Page 193 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

provider and present this information in an onscreen programming guide. Many receivers have parental lock-out
options, and some have built-in Digital Video Recorders (DVRs), which let to pause live television or record it on
a hard drive.
Advantages of DTH Technology:

• The advantages of DTH Technology include:
• Greater service coverage.
• More channels.
• Better signal quality.

• Multiple language options.
• Pay only for the channels and services that the user wants.
• Applications such as Parental Lock, Pre-booked Pay-Per-View and Impulse Pay-Per-View.
Disadvantages of DTH Technology
The disadvantages of DTH Technology include:

One of the major problems for the subscribers of Direct To Home service is unable to view any channel during
heavy rains due to weak signals.
Changing service provider is not easy as the user has to pay additional cost to buy new Set Top Box from new
service provider.
Satellite television installation basics
To receive satellite television broadcasts, a TV antenna capable of receiving the satellite broadcasts is required
as well as a television that can cover the required frequencies and also power the electronics in the satellite
television antenna.

The system for a satellite television installation is a little different to that required for terrestrial television.
The overall satellite dish installation requires a number of different elements:
Satellite dish antenna: This refers to the antenna itself. Typically parabolic reflector antennas are used as these
operate well at the frequencies used, giving high levels of gain within a relatively small space.
LNB / LNBF: The satellite TV LNB or low noise block is used to amplify the signal at the antenna and convert it
to a lower frequency that can be fed along coax feeder with acceptable levels of loss.
Coaxial feeder: The coax feeder is used to transport the signal from the low noise block to the television receiver.
Satellite capable television / set top box: the satellite television or set top box receives the down-converted
signals within the required band and also supplies power along the centre conductor of the coax feeder to power
the satellite TV LNB or LNBF.
Deeper descriptions and explanations of these different elements of a satellite antenna installation are given
below.
Types of Cables
Cables are classified as
• Twisted pair
• Coaxial
• Optical fiber
Twisted pair cables consist of color-coded pairs of insulated copper wires, one wire carries the signal, and the
other is used for ground reference. Every two wires are twisted around each other to form pairs that are encased
in a plastic sheath each wire with a diameter of 0.4 mm to 0.8 mm.
The number of pairs varies depending on the cable type. More twists per foot in a pair of wires, less the cross talk.
The significance of twisting is it reduces or nullifies the interference such as noise or cross talk caused due to
radiofrequency of electromagnetic interference.
By twisting the wires, the effect of noise or disturbance is the same on both wires. Since the receiver takes only
the difference between the two wires the effective noise is canceled.

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