ADVANCED TELEVISION SYSTEMS
List
the merits of Digital TV receiver. /
List the merits of digital TV receivers that are not achievable in a analog
receiver.
Reduced
Ghosts
Reduction of 50Hz flicker
High
resolution pictures
Slow
motion action
What
do you mean by EDTV.
EDTV is
mainly intended for direct broadcasting satellite system.
To
improve the performance of the TV system it requires different transmission
standards but it maintain the present line numbers and field rates.
Why
FM is used in satellite TV system?
If we
compare analog frequency modulation (FM) with analog amplitude modulation (AM),
the FM better performance is due to the fact that the signal to noise ratio at
the demodulator output is higher for wideband FM than for AM. For the
transmission of a television signal over a satellite, the amplitude modulation
would be severely affected by losses, various forms of interference, and
nonlinearities in the transponder.
By the
other hand frequency modulation is also more robust against signal amplitude
fading phenomena. For a video signal, using the Carson’s rule, the required
bandwidth is 32.4 MHz, thus a bandwidth of 36 MHz was originally chosen for a
satellite transponder in order to accommodate one analog FM television channel.
And
since the FM television channel occupies the entire transponder bandwidth, this
can be operated at full power without any inter modulation interference caused
by the nonlinear transfer characteristic.
State
the use of geostationary satellite for TV system.
The shear
range of programmes currently available on satellite channel is very much
impressive such as 24-hour music videos, news, and feature films.
Commercial
radio, TV broadcasting, telecommunications, weather forecasting, Global
positioning
A variety
of general entertainment programmes, sports, children’s programmes, foreign
language broadcasts and cultural programmes are all available for the keyboard
dish owner.
Some of
these come through subscription channels and others by free to watch channels
which are sponsored by advertising
What
are the advantages of HDTV?
High
quality image and sound
Wide
screen aspect ratio for 103 cm trinitron(16 : 9)
The HDTV
has the resolution of approximately twice the vertical and horizontal
resolution of ordinary TV
Differentiate DVD from CD.
Distinguish between VCD and DVD.
Programmes on DVD can be four times longer
than VCD
DVD
video disc holds over 4 hours while the VCD holds 74 minutes.
DVD
video has up to 8 digital audio tracks. Each track can hold uncompressed audio
with quality better than audio CD
The
quality of DVD video vast exceeds that of video CD, with 4 times the resolution
in normal mode and 5.5 times in wide screen mode.
What
are the transmission principles behind digital TV?
Sampling
Analog
to digital conversion
Video /
Audio signal quantizing
Binary
Encoding
What
is the value of characteristic impedance of coaxial cable used for CATV?
The
value of characteristic impedance of coaxial cable (RG-59U ½ inch flexible
cable) used for CATV is 75 Ω
What
are two types of video disc system?
Laser or
optical disc system
Capacitance disc system
What
do you mean by longitudinal video recording?
A method
in which video signals are recorded on at least several tracks along the length
of the tape.
Give
the applications of video tape recorders.
Smaller
and lower priced video tape recorders using ½ inch tape are available for
closed type circuit TV or for use in the home. They can record and playback
programs on a television receiver in color and monochrome.
In
addition to that small portable cameras are provided for a complete television
system with the recorder. These portable systems are also employed for taping
television programs from a remote are also employed for taping television
programs from a remote location for away from the TV broadcast studio.
Define
bullet amplifier.
The LNA
low noise amplifier is provided in the middle of coaxial cable to compensate
any losses in it. This LNA is often called as bullet amplifier.
What
do you mean by helical scan recording?
In
helical scan recording, the two recording heads ‘look at ‘ the tape surface as
it is drawn past them through two tiny rectangular slits mounted on opposite
sides of the drum. The heads thus trace out diagonal tracks across the tape,
one track per head.
Why
are up-link and down-link frequencies chosen to be in the GHz range and kept
fairly apart from each other?
The
transponder cannot transmit and receive on same frequency, because the
transmitter signal can overload the receiver and block the small up-link
frequency signal and thereby prohibiting the communication.
The
frequencies used for this purpose are in microwave frequency range from (3 to
30 GHz). During UHF, the atmosphere does not act as a barrier and signals can
able to travel out into space and return back without any absorption or
deflection.
Write
short notes on CATV.
CATV
stands for community antenna television systems. The CATV system is a cable
system distributes good quality television signal to a very large number of
receivers throughout an entire community.
Generally
this system gives increased TV programmes to subscribers who pay a fee for this
service. A cable system may have many more active VHF and UHF channels than a
receiver tuner can directly select.
What
do you mean by translator?
Translator
is a frequency converter which heterodynes the UHF channel frequencies down to
a VHF channel.
Define
uplink frequency in satellite communication.
The
frequency at which the information signals are transmitted from earth station
to the satellite is called uplink frequency. Most the communication satellite
uses C band frequencies.
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