89-607: Artistic Media Partners (formerly University Broadcasting Company ) owns three radio stations in three markets in Indiana . It was formed on June 23, 1987. Founded in 1986 as Broadcast Management Inc. the company owned radio station WXCX-AM-FM in Columbus, Indiana along with WMDH-AM-FM in New Castle, Indiana. For a very short time in the 1990s the company also owned WWKI-FM in Kokomo which sold
178-570: A v {\displaystyle V_{\mathrm {av} }} results from the integral under the graph of a positive half-wave with the period duration of 2 3 π {\displaystyle {\frac {2}{3}}\pi } (from 30° to 150°): If the AC supply is fed via a transformer with a center tap, a rectifier circuit with improved harmonic performance can be obtained. This rectifier now requires six diodes, one connected to each end of each transformer secondary winding . This circuit has
267-780: A radio network that provides content in a common radio format , either in broadcast syndication or simulcast , or both. The encoding of a radio broadcast depends on whether it uses an analog or digital signal . Analog radio broadcasts use one of two types of radio wave modulation : amplitude modulation for AM radio , or frequency modulation for FM radio . Newer, digital radio stations transmit in several different digital audio standards, such as DAB ( Digital Audio Broadcasting ), HD radio , or DRM ( Digital Radio Mondiale ). The earliest radio stations were 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 ,
356-402: A three-phase supply . Rectifiers yield a unidirectional but pulsating direct current; half-wave rectifiers produce far more ripple than full-wave rectifiers, and much more filtering is needed to eliminate harmonics of the AC frequency from the output. The no-load output DC voltage of an ideal half-wave rectifier for a sinusoidal input voltage is: where: A full-wave rectifier converts
445-509: A " cat's whisker " of fine wire pressing on a crystal of galena (lead sulfide) to serve as a point-contact rectifier or "crystal detector". Rectifiers have many uses, but are often found serving as components of DC power supplies and high-voltage direct current power transmission systems. Rectification may serve in roles other than to generate direct current for use as a source of power. As noted, rectifiers can serve as detectors of radio signals. In gas heating systems flame rectification
534-427: A "radio station" as a government-licensed AM or FM station; an HD Radio (primary or multicast) station; an internet stream of an existing government-licensed station; one of the satellite radio channels from XM Satellite Radio or Sirius Satellite Radio ; or, potentially, a station that is not government licensed. AM stations were the earliest broadcasting stations to be developed. AM refers to amplitude modulation ,
623-494: A business opportunity to sell advertising or subscriptions to a broader audience. This is more efficient than broadcasting to a single country, because domestic entertainment programs and information gathered by domestic news staff can be cheaply repackaged for non-domestic audiences. Governments typically have different motivations for funding international broadcasting. One clear reason is for ideological, or propaganda reasons. Many government-owned stations portray their nation in
712-421: A circuit as a split rail power supply. A variant of this is to use two capacitors in series for the output smoothing on a bridge rectifier then place a switch between the midpoint of those capacitors and one of the AC input terminals. With the switch open, this circuit acts like a normal bridge rectifier. With the switch closed, it acts like a voltage doubling rectifier. In other words, this makes it easy to derive
801-460: A full-wave bridge circuit. Thyristors are commonly used in place of diodes to create a circuit that can regulate the output voltage. Many devices that provide direct current actually 'generate' three-phase AC. For example, an automobile alternator contains nine diodes, six of which function as a full-wave rectifier for battery charging. An uncontrolled three-phase, half-wave midpoint circuit requires three diodes, one connected to each phase. This
890-458: A kind of vacuum tube , was invented in 1904 by the English physicist John Ambrose Fleming . He developed a device that 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
979-543: A mode of broadcasting radio waves by varying the amplitude of the carrier signal in response to the amplitude of the signal to be transmitted. The medium-wave band is used worldwide for AM broadcasting. Europe also uses the long wave band. In response to the growing popularity of FM stereo radio stations in the late 1980s and early 1990s, some North American stations began broadcasting in AM stereo , though this never gained popularity and very few receivers were ever sold. The signal
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#17330937997361068-585: A national boundary. In other cases, a broadcast may be considered "pirate" due to the type of content, its transmission format, or the transmitting power (wattage) of the station, even if the transmission is not technically illegal (such as a webcast or an amateur radio transmission). Pirate radio stations are sometimes referred to as bootleg radio or clandestine stations. Digital radio broadcasting has emerged, first in Europe (the UK in 1995 and Germany in 1999), and later in
1157-426: A positive, non-threatening way. This could be to encourage business investment in or tourism to the nation. Another reason is to combat a negative image produced by other nations or internal dissidents, or insurgents. Radio RSA , the broadcasting arm of the apartheid South African government, is an example of this. A third reason is to promote the ideology of the broadcaster. For example, a program on Radio Moscow from
1246-414: A pulse-number of six, and in effect, can be thought of as a six-phase, half-wave circuit. Before solid state devices became available, the half-wave circuit, and the full-wave circuit using a center-tapped transformer, were very commonly used in industrial rectifiers using mercury-arc valves . This was because the three or six AC supply inputs could be fed to a corresponding number of anode electrodes on
1335-457: A series connection of two three-pulse center circuits. For low-power applications, double diodes in series, with the anode of the first diode connected to the cathode of the second, are manufactured as a single component for this purpose. Some commercially available double diodes have all four terminals available so the user can configure them for single-phase split supply use, half a bridge, or three-phase rectifier. For higher-power applications,
1424-457: A significant threat to the AM broadcasting industry. It required purchase of a special receiver. The frequencies used, 42 to 50 MHz, were not those used today. The change to the current frequencies, 88 to 108 MHz, began after the end of World War II and was to some extent imposed by AM broadcasters as an attempt to cripple what was by now realized to be a potentially serious threat. FM radio on
1513-426: A single discrete device is usually used for each of the six arms of the bridge. For the very highest powers, each arm of the bridge may consist of tens or hundreds of separate devices in parallel (where very high current is needed, for example in aluminium smelting ) or in series (where very high voltages are needed, for example in high-voltage direct current power transmission). The pulsating DC voltage results from
1602-436: A single tank, sharing a common cathode. With the advent of diodes and thyristors, these circuits have become less popular and the three-phase bridge circuit has become the most common circuit. For an uncontrolled three-phase bridge rectifier, six diodes are used, and the circuit again has a pulse number of six. For this reason, it is also commonly referred to as a six-pulse bridge . The B6 circuit can be seen simplified as
1691-408: A supply transformer that produces a 30° phase shift between the two bridges. This cancels many of the characteristic harmonics the six-pulse bridges produce. The 30-degree phase shift is usually achieved by using a transformer with two sets of secondary windings, one in star (wye) connection and one in delta connection. The simple half-wave rectifier can be built in two electrical configurations with
1780-499: A trailing boost stage or primary high voltage (HV) source, are used in HV laser power supplies, powering devices such as cathode-ray tubes (CRT) (like those used in CRT based television, radar and sonar displays), photon amplifying devices found in image intensifying and photo multiplier tubes (PMT), and magnetron based radio frequency (RF) devices used in radar transmitters and microwave ovens. Before
1869-436: A transformer without center tap), are needed. Single semiconductor diodes, double diodes with a common cathode or common anode, and four- or six- diode bridges are manufactured as single components. For single-phase AC, if the transformer is center-tapped, then two diodes back-to-back (cathode-to-cathode or anode-to-anode, depending on output polarity required) can form a full-wave rectifier. Twice as many turns are required on
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#17330937997361958-428: A voltage of roughly 320 V (±15%, approx.) DC from any 120 V or 230 V mains supply in the world, this can then be fed into a relatively simple switched-mode power supply . However, for a given desired ripple, the value of both capacitors must be twice the value of the single one required for a normal bridge rectifier; when the switch is closed each one must filter the output of a half-wave rectifier, and when
2047-426: Is all that is necessary for a narrowband FM signal. The 200 kHz bandwidth allowed room for ±75 kHz signal deviation from the assigned frequency, plus guard bands to reduce or eliminate adjacent channel interference. The larger bandwidth allows for broadcasting a 15 kHz bandwidth audio signal plus a 38 kHz stereo "subcarrier" —a piggyback signal that rides on the main signal. Additional unused capacity
2136-536: Is directly related to the DC current, and the above equation may be re-expressed as where: Although better than single-phase rectifiers or three-phase half-wave rectifiers, six-pulse rectifier circuits still produce considerable harmonic distortion on both the AC and DC connections. For very high-power rectifiers the twelve-pulse bridge connection is usually used. A twelve-pulse bridge consists of two six-pulse bridge circuits connected in series, with their AC connections fed from
2225-421: Is little affected by daily changes in the ionosphere, so broadcasters need not reduce power at night to avoid interference with other transmitters. FM refers to frequency modulation , and occurs on VHF airwaves in the frequency range of 88 to 108 MHz everywhere except Japan and Russia . Russia, like the former Soviet Union , uses 65.9 to 74 MHz frequencies in addition to the world standard. Japan uses
2314-454: Is operated symmetrically (as positive and negative supply voltage), the center point of the rectifier on the output side (or the so-called isolated reference potential) opposite the center point of the transformer (or the neutral conductor) has a potential difference in the form of a triangular common-mode voltage . For this reason, these two centers must never be connected to each other, otherwise short-circuit currents would flow. The ground of
2403-515: Is required—e.g., where variable output voltage is needed. High-power rectifiers, such as those used in high-voltage direct current power transmission, employ silicon semiconductor devices of various types. These are thyristors or other controlled switching solid-state switches, which effectively function as diodes to pass current in only one direction. Rectifier circuits may be single-phase or multi-phase. Most low power rectifiers for domestic equipment are single-phase, but three-phase rectification
2492-466: Is sometimes mandatory, such as in New Zealand, which uses 700 kHz spacing (previously 800 kHz). The improved fidelity made available was far in advance of the audio equipment of the 1940s, but wide interchannel spacing was chosen to take advantage of the noise-suppressing feature of wideband FM. Bandwidth of 200 kHz is not needed to accommodate an audio signal — 20 kHz to 30 kHz
2581-453: Is subject to interference from electrical storms ( lightning ) and other electromagnetic interference (EMI). One advantage of AM radio signal is that it can be detected (turned into sound) with simple equipment. If a signal is strong enough, not even a power source is needed; building an unpowered crystal radio receiver was a common childhood project in the early decades of AM broadcasting. AM broadcasts occur on North American airwaves in
2670-438: Is the automation of radio stations. Some stations now operate without direct human intervention by using entirely pre-recorded material sequenced by computer control. Rectifier A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification , since it "straightens"
2759-511: Is the broadcasting of audio (sound), sometimes with related metadata , by radio waves to radio receivers belonging to a public audience . In terrestrial radio broadcasting the radio waves are broadcast by a land-based radio station , while in satellite radio the radio waves are broadcast by a satellite in Earth orbit. To receive the content the listener must have a broadcast radio receiver ( radio ). Stations are often affiliated with
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2848-487: Is the simplest type of three-phase rectifier but suffers from relatively high harmonic distortion on both the AC and DC connections. This type of rectifier is said to have a pulse-number of three, since the output voltage on the DC side contains three distinct pulses per cycle of the grid frequency: [REDACTED] The peak values V p e a k {\displaystyle V_{\mathrm {peak} }} of this three-pulse DC voltage are calculated from
2937-447: Is used by some broadcasters to transmit utility functions such as background music for public areas, GPS auxiliary signals, or financial market data. The AM radio problem of interference at night was addressed in a different way. At the time FM was set up, the available frequencies were far higher in the spectrum than those used for AM radio - by a factor of approximately 100. Using these frequencies meant that even at far higher power,
3026-434: Is used to detect the presence of a flame. Depending on the type of alternating current supply and the arrangement of the rectifier circuit, the output voltage may require additional smoothing to produce a uniform steady voltage. Many applications of rectifiers, such as power supplies for radio, television and computer equipment, require a steady constant DC voltage (as would be produced by a battery ). In these applications
3115-423: Is very important for industrial applications and for the transmission of energy as DC (HVDC). In half-wave rectification of a single-phase supply, either the positive or negative half of the AC wave is passed, while the other half is blocked. Because only one half of the input waveform reaches the output, mean voltage is lower. Half-wave rectification requires a single diode in a single-phase supply , or three in
3204-554: The Marconi Research Centre 2MT at Writtle near Chelmsford, England . A famous broadcast from Marconi's New Street Works factory in Chelmsford was made by the famous soprano Dame Nellie Melba on June 15, 1920, where she sang two arias and her famous trill. She was the first artist of international renown to participate in direct radio broadcasts. The 2MT station began to broadcast regular entertainment in 1922. The BBC
3293-506: The medium wave frequency range of 525 to 1,705 kHz (known as the "standard broadcast band"). The band was expanded in the 1990s by adding nine channels from 1,605 to 1,705 kHz. Channels are spaced every 10 kHz in the Americas , and generally every 9 kHz everywhere else. AM transmissions cannot be ionospheric propagated during the day due to strong absorption in the D-layer of
3382-680: The 1960s to the 1980s was What is Communism? A second reason is to advance a nation's foreign policy interests and agenda by disseminating its views on international affairs or on the events in particular parts of the world. During the Cold War the American Radio Free Europe and Radio Liberty and Indian Radio AIR were founded to broadcast news from "behind the Iron Curtain " that was otherwise being censored and promote dissent and occasionally, to disseminate disinformation . Currently,
3471-582: The 76 to 90 MHz frequency band. Edwin Howard Armstrong invented wide-band FM radio in the early 1930s to overcome the problem of radio-frequency interference (RFI), which plagued AM radio reception. At the same time, greater fidelity was made possible by spacing stations further apart in the radio frequency spectrum. Instead of 10 kHz apart, as on the AM band in the US, FM channels are 200 kHz (0.2 MHz) apart. In other countries, greater spacing
3560-419: The 80/5Y3 (4 pin)/(octal) were popular examples of this configuration. Single-phase rectifiers are commonly used for power supplies for domestic equipment. However, for most industrial and high-power applications, three-phase rectifier circuits are the norm. As with single-phase rectifiers, three-phase rectifiers can take the form of a half-wave circuit, a full-wave circuit using a center-tapped transformer, or
3649-606: The RMS value V L N {\displaystyle V_{\mathrm {LN} }} of the input phase voltage (line to neutral voltage, 120 V in North America, 230 V within Europe at mains operation): V p e a k = 2 ⋅ V L N {\displaystyle V_{\mathrm {peak} }={\sqrt {2}}\cdot V_{\mathrm {LN} }} . The average no-load output voltage V
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3738-506: The U.S. Federal Communications Commission designates the 88–92 megahertz band in the U.S. for non-profit or educational programming, with advertising prohibited. In addition, formats change in popularity as time passes and technology improves. Early radio equipment only allowed program material to be broadcast in real time, known as live broadcasting. As technology for sound recording improved, an increasing proportion of broadcast programming used pre-recorded material. A current trend
3827-744: The US and Canada , just two services, XM Satellite Radio and Sirius Satellite Radio exist. Both XM and Sirius are owned by Sirius XM Satellite Radio , which was formed by the merger of XM and Sirius on July 29, 2008, whereas in Canada , XM Radio Canada and Sirius Canada remained separate companies until 2010. Worldspace in Africa and Asia, and MobaHO! in Japan and the ROK were two unsuccessful satellite radio operators which have gone out of business. Radio program formats differ by country, regulation, and markets. For instance,
3916-576: The US operates similar services aimed at Cuba ( Radio y Televisión Martí ) and the People's Republic of China , Vietnam , Laos and North Korea ( Radio Free Asia ). Besides ideological reasons, many stations are run by religious broadcasters and are used to provide religious education, religious music, or worship service programs. For example, Vatican Radio , established in 1931, broadcasts such programs. Another station, such as HCJB or Trans World Radio will carry brokered programming from evangelists. In
4005-681: The United States and Canada have chosen to use HD radio , an in-band on-channel system that puts digital broadcasts at frequencies adjacent to the analog broadcast. HD Radio is owned by a consortium of private companies that is called iBiquity . An international non-profit consortium Digital Radio Mondiale (DRM), has introduced the public domain DRM system, which is used by a relatively small number of broadcasters worldwide. Broadcasters in one country have several reasons to reach out to an audience in other countries. Commercial broadcasters may simply see
4094-568: The United States came from KDKA itself: the results of the Harding/Cox Presidential Election . The Montreal station that became CFCF began broadcast programming on May 20, 1920, and the Detroit station that became WWJ began program broadcasts beginning on August 20, 1920, although neither held a license at the time. In 1920, wireless broadcasts for entertainment began in the UK from
4183-626: The United States, France, the Netherlands, South Africa, and many other countries worldwide. The simplest system is named DAB Digital Radio, for Digital Audio Broadcasting , and uses the public domain EUREKA 147 (Band III) system. DAB is used mainly in the UK and South Africa. Germany and the Netherlands use the DAB and DAB+ systems, and France uses the L-Band system of DAB Digital Radio. The broadcasting regulators of
4272-709: The case of the Broadcasting Services of the Kingdom of Saudi Arabia , both governmental and religious programming is provided. Extensions of traditional radio-wave broadcasting for audio broadcasting in general include cable radio , local wire television networks , DTV radio , satellite radio , and Internet radio via streaming media on the Internet . The enormous entry costs of space-based satellite transmitters and restrictions on available radio spectrum licenses has restricted growth of Satellite radio broadcasts. In
4361-404: The circuit is operated asymmetrically (as a simple supply voltage with just one positive pole), both the positive and negative poles (or the isolated reference potential) are pulsating opposite the center (or the ground) of the input voltage analogously to the positive and negative waveforms of the phase voltages. However, the differences in the phase voltages result in the six-pulse DC voltage (over
4450-718: The college teamed up with WLOE in Boston to have students broadcast programs. By 1931, a majority of U.S. households owned at least one radio receiver . In line to ITU Radio Regulations (article1.61) each broadcasting station shall be classified by the service in which it operates permanently or temporarily. Broadcasting by radio takes several forms. These include AM and FM stations. There are several subtypes, namely commercial broadcasting , non-commercial educational (NCE) public broadcasting and non-profit varieties as well as community radio , student-run campus radio stations, and hospital radio stations can be found throughout
4539-653: The company and the Carver Corporation later cut the number of models produced before discontinuing production completely. As well as on the medium wave bands, amplitude modulation (AM) is also used on the shortwave and long wave bands. Shortwave is used largely for national broadcasters, international propaganda, or religious broadcasting organizations. Shortwave transmissions can have international or inter-continental range depending on atmospheric conditions. Long-wave AM broadcasting occurs in Europe, Asia, and Africa. The ground wave propagation at these frequencies
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#17330937997364628-483: The company during this time. When radio station sales became hot again in 2007, Artistic Media Partners sold WBTU-FM along with WSHY-FM to Oasis Radio who still owns both Fort Wayne stations to this day. In October 2016, Artistic Media Partners sells WBPE along with WYCM, WAZY and WSHY to Bill Christian and Mike Reed as part of planned to launch TV station WPBI-LD in Lafayette. Radio station Radio broadcasting
4717-467: The country at night. During the night, absorption largely disappears and permits signals to travel to much more distant locations via ionospheric reflections. However, fading of the signal can be severe at night. AM radio transmitters can transmit audio frequencies up to 15 kHz (now limited to 10 kHz in the US due to FCC rules designed to reduce interference), but most receivers are only capable of reproducing frequencies up to 5 kHz or less. At
4806-459: The differences of the instantaneous positive and negative phase voltages V L N {\displaystyle V_{\mathrm {LN} }} , phase-shifted by 30°: [REDACTED] The ideal, no-load average output voltage V a v {\displaystyle V_{\mathrm {av} }} of the B6 circuit results from the integral under the graph of a DC voltage pulse with
4895-415: The diodes pointing in opposite directions, one version connects the negative terminal of the output direct to the AC supply and the other connects the positive terminal of the output direct to the AC supply. By combining both of these with separate output smoothing it is possible to get an output voltage of nearly double the peak AC input voltage. This also provides a tap in the middle, which allows use of such
4984-450: The direction of current. Physically, rectifiers take a number of forms, including vacuum tube diodes , wet chemical cells, mercury-arc valves , stacks of copper and selenium oxide plates , semiconductor diodes , silicon-controlled rectifiers and other silicon-based semiconductor switches. Historically, even synchronous electromechanical switches and motor-generator sets have been used. Early radio receivers, called crystal radios , used
5073-486: The dominant medium, especially in cities. Because of its greater range, AM remained more common in rural environments. Pirate radio is illegal or non-regulated radio transmission. It is most commonly used to describe illegal broadcasting for entertainment or political purposes. Sometimes it is used for illegal two-way radio operation. Its history can be traced back to the unlicensed nature of the transmission, but historically there has been occasional use of sea vessels—fitting
5162-442: The duration of a period). The strict separation of the transformer center from the negative pole (otherwise short-circuit currents will flow) or a possible grounding of the negative pole when powered by an isolating transformer apply correspondingly to the symmetrical operation. The controlled three-phase bridge rectifier uses thyristors in place of diodes. The output voltage is reduced by the factor cos(α): Or, expressed in terms of
5251-507: The group to Wilks Broadcasting. The company changed names in 1987 as University Broadcasting Company when purchasing WAZY-AM-FM. In 1993 University Broadcasting retained the company name in Lafayette and its new market of Bloomington Indiana where they purchased WGCT-FM and WBWB-FM from Oasis Radio while the rest of the company was renamed under the Artistic Media Partners banner. In 1995, the entire company became Artistic Media and
5340-570: The highest and lowest sidebands is quite apparent to the listener. Such distortion occurs up to frequencies of approximately 50 MHz. Higher frequencies do not reflect from the ionosphere, nor from storm clouds. Moon reflections have been used in some experiments, but require impractical power levels. The original FM radio service in the U.S. was the Yankee Network , located in New England . Regular FM broadcasting began in 1939 but did not pose
5429-554: The introduction of semiconductor electronics, transformerless vacuum tube receivers powered directly from AC power sometimes used voltage doublers to generate roughly 300 VDC from a 100–120 V power line. Several ratios are used to quantify the function and performance of rectifiers or their output, including transformer utilization factor (TUF), conversion ratio ( η ), ripple factor, form factor, and peak factor. The two primary measures are DC voltage (or offset) and peak-peak ripple voltage, which are constituent components of
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#17330937997365518-450: The introduction of semiconductor electronics, vacuum tube rectifiers became obsolete, except for some enthusiasts of vacuum tube audio equipment . For power rectification from very low to very high current, semiconductor diodes of various types ( junction diodes , Schottky diodes , etc.) are widely used. Other devices that have control electrodes as well as acting as unidirectional current valves are used where more than simple rectification
5607-411: The ionosphere. In a crowded channel environment, this means that the power of regional channels which share a frequency must be reduced at night or directionally beamed in order to avoid interference, which reduces the potential nighttime audience. Some stations have frequencies unshared with other stations in North America; these are called clear-channel stations . Many of them can be heard across much of
5696-451: The line to line input voltage: where: The above equations are only valid when no current is drawn from the AC supply or in the theoretical case when the AC supply connections have no inductance. In practice, the supply inductance causes a reduction of DC output voltage with increasing load, typically in the range 10–20% at full load. The effect of supply inductance is to slow down the transfer process (called commutation) from one phase to
5785-402: The most common perception of a pirate—as broadcasting bases. Rules and regulations vary largely from country to country, but often the term pirate radio describes the unlicensed broadcast of FM radio, AM radio, or shortwave signals over a wide range. In some places, radio stations are legal where the signal is transmitted, but illegal where the signals are received—especially when the signals cross
5874-486: The new band had to begin from the ground floor. As a commercial venture, it remained a little-used audio enthusiasts' medium until the 1960s. The more prosperous AM stations, or their owners, acquired FM licenses and often broadcast the same programming on the FM station as on the AM station (" simulcasting "). The FCC limited this practice in the 1960s. By the 1980s, since almost all new radios included both AM and FM tuners, FM became
5963-420: The next. As result of this is that at each transition between a pair of devices, there is a period of overlap during which three (rather than two) devices in the bridge are conducting simultaneously. The overlap angle is usually referred to by the symbol μ (or u), and may be 20 30° at full load. With supply inductance taken into account, the output voltage of the rectifier is reduced to The overlap angle μ
6052-703: The output of the rectifier is smoothed by an electronic filter , which may be a capacitor , choke , or set of capacitors, chokes and resistors , possibly followed by a voltage regulator to produce a steady voltage. A device that performs the opposite function, that is converting DC to AC, is called an inverter . Before the development of silicon semiconductor rectifiers, vacuum tube thermionic diodes and copper oxide- or selenium-based metal rectifier stacks were used. The first vacuum tube diodes designed for rectifier application in power supply circuits were introduced in April 1915 by Saul Dushman of General Electric. With
6141-403: The output voltage. Conversion ratio (also called "rectification ratio", and confusingly, "efficiency") η is defined as the ratio of DC output power to the input power from the AC supply. Even with ideal rectifiers, the ratio is less than 100% because some of the output power is AC power rather than DC which manifests as ripple superimposed on the DC waveform. The ratio can be improved with
6230-419: The peak value of the phase input voltage V p e a k {\displaystyle V_{\mathrm {peak} }} and is calculated with V p e a k {\displaystyle V_{\mathrm {peak} }} minus half of the DC voltage at 60° of the period: The RMS value of the common-mode voltage is calculated from the form factor for triangular oscillations: If
6319-412: The period duration of 1 3 π {\displaystyle {\frac {1}{3}}\pi } (from 60° to 120°) with the peak value v ^ D C = 3 ⋅ V p e a k {\displaystyle {\hat {v}}_{\mathrm {DC} }={\sqrt {3}}\cdot V_{\mathrm {peak} }} : If the three-phase bridge rectifier
6408-455: The range of a given FM signal was much shorter; thus its market was more local than for AM radio. The reception range at night is the same as in the daytime. All FM broadcast transmissions are line-of-sight, and ionospheric bounce is not viable. The much larger bandwidths, compared to AM and SSB, are more susceptible to phase dispersion. Propagation speeds are fastest in the ionosphere at the lowest sideband frequency. The celerity difference between
6497-470: 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, an amplifier
6586-569: The sale of Columbus, Indiana and New Castle, Indiana stations took place. In 1996 Artistic Media Partners purchased a radio station in Attica Indiana moving it to nearby Lafayette and in 1998 purchased WNDU-AM-FM from Notre Dame and WEZV from Bomar Broadcasting to give them additional properties in South Bend and Lafayette Indiana, respectively. In 2002 Artistic Media Partners purchased radio stations in South Bend and Fort Wayne and continued to grow
6675-410: The same service area. This prevents the sideband power generated by two stations from interfering with each other. Bob Carver created an AM stereo tuner employing notch filtering that demonstrated that an AM broadcast can meet or exceed the 15 kHz baseband bandwidth allotted to FM stations without objectionable interference. After several years, the tuner was discontinued. Bob Carver had left
6764-521: The station was moved to the top of the Westinghouse factory building in East Pittsburgh, Pennsylvania . Westinghouse relaunched the station as KDKA on November 2, 1920, as the first commercially licensed radio station in the United States. The commercial broadcasting designation came from the type of broadcast license ; advertisements did not air until years later. The first licensed broadcast in
6853-485: The switch is open the two capacitors are connected in series with an equivalent value of half one of them. In a Cockcroft-Walton voltage multiplier , stages of capacitors and diodes are cascaded to amplify a low AC voltage to a high DC voltage. These circuits are capable of producing a DC output voltage potential up to about ten times the peak AC input voltage, in practice limited by current capacity and voltage regulation issues. Diode voltage multipliers, frequently used as
6942-455: The three-phase bridge rectifier in symmetrical operation is thus decoupled from the neutral conductor or the earth of the mains voltage. Powered by a transformer, earthing of the center point of the bridge is possible, provided that the secondary winding of the transformer is electrically isolated from the mains voltage and the star point of the secondary winding is not on earth. In this case, however, (negligible) leakage currents are flowing over
7031-408: The time that AM broadcasting began in the 1920s, this provided adequate fidelity for existing microphones, 78 rpm recordings, and loudspeakers. The fidelity of sound equipment subsequently improved considerably, but the receivers did not. Reducing the bandwidth of the receivers reduces the cost of manufacturing and makes them less prone to interference. AM stations are never assigned adjacent channels in
7120-420: The transformer secondary to obtain the same output voltage than for a bridge rectifier, but the power rating is unchanged. The average and RMS no-load output voltages of an ideal single-phase full-wave rectifier are: Very common double-diode rectifier vacuum tubes contained a single common cathode and two anodes inside a single envelope, achieving full-wave rectification with positive output. The 5U4 and
7209-459: The transformer windings. The common-mode voltage is formed out of the respective average values of the differences between the positive and negative phase voltages, which form the pulsating DC voltage. The peak value of the delta voltage v ^ c o m m o n − m o d e {\displaystyle {\hat {v}}_{\mathrm {common-mode} }} amounts 1 / 4 of
7298-414: The use of smoothing circuits which reduce the ripple and hence reduce the AC content of the output. Conversion ratio is reduced by losses in transformer windings and power dissipation in the rectifier element itself. This ratio is of little practical significance because a rectifier is almost always followed by a filter to increase DC voltage and reduce ripple. In some three-phase and multi-phase applications
7387-431: The whole of the input waveform to one of constant polarity (positive or negative) at its output. Mathematically, this corresponds to the absolute value function. Full-wave rectification converts both polarities of the input waveform to pulsating DC (direct current), and yields a higher average output voltage. Two diodes and a center-tapped transformer , or four diodes in a bridge configuration and any AC source (including
7476-557: The world. Many stations broadcast on shortwave bands using AM technology that can be received over thousands of miles (especially at night). For example, the BBC , VOA , VOR , and Deutsche Welle have transmitted via shortwave to Africa and Asia. These broadcasts are very sensitive to atmospheric conditions and solar activity. Nielsen Audio , formerly known as Arbitron, the United States –based company that reports on radio audiences, defines
7565-517: Was amalgamated in 1922 and received a Royal Charter in 1926, making it the first national broadcaster in the world, followed by Czechoslovak Radio and other European broadcasters in 1923. Radio Argentina began regularly scheduled transmissions from the Teatro Coliseo in Buenos Aires on August 27, 1920, making its own priority claim. The station got its license on November 19, 1923. The delay
7654-500: Was carrying audio by the next year. (Herrold's station eventually became KCBS ). In The Hague, the Netherlands, PCGG started broadcasting on November 6, 1919, making it arguably the first commercial broadcasting station. In 1916, Frank Conrad , an electrical engineer employed at the Westinghouse Electric Corporation , began broadcasting from his Wilkinsburg, Pennsylvania garage with the call letters 8XK. Later,
7743-456: Was due to the lack of official Argentine licensing procedures before that date. This station continued regular broadcasting of entertainment, and cultural fare for several decades. Radio in education soon followed, and colleges across the U.S. began adding radio broadcasting courses to their curricula. Curry College in Milton, Massachusetts introduced one of the first broadcasting majors in 1932 when
7832-531: Was quickly becoming viable. However, an early audio transmission that could be termed a broadcast may have occurred on Christmas Eve in 1906 by Reginald Fessenden , although this is disputed. While many early experimenters attempted to create systems similar to radiotelephone devices by which only two parties were meant to communicate, there were others who intended to transmit to larger audiences. Charles Herrold started broadcasting in California in 1909 and
7921-487: Was still required. The triode (mercury-vapor filled with a control grid) was created on March 4, 1906, by the Austrian Robert von Lieben ; independently, on October 25, 1906, Lee De Forest patented his three-element Audion . It was not put to practical use until 1912 when its amplifying ability became recognized by researchers. By about 1920, valve technology had matured to the point where radio broadcasting
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