Coaxial cable, or coax is a type of electrical cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield. Many coaxial cables have an insulating outer sheath or jacket; the term coaxial comes from the outer shield sharing a geometric axis. Coaxial cable was invented by English engineer and mathematician Oliver Heaviside, who patented the design in 1880. Coaxial cable is a type of transmission line, used to carry high frequency electrical signals with low losses, it is used in such applications as telephone trunklines, broadband internet networking cables, high speed computer data busses, carrying cable television signals, connecting radio transmitters and receivers to their antennas. It differs from other shielded cables because the dimensions of the cable and connectors are controlled to give a precise, constant conductor spacing, needed for it to function efficiently as a transmission line. Coaxial cable is used as a transmission line for radio frequency signals.
Its applications include feedlines connecting radio transmitters and receivers to their antennas, computer network connections, digital audio, distribution of cable television signals. One advantage of coaxial over other types of radio transmission line is that in an ideal coaxial cable the electromagnetic field carrying the signal exists only in the space between the inner and outer conductors; this allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines. Coaxial cable provides protection of the signal from external electromagnetic interference. Coaxial cable conducts electrical signal using an inner conductor surrounded by an insulating layer and all enclosed by a shield one to four layers of woven metallic braid and metallic tape; the cable is protected by an outer insulating jacket. The shield is kept at ground potential and a signal carrying voltage is applied to the center conductor; the advantage of coaxial design is that electric and magnetic fields are restricted to the dielectric with little leakage outside the shield.
Conversely and magnetic fields outside the cable are kept from interfering with signals inside the cable. Larger diameter cables and cables with multiple shields have less leakage; this property makes coaxial cable a good choice for carrying weak signals that cannot tolerate interference from the environment or for stronger electrical signals that must not be allowed to radiate or couple into adjacent structures or circuits. Common applications of coaxial cable include video and CATV distribution, RF and microwave transmission, computer and instrumentation data connections; the characteristic impedance of the cable is determined by the dielectric constant of the inner insulator and the radii of the inner and outer conductors. In radio frequency systems, where the cable length is comparable to the wavelength of the signals transmitted, a uniform cable characteristic impedance is important to minimize loss; the source and load impedances are chosen to match the impedance of the cable to ensure maximum power transfer and minimum standing wave ratio.
Other important properties of coaxial cable include attenuation as a function of frequency, voltage handling capability, shield quality. Coaxial cable design choices affect physical size, frequency performance, power handling capabilities, flexibility and cost; the inner conductor might be stranded. To get better high-frequency performance, the inner conductor may be silver-plated. Copper-plated steel wire is used as an inner conductor for cable used in the cable TV industry; the insulator surrounding the inner conductor may be solid plastic, a foam plastic, or air with spacers supporting the inner wire. The properties of the dielectric insulator determine some of the electrical properties of the cable. A common choice is a solid polyethylene insulator, used in lower-loss cables. Solid Teflon is used as an insulator; some coaxial lines have spacers to keep the inner conductor from touching the shield. Many conventional coaxial cables use braided copper wire forming the shield; this allows the cable to be flexible, but it means there are gaps in the shield layer, the inner dimension of the shield varies because the braid cannot be flat.
Sometimes the braid is silver-plated. For better shield performance, some cables have a double-layer shield; the shield might be just two braids, but it is more common now to have a thin foil shield covered by a wire braid. Some cables may invest in more than two shield layers, such as "quad-shield", which uses four alternating layers of foil and braid. Other shield designs sacrifice flexibility for better performance; those cables cannot be bent as the shield will kink, causing losses in the cable. When a foil shield is used a small wire conductor incorporated into the foil makes soldering the shield termination easier. For high-power radio-frequency transmission up to about 1 GHz, coaxial cable with a solid copper outer conductor is available in sizes of 0.25 inch upward. The outer conductor is corrugated like a bellows to permit flexibility and the inner conductor is held in position by a plastic spiral to approximate an air dielectric. One brand name for such cable is Heliax. Coaxial cables require an internal structure of an insulating material to maintain the spacing between the center conductor and shield.
The TNC connector is a threaded version of the BNC connector. The interface specifications for the TNC and many other connectors are referenced in MIL-STD-348; the connector operates best in the 0 -- 11 GHz frequency spectrum. It has better performance than the BNC connector at microwave frequencies. Invented in the late 1950s and named after Paul Neill of Bell Labs and Carl Concelman of Amphenol, the TNC connector has been employed in a wide range of radio and wired applications; the abbreviation TNC is sometimes given as standing for Threaded Navy Connector. The TNC connector features a 7/16"-28 thread. Reverse-polarity TNC is a variation of the TNC specification which reverses the polarity of the interface; this is achieved by incorporating the female contacts found in jacks into the plug, the male contacts found in plugs into the jack. Because they were not available, RP-TNC connectors have been used by Wi-Fi equipment manufacturers to comply with specific local regulations, such as those from the FCC, which are designed to prevent consumers from connecting antennas which exhibit gain and therefore breach compliance.
The FCC considered. As of 2013, leading manufacturers are still using RP-TNC connectors on their Wi-Fi equipment. Most TNC connectors are 50-ohm type when used with coaxial cable of other impedances, but a 75-ohm series is available, providing a good SWR to about 1 GHz; these can be recognized by a reduced amount of dielectric in the mating ends. They are intermatable with standard types. RF connector SMA connector SMB connector SMC connector N connector Optical fiber connector
Hirose U. FL, I-PEX MHF series, IPAX, IPX, AMC and UMCC is a miniature RF connector for high-frequency signals up to 6 GHz manufactured by Hirose Electric Group and others. U. FL connectors are used in applications where space is of critical concern, most Mini PCI cards for laptop computers. U. FL connectors are used inside laptops and embedded systems to connect the Wi-Fi antenna to a Mini PCI card. Another common use is connecting GPS antennas. Female U. FL connectors are not designed with reconnection in mind, they are only rated for a few reconnects before replacement is needed; the female U. FL connectors are not sold separately, but rather as part of a pigtail with a high-quality 1.32 mm doubly shielded cable, which allows for a low-loss connection. The male connectors are soldered directly to the printed circuit board, they are designed to have a characteristic impedance of 50 ohms. The mated connection takes as little as 9 mm2 of board space. Much like many other electronic components, Hirose U.
FL connectors were protected by trademarks. However, compatible third party connectors are available. Hirose W. FL
The BNC connector is a miniature quick connect/disconnect radio frequency connector used for coaxial cable. The interface specifications for the BNC and many other connectors are referenced in MIL-STD-348, it features two bayonet lugs on the female connector. BNC connectors are used with miniature-to-subminiature coaxial cable in radio and other radio-frequency electronic equipment, test instruments, video signals; the BNC was used for early computer networks, including ARCnet, the IBM PC Network, the 10BASE2 variant of Ethernet. BNC connectors are made to match the characteristic impedance of cable at either 75 ohms, they are applied for frequencies below 4 GHz and voltages below 500 volts. Similar connectors using the bayonet connection principle exist, a threaded connector is available. United States military standard MIL-PRF-39012 entitled Connectors, Radio Frequency, General Specification for covers the general requirements and tests for radio frequency connectors used with flexible cables and certain other types of coaxial transmission lines in military and spaceflight applications.
The BNC was designed for military use and has gained wide acceptance in video and RF applications to 2 GHz. The BNC uses some plastic dielectric on each gender connector; this dielectric causes increasing losses at higher frequencies. Above 4 GHz, the slots may radiate signals, so the connector is usable, but not stable up to about 11 GHz. Both 50 ohm and 75 ohm versions are available; the BNC connector is used for signal connections such as: analog and serial digital interface video signals radio antennas aerospace electronics nuclear instrumentation test equipment. The BNC connector is used for composite video on commercial video devices. Consumer electronics devices with RCA connector jacks can be used with BNC-only commercial video equipment by inserting an adapter. BNC connectors were used on 10base2 thin Ethernet network cables and network cards. BNC connections can be found in recording studios. Digital recording equipment uses the connection for synchronization of various components via the transmission of word clock timing signals.
The male connector is fitted to a cable, the female to a panel on equipment. Cable connectors are designed to be fitted by crimping using a special power or manual tool. Wire strippers which strip outer jacket, shield braid, inner dielectric to the correct lengths in one operation are used; the connector was named the BNC after its bayonet mount locking mechanism and its inventors, Paul Neill and Carl Concelman. Neill worked at Bell Labs and invented the N connector. A backronym has been mistakenly applied to it: British Naval Connector. Another common incorrectly attributed; the basis for the development of the BNC connector was the work of Octavio M. Salati, a graduate of the Moore School of Electrical Engineering of the University of Pennsylvania. In 1945, while working at Hazeltine Electronics Corporation, he filed a patent for a connector for coaxial cables that would minimize wave reflection/loss; the patent was granted in 1951. BNC connectors are most made in 50 and 75 ohm versions, matched for use with cables of the same characteristic impedance.
The 75 ohm types can sometimes be recognized by the reduced or absent dielectric in the mating ends but this is by no means reliable. There was a proposal in the early 1970s for the dielectric material to be coloured red in 75 ohm connectors, while this is implemented, it did not become standard; the 75 ohm connector is dimensionally different from the 50 ohm variant, but the two can be made to mate. The 50 ohm connectors are specified for use at frequencies up to 4 GHz and the 75 ohm version up to 2 GHz. A 95 ohm variant is used within the aerospace sector, but elsewhere, it is used with the 95 ohm video connections for glass cockpit displays on some aircraft. Video and DS3 Telco central office applications use 75 ohm BNC connectors, whereas 50 ohm connectors are used for data and RF. Many VHF receivers used 75 ohm antenna inputs, so they used 75 ohm BNC connectors. Reverse-polarity BNC is a variation of the BNC specification which reverses the polarity of the interface. In a connector of this type, the female contact found in a jack is in the plug, while the male contact found in a plug is in the jack.
This ensures that reverse polarity interface connectors do not mate with standard interface connectors. The SHV connector is a high-voltage BNC variant. Smaller versions of the BNC connector, called Mini BNC and High Density BNC, are manufactured by Amphenol. While retaining the electrical characteristics of the original specification, they have smaller footprints giving a higher packing density on circuit boards and equipment backplanes; these connectors have true 75 ohm impedance making them suitable for HD video applications. The different versions are designed to mate with each other, a 75 ohm and a 50 ohm BNC connector which both comply with the 2007 IEC standard, IEC 60169-8, will mate non-destructively. At least one manufacturer claims high reliability for the connectors' compatibility. At frequencies below 10 MHz the impedance mismatch between a 50 ohm connector or cable and a 75 ohm one has negligible effects. BNC connectors were thus made only in 50 ohm
The C connector is a type of RF connector used for terminating coaxial cable. The interface specifications for the C and many other connectors are referenced in MIL-STD-348; the connector uses two-stud bayonet-type locks. The C connector was invented by Amphenol engineer Carl Concelman, it is weatherproof without being overly bulky. The mating arrangement is similar to that of the BNC connector, it can be used up to 11 Ghz, is rated for up to 1500 volts
The F connector is a coaxial RF connector used for "over the air" terrestrial television, cable television and universally for satellite television and cable modems with RG-6/U cable or, in older installations, with RG-59/U cable. The F connector was invented by Eric E. Winston in the early 1950s while working for Jerrold Electronics on their development of cable television. In the 1970s, it became commonplace on VHF, UHF, television antenna connections in the United States, as coaxial cables replaced twin-lead, it is now specified in IEC 60169 Radio-frequency connectors, part 24. The F connector is an inexpensive, threaded, compression connector for radio frequency signals, it has good 75 Ω impedance match for frequencies well over 1 GHz and has usable bandwidth up to several GHz. Connectors mate using a 3⁄8 in-32 unified extra fine thread; the female connector has a socket for external threads. The male connector has a center pin, a captive nut with internal threads; the design allows for low-cost construction, where cables are terminated exclusively with male connectors.
The coaxial cable center conductor forms the pin, cable dielectric extends up to the mating face of the connector. Thus, the male connector consists of only a body, crimped onto or screwed over the cable shielding braid, a captive nut, neither of which require tight tolerances. Push-on versions are available. Female connectors are used on bulkheads or as couplers being secured with the same threads as for the connectors, thus can be manufactured as a single piece, with center sockets and dielectric at the factory where tolerances can be controlled. This design is subject to the surface properties of the inner conductor and is not corrosion resistant. Hence waterproof versions are needed for outside use. Corrosion resistance can be improved by coating all bare copper wires with silicone grease; the F connector is not weatherproof. Neither the threads nor the joint between male connector body and captive nut seal. However, male connectors are enhanced with an o-ring inside the captive nut; this seals between the mating faces of both connectors, providing good waterproofing for the center conductor.
The cable and satellite television entities use compression fittings with F connectors on customer premises. In Europe, block down-converted satellite signals from LNBs and DC power and block signalling from satellite receivers are near passed through F connectors. F connectors are the most suitable for domestic terrestrial and satellite TV installations where the delivery of high frequency information is required. Belling-Lee connectors are not well suited for long-haul building delivery of frequencies above 500 MHz, because the standard was designed around tube receivers and mediumwave antennas. F connectors require more care to properly install the male connectors to the cable than the Belling-Lee type, with the exception of compression or flex type connections. Push-on F connectors provide poorer shielding against microwave signals of high field strength; this leakage problem is more an artifact of bent or broken push on connectors, but is not observed with compression connectors. Nearby television, FM radio, mobile & cordless phones, government radiolocation transmitters can interfere with a CATV or DTH Satellite reception or operation if the Flex connector poorly installed.
Belling-Lee connector Coaxial cable Component video Composite video Diplexer RCA connector Satellite dish TV aerial plug MCX connector Compression Tool for crimping Antenna-cables&connectors
SMB connectors are coaxial RF connectors developed in the 1960s. SMB connectors are smaller than SMA connectors, they are available in either 50 Ω or 75 Ω impedance. They offer excellent electrical performance from DC to 4 GHz. An SMB jack has a male center pin. Connectors are available for two SMB cable sizes: Cable 2.6/50+75 S and Cable 2/50 S The SSMB connector is a small version of the standard SMB connector with a'snap-on' coupling. Impedance: 50 Ohm Operating frequency: DC–12.4 GHz SMA connector, SMC connector BNC connector, TNC connector, N connector MIL-C-39012 MIL-STD-348 MIL-STD-202 Image of SMB and Mini SMB 75 Ω plugs