Info about Coaxial Cable, Types of Coaxial Cable, Tips and Advice of Coaxial Cable, Coaxial cable interference, Antenna Coaxial Cables, coaxial cable history

Coaxial cable

From Wikipedia, the free encyclopedia.

Coaxial cable is an electrical cable consisting of a round conducting wire, surrounded by an insulating spacer, surrounded by a cylindrical conducting sheath, and usually surrounded by a final insulating layer.

The coaxial cable is designed to carry a high-frequency or broadband signal, as in a high-frequency transmission line. Sometimes DC power (called bias) is added to the signal to supply the equipment at the other end, as in direct broadcast satellite receivers. Because the electromagnetic field carrying the signal exists (ideally) only in the space between the inner and outer conductors, it cannot interfere with or suffer interference from external electromagnetic fields.

Coaxial cables may be rigid or flexible. Rigid types have a solid sheath, while flexible types have a braided sheath, both usually of thin copper wire. The inner insulator, also called the dielectric, has a significant effect on the cable's properties, such as its characteristic impedance and its attenuation. The dielectric may be solid or perforated with air spaces. Connections to the ends of coaxial cables are usually made with RF connectors.

Important parameters

The characteristic impedance in ohms (Ω) is calculated from the ratio of the inner and outer diameters and the dielectric constant. Assuming the dielectric properties of the material inside the cable does not vary appreciably over the operating range of the cable, this impedance is frequency independent.
Capacitance, in farads per metre.
Resistance, in ohms per metre.
Attenuation or loss, in decibels per metre. This is dependent on the loss in the dielectric material filling the cable, and resistive losses in the center conductor and shield. These losses are frequency dependent, the losses becoming higher as the frequency increases. In designing a system, engineers must consider not only the loss in the actual cable itself, but also the insertion loss in the connectors.
Outside diameter, which dictates which connectors must be used to terminate the cable.
Velocity of propagation, which depends on the type of dielectric.

Types of coaxial cable

In broadcasting and other forms of radio communication, hard line is a very heavy-duty coaxial cable, where the outside shielding is a rigid or semi-rigid pipe, rather than flexible and braided wire. Hard line is very thick, typically at least a half inch or 13 mm and up to several times that, and has low loss even at high power. It is almost always used in the connection between a transmitter on the ground and the antenna or aerial on the tower. Hard lines are often made to be pressurised with nitrogen or desiccated air, which provide an excellent dielectric even at the high temperatures generated by thousands of watts of RF power, especially during intense summer heat and sunshine. Physical separation between the inner conductor and outer shielding is maintained by spacers, usually made out of tough solid plastics like nylon.

Triaxial cable or triax is coaxial cable with a third layer of shielding, insulation and sheathing. The outer shield, which is earthed, protects the inner shield from electromagnetic interference from outside sources.

Twin-axial cable or twinax is a balanced, twisted pair within a cylindrical shield. It allows a nearly perfect differential signal which is both shielded and balanced to pass through. Multi-conductor coaxial cable is also sometimes used.

Biaxial cable or biax is a figure-8 configuration of two 50 ohm coaxial cables, used in some proprietary computer networks.

Tips and Advice: Coaxial Cable

Tip: Coaxial Cable Safety and Maintenance

As with any wiring and infrastructure, all coaxial cable types, including digital coaxial cable, require careful handling. Although the coaxial copper shielding is strong, whether rigid or braided, it’s not indestructible. Some safety and maintenance tips:

Make sure your coaxial cables and coaxial connectors are fire resistant (FR).
Don’t buy secondhand, used or cheaply manufactured coaxial cables.
Make sure coaxial cable shield is grounded for safety.
If possible, house coaxial cables separately from the rest of your computer equipment and especially other cables and wires.
Do not expose coaxial cables to water.
Make sure the cable outlet wiring is intact.
Keep your coaxial cables repaired with tools such as the Shake ‘n Seal Coaxial Cable Repair Kit.

Tip: Ethernet and Coaxial Cables

Thin Ethernet or 10 Base-2 is a lighter, less expensive version of 10 Base-5 or Thick Ethernet. It uses a lighter, thinner copper coaxial cable. What is the advantage of a sleeker coaxial? Besides skipping the 10 Base-5 external transceivers and simplifying the coaxial setup, thin Ethernet features well-shielded coaxial cable. The drawback is that the RG-58A/U coaxial cable used with thin Ethernet can’t be interchanged with other coaxial cable types, including digital coaxial cable. Also, changing the network is difficult since the network breaks easily. Making it difficult to troubleshoot.

Despite drawbacks, thin Ethernet is a simple, inexpensive infrastructure to implement for basic cable Internet networking on a budget.

Tip: High-Band Coaxial Cables

Coaxial cable has an extremely broad bandwidth, especially digital coaxial cable, which tends to prevent lossy signals. Coaxial cables have a lower attenuation and can carry hundreds of cable Internet signals. The coaxial is a relatively simple cable, yet it can carry large amounts of data. In the case of telephone and video signals, coaxial cables can handle hundreds of phone conversations and a television program taking up 3,500,000 Hz. Certainly, given this capacity, coaxial cables can handle bandwidths of 2-3 Mpbs. There is no bandwidth performance difference between the coaxial cable types.

Source from: cableinternet.lifetips.com

About Coaxial Cables and Triaxial Cables

Coaxial cables have one conductor insulated with a dielectric material and then surrounded by the other conductor, usually referred to as the center conductor and shield. Triaxial cables are specialized coaxial cables. Coaxial cables consist of two cylindrical conductors with a common axis. The two conductors are separated by a dielectric. The outer conductor, normally at ground-potential, acts as a return path for current flowing through the center conductor and prevents energy radiation from the cable. The outer conductor, or shield, is also commonly used to prevent external radiation from affecting the current flowing in the inner conductor. The outer shield or conductor consists of woven strands of wire or is a metal sheath. Triaxial cables are three-conductor cables with one conductor in the center, a second circular conductor shield concentric with the first, and third circular conductor shield insulated from and concentric with the first and second, usually with insulation, and a braid or impervious sheath overall.

Important performance specifications to consider when searching for coaxial cables and triaxial cables include impedance, attenuation, outer diameter, and cable weight. Characteristic impedance of a uniform line is ratio of an applied potential difference to the resultant current at the point where the potential difference is applied, when the line is of infinite length. Note that the term is applied only to a uniform line. Coaxial cable is such a uniform line. There are three main impedance groups in coaxial cable, namely, 50, 70, and 93 ohms. Attenuation is the decrease in magnitude of a signal as it travels through any transmitting medium, such as a cable or circuitry. Attenuation is measured as the logarithm of a ratio. It is expressed in decibels or dB. The outer diameter is the diameter of the cable including dielectric and jacket. The weight of the wire is given in units of weight per distance. Important cable construction parameters to consider include cable dielectric, cable shielding, cable jacket, and cable conductor. Choices for coaxial cable and triaxial cable dielectric include polyethylene, fluorinated ethylene propylene, foamed polyethylene, and foamed fluorinated ethylene propylene. Shielding is a metallic layer placed around an insulated conductor or group of conductors to prevent electrostatic or electromagnetic interference between the enclosed wires and external fields. Cable shielding can be braid, drain wire, foil, and foil braid. Cable jacket is a material having a high resistance to the flow of electric current to prevent leakage of current from a conductor. The cable jacket on coaxial cables and triaxial cables can be ethylene propylene diene elastomer, mica tape, neoprene, polyethylene, polypropylene, polyvinyl chloride, silicon, rubber, Teflon?, and Tefzel? . (Teflon and Tefzel are registered trademarks of the DuPont company.) The cable conductor is a wire or combination of wires not insulated from one another, suitable for carrying electric current. Choices for cable conductors for coaxial cables and triaxial cables include aluminum and aluminum alloys, aluminum clad steel, copper clad steel, and copper and copper alloys.

Conductor size is an important criteria to consider when selecting between available coaxial cables and triaxial cables. In North America, wire area is measured by the American Wire Gauge (AWG) to indicate conductor size. The AWG is used to measure certain conductors including copper. The higher the AWG number the thinner the wire. This is because AWG stems from a measurement that represented the number of times the copper wire was run through a wire machine, which reduced the diameter of the wire. Thus 24-gauge wire went through the machine 6 more times than 18-gauge wire. Outside North America, countries measure conductor size by the size of the area of the wire, measured in mm2. Common features for coaxial cables and triaxial cables include dual cable construction, plenum rated, and stranded. Common approvals given to coaxial cables and triaxial cables include CSA Mark, UL Listing Mark, and UL Recognized Component Mark.

Coaxial cables have one conductor insulated with a dielectric material and then surrounded by the other conductor, usually referred to as the center conductor and shield. Triaxial cables are specialized coaxial cables. Common search terms for coaxial cables include coaxial cable connector, digital coaxial cable, flat coaxial cable, coaxial cable manufacturer, high performance coaxial cable, coaxial cable type, coaxial cable assembly, coaxial cable specification, coaxial cable design, high temperature coaxial cable, and 75-ohm coaxial cable.

Coaxial cables consist of two cylindrical conductors with a common axis. The two conductors are separated by a dielectric. The outer conductor, normally at ground-potential, acts as a return path for current flowing through the center conductor and prevents energy radiation from the coaxial cable. The outer conductor, or shield, is also commonly used to prevent external radiation from affecting the current flowing in the coaxial cables inner conductor. The outer shield or conductor consists of woven strands of wire or is a metal sheath. Triaxial cables are three-conductor cables with one conductor in the center, a second circular conductor shield concentric with the first, and third circular conductor shield insulated from and concentric with the first and second, usually with insulation, and a braid or impervious sheath overall.

Important performance specifications to consider when searching for coaxial cables and triaxial cables include impedance, attenuation, outer diameter, and cable weight. Characteristic impedance of a uniform line is ratio of an applied potential difference to the resultant current at the point where the potential difference is applied, when the line is of infinite length. Note that the term is applied only to a uniform line. Coaxial cable is such a uniform line. There are three main impedance groups in coaxial cable, namely, 50, 70, and 93 ohms. Attenuation is the decrease in magnitude of a signal as it travels through any transmitting medium, such as a cable or circuitry. Attenuation is measured as the logarithm of a ratio. It is expressed in decibels or dB. The outer diameter is the diameter of the coaxial cable including dielectric and jacket. The weight of the wire is given in units of weight per distance.

Important coaxial cable construction parameters to consider include cable dielectric, cable shielding, cable jacket, and cable conductor. Choices for coaxial cable and triaxial cable dielectric include polyethylene, fluorinated ethylene propylene, foamed polyethylene, and foamed fluorinated ethylene propylene. Shielding is a metallic layer placed around an insulated conductor or group of conductors to prevent electrostatic or electromagnetic interference between the enclosed wires and external fields. Coaxial cable shielding can be braid, drain wire, foil, and foil braid. Cable jacket is a material having a high resistance to the flow of electric current to prevent leakage of current from a conductor. The cable jacket on coaxial cables and triaxial cables can be ethylene propylene diene elastomer, mica tape, neoprene, polyethylene, polypropylene, polyvinyl chloride, silicon, and rubber. The coaxial cable conductor is a wire or combination of wires not insulated from one another, suitable for carrying elect ric current. Choices for cable conductors for coaxial cables and triaxial cables include aluminum and aluminum alloys, aluminum clad steel, copper clad steel, and copper and copper alloys.

Conductor size is an important criterion to consider when selecting between available coaxial cables and triaxial cables. In North America, wire area is measured by the American Wire Gauge (AWG) to indicate conductor size. The AWG is used to measure certain conductors including copper. The higher the AWG number the thinner the wire. This is because AWG stems from a measurement that represented the number of times the copper wire was run through a wire machine, which reduced the diameter of the wire. Thus 24-gauge wire went through the machine 6 more times than 18-gauge wire. Outside North America, countries measure conductor size by the size of the area of the wire, measured in mm2. Common features for coaxial cables and triaxial cables include dual cable construction, plenum rated, and stranded. Common approvals given to coaxial cables and triaxial cables include CSA Mark, UL Listing Mark, and UL Recognized Component Mark.

Source from: coaxial-cable.globalspec.com

Video Security Basics

Coaxial Cable - An Overview

The most common means of conducting video signals from one piece of equipment to another is coaxial cable. Coaxial cable is often referred to as simply "coax". Not only is coax the most commonly used cable, but also the least expensive, most reliable, most convenient, and easily maintained way of transferring electronic images in a CCTV system.

Coax is available from many manufacturers and comes in a variety of sizes, shapes, colors, specifications and capabilities. The most commonly recommended "coax" type is RG59/U, but this designation actually represents a family of cables with widely varying electrical characteristics. Other varieties like RG59/U are RG6/U and RG11/U; these are used predominately in CCTV and video work.

Though similar in many ways, each cable group has its own various physical and electrical characteristics, which must be taken into consideration.

All three "coax" cable groups are included in the same general family classification for coaxial cables. The RG reference is the cable specification for use as a "radio guide ",while the numerical value helps differentiate the specifications of each individual cable. Although each cable has its own number, characteristics, and size, there is no difference in the way these different numbered cables work.

Coax Construction
Common "coax" cable RG59//U,RG6/U, and RG11/U is circular. Each has a center conductor surrounded by dielectric insulating material, which in turn is covered by a braid to shield against electromagnetic interference (EMI). The outer covering is the "jacket".

The coaxial cable's two conductors are separated by a nonconductive or dielectric material. The outer conductor (braid) acts as a shield and helps isolate the center conductor from spurious electromagnetic interference. The outer covering helps physically protect the conductors.

Center Conductor
The center conductor is the primary means of carrying a video signal. The center conductor comes in varying diameters, usually ranging from 14 gauge to 22 gauge. The structure of the center conductor generally is solid copper or copper- clad steel, designated as bare copper weld, or BCW. For CCTV applications, solid copper conductors are required. Copper clad, copper weld, or BCW cables have much greater loop resistance at baseband video frequencies and should never be used for CCTV. To determine the type, look at the cut end of the center conductor. Copper clad cable will be silver in the center instead of copper all the way through. Variation in the size of the center conductor has an overall effect on the amount of DC resistance offered by cable. Cables which contain large diameter center conductors have lower resistances than cables with smaller diameters. This decreased resistance of large diameter cable enhances the ability of a cable to carry a video signal over a longer distance with better clarity, but, it is also more expensive and harder to work with.

For applications where the cable may move up/down or side-to-side, select cable that has a center conductor consisting of many small strands of wire. As the cable moves, these strands flex and resist wear due to fatigue better than a cable with a solid center conductor.

More about video security basics from: pelco.com

Coaxial Cable

GORE? coaxial cable provides greater packaging density, signal fidelity, and flex durability, and lower capacitance and propagation delay. Available in a variety of sizes/configurations. Can be designed to your specifications:

Conductor sizes from AWG 50
Controlled impedance pairs for differential signals
Coaxes and pairs-ribbon or round cable for signal busing applications
Quad cables-high speed, differential cables with two shielded pairs in a package 15 percent larger than a single-pair cable diameter

Source from: gore.com

common coaxial cable impedances

50 ohms: 50 ohms coaxial cable is very widely used with radio transmitter applications. It is used here because it matches nicely to many common transmitter antenna types, can quite easily handle high transmitter power and is traditionally used in this type of applications (transmitters are generally matched to 50 ohms impedance). In addition to this 50 ohm coaxial cable can be found on coaxial Ethernet networks, electronics laboratory interconnection (foe example high frequency oscilloscope probe cables) and high frequency digital applications (fe example ECL and PECL logic matches nicely to 50 ohms cable). Commonly used 50 Ohm constructions include RG-8 and RG-58.
60 Ohms: Europe chose 60 ohms for radio applications around 1950s. It was used in both transmitting applications and antenna networks. The use of this cable has been pretty much phased out, and nowdays RF system in Europe use either 50 ohms or 75 ohms cable depending on the application.
75 ohms: The characteristic impedance 75 ohms is an international standard, based on optimizing the design of long distance coaxial cables. 75 ohms video cable is the coaxial cable type widely used in video, audio and telecommunications applications. Generally all baseband video applications that use coaxial cable (both analogue and digital) are matched for 75 ohm impedance cable. Also RF video signal systems like antenna signal distribution networks in houses and cable TV systems are built from 75 ohms coaxial cable (those applications use very low loss cable types). In audio world digital audio (S/PDIF and coaxial AES/EBU) uses 75 ohms coaxial cable, as well as radio receiver connections at home and in car. In addition to this some telecom applications (for example some E1 links) use 75 ohms coaxial cable. 75 Ohms is the telecommunications standard, because in a dielectric filled line, somewhere around 77 Ohms gives the lowest loss. For 75 Ohm use common cables are RG-6, RG-11 and RG-59.
93 Ohms: This is not much used nowadays. 93 ohms was once used for short runs such as the connection between computers and their monitors because of low capacitance per foot which would reduce the loading on circuits and allow longer cable runs. In addition thsi was used in some digital commication systems (IBM 3270 terminal networks) and some early LAN systems.
The characteristic impedance of a coaxial cable is determined by the relation of outer conductor diameter to inner conductor diameter and by the dielectric constant of the insulation. The impednage of the coaxial cable chanes soemwhat with the frequency. Impedance changes with frequency until resitance is a minor effect and until dielectric dielectric constant is table. Where it levels out is the "characteristic impedance". The freqnency where the impedance matches to the characteristic impedance varies somwehat between different cables, but this generally happens at frequency range of around 100 kHz (can vary).

Essential properties of coaxial cables are their characteristic impedance and its regularity, their attenuation as well as their behaviour concerning the electrical separation of cable and environment, i.e. their screening efficiency. In applications where the cable is used to supply voltage for active components in the cabling system, the DC resistance has significance. Also the cable velocity information is needed on some applications. The coaxial cable velocity of propagation is defined by the velocity of the dielectric. It is expressed in percents of speed of light. Here is some data of come common coaxial cable insulation materials and their velocities.

Source from epanorama.net

Precision Coaxial Cable

Designers of high-speed digital systems use Gore custom-designed coaxial cables to meet their most challenging packaging and electrical requirements. Our expanded PTFE material provides a low dielectric constant (1.3) insulation system, durable enough to apply in thin walls over small conductors. The result is a reliable interconnect, optimized to meet specific system needs.

Benefits
Higher packaging density
Higher signal fidelity
Lower capacitance
Lowest propagation delay (about 1.2 ns/ft)

Form factors
In addition to coaxial, Gore builds controlled impedance pairs for differential signals. We can manufacture our coaxial cables and pairs in ribbon form for critical signal bussing applications.

Gore can provide fully tested assemblies. When standard connectors will not work, we can design and build custom assemblies to customer mechanical and electrical requirements.

Impedance control improves signal fidelity

Proper impedance matching minimizes reflections at terminations, enhances signal fidelity, and is critical for precise performance in finished cable assemblies. To ensure proper impedance matching, we build all Gore coaxial assemblies as precision-engineered components and perform numerous quality checks during manufacturing.

Low loss preserves fidelity

The low signal-loss characteristics of Gore's precision coaxial assemblies stem from sophisticated design engineering, meticulous manufacturing procedures, and the superb dielectric properties of the finished product. Finished cables preserve waveforms, allow longer signal lengths, and handle weaker signals without distortion or degradation. In LSI applications, for example, low-loss cable assemblies can eliminate the need for amplifying line drivers.

For more info about this coaxial cable by visiting gore.com

Coaxial cable interference

I called Comcast because one of our cable TV channels had lots of interference. The repair guy replaced the regular coaxial cable I had bought at Best Buy with better-shielded RG6 cable, and the interference disappeared.

Electronics stores have RG6 cable set aside with the satellite stuff, but it's worth buying because it can really help to clear up problems with cable TV and cable modem connections.

Cable is the medium through which information usually moves from one network device to another. There are several types of cable which are commonly used with LANs. In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size. Understanding the characteristics of different types of cable and how they relate to other aspects of a network is necessary for the development of a successful network.

The following sections discuss the types of cables used in networks and other related topics.

Unshielded Twisted Pair (UTP) Cable
Shielded Twisted Pair (STP) Cable
Coaxial Cable
Fiber Optic Cable
Wireless LANs
Cable Installation Guides
Unshielded Twisted Pair (UTP) Cable
Twisted pair cabling comes in two varieties: shielded and unshielded. Unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks (See fig.

Source from macit.org

Fire-Flex 18ft Single Antenna Coaxial Cables

Model K-8:
MSRP* $10.99 Model K-8A:
MSRP* $12.99
*MSRP (Manufactures Suggested Retail Price) in U.S. Dollars
Good arteries are important to your heart like good coax cable is important to your radio. Our single lead cable assemblies are made from our RG-58A/U, Fire-Flex coaxial cable. They are to be used on any single antenna installation. This includes CB, scanner, 2-meter, and 10 meter. Check out these features:

Stranded center conductor to maximize flexibility and prevent untimely breakage.
Shielding coverage that averages 95% to protect against RF leaks and interferrence.
Polyvinyl center insulation for ruggedness and longivity.
Performance that exceeds mil-spec requirements for 50 ohm RG-58A/U coax.

Our K-8 cable is 18' (5.5m) long. One end is terminated with a PL-259 type connector to match the connector on your radio and the other end is terminated with a ring terminal on the center conductor and a spade connector on the shields. Use this cable with our K-4 or R-4 stud mount and any mount that uses either one of the lug-style stud mounts.

Our K-8A cable is 18' (5.5m) long. Both ends of this cable assembly is terminated with a PL-259 type connector. This cable is designed to be used with our K-4A or R-4A antenna studs and any mount that uses either of these SO-239 stud mounts.

We also offer a 50' (15.2m) version of our RG-58A/U coax for base antenna installations. These assemblies are made from the same great coax cable as our mobile assemblies. Each is terminated on one end with a PL-259. We left the other end unprocessed so you can terminated it as required by either your antenna or your radio/scanner. Order our Model K-850 (MSRP $24.99)

Source from firestik.com

COAXIAL CABLE History

Coaxial cable, or coax, has a long history. If you have cable television in your home, you have coaxial cable. Broadband transmission uses the same principles as cable TV and runs on coax. Broadband and cable TV take advantage of coax's ability to transmit many signals at the same time. Each signal is called a channel. Each channel travels along at a different frequency, so it does not interfere with other channels.

Coax has a large bandwidth, which means it can handle plenty of traffic at high speeds. Other advantages include its relative immunity to electromagnetic interference (as compared to twisted-pair), its ability to carry signals over a significant distance, and its familiarity to many cable installers.

Coax cable has four parts (Figure 1). The inner conductor is a solid metal wire surrounded by insulation. A thin, tubular piece of metal screen surrounds the insulation. Its axis of curvature coincides with that of the inner conductor, hence the name coaxial. Finally, an outer plastic cover surrounds the rest.

Coax comes in several sizes. Standard Ethernet cable, the yellow stuff called thick Ethernet, is about the diameter of a man's thumb. Thin Ethernet, the black cable, is about as thick as a woman's pinky finger. ARCnet uses RG/68 coax cable. Thicker coax is more robust, harder to damage, and transmits data over longer distances. It's also more difficult to connect.

Standard Ethernet requires a "vampire tap" and drop cable to connect a LAN device. This combination is bulky and expensive. Thin Ethernet uses a biconic (or BNC) connector, which is easier to install than vampire taps.

Source from itarchitect.com