The Musa connector (for Multiple Unit Steerable Array/Antenna) is a type of
coaxial
In geometry, coaxial means that several three-dimensional linear or planar forms share a common axis. The two-dimensional analog is ''concentric''.
Common examples:
A coaxial cable is a three-dimensional linear structure. It has a wire condu ...
("coax") connector, originally developed for the manual switching of radio signals. It has a
characteristic impedance of 75 Ω, and was adopted for use in the emerging television broadcast industry.
History
"Multiple Unit Steerable Antenna" refers to an array of rhombic antennas used for high frequency (3–30 MHz) trans-Atlantic communication, "steerable" by the act of connecting several antennas together via a phasing circuit, thus achieving maximum antenna gain in the required direction.
The Musa connector was developed by the British Post Office, as a reliable and readily deployed means of achieving the desired configuration.
Some time after commercial television appeared around 1936, the Musa connector came to be used as a standard video connector; its distinctive feature being that unlike most other types of coaxial connector, it is engaged and disengaged by a straight push-pull action, making it ideal for
patch bays. In such professional
telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
and
video
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syst ...
applications, the connector performed well until the end of analogue (525 or 625 line) television.
The Musa connector was designed as to be rugged and reliable, typically using solid
sterling silver
Sterling silver is an alloy of silver containing 92.5% by weight of silver and 7.5% by weight of other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925.
'' Fine silver'', which is 99.9% pure silver, i ...
contacts, and turned silver-plated brass or
phosphor bronze
Phosphor bronze is a member of the family of copper alloys. It is composed of copper that is alloyed with 0.5–11% of tin and 0.01–0.35% phosphorus, and may contain other elements to confer specific properties (e.g. lead at 0.5–3.0% to form ...
bodies.
In consumer products, much less expensive connectors, such as the
Belling Lee coax connector, have performed the same function.
Modern use
Use of 75 Ω impedance as the standard for video broadcast equipment may be largely due to the better wideband performance obtainable from 75 Ω than 50 Ω cable of similar physical size, and is generally less expensive. The
historical choice of 75 Ω has turned out to be advantageous with the latest technology.
Often, 75 Ω
BNC connector
The BNC connector (initialism of "Bayonet Neill–Concelman") is a miniature quick connect/disconnect radio frequency connector used for coaxial cable. It is designed to maintain the same characteristic impedance of the cable, with 50 ohm and 7 ...
s are used, however these are not freely pluggable like MUSA connectors, due to the bayonet locking action, except for specially engineered patch panels which omit the bayonet function, just relying upon the friction of the connector's mating surfaces.
References
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