wireless computer networks , Bluetooth enabled devices, garage door openers , two-way radios in aircraft, ships, spacecraft, radar sets and navigational beacons. The term transmitter

228-467: A 75-mile range of league cities, were the one-two blow which ended the network. Since the baseball games were a major draw for both listeners and affiliates, the blackout was a disaster for the fledgling company, which had only posted modest profits during its first few years of operation. More than 100 stations left the network, and, faced with mounting debts, on May 16, 1952, the network ceased broadcasting. Liberty also broadcast NBA games from roughly,

266-434: A concept called trunking is commonly used to achieve better efficiency of radio spectrum use and provide very wide-ranging coverage with no switching of channels required by the mobile radio user as it roams throughout the system coverage. Trunking of two-way radio is identical to the concept used for cellular phone systems where each fixed and mobile radio is specifically identified to the system controller and its operation

304-518: A high voltage spark between two conductors. Beginning in 1895, Guglielmo Marconi developed the first practical radio communication systems using these transmitters, and radio began to be used commercially around 1900. Spark transmitters could not transmit audio (sound) and instead transmitted information by radiotelegraphy : the operator tapped on a telegraph key which turned the transmitter on-and-off to produce radio wave pulses spelling out text messages in telegraphic code, usually Morse code . At

342-413: A radio wave. A radio transmitter is an electronic circuit which transforms electric power from a power source, a battery or mains power, into a radio frequency alternating current to apply to the antenna, and the antenna radiates the energy from this current as radio waves. The transmitter also encodes information such as an audio or video signal into the radio frequency current to be carried by

380-586: A variety of license classes depending on use such as broadcast , marine radio , Airband , Amateur and are restricted to certain frequencies and power levels. A body called the International Telecommunication Union (ITU) allocates the frequency bands in the radio spectrum to various classes of users. In some classes, each transmitter is given a unique call sign consisting of a string of letters and numbers which must be used as an identifier in transmissions. The operator of

418-600: A variety of networks. Radio networks rose rapidly with the growth of regular broadcasting of radio to home listeners in the 1920s. This growth took various paths in different places. In Britain the BBC was developed with public funding , in the form of a broadcast receiver license , and a broadcasting monopoly in its early decades. In contrast, in the United States various competing commercial broadcasting networks arose funded by advertising revenue. In that instance,

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456-425: Is called a transceiver . The purpose of most transmitters is radio communication of information over a distance. The information is provided to the transmitter in the form of an electronic signal called the modulation signal, such as an audio (sound) signal from a microphone, a video (TV) signal from a video camera, or in wireless networking devices, a digital signal from a computer. The transmitter generates

494-540: Is switched by the controller. The broadcast type of radio network is a network system which distributes programming to multiple stations simultaneously, or slightly delayed, for the purpose of extending total coverage beyond the limits of a single broadcast signal. The resulting expanded audience for radio programming or information essentially applies the benefits of mass-production to the broadcasting enterprise. A radio network has two sales departments, one to package and sell programs to radio stations, and one to sell

532-411: Is usually limited to equipment that generates radio waves for communication purposes; or radiolocation , such as radar and navigational transmitters. Generators of radio waves for heating or industrial purposes, such as microwave ovens or diathermy equipment, are not usually called transmitters, even though they often have similar circuits. The term is popularly used more specifically to refer to

570-596: The 1950-51 through 1951-52 seasons . In the mid-2000s, a Spokane, Washington -based broadcaster, the Mutual Broadcasting System (not related to the former network ), began using the Mutual and Liberty names on its two stations, KTRW AM 970 Spokane; and KTAC FM 93.9 Ephrata, Washington . These stations have no connections with the original network, but present adult standards, nostalgia, and some Christian programming, using these names as part of

608-640: The UHF and microwave ranges, using new active devices such as the magnetron , klystron , and traveling wave tube . The invention of the transistor allowed the development in the 1960s of small portable transmitters such as wireless microphones , garage door openers and walkie-talkies . The development of the integrated circuit (IC) in the 1970s made possible the current proliferation of wireless devices , such as cell phones and Wi-Fi networks, in which integrated digital transmitters and receivers ( wireless modems ) in portable devices operate automatically, in

646-685: The 1920s. All these early technologies were replaced by vacuum tube transmitters in the 1920s, which used the feedback oscillator invented by Edwin Armstrong and Alexander Meissner around 1912, based on the Audion ( triode ) vacuum tube invented by Lee De Forest in 1906. Vacuum tube transmitters were inexpensive and produced continuous waves , and could be easily modulated to transmit audio (sound) using amplitude modulation (AM). This made AM radio broadcasting possible, which began in about 1920. Practical frequency modulation (FM) transmission

684-637: The Giants' network, McLendon's call is how most Americans heard the NL clincher, including Giant Bobby Thomson 's ninth-inning three-run homer into the left-field stands to win it for New York. Excerpts of the McLendon broadcast were highlighted in the 2001 HBO documentary Shot Heard 'Round the World . According to Time magazine articles of the era, McLendon only paid Major League Baseball $ 1,000.00 per year for

722-563: The US, these fall under Part 15 of the Federal Communications Commission (FCC) regulations. Although they can be operated without a license, these devices still generally must be type-approved before sale. The first primitive radio transmitters (called spark gap transmitters ) were built by German physicist Heinrich Hertz in 1887 during his pioneering investigations of radio waves. These generated radio waves by

760-610: The antenna may be located on top of a building or on a separate tower, and connected to the transmitter by a feed line , that is a transmission line . Electromagnetic waves are radiated by electric charges when they are accelerated . Radio waves , electromagnetic waves of radio frequency , are generated by time-varying electric currents , consisting of electrons flowing through a metal conductor called an antenna which are changing their velocity and thus accelerating. An alternating current flowing back and forth in an antenna will create an oscillating magnetic field around

798-508: The audience of those programs to advertisers. Most radio networks also produce much of their programming. Originally, radio networks owned some or all of the stations that broadcast the network's radio format programming. Presently however, there are many networks that do not own any stations and only produce and/or distribute programming. Similarly station ownership does not always indicate network affiliation. A company might own stations in several different markets and purchase programming from

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836-461: The background, to exchange data with wireless networks . The need to conserve bandwidth in the increasingly congested radio spectrum is driving the development of new types of transmitters such as spread spectrum , trunked radio systems and cognitive radio . A related trend has been an ongoing transition from analog to digital radio transmission methods. Digital modulation can have greater spectral efficiency than analog modulation ; that

874-681: The broadcasters were not announcing the action live. At that time some major league teams and almost all minor league baseball clubs used recreations of their road games as an economy measure. Founded in 1948, the network was mainly in Texas and the southwest but did have nine affiliates in Oregon , an outlet in Los Angeles , Seattle, and as of September 29, 1950, WHAV in Haverhill, Massachusetts. At one time, it had about 500 radio stations on

912-419: The conductor. The alternating voltage will also charge the ends of the conductor alternately positive and negative, creating an oscillating electric field around the conductor. If the frequency of the oscillations is high enough, in the radio frequency range above about 20 kHz, the oscillating coupled electric and magnetic fields will radiate away from the antenna into space as an electromagnetic wave,

950-584: The line, being second in size only to the Mutual Broadcasting System . It carried various types of programs (for instance, late night band remotes were another feature carried by Liberty) but McLendon, known as the "Old Scotchman", and his daily ball game recreations off the Western Union ticker provided the big money maker. The recreations used himself and future sportscasting stars such as Lindsey Nelson and Jerry Doggett . It

988-619: The nostalgia-style branding. Radio network The two-way type of radio network shares many of the same technologies and components as the broadcast-type radio network but is generally set up with fixed broadcast points ( transmitters ) with co-located receivers and mobile receivers/transmitters or transceivers . In this way both the fixed and mobile radio units can communicate with each other over broad geographic regions ranging in size from small single cities to entire states/provinces or countries. There are many ways in which multiple fixed transmit/receive sites can be interconnected to achieve

1026-421: The output frequency. Older designs used an oscillator at a lower frequency, which was multiplied by frequency multipliers to get a signal at the desired frequency. Modern designs more commonly use an oscillator at the operating frequency which is stabilized by phase locking to a very stable lower frequency reference, usually a crystal oscillator. Two radio transmitters in the same area that attempt to transmit on

1064-400: The radio waves. When they strike the antenna of a radio receiver , the waves excite similar (but less powerful) radio frequency currents in it. The radio receiver extracts the information from the received waves. A practical radio transmitter mainly consists of the following parts: In higher frequency transmitters, in the UHF and microwave range, free running oscillators are unstable at

1102-434: The range of coverage required by the jurisdiction or authority implementing the system: conventional wireless links in numerous frequency bands, fibre-optic links, or microwave links. In all of these cases the signals are typically backhauled to a central switch of some type where the radio message is processed and resent (repeated) to all transmitter sites where it is required to be heard. In contemporary two-way radio systems

1140-486: The receiver, these pulses were sometimes directly recorded on paper tapes, but more common was audible reception. The pulses were audible as beeps in the receiver's earphones, which were translated back to text by an operator who knew Morse code. These spark-gap transmitters were used during the first three decades of radio (1887–1917), called the wireless telegraphy or "spark" era. Because they generated damped waves , spark transmitters were electrically "noisy". Their energy

1178-420: The rights to broadcast the games, but in 1951, the leagues raised the price to $ 250,000.00 per year, and prohibited broadcasts in any city which had a minor league franchise and in the northeastern and midwestern United States . Sports were the lifeblood of Liberty. Restrictions on Major League Baseball broadcasts in minor league franchise areas, as well as bans on National Football League broadcasts within

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1216-537: The same corporation that owned or operated the network often manufactured and marketed the listener's radio. Major technical challenges to be overcome when distributing programs over long distances are maintaining signal quality and managing the number of switching/relay points in the signal chain . Early on, programs were sent to remote stations (either owned or affiliated) by various methods, including leased telephone lines, pre-recorded gramophone records and audio tape. The world's first all-radio, non-wireline network

1254-475: The same frequency will interfere with each other, causing garbled reception, so neither transmission may be received clearly. Interference with radio transmissions can not only have a large economic cost, it can be life-threatening (for example, in the case of interference with emergency communications or air traffic control ). For this reason, in most countries, use of transmitters is strictly controlled by law. Transmitters must be licensed by governments, under

1292-512: The transmitter usually must hold a government license, such as a general radiotelephone operator license , which is obtained by passing a test demonstrating adequate technical and legal knowledge of safe radio operation. Exceptions to the above regulations allow the unlicensed use of low-power short-range transmitters in consumer products such as cell phones , cordless telephones , wireless microphones , walkie-talkies , Wi-Fi and Bluetooth devices, garage door openers , and baby monitors . In

1330-669: Was a live, not recreated, game that provided McLendon and Liberty with their greatest career moment. The Scotchman himself was behind the Liberty mic at the Polo Grounds in New York on October 3, 1951, for the finale of the three-game National League play-off series between the New York Giants and Brooklyn Dodgers ). Radio was still the more popular nationwide medium then. With Russ Hodges ' famous radio call limited to

1368-581: Was claimed to be the Rural Radio Network , a group of six upstate New York FM stations that began operation in June 1948. Terrestrial microwave relay, a technology later introduced to link stations, has been largely supplanted by coaxial cable , fiber , and satellite , which usually offer superior cost-benefit ratios. Many early radio networks evolved into Television networks . Transmitter In electronics and telecommunications ,

1406-440: Was invented by Edwin Armstrong in 1933, who showed that it was less vulnerable to noise and static than AM. The first FM radio station was licensed in 1937. Experimental television transmission had been conducted by radio stations since the late 1920s, but practical television broadcasting didn't begin until the late 1930s. The development of radar during World War II motivated the evolution of high frequency transmitters in

1444-498: Was spread over a broad band of frequencies , creating radio noise which interfered with other transmitters. Damped wave emissions were banned by international law in 1934. Two short-lived competing transmitter technologies came into use after the turn of the century, which were the first continuous wave transmitters: the arc converter ( Poulsen arc ) in 1904 and the Alexanderson alternator around 1910, which were used into

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