Coaxial cable , or coax (pronounced ), is a type of power cord that has an inner conductor surrounded by a tube insulation layer, surrounded by a tubular conduction shield. Many coaxial cables also have an outer sheath of insulation or jacket. The term coaxial comes from the inner conductor and the external shield that shares the geometric axis. The coaxial cable was invented by British engineer and mathematician Oliver Heaviside, who patented the design in 1880. The coaxial cable is different from other shielded cables because the wiring dimension is controlled to provide the correct constant conductor distances required to function efficiently as a transmission line.
Video Coaxial cable
Apps
The 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 (Internet), digital audio (S/PDIF) connections, and distributing cable television signals. One of the advantages of coaxial over other types of radio transmission lines is that in an ideal coaxial cable the electromagnetic field carries a signal exists only in the space between the inner and outer conductors. This allows the coaxial cable to run to be installed next to metallic objects such as gutter without loss of power that occurs in other types of transmission lines. The coaxial cable also provides protection against signals from external electromagnetic interference.
Maps Coaxial cable
Description
The coaxial cable conducts electrical signals using an inner conductor (usually solid copper, jagged copper wire or copper-coated steel wire) surrounded by an insulating layer and all covered by a shield, typically one to four layers of metallic braid and metal tape. The cable is protected by an outer insulation jacket. Normally, the shield is stored at the ground potential and the signal carrier voltage is applied to the center of the conductor. The advantage of coaxial design is that the electric and magnetic fields are limited to the dielectric with little leakage outside the shield. In contrast, the electric and magnetic fields outside the cables are largely kept from interfering with signals inside the cables. Cables and cables with larger diameters with multiple shields have less leakage. This property makes the coaxial cable a good choice for carrying weak signals that can not tolerate interference from the environment or for stronger electrical signals that should not be allowed to radiate or mate into adjacent structures or circuits.
Common applications of coaxial cables include video and CATV distribution, RF and microwave transmission, and computer data and instrumentation connections.
Impedansi characteristik kabel ( ) ditentukan oleh constant dielektrik dari insulator dalam dan jari-jari dari conductor dalam dan luar. Suatu impedansi karakteristik kabel yang terkontrol adalah penting karena sumber dan impedansi beban harus dicocokkan untuk memastikan transfer daya maximum dan rasio gelombang berdiri minimum. Sifat penting lainnya dari kabel koaksial termasuk atenuasi sebagai fungsi frekuensi, kemampuan penanganan tegangan, dan kualitas perisai.
Build
Coaxial cable design options affect physical size, frequency performance, attenuation, power handling capabilities, flexibility, strength, and cost. The inner conductor may be solid or stranded; stranded more flexible. To get better high frequency performance, the inner conductor can be silver plated. Copper-coated steel wire is often used as an inner conductor for cables used in the cable TV industry.
The insulator surrounding the inner conductor may be a solid plastic, foam plastic, or air with a spacer that supports the inner wire. The properties of the dielectric insulator determine some electrical properties of the cable. A common choice is a solid polyethylene (PE) isolator, which is used in lower cables. Solid Teflon (PTFE) is also used as an insulator. Some coaxial lines use air (or some other gas) and have a spacer to keep the inner conductor from touching the shield.
Many conventional coaxial cables use a braided copper wire that forms a shield. This allows the cable to be flexible, but it also means there is a gap in the protective layer, and the inner dimensions of the shield are slightly different because the braids can not be flat. Sometimes the fabric is coated in silver. For better shield performance, some cables have multiple layer shields. Shields may be only two braids, but more commonly now have a thin foil protector that is covered by a wire mesh. Some cables can invest in more than two layers of shield, such as "quad-shield", which uses four layers back and forth foil and braid. Other shield designs sacrifice flexibility for better performance; some shields are solid metal tubes. The cables can not be bent sharply, because the shield will vibrate, causing wire losses. When the foil shield is used a small wire conductor is inserted into the foil making soldering shielding easier.
For high-frequency radio-frequency transmissions of up to about 1 GHz, coaxial cables with solid copper outer conductors are available in a size of 0.25 inches up. The outer conductor is wavy like a bellows to allow flexibility and the inner conductor is held in position by a plastic spiral to estimate an air dielectric. One brand name for the cable is Heliax .
The coaxial cable requires the internal structure of the insulating material (dielectric) to keep the distance between the center conductor and the shield. Dielectric losses increase in this order: ideal dielectric (no loss), vacuum, air, polytetrafluoroethylene (PTFE), polyethylene foam, and solid polyethylene. The relatively low permittivity allows the use of higher frequencies. Non-homogeneous dielectrics must be compensated by non-circle conductors to avoid current hotspots.
While many cables have solid dielectrics, many other cables have dielectric foams that contain as much air or other gases as possible to reduce losses by allowing the use of larger diameter central conductors. Foam coax will have about 15% less attenuation but some types of foam dielectrics can absorb moisture - especially on many of its surfaces - in humid environments, significantly increasing losses. Supports shaped like a star or radius even better but more expensive and very susceptible to moisture infiltration. The more expensive is the air-conditioned coaxial used for some inter-city communications in the mid-20th century. The center of the conductor is suspended by a polyethylene disk every few centimeters. In some low-loss coaxial cables such as the RG-62 type, the inner conductor is supported by a spiral strand of polyethylene, so there is air space between most of the conductors and the inside of the jacket. The dielectric constants under air allow for greater inner diameter at the same impedance and greater outer diameter at the same cutoff frequency, decreasing the ohmic losses. The inner conductor is sometimes silver coated to smooth the surface and reduce the loss due to skin effect. The rough surface extends the current path and concentrates the current at the peak, thus increasing the ohmic loss.
Insulation jackets can be made from many materials. The common choice is PVC, but some applications may require a refractory material. Outdoor applications may require a jacket to withstand ultraviolet light, oxidation, rodent damage, or direct burial. The flooded coaxial cable uses a waterproof gel to protect the cable from water infiltration through a small wound on the jacket. For internal chassis connections, the insulation jacket can be removed.
Signal propagation
The twin-lead transmission channel has a property that the electromagnetic waves propagate down the longitudinal line to the space around the parallel cable. These lines have a low loss, but also have undesirable characteristics. They can not be bent, rotated firmly, or formed without changing their characteristic impedance, causing a reflection of the signal back to its source. They also can not be buried or crushed or attached to something conductive, since an extended field will cause currents in nearby conductors to cause unwanted radiation and line detuning. The coaxial line mostly solves this problem by limiting almost all electromagnetic waves to the area inside the cable. Coaxial lines can be bent and twisted moderately with no negative effects, and they can be tied to a conductive support without inducing undesirable currents inside.
In radio frequency applications up to several gigahertz, the waves spread mainly in transverse electric magnetic mode (TEM), which means that the electric and magnetic fields are both perpendicular to the direction of propagation. However, above certain cutoff frequencies, electric transversal (TE) or magnetic transverse (TM) modes can also propagate, as they do in waveguide. It is usually undesirable to transmit signals above the cutoff frequency, as it can cause several modes with different phase speeds to propagate, interfere with each other. The outer diameter is roughly inversely proportional to the cutoff frequency. A dispersed surface wave mode that does not involve or require an external shield but only one central conductor also exists in coax but this mode is effectively suppressed in conventional geometry and general impedance. The electric field line for mode [TM] has longitudinal components and requires a half-wavelength or longer line length.
Coaxial cable can be seen as a waveguide type. Power is transmitted through a radial electric field and a circular magnetic field in a TEM00 transversal mode. This is the dominant mode of zero frequency (DC) to the upper limit determined by the electrical dimension of the cable.
Connector
The end of the coaxial cable usually ends with a connector. The coaxial connectors are designed to maintain coaxial shapes across connections and have the same impedance as the installed cable. Connectors are usually coated with high conductivity metals such as tarnish silver or gold. Due to skin effect, RF signals are only carried by coating at higher frequencies and do not penetrate to the body of the connector. However the silver tarnishes fast and the resulting silver sulfide is poorly conductive, lowering the connector performance, making silver a bad choice for this application.
Important parameters
The coaxial cable is a particular type of transmission line, so the circuit model developed for the general transmission line is appropriate. See Telegrapher equations.
Physical parameters
The best coaxial cable impedance in high-power, high-voltage, and low-attenuation applications was experimentally determined at Bell Laboratories in 1929 to 30, 60, and 77, respectively. For coaxial cable with air dielectric and shield of the given inner diameter, attenuation is minimized by selecting the inner conductor diameter to provide characteristic impedance of 76.7 °. When the more common dielectric is considered, the best-loss impedance falls to the value between 52-64? Maximum power handling achieved at 30Ã,?
The approximate impedance required to match the center-fed dipole antenna in free space (ie, dipole without soil reflection) is 73 °,, so 75? coax is usually used to connect a short wave antenna to the receiver. This usually involves low levels of RF power so that power handling and high voltage noise characteristics are not important when compared to attenuation. So also with CATV, although many broadcast TV installations and CATV headrest use 300Ã? a dipole antenna that is folded to receive an off-the-air signal, 75Ã,? coaxing makes a 4: 1 transformer comfortable for this as well as having low attenuation.
Mean arithmetic between 30? and 77? What is 53,5Ã? the geometric mean is 48? Selection 50Ã,? as a compromise between power handling capability and attenuation is generally referred to as the reason for that number. 50Ã,? also works reasonably well because it corresponds roughly to the impedance of the drive (ideally 36 ohms) of a quarter wave monopole, which is mounted on a less than optimal ground plane such as a vehicle roof. Matches are better at low frequencies, such as for CB Radio about 27 MHz, where roof dimensions are much less than a quarter wavelength, and relatively poor at higher frequencies, VHF and UHF, where the roof dimensions may be some wavelength. The worst match, because the impedance of the antenna drive, because of the incomplete ground plane, is reactive rather than purely resistive, so the 36 ohm coaxial cable will not fit properly. Installations that require exact matching will use some kind of matching circuit on the antenna base, or elsewhere, in relation to the carefully chosen coaxial length (such that length), so that an appropriate match is reached, which will only be through the frequency range which is quite narrow.
RG-62 is 93Ã ¢ â,¬? coaxial cable was originally used in mainframe computer networks in the 1970s and early 1980s (it was the cable used to connect the IBM 3270 terminal to the IBM 3274/3174 terminal cluster controller). Later, some LAN equipment manufacturers, such as Datapoint for ARCNET, adopted the RG-62 as their standard coaxial cable. The cable has the lowest capacitance per unit length when compared to other coaxial cables of the same size. Capacitance is the enemy of square-wave data transmission (in particular, slowing edge transitions), and this is a much more important factor for transmitting baseband digital data than power handling or attenuation.
All components of the coaxial system must have the same impedance to avoid internal reflection on the connection between components. Such reflections may cause signal attenuation and display of shaded TV images; double reflection can cause the original signal to be followed by more than one echo. In an analog video or TV system, this causes image shadows. Reflection also introduces standing waves, which leads to an increase in losses and can even lead to cable dielectric damage with high power transmission (see Impedance Matching). In short, if the coaxial cable is open, termination has almost infinite resistance, this causes reflection; if the coaxial cable is short-circuited, the termination resistance is almost zero, there will be a reflection with the opposite polarity. Reflection will be almost eliminated if the coaxial cable is terminated with the same pure resistance as the impedance.
Problem
Signal leakage
Signal leakage is the passage of the electromagnetic field through the cable shield and occurs in both directions. Ingress is part of the outer signal into the cable and can cause noise and disturbance of the desired signal. The exit is part of a signal intended to remain inside the cable to the outside world and can generate weaker signals at the ends of wires and radio frequency interference to nearby devices. Severe leakage is usually generated from faulty connectors or fault mounted on the cable shield.
For example, in the United States, signal leaks from cable television systems are regulated by the FCC, since cable signals use the same frequency as aeronautical bands and radio navigation. CATV operators may also choose to monitor their networks for leaks to prevent entry. External signals entering the cables can cause unwanted noise and shaded images. Excessive noise can overwhelm the signal, making it useless.
The ideal protector will be a perfect conductor without a hole, a gap, or a bulge connected to the perfect ground. However, a very strong and solid protector will be heavy, inflexible, and expensive. Such coaxes are used to feed a straight line to a commercial radio broadcast tower. More economical cables should make a compromise between shielding efficacy, flexibility, and cost, such as wavy surfaces from flexible hard liners, flexible braids, or foil protectors. Since the shield can not be a perfect conductor, the current flowing inside the shield produces an electromagnetic field on the outer surface of the shield.
Consider the skin effect. The amount of alternating current in the conductor decays exponentially with the distance below the surface, with a penetration depth which is proportional to the square root of resistivity. This means that, in a shield with finite thickness, a small amount of current will still flow on the opposite surface of the conductor. With a perfect conductor (ie, zero resistivity), all currents will flow on the surface, without penetration into and through the conductors. The original cable has a shield made of an imperfect conductor, although it is usually very good, so there should always be a leak.
The gap or hole, allowing some electromagnetic fields to penetrate to the other side. For example, a braided shield has many small slits. The gap is smaller when using a foil protector (solid metal), but there are still stitches that run the length of the cable. The foil becomes stiffer with increasing thickness, so the thin foil layer is often surrounded by a braided metal layer, which offers greater flexibility for the given cross section.
Signal leakage can be severe if there is poor contact at the interface to the connector on either end of the cable or if there is a gap in the shield.
To reduce the leakage of incoming or outgoing signals from cables, by a factor of 1000, or even 10,000, superscreened cables are often used in critical applications, such as for neutron flux counters in nuclear reactors.
Superscreened cables for nuclear use are defined in IEC 96-4-1, 1990, but due to long gaps in the construction of nuclear power plants in Europe, many existing installations use superscreened cables to UK AESS (TRG) 71181 standards referenced in IEC 61917.
Round ground
Continuous currents, albeit small, along the imperfect shields of coaxial cables can cause visible or audible disturbances. In CATV systems distributing analog signals the potential difference between coaxial networks and home electrical grounding systems can cause the "hum bar" seen in the image. It appears as a horizontal wide distortion bar in the image that rolls slowly upward. Such potential differences can be reduced by proper bonding to common ground at home. View ground loop.
Noise
The external field creates a voltage across the outside inductance of the outer conductor between the sender and the receiver. The effect is less when there are some parallel cables, as this reduces the inductance and, therefore, the voltage. Since the outer conductor carries a potential reference for the signal on the inner conductor, the receiver circuit measures the wrong voltage.
Trafo effect
The transformer effect is sometimes used to reduce the effect of the induced currents on the shield. The inner and outer conductors form the primary and secondary windings of the transformer, and their effects are enhanced in some high-quality cables that have a mu-metal outer layer. Because of this 1: 1 transformer, the voltage mentioned above the outer conductor is transformed into the inner conductor so that two voltages can be canceled by the receiver. Many senders and receivers have the means to reduce further leakage. They increase the effect of the transformer by passing the entire cable through the ferrite core one or more times.
Common mode and radiation currents
Common mode currents occur when the wild currents inside the shield flow in the same direction as the current at the center of the conductor, causing the coax to radiate.
Most of the shielding effect in coaxing the result of opposing currents in the center conductor and shield creates an opposing magnetic field that cancels, and thus does not radiate. The same effect helps the ladder line. However, the ladder line is very sensitive to the surrounding metal objects, which can enter the field before it is completely canceled. Coax does not have this problem, because the field is covered in a shield. However, it is still possible for the field to form between the shield and other connected objects, such as the antenna that coaxs the bait. The current formed by the field between the antenna and the coax shield will flow in the same direction as the current at the center of the conductor, and thus not canceled. Energy will radiate from the coax itself, affecting the radiation pattern of the antenna. With enough power this can be a danger to people near the cable. Properly sized and properly sized balun can prevent general mode radiation by inducing. The isolation transformer or the blocking capacitor can be used to pair the coaxial cable to the equipment, where it is desired to pass the radio frequency signal but to block direct current or low frequency power.
Standard
Most coaxial cables have characteristic impedances either 50, 52, 75, or 93 ?. The RF industry uses the standard type name for coaxial cable. Thanks to television, RG-6 is the most commonly used coaxial cable for home use, and most of the connections are outside Europe by F connectors.
A series of standard type coaxial cables are specified for military purposes, in the form of "RG- #" or "RG - #/U". They were from World War II and registered in MIL-HDBK-216 published in 1962. This marking is now obsolete. The term RG stands for Radio Guide; Designation U means Universal. The current military standard is MIL-SPEC MIL-C-17. MIL-C-17 numbers, such as "M17/75-RG214", are assigned to military cables and manufacturer's catalog numbers for civilian applications. However, the RG-series designation is so common for generations that are still in use, although critical users should be aware that since the handbook is withdrawn there is no standard to guarantee the electrical and physical characteristics of the cable described as "RG- # typing". The GE designers are mostly used to identify compatible connectors that match the dimensions of the inner conductor, dielectric, and jacket of the old RG-series cable.
Code of the dielectric material
- FPE is a foamy polyethylene
- PE is solid polyethylene
- PF is a polyethylene foam
- PTFE is polytetrafluoroethylene;
- ASP is air space polyethylene
VF adalah Faktor Kecepatan; ini ditentukan oleh dan
- VF untuk PE padat sequente 0,66
- VF untuk busa PE adalah sequir 0,78 hingga 0,88
- VF untuk udara sek 1,00
- VF untuk PTFE padat adalah sequens 0.70
- VF untuk PTFE bus sequir 0,84
There are also other designation schemes for coaxial cables such as URM, CT, BT, RA, PSF and WF series.
Usage
Short coaxial cables are commonly used to connect home video equipment, in ham radio settings, and in electronic measurements. Although previously common for implementing computer networks, specifically Ethernet ("thick" 10BASE5 and "thin" 10BASE2), twisted pair cables have replaced them in most applications except in the growing consumer cable modem market for broadband Internet access.
Long distance coaxial cable was used in the 20th century to connect radio networks, television networks, and Long Distance telephone networks although largely replaced by subsequent methods (optical fiber, T1/E1, satellites).
The shorter coaxials still carry cable television signals to the majority of television receivers, and this goal consumes the majority of coaxial cable production. In the 1980s and early 1990s coaxial cable was also used in computer networks, the most prominent in Ethernet networks, where it was then in the late 1990s to early 2000s replaced by UTP cable in North America and STP cable in Western Europe, both with modular 8P8C connectors.
Micro coaxial cable is used in various consumer devices, military equipment, as well as ultra-sound scanning equipment.
The most commonly used impedances are 50 or 52 ohms, and 75 ohms, though other impedances are available for specialized applications. 50/52 ohm cables are widely used for industrial and commercial two-way radios (including radio and telecommunications) applications, although 75 ohms are commonly used for television and radio broadcasts.
Coax cables are often used to carry data/signals from antenna to receiver - from satellite dish to satellite receiver, from television antenna to television receiver, from radio mast to radio receiver, etc. In many cases, a single coax cable carries power in the opposite direction, to the antenna, to turn on low-noise amplifiers. In some cases, single coax cables carry power (directional) and data/two-way signals, as in DiSEqC.
Type
Hardline
Hard lines are used in broadcasting as well as many other forms of radio communication. It is a coaxial cable built using copper, silver or gold pipes or a combination of such metal as a shield. Some lower-quality hardliners may use aluminum protector, but aluminum is easily oxidized and unlike silver oxide, aluminum oxide drastically loses effective conductivity. Therefore, all connections must be air-tight and water-resistant. The center conductor may consist of solid copper, or copper-coated aluminum. Since the skin effect is a problem with RF, copper coating provides a sufficient surface for an effective conductor. Most hardline varieties used for external chassis or when exposed to elements have PVC jackets; However, some internal applications can eliminate the insulation jacket. Hard lines can be very thick, usually at least half an inch or 13 mm and up to several times, and have a low loss even at high power. These large-scale hard lines are almost always used in the relationship between the transmitter on the ground and the antenna or antenna of the tower. Hard lines can also be known by trademark names such as Heliax (CommScope), or Cablewave (RFS/Cablewave). Larger linear varieties may have a conductor center built of rigid or corrugated copper pipes. Dielectrics in hard lines may comprise polyethylene foams, air, or pressurized gases such as nitrogen or dry air (dry air). On a gas-loaded lane, hard plastic like nylon is used as a spacer to separate the inner and outer conductors. The addition of these gases into the dielectric chamber reduces moisture contamination, provides a stable dielectric constant, and provides a reduction in the risk of internal arcing. Gas filled hardlines are commonly used in high power RF transmitters such as radio or radio broadcasts, military transmitters and amateur radio applications, but can also be used in some very important low power applications such as those in microwaves. However, in the microwave region, waveguide is used more often than hardliners for an antenna-to-transmitter application, or an antenna-to-receiver. The various shields used in hard lines are also different; some forms use rigid pipes, or pipes, others may use corrugated tubes, which make flexing easier, and reduce the flexibility when the cable is bent to adjust. Smaller harder varieties can be used internally in some high-frequency applications, especially in equipment in the microwave range, to reduce inter-device interference.
Radiate
Radiation or leaked cable is another form of coaxial cable constructed in a similar way to hardliners, but it is built with a slotted slot cut into the shield. This slot is set to the RF wavelength of a particular operation or set to a certain radio frequency band. This type of cable is to provide the desired two-way desired "desired" leakage effect between transmitter and receiver. These are often used in elevator tunnels, US Navy ships, underground transportation tunnels and in other areas where antennas are not feasible. One example of this type of cable is Radiax (CommScope).
RG-6
RG-6 is available in four different types designed for various applications. In addition, the core may be copper clad steel (CCS) or bare solid copper (BC). "Ordinary" or "home" RG-6 is designed for home wiring inside or outside the home. The "Flood" cable is infused with waterblocking gel for use in underground channels or direct burials. "Messenger" may contain some waterproofing but is distinguished by the addition of steel messenger wire along its length to bring the tension involved in the air drop from the power pole. The "Plenary" cable is expensive and comes with a special Teflon-based outdoor jacket designed for use in ventilation ducts to meet fire codes. It was developed because the plastic used as the outer jacket and inside insulation of many "Plain" or "house" cables emit toxic gas when burned.
Triaxial cable
Triaxial cable or triax is a coaxial cable with a third layer of protection, insulation, and sheath. The outer shield, grounded, protects the inner shield from electromagnetic interference from an external source.
Twin-axial cable
Twin-axial cables or twinax are balanced and twisted pairs in a cylindrical shield. This allows near-perfect differential signals that are both shielded and balanced to pass. Multi-conductor coaxial cables are also sometimes used.
Semi-stiff
The Semi-rigid cable is a coaxial form using a solid copper outer shell. This type of coax offers superior screening compared to cables with outer braided conductors, especially at higher frequencies. The main disadvantage is that the cable, as the name implies, is not very flexible, and is not meant to be bent after initial formation. (See "hard line")
The adjustable cable is a flexible repeatable alternative to the semi-rigid coaxial cable used where flexibility is required. The shapsible cable can be stripped and shaped by hand without the need for special tools, similar to standard coaxial cables.
Rigid lines
Rigid lines are coaxial lines formed by two copper tubes that are maintained concentrically every other meter using PTFE-support. Rigid lines can not be bent, so they often require elbows. Interconnection with rigid lines is done with inner bullet/inner support and flange or connection kits. Rigid lines are usually connected using a standard EIA RF Connector that measures the bullets and their flange according to the standard line diameter, for each outer diameter, either 75 or 50 ohm inner tubes can be obtained. Rigid lines are usually used indoors for interconnection between high power transmitters and other RF components, but rougher rigid lines with weatherproof flanges are used outdoors on antenna poles, etc. To save weight and cost, on poles and similar structures the outline is often aluminum, and special care must be taken to prevent corrosion. With flange connectors it is also possible to switch from rigid lines to hard lines. Many antenna broadcasting and antenna separators use flanged sticky interfaces even when connecting to flexible and hard-line coaxial cables. Rigid lines are produced in various sizes:
Cable used in the UK
In the beginning of analog satellite TV broadcasting in the UK by BskyB, a 75 ohm cable referred to as RG6 was used. This cable has a 1 mm copper core, polyethylene dielectric and copper braid on aluminum foil shield. When installed outside without protection, the cable is exposed to UV radiation, which cracks the outer shell of PVC and allows fluid entry. The combination of copper, aluminum, moisture and air causes rapid corrosion, sometimes resulting in the appearance of 'swallowing eggs'. As a result, despite the higher costs, the RG6 cable fell in favor of CT100 when BSKYB launched its digital broadcast.
From about 1999 to 2005 (when CT100 producers left the business), CT100 remains the 75 ohm cable option for satellite TV and especially BskyB. It has a spaced polyethylene dielectric, a 1 mm solid copper core and a copper braid on a copper foil shield. CT63 is a thin cable in the 'shotgun' style, which means that it is two wires formed together and is used mainly by BskyB for the twin connections required by the satellite TV receiver Sky , which incorporates the hard drive recording. system and second independent tuner.
In 2005, this cable was replaced by WF100 and WF65, respectively, manufactured by Webro and has a similar construction but a foam dielectric that delivers the same electrical performance with the airspace but is stronger and tends not to be destroyed.
At the same time, as copper prices continue to rise, the original RG6 is dropped for construction using a copper-coated steel core and aluminum braid on aluminum foil. The lower price makes it attractive to air installers looking for a replacement for the so-called low-loss cable traditionally used for UK terrestrial air installations. This cable has been produced with the number of stranded braids that are declining, as copper prices increase, so the shield performance of cheaper brands falls to the 40 percent level. With the advent of digital terrestrial transmissions in the UK, these low loss cables no longer match.
The new RG6 still performs well at high frequency due to skin effect in cladding of copper. However, the aluminum shield has a high DC resistance and a higher steel core. The result is that this type of cable can not be reliably used in satellite TV installations, where it is necessary to carry significant current, because the voltage drop affects the operation of low noise block downconverter (LNB) on the disk.
The problem with all of the previously mentioned cables, when passing currents, is that electrolytic corrosion can occur in connection unless humidity and air are removed. As a result, various solutions to exclude moisture have been proposed. The first is to close the connection by wrapping it with a rubber band, which binds itself when activated by stretching. The second proposal, by the American Channel Master company (now owned by Andrews corp.) At least in early 1999, was to apply silicone oil to the wire making connection. The third proposal is to install a self-sealing connector to the cable. All of these methods are quite successful if implemented correctly.
Troubleshooting and troubleshooting
Coaxial cable isolation may decrease, requiring cable replacement, especially if it has been exposed to the element continuously. Shields are usually earthed, and if even a single braid or filament foil touches the center of the conductor, the signal will be shorted causing
Source of the article : Wikipedia
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