Transmission Media - (2)

Transmission Media - (2)

Summary on What we have Studied on last Tutorial :-

• Networking involves connection of computers, workstations and peripheral devices.
• Wire is a single, cylindrical strand of metal conductor with low resistance to the current flow.
• Every cable has a limitation to carry signals only to a particular distance after which the quality of the signal degrades and becomes corrupt.
• As the signals travel through cables, they lose their strength. This loss of signal strength in a cable is called as attenuation.
• It is the amount of digital data that a cable can carry. Each type of cable can carry only a certain amount of information or data over a given period of time.
• Each type of cable is susceptible to some interference such as internal or external noise. It depends on the environment where the cable is to be laid.

(2.1) Coaxial Cable :-

      Coaxial Cables consists of a solid copper core surrounded by an insulator made up of Polyvinyl Chloride ( PVC ) of Teflon. PVC is a plastic made from the Chemical Vinyl Chloride. It is surrounded by a Mesh like ground wire called the braiding or shielding and an outer cover known as Sheath.

      The insulator acts as a barrier between the braiding and inner core. If the insulator is absent, the shield and the core may come in the contact and cause a short circuit. The braiding protects the cable from external interfaces such as Electro Magnetic Interface ( RFI ).

Coaxial Cable

Coaxial Cable

Note :-

      Coaxial cables are less prone to interference ( bothe internal and external as compared to twisted pair cables.

(2.1.1) Various parts of coaxial cable are :-

• Outer insulation or Jacket : It is made up of (Teflon) or nonplenum (polyethylene or polyvinyl chloride).
• Copper Mesh or Shields : Some coaxial cables have a braid shield, some have a foil shield and others have both a braid and foil shields. These shields can supply ground for the carrier wire ( copper ) and help protect the copper wire from EMI and RFI.
• Insulation : It is a nonconductor ( dielectric ) around the carrier wire. It is usually made up of polyethylene or Teflon.
• Copper Wire or Carrier Wire : It is a wire conductor at a the centre of the cable and is made up of copper and may be either solid or stranded. 

Note :-

      IEEE specifies stranded copper carrier wire with tin coating for thin coaxial cable and solid copper wire for thick coaxial cable

(2.1.2) Advantages of Coaxial Cables :-

• Secured data transmission
• Protected from crosstalk
• Protection from EMI and RFI

(2.1.3) Disadvantages of Coaxial Cables :-

• Most expensive of all types of cables
• Difficult to install

(2.1.4) Types of Coaxial Cable :-

1. RJ58 cable (Thinnet/Thinwire/Cheapnet) : RJ58 cable is approximately 0.64 centimeter in diameter and is mainly used in network in which the devices are frequently added or removed. It becomes easy to add or remove devices from the network using RG58 cable. Coaxial cables specifications are governed by Radio Government ( RG ) in collaboration with U.S. Military. Thinwire falls in category of RG58. The thinwire Ethernet is also known ad 10Base2 where 2 denotes the maximum segment length of 200 meter ( practically 185 meter ) which is a backbone cable. The canter conductor of the coax must be Stranded.  
2. RG8 ( Thickwire Ethernet/Thicknet ) : RG8 is a type of coaxial cable that is approximately 1 centimeter in diameter and mainly used as a backbone cable in Thicknet. It has a solid center conductor and is physically much thicker than thinnet cable. Thick wire provides better protection from external and internal Interferance. It can also carry signals to a great distance. The only disadvantage is rigidness due to which it is only used as backbone cable to carry signals over a long distances. Thickwire falls mainly in the category in RG8. The Thickwire Ethernet is also known as 10Base5 where 5 denotes the maximum segment length of 500 meter. A maximum of 100 nodes can be attached to each 10Base5 Segment.

This type of wire is stiff cable with a solid center core covered by a foam insulator, a shielding braid and an ourter sheath. The outer sheath is mostly yellow in colour. 

Read: Transmission Media - (1)

Read: Transmission Media - (3)

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