Coaxial cable is a transmission cable with low loss characteristics. It not only shields external signals, but also provides a stable transmission for various applications involving a wide range of frequency bands. Cable operators, telephone companies, and Internet providers use coaxial cables to transmit data, video, and voice communications to customers. It is sometimes used in homes, but it is gradually replaced by cheaper twisted pair cables.
What is a coaxial cable?
Coaxial cable, also called coax cable, is made of four layers of materials: copper wire, Inner dielectric insulator, foil sheild, woven copper shield, outer plastic sheath. The term coaxial refers to the inner conductor and the outer shield sharing a geometric axis.
1. Conducotr: The center conducotr is a thin wire made of solid copper wire or braided copper wire.
2. Dielectric (foil covered): polyethylene providing mechanically stable, closed cell foam with high VP.
3. Shield: High quality braid is used to further improve LF shield isolation in extreme RF noise environments.
4. Jacket: a UV stable outer jacket of either polyethylene (PE) or flame retardant polyvinyl chloride (PVC) is available to protect the core.
How do coaxial cables work?
Coaxial cable works by carrying data in the center conductor, while the surrounding layers of shielding stop any signal loss and help reduce EMI.
Coaxial cables conduct alternating current instead of direct current, which means that the direction of the current is reversed several times per second.
If a general wire is used to transmit high-frequency current, this wire will be equivalent to an antenna that emits radio outwards. This effect loses the power of the signal and reduces the strength of the received signal.
The coaxial cable is designed to solve this problem. The radio emitted by the center wire is isolated by the mesh conductive layer, which can be grounded to control the emitted radio.
Types of Coax Cables
There are numerous types of coaxial cables, let’s jump into the different types of coax cables that are available.
1. Hard line coaxial cable
Hard line is used in broadcasting as well as many other forms of radio communication. It is a coaxial cable constructed using round copper, silver or gold tubing or a combination of such metals as a shield. Some lower-quality hard line may use aluminum shielding, aluminum however is easily oxidized and unlike silver oxide, aluminum oxide drastically loses effective conductivity. Therefore, all connections must be air and water tight.
Hard line can be 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. These large-scale hard lines are almost always used in the connection between a transmitter on the ground and the antenna or aerial on a tower.
2. Radiating coaxial cable
Radiating or leaky cable is another form of coaxial cable which is constructed in a similar fashion to hard line, however it is constructed with tuned slots cut into the shield. This type of cable is to provide a tuned bi-directional “desired” leakage effect between transmitter and receiver. It is often used in elevator shafts, US Navy Ships, underground transportation tunnels and in other areas where an antenna is not feasible.
3. RG-6 coaxial cable
RG-6 is available in four different types designed for various applications.
- Plain or house RG-6 is designed for indoor or external house wiring.
- Flooded cable is infused with waterblocking gel for use in underground conduit or direct burial.
- Messenger may contain some waterproofing but is distinguished by the addition of a steel messenger wire along its length to carry the tension involved in an aerial drop from a utility pole.
- Plenum cabling is expensive and comes with a special Teflon-based outer jacket designed for use in ventilation ducts to meet fire codes.
4. Triaxial coaxial cable
Triaxial cable or triax is coaxial cable with a third layer of shielding, insulation and sheathing. The outer shield protects the inner shield from electromagnetic interference from outside sources.
5. Twin-axial coaxial cable
Twin-axial cable or twinax is a balanced, twisted pair within a cylindrical shield. It allows a nearly perfect differential mode signal which is both shielded and balanced to pass through.
6. Semi-rigid coaxial cable
This type of coax offers superior screening compared to cables with a braided outer conductor, especially at higher frequencies. The major disadvantage is that the cable, as its name implies, is not very flexible, and is not intended to be flexed after initial forming.
7. Rigid coaxial cable
Rigid line is a coaxial line formed by two copper tubes maintained concentric every other meter using PTFE-supports. Rigid lines cannot be bent, so they often need elbows.
Rigid line is commonly used indoors for interconnection between high-power transmitters and other RF-components, but more rugged rigid line with weatherproof flanges is used outdoors on antenna masts, etc.
Many broadcasting antennas and antenna splitters use the flanged rigid line interface even when connecting to flexible coaxial cables and hard line.
Coaxial cable Vs. Fiber-Optic cable Vs. Twisted pair cable
Coaxial cable, Fiber optic cable and twisted pair cable are three major types of network cables used in communication systems. Each of them is different and suitable for different applications.
Coaxial cable, or coax cable, is designed to transmit high-frequency signals. It’s comprised of a round copper conductor and three layers of insulation and shielding which prevents crosstalk from motors, lighting and other sources of EMI. With the shield construction, the coaxial cable can support longer cable lengths between two devices.
Fiber Optic Cable
Fiber optic cable, also called as optical fiber cable, is a type of Ethernet cable which consists of one or more optic fibers that are used to transmit data. Fiber optic cable transmits data as pulses of light go through tiny tubes of glass. The transmission capacity of optical fiber cable is 26,000 times higher than that of twisted pair cable.
Twisted Pair Cable
Twisted pair cable is often used for telephone communications and most modern Ethernet networks. It is a kind of wiring in which two conductors of a single circuit are twisted together. A pair of wires forms a circuit that can transmit data. And the pairs are twisted together to provide protection against crosstalk, the noise generated by adjacent pairs.
Except for the construction, these three types of cables distinguish from each other in cable performance and capacity.
|No.||Key||Coaxial Cable||Optical Fibre||Twisted Pair Cable|
|1||Material||Plastic and copper wires||Plastic and glass||Plastic and copper wires|
|2||Speed||More than 10Gbps||10/100/1000 Mbps, 10/40/100/200 Gbps||Up to 10 Gbps|
|3||Distance||Up to 500m||Up to 80km||Up to 100m|
|4||Bandwidth||750 MHz (Default)||Up to 4700 MHz||Up to 4700 MHz|
|5||Cost||100ft RG6 digital shielded coaxial cable – $20-26||50ft LC to LC duplex 9/125 single mode fiber patch cable – $7-8||10ft Cat6 24AWG snagless-booted UTP Ethernet network patch cable – $8-9|
Many of today’s companies use cable connections for their business broadband service. When choosing an access solution for your business, be sure to identify your needs and expectations for speed, bandwidth and functionality.
Coaxial Cable Recommendation
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