Page 195 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

The dielectric insulator separates the inner conductor and outer copper braided mesh. The dielectric insulator is
covered by copper mesh (foil or braided conductor). The dielectric insulator may be polyethylene foam or PTFE
which minimizes ohmic losses arising from contact with the conductors. Outer jacket is to protect the cable from
environmental and mechanical damages. A common choice is PVC.
Both inner conductor and braided wire mesh conductor is in the cable share a common central axial, hence the
term coaxial. Coaxial cables are rated in ohms for their impedance. Common impedances are 50 ohms, 75 ohms,
95 ohms.
There are many types of coaxial cable connectors.

Four are common. BNC, SMA, N, F types. Coaxial cables are categorized based on the type of signal transmission.
One is Baseband and the other is Broadband cable.
Baseband cable
It is a 50 ohms resistance cable that is capable of digital transmission. Used in short distances for optimum
performance.
Broadband cable
It is a 75 ohms resistance cable used for analog data transmission. It is used up to 100 km.

Based on Radio Gauge (RG) standards, there are two types of Coaxial cables:
Thicknet and Thinnet
Thicknet: RG 8, RG 9, RG 11 coaxial cable is also known as Thick Ethernet or 10Base5 systems. 10 means, it is
10 Mbps speed and 5 refers to 500 meters distance between nodes or repeaters. Where Base indicates that the
transmission type is a “Baseband transmission”
Thicknet cabling uses heavier gauge coaxial cable than Thinnet.
Thinnet: RG 58 Coaxial cable is used 10Base2 systems. 10 means 10mbps speed and 2 refers to 200 meters
distance between nodes or repeaters.
Advantages
Coaxial cable is useful for both analog and digital data transmission.

It has a higher bandwidth, so it supports a mixed range of services.
Relatively less expensive compare to fiber optic cable.
Disadvantages
The number of node connections is limited.
Prone to damage due to lightning strikes.
Applications

Broadband internet, high-speed computer data buses, cable TV, Ethernet.
Optical Fiber Cable
It also is known as fiber optic cable consists of strands of one or more fibers inside the casing and its assembly
is similar to electrical cable.
Optical fiber has three parts
Core
It is the inner layer is called the core, with refractive index n1. Light is guided in this part. The core will have a
higher refractive index than cladding.
Cladding
which surrounds the core, with refractive index n2. Whose refractive index is less than the core? The purpose of
cladding is to keep the light reflections in core instead of being reflections.
Casing
Which is an outer layer for protecting the cable from damages.

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CITS : E & H - Electronics Mechanic - Lesson 108 - 117