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38-441: In the early 1940s, the U.S. military sought a high-powered radio transmitter capable of infallible voice communications over 100 miles (160 km), sturdy enough to work in all conditions, flexible enough to be able to cover a wide range of frequencies, self-powered and able to operate in motion or at fixed locations. The Hallicrafters HT-4 transmitter was chosen from units available from various U.S. radio manufacturers. The HT-4

76-457: 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

190-465: A Chicago suburb) in 1975, bringing non-military electronics production to an end. The Hallicrafters plant became Northrop Corporation's Defense Systems Division. The name and assets of Hallicrafters were traded over the following years, even though there were no products bearing the name. Since around 1988, the remaining assets and rights to the 'Hallicrafters' name and logos have been held by court-appointed trustees. (Note: one known 1980s product bearing

228-518: 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

266-413: 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

304-571: 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

342-718: 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

380-425: 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

418-558: Is less at higher frequencies. It was quartz crystal controlled, but could be used over a wide range of frequencies through use of the master-oscillator power amplifier. Modifications requested by the Signal Corps were performed by Hallicrafters' engineers working with U.S. Army technicians at Fort Monmouth . They made a new version of the HT-4, which was known as the BC-610 transmitter, a part of

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456-411: 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

494-1070: The Cold war era , the company took active participation in the Blue Streak (UK) and Atlas (U.S.) missile projects, helped to develop capability for many areas of electronic warfare and in missile field, including code translator data systems, ground support equipment , electronic countermeasures testing and antenna systems, infrared homing techniques, also company provided tactically deployed maintenance and technical support teams for mentioned missile systems, it supplied airborne target simulator system for Nike Zeus , electronic countermeasure systems for Douglas EB-66E and Boeing B-52 aircraft. Its R&D divisions (Manson Laboratories in Wilton, Connecticut , and Military Electronics Division in Chicago) developed penetration aids for intercontinental ballistic missiles and participated in various other classified programs. In

532-631: The SCR-299 mobile communications unit, and production began in 1942. General Dwight Eisenhower credited the SCR-299 in the reorganization of U.S. forces, which led to their victory against the Nazis at Kasserine Pass . The SCR-299 was also used in the Invasion of Sicily and later, Italy. A BC-610 transmitter was used by double agent Juan Pujol García during WWII as part of Operation Fortitude . Clear reception by

570-637: 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

608-676: 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

646-638: The Germans of messages transmitted by García, code name GARBO, were so crucial to the Allied deception that use of the relatively high-powered transmitter was deemed necessary. Over 25,000 units were produced by Hallicrafters and other allied companies. In 1944, a short subject film was produced by the Jam Handy Organization and sponsored by the Hallicrafters Company detailing how the HT-4 transmitter

684-534: The Hallicrafters name does exist - a 4-line plus intercom telephone . ) Hallicrafters equipment remains in use by collectors and vintage amateur radio enthusiasts. Some of the more well-known Hallicrafters equipment from the pre-war period include: Postwar Hallicrafters models include: Radio transmitters In electronics and telecommunications , a radio transmitter or just transmitter (often abbreviated as XMTR or TX in technical documents)

722-547: 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

798-461: 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

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836-540: The company to the Northrop Corporation and Halligan family involvement ended. Northrop ran the company until the early 1970s, but by this time, fierce Japanese competition was putting pressure on the US domestic electronics market. Northrop sold the company name (but kept the factory, by then located in Rolling Meadows , a Chicago suburb) in 1975, bringing non-military electronics production to an end, and turning

874-497: The concern of Silver-Marshall Inc. in 1933 and, with it, an RCA patent license as the most valuable asset. In order to meet their financial obligations, Hallicrafters produced radios for other manufacturers until they were financially able to begin production of their own line of communications receivers, starting with the SX-9 'Super Skyrider', in late 1935. By 1938, Hallicrafters was doing business in eighty-nine countries and manufactured

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,

950-413: The factory and was a block long. In addition to the main plant was a 3-story building of 72,000 square feet (6,700 m ) two blocks away, a 1-story coil plant of 12,000 square feet (1,100 m ) on Chicago's north side, and 150,000 square feet (14,000 m ) of production and storage space in three other buildings within a five-mile radius of the main plant. The company employed 2,500 people. During

988-529: The most popular sets in the USA. That year, the company began to produce radio transmitters . With the outbreak of World War II , the company prepared for wartime production, and was responsible for new designs and innovations for use by the U.S. troops; probably the best-known were the HT-4/ BC-610 and related equipment used in the military SCR-299 communications package. Production of Ham radio gear and other items

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

1064-644: The plant into Northrop Corporation's Defense Systems Division. William J. Halligan (1898–1992), founded Hallicrafters Company in Chicago in late 1932. Prior to this, he had been involved in radio parts sales for some years but decided the time was right for a handcrafted amateur radio receiver - the company name being a combination of Halli(gan) and (hand)crafters. The new company was located at 417 North State Street and immediately ran into patent difficulties when RCA decided to sue them for building radio sets without an RCA patent license. An opportunity came to purchase

1102-400: 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

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

1178-475: 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

BC-610 - Misplaced Pages Continue

1216-512: 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

1254-444: The words of its advertising sloganry , the company supported “America’s defense umbrella.” In 1966 Halligan sold the company to the Northrop Corporation and Halligan family involvement ended. Northrop ran the company until the early 1970s, but by this time, fierce Japanese competition was putting pressure on the US domestic electronics market. Northrop sold the company name (but kept the factory, by then located in Rolling Meadows ,

1292-504: Was adapted for military service and dramatizing its use by the U.S. military during World War II. The "A" through "I" models are the same basic unit with relatively minor component and cosmetic differences. Hallicrafters The Hallicrafters Company manufactured, marketed, and sold radio equipment, and to a lesser extent televisions and phonographs, beginning in 1932. The company was founded by William J. Halligan and based in Chicago, Illinois , United States. In 1966 Halligan sold

1330-421: Was designed for amateur radio use and had been commercially available for several years at a price of approximately $ 700, rivaling the cost of a car. It was considered compact and stable for its era and could deliver in excess of 300 watts of power for voice or MCW communications and 400 watts during Morse code operation. As was typical in physically large vacuum tube equipment, the manual cautions power output

1368-440: 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

1406-492: 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

1444-545: Was suspended until 1945. After the war, focus was again on consumer electronics, including radio phonographs, AM/FM receivers, clock radios and televisions . The boom years for Hallicrafters were from 1945 to 1963, during which the company produced equipment considered by many to be superbly designed, including the famous S-38 receiver, which received a cosmetic "makeover" by industrial designer Raymond Loewy . In 1952 Hallicrafters' main plant in Chicago housed general offices and

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