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A wireless microphone, as the name implies, is a microphone without a physical cable connecting it directly to the sound recording or amplifying equipment with which it is associated. Image File history File links This is a lossless scalable vector image. ... “Microphones” redirects here. ...

Various individuals and organisations claim to be the inventors of the Wireless Microphone.

John F. Stephens developed an FM wireless microphone for a Navy musical show in 1951 on the Memphis Naval base. Each of the principal players/singers had their own microphone/transmitter. Subsequently, the Secret Service had Stephens modify his invention to be used in government "bugging" operations. In the '60s, Stephens marketed his more famous capstanless multitrack recorder/reproducers.

Shure Incorporated claim that their "Vagabond" system from 1953 was the first. Shure Incorporated is a consumer and professional audio electronics corporation. ...

In 1957 German audio equipment manufacturer Sennheiser, at that time called Lab W, working with the German broadcaster Norddeutscher Rundfunk (NDR) exhibited a wireless microphone system. From 1958 the system was marketed through Telefunken under the name of Mikroport. The Sennheiser Logo Sennheiser is a German pro audio company. ... Current logo of Norddeutscher Rundfunk. ...

Another German equipment manufacturer, Beyerdynamic, claim that first wireless microphone, was invented by Hung C. Lin. Called the "transistophone", it went into production in 1962. It is claimed that the first time a wireless microphone was used to record sound during filming of a motion picture was on Rex Harrison in the 1964 film My Fair Lady. Hung Chang Lin (born August 8, 1919) is an Chinese-American Inventor who currently resides in Maryland. ... Sir Reginald Carey Rex Harrison, KBE (5 March 1908 – 2 June 1990) was an Academy Award- and Tony Award-winning English theatre and film actor. ... My Fair Lady is an Academy Award-winning 1964 film adaptation of the stage musical, My Fair Lady, based in turn on the play Pygmalion by George Bernard Shaw. ...

More commonly known as a Radio Microphone, there are many different standards, frequencies and transmission technologies used to replace the microphone's cable connection and make it into a wireless microphone. They can transmit, for example, in radiowaves using UHF or VHF frequencies, FM, AM, or various digital modulation schemes. Some low cost models use infrared light. Infrared microphones require a direct line of sight between the microphone and the receiver, while costlier radio frequency models do not. “Microphones” redirects here. ... This article is about the radio frequency. ... Very high frequency (VHF) is the radio frequency range from 30 MHz (wavelength 10 m) to 300 MHz (wavelength 1 m). ... In telecommunications, frequency modulation (FM) conveys information over a carrier wave by varying its frequency. ... Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. ... For other uses, see Infrared (disambiguation). ...

Some models operate on a single fixed frequency, but the more advanced models operate on a user selectable frequency to avoid interference, and allow the use of several microphones at the same time.

Advantages and disadvantages

Wireless microphones awaiting pickup by performers in a musical.

The advantages are: Image File history File linksMetadata Download high-resolution version (1920x2560, 1070 KB) Radio mics waiting for pick up by actors in a green room. ... Image File history File linksMetadata Download high-resolution version (1920x2560, 1070 KB) Radio mics waiting for pick up by actors in a green room. ...

• The freedom of movement for the artist or speaker.
• Avoidance of cabling problems that are common on wired microphones, caused by constant moving and stressing the cables.

The disadvantages are:

• Sometimes limited range (a wired balanced XLR microphone can run up to 300 ft or 100 meters). Some wireless systems have a shorter range, while more expensive models can exceed that distance.
• Possible interference with other radio equipment or other microphones, though models with many frequency-synthesized switch-selectable channels are now plentiful and cost effective.
• Limited operation time due to battery life.
• Noise or dead spots (places where it doesn't work, in non-diversity systems)
• Limited number of operating microphones at the same time and place, due to the limited number of radio channels (frequencies).

“Microphones” redirects here. ...

Techniques

The professional models transmit in VHF or UHF radio frequency and have 'true' diversity reception (two separate receiver modules each with its own antenna), which eliminates dead spots (caused by phase cancellation) and the effects caused by the reflection of the radiowaves on walls and surfaces in general. (See antenna diversity). In telecommunications, diversity reception refers to a method for improving reception of a transmitted signal, by receiving and processing multiple versions of the same transmitted signal. ... Antenna Diversity is a transmission technique in which the information-carrying signal is transmitted along different propagation paths. ...

Another technique used to improve the sound quality (actually, to improve the dynamic range), is companding. A waveform before and after the compression stage of non-linear companding In telecommunication, signal processing, and thermodynamics, companding (occasionally called compansion) is a method of reducing the effects of a channel with limited dynamic range. ...

Some models have adjustable gain on the microphone itself, to be able to accommodate different level sources, such as loud instruments or quiet voices. Adjustable gain helps to avoid clipping. In electronics, gain is usually taken as the mean ratio of the signal output of a system to the signal input of the system. ... The picture shows an oscilloscope screen of an amplifier clipping. ...

Some models have adjustable squelch, which silences the output when the receiver does not get a strong or quality signal from the microphone, instead of reproducing noise. When squelch is adjusted, the threshold of the signal quality or level is adjusted. In telecommunications, squelch is a circuit function that acts to suppress the audio (or video) output of a receiver in the absence of a sufficiently strong desired input signal. ...

Products

Shure, Sennheiser, Lectrosonics, Samson Technologies, AKG Acoustics and Audio-Technica are all major manufacturers of wireless microphone systems. They have made significant advances in dealing with many of the disadvantages listed above. For example, while there is a limited band in which the microphones may operate, the new UHF-R series from Shure can have up to 108 different microphones operating simultaneously. However, allowing more microphones to operate at the same time increases the cost. That is one reason for such large price differences between different series of wireless systems. The audio quality has also greatly improved as newer systems have become available. Shure Incorporated is a consumer and professional audio electronics corporation. ... The Sennheiser Logo Sennheiser is a German pro audio company. ... Samson Technologies is a largely respected and successful audio production conglomerate that is made up of the following companies or elements: Samson Wireless Samson Audio Hartke Systems Zoom Armoured Cable External links Official Samson Website Category: Audio companies ... AKG Acoustics (originally ) is an Austrian manufacturer of audio electronics and accessories for professional and consumer markets. ... Audio-Technica, established in 1962 and headquartered in Tokyo, Japan, is a company that designs and manufactures microphones, headphones and other audio equipment. ...

Generally they are two wireless microphone types: handheld and bodypack:

• Handheld is like a normal microphone, but it has a bigger body to accommodate the transmitter and battery pack.
• Bodypack is a small box housing the transmitter and battery pack, but not the microphone itself. It is attachable to belt or elsewhere and has a wire going to headset, lavalier microphone or a guitar.

Several manufacturers including Sennheiser, AKG, Lectrosonics and Zaxcom offer a plug-on transmitter for existing wired microphones, which plugs into the XLR output of the microphone and transmits to the manufacturer's standard receiver. This offers many of the benefits of an integrated system, and also allows microphone types (of which there may be no wireless equivalent) to be used without a cable. For example a television, or film, sound recordist may use a plug-on transmitter to enable wireless transmission of a highly directional rifle (or "shotgun") microphone, removing the safety hazard of a cable connection and permitting the recordist greater freedom to follow the action. Plug-in transmitters also allow the conversion of vintage microphone types to cordless operation. This is useful where a vintage microphone is needed for visual or other artistic reasons, and the absence of cables allows for rapid scene changes and reducing trip hazards. In some cases these plug-on transmitters can also provide 48 volt phantom power allowing the use of condenser microphone types. DC-DC converter circuitry within the transmitter is used to multiply the battery supply, which may be three volts or less, up to the required 48 volts. Antenna tower of Crystal Palace transmitter, London A transmitter (sometimes abbreviated XMTR) is an electronic device which with the aid of an antenna propagates an electromagnetic signal such as radio, television, or other telecommunications. ... Phantom power (labeled as +48 V on some audio equipment) is a method that sends an electrical current through microphone cables. ... A microphone with a cord A microphone, sometimes called a mic (pronounced mike), is a device that converts sound into an electrical signal. ... Headquarter in Taiwan, we are the professional manufacturer of low-power DC/DC converter and Isolation Amplifier Modules. ...

There are three main types of receiver, available in two main types of housing. True Diversity receivers have two radio modules and two antennas. Diversity receivers have one radio module and two antennas. Non-diversity modules have one antenna.

Receivers are commonly housed in a half-rack configuration, so that two can be mounted together in a rack system. For large complex multi channel radio microphone systems, as used in broadcast television studios and musical theatre productions, modular receiver systems with several (commonly eight) true diversity receivers slotting into a rack mounted mainframe housing are available. Several mainframes may be used together in a rack to supply the number of receivers required. In some musical theatre productions, systems with forty or more radio microphones are not unusual.

Receivers specifically for use with video cameras are often mounted in a bodypack configuration, typically with a hotshoe mount to be fitted onto the hotshoe of the camcorder. Small true diversity receivers which slot in to a special housing on many professional broadcast standard video cameras are produced by manufacturers including Sennheiser and Sony. For less demanding or more budget conscious video applications small non-diversity receivers are common. When used at relatively short operating distances from the transmitter this arrangement gives adequate and reliable performance. Sony Corporation ) is a Japanese multinational corporation and one of the worlds largest media conglomerates with revenue of $66. ...

Technologies

VHF

The VHF band is located in the frequency range between 30 MHz and 300 MHz. This is the other common band used in wireless microphone systems, but it is not used as commonly as UHF. VHF wireless microphones are typically those of the fixed frequency type, meaning that the user has no opportunity to switch frequencies if interference is encountered.

UHF

The UHF band is located in the frequency range between 300 MHz and 3 GHz and is the most common band used in wireless microphone systems. Depending on national regulations, which differ for every country, wireless microphones may operate in the various parts of the range between 470 MHz and 865 MHz. (for example, 470 - 806 MHz in the US). These frequencies are shared with over-the-air TV broadcasts, so when selecting a frequency, the user must know what frequencies to stay away from to avoid interference.

In the UK, use of wireless microphone systems requires a licence, except for the licence free bands of 173.8 MHz - 175.0 MHz and 863 MHz - 865 MHz (N.B. This is emphatically NOT TV Channel 69. Channel 69 is from 854 - 862 MHz. In the UK Channel 69 frequencies do require a licence from JFMG Ltd.: [1] ). Ultra high frequency (UHF) designates a range (band) of electromagnetic waves whose frequency is between 300 MHz and 3. ...

The UK communications regulator, Ofcom, has said it will auction part of the spectrum currently reserved for wireless microphones, to which objections have been raised by Andrew Lloyd Webber. [2] [3] Ofcom is a regulator for communication industries in the United Kingdom. ... Andrew Lloyd Webber, Baron Lloyd-Webber (born 22 March 1948) is a highly successful English composer of musical theatre, and also the elder brother of cellist Julian Lloyd Webber. ...

In many other countries wireless microphone use requires a licence. Some governments regard all radio frequencies as military assets and the use of unlicenced radio transmitters, even wireless microphones, may be severely punished.

Digital and Hybrid

Wireless microphone signals can not be transmitted digitally in an analog format over normal frequency modulated carriers (digital hybrid)is a system containing a compander that does a better job than traditional FM wireless but is still 100 percent analog FM modulation with no digital content. Digital wireless like the Zaxcom system is a narrow band digital wireless that offers 100% digital modulation of the carrier. One advantage of 100% digital encoding of the signal at the transmitter is that companding artifacts are bypassed, allowing for more linearity and dynamic range. The Zaxcom system allows Stereo signals can be sent over one RF carrier. Linear response down to 20 Hz is possible, unlike analog wireless microphones that often have reduced response below 100 Hz (though there are a few analog wireless products linear down to 50 Hz.) Also, control and status signals can be sent along with the digital audio data stream, yielding more accurate reporting on battery life and changes in user settings. With fully digital solutions, FM modulation artifacts dosn't affect the digital audio stream. A disadvantage to both hybrid and full digital wireless is that the radio spectrum used by a single transmitter is wider than for analog wireless, making it more difficult to coordinate a large-scale system with many wireless devices. Practical range for digital hybrid wireless is typically less than for full digital and normal analog wireless.

Spread Spectrum technology can be used to put more wireless microphones in the same RF space. Spread-spectrum telecommunications is a technique in which a signal is transmitted in a bandwidth considerably greater than the frequency content of the original information. ...

Manufacturers working with digital wireless microphone technology include Lectrosonics, Sabine, and Zaxcom.

External links

• Introduction to Wireless Microphones at Sweetwater.com
• Discussion regarding the reassignment of Channel 69 frequencies