1. History: The real discovery and its actual use dates back to 1929 due to the need for a more efficient and with less interferences conductor for the transmissions of many telephone channels on a single "carrier". Perhaps none of us have never thought that the development of radio communications would never have been possible without the invention of coaxial cable, it is continuously used in our applications that we dont think about that.

2. Introduction: Coaxial cables are the most common, basic transmission lines. They are used to transmit electrical energy, or signals, from one location to another: to connect a source to a load, such as a transmitter to an antenna. A coax cable consists of two conductors separated by a dielectric material. The center conductor and the outer conductor, are configured in such a way that they form concentric cylinders with a common axis. Hence the term and name co-axial. 3. Description of coaxial cable: 4. Construction The center conductor may be made of various materials and constructions. Most common constructions are solid or seven-strand conductors. Solid conductors are used in permanent and infrequently handled applications. stranded conductors are used in flexible cable applications. Common materials include copper, tinned or silver plated copper, copper clad steel and copper clad aluminum. Plated copper is used to aid in solder ability of connectors or to minimize corrosion effects. 5. Data is transmitted through the center wire. The outer braided layer serves as a line to ground. Both of these conductors are parallel and share the same axis. Thats is why the wire is called coaxial. 6. Because of a phenomena known as skin-effect, copper clad materials may be used in higher frequency applications ( > 50 MHz) to improve tensile strength and reduce weight and cost. Skin-effect is the result of higher frequency signals propagating along the outermost surface, or skin, of the conductor. 7. The insulation, or dielectric material, is used to provide separation between the conductors. It is desirable that the material has stable electrical characteristics across a broad frequency range. 8. Temperature range of the cable is often limited by the choice of jacket material. The jacket material serves as a protective covering from the environment. 9. Categories of Coaxial Cable: Coaxial cables are categorize by Radio Guide (RG). Each RG number denotes a unique set of specifications, including: The gauge of the inner conductor. The thickness and the type of the inner insulator. The construction of shield. The size and type of outer casing. 10. Types of Coaxial Cable: Flexible coaxial cable: Flexible coaxial cable is used where the demand is to fit the cable into a tight space without performance loss. 11. Semi Rigid Coaxial cable: Semi rigid cable is using a solid copper outer sheath. This type of coax offers superior transmission, especially at higher frequencies. The major disadvantage of this type is that the cable, as its name implies, is not very flexible. 12. Hand Formable Coaxial Cable: These cables are between flexible and semi rigid cables. These cables are good choices when forming at a point of installation is required. 13. Twin-axial cable: Twin-axial cable is a balanced, twisted pair within a cylindrical shield. It allows a perfect signal which is shielded and balanced to pass through. 14. Triaxial cable: Triaxial cable is a coaxial cable with a third layer of shielding, insulation and sheathing. The outer shield is grounded and protects the inner shield from interference from outside sources. 15. Connectors: The ends of coaxial cables usually terminate with connectors. Coaxial connectors are designed to maintain a coaxial form across the connection and have the same impedance as the attached cable. Connectors are usually plated with high conductivity metals such as silver or gold. In the case of computer networks, BNC (Bayonet Niell- Concelman) RF connectors are used. 16. Electrical Properties: The most common electrical property of coaxial cable is the characteristic impedance. Impedance is the total opposition to the flow of electrical energy within the cable. It is a complex value defined by the cables resistance and capacitance. It is expressed in Ohms. A simple formula to determine the impedance of a coaxial cable is: Impedance= 138*Vp*log10(D/d) Vp= Velocity of Propagation(is the speed at which a signal travels through the cable with respect to the speed of light.) D = Diameter of the Dielectric d = Diameter of the Conductor 17. Capacitance: Capacitance is the ability of the cable to hold a charge. The larger the capacitance value, the longer it takes a signal to reach full amplitude within the cable. Therefore, higher capacitance is usually a bad attribute. 18. Physical Properties: Temperature Rating: Temperature Ratings provides the limitations on temperature extremes that the cable material can handle. The safe range is based upon the thermal properties of the dielectric and jacket materials that assures that the product will not fracture or melt. Pulling Tension: It is typically a safe value well below the break strength of the cable. Staying below this maximum assures that the conductor will not be stretched in the cable. 19. Attenuation: Reduction of signal strength during transmission. It is dependent upon the cable design and is both frequency and length dependent. It increases with the increase in frequency. It is most effected by DC resistance of the center conductor and dissipation factor of the dielectric material. Attenuation is measured in decibels. 20. Attenuation: IP P dBnAttenuatio 0 10log10)( PO is the output power PI is the input power 21. Repeaters: Repeaters are used in coaxial cables to reduce attenuation. A repeater can couple together two 500m segments of coaxial cable. The repeater occupies one transceiver on each segment and must pass all the signals from one cable to other. 22. Reflection losses: Reflection losses are based upon signals reflecting back to the source rather than propagating through the cable. These reflections are caused by impedance mismatches or variations in the cable. Randomly spaced throughout the cable, these mismatches will cause minimal loss, but when spaced periodically, that is at the same repeat distance, they add up together causing a large loss corresponding to that period wavelength. This loss can be minimized by quality cable manufacturing techniques and proper installation practices. 23. Cross Talk: Crosstalk refers to the amount of coupling between adjacent wire pairs, which occurs when a wire absorbs signals from adjacent wires. Crosstalk is measured by injecting a signal into one pair and then measuring the strength of that signal on each of the other pairs in the cable. 24. Cross Talk: 25. Applications: Long distance coaxial cable was used to connect radio networks and television networks. It is used by consumers to connect television receivers to external antennas. Short coaxial cables are also employed to connect home video equipment and radio systems. Micro coaxial cables are used in a range of consumer devices, military equipment, and also in ultra-sound scanning equipment. Coaxial cable are also widely used in local area networks(LANs). 26. Benefit: The main benefit of using a coaxial cable is that it is the default cable of its type. This means that most electronics is already compatible with coaxial. Other benefits of the coaxial cable include its ability to shield television from outside interference. This can maximize picture quality and help to avoid static. It is inexpensive also. 27. Advantages of Coaxial Cable: They are most common means of data transmission over short distances. They are cheap to make Cheap to install Easy to modify Good bandwidth Great channel capacity 28. Disadvantages of Coaxial Cable: Signals entering the cables can cause unwanted noise and picture ghosting, making it useless. A continuous current flow, even if small, along the imperfect shield of a coaxial cable can cause visible and audible interference. More expensive than twisted pairs and is not supported for some network standards. It is also has high attenuation, have the need to implement repeaters. 29. Thank you!