training report doordarshan kendra
TRANSCRIPT
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9th July 2013
Posted 9th July 2013by Kunal Kishor
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9th July 2013
Training Report
On
DOORDARSHAN KENDRA
Submitted in the partial fulfillment of the requirement for the award of
degree of
Bachelors of Technology
in Electronics & Communication Engineering
Submitted by:
Name: KUNAL KISHOR
Name and Location of Company: DOORDARSHAN KENDRA
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MUZAFFARPUR
ACKNOWLEDGEMENT
I want to thanks to Mr. R. sahni sir and Mr. B.S. chaudhary sir because he give me right
concept to complete this training .Also I want to thanks doordarshan Kendra because
different types of metterials are present there help me a lot .
Doordarshan Kendra has provided such a big support in marking this training work
because it would be possible without the books available in the industry
INDEX
Chapter
1. Introduction.
2. History.
3. Satellite Communication.
3.1 Satellite orbits.
3.2Antenna.
4. Propagation modes.
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5. TV studio .
5.1 Procedure in recording.
5.2 Procedure in transmission.
5.3 Video Signal Generation.
5.4 CCVS.
5.5 Components of TV studio.
6. TV Camera.
6.1 Camera lens.
6.2 Transducer.7. Lighting.
8. Microphone.
8.1 Types of microphone.
9. Video chain.
10. Audio chain.
11. Vision Mixer.
11.1 switchin .
12. MSR.
13. Earth Station.
13.1 componenet.
14. Transmitter.
15. Receiver.
16. ENG.
17. OB Van.
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18. DD Direct+ DTH.
19. Future scope.
20. Conclusion.
Abbreviation CCVS COLOR COMPOSITE VIDEO CHAIN
ENG ELECTRONICS NEWS GATHERING
LOS LINE OF SIGHT
MSR MASTER SWITCHING ROOM
VM VIDEO MIXER
CG COMPUTER GRAPHICS
PDA PARABOLIC DISH ANTENNA
IRD INTEGRATOR RECEIVER
DECODER
LNA LOW NOISE AMPLIFIER
LNBC LOW NOISE BLOCKCONVERTER
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Electronics &
Communication
Chapter 1-
INTRODUCTION
Doordarshan is the public television broadcaster of India and a division of Prasar Bharti,
and nominated by the Government of India. It is one of the largest broadcasting
organizations in the world in terms of the infrastructure of studios and transmitters.
Doordarshan Kendra is amilestone in the field of entertainment and education media
source. Doordarshan, muzaffarpur is the Program Production Center and transmition ..
The studios are housed at same campus and the transmitter is located at the
muzaffarpur.
AIR and Doordarshan aims to provide information, education and entertainment for
the public. Its network of 1400 terrestrial transmitters cover more than 90.7% of
India's population.
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Electronics &
Communication
Chapter 2-
HISTORY
The birth of broadcasting in India has started on an experimental basis in year 1921
whenTimes of India in collaboration with P&T department broadcasts a musical
programme. In the year 1930 radio broadcasting started operating under the Indian
broadcasting company. Government took over the charge of broadcasting in March
1935, a separate office of the controller of broadcasting was created. The land mark in
the history of broadcasting is change of name of the Indian broadcasting to AIR in 1936and in same year Delhi station was formed. From 1936 onwards the development of
AIR was very slow, nine stations were opened up in different places like Delhi,
Calcutta, Bombay, madras, lucknow and tiruchi. From 1956 onwards AIR was
popularly known as akashwani.
On 12thNovember 1947 the voice of Gandhi ji was broadcasted in AIR and since then
it is celebrated as broadcasting day. Television (Doordarshan) started in India in the
year 1959 with black and white transmission. The black & white transmission was
converted fully into colour in 1982 during Asian games.
Electronics &
Communication
Chapter 3- SATELLITE
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COMMUNICATION
In telecommunications, the use of artificial satellites to provide communication links
between various points on Earth. Satellite communications play a vital role in the global
telecommunications system. Approximately 2,000 artificial satellites orbiting Earth relay
analog and digital signals carrying voice, video, and data to and from one or many
locations worldwide.
Satellite communication has two main components: the ground segment, which consists
of fixed or mobile transmission, reception, and ancillary equipment, and the space
segment, which primarily is the satellite itself. A typical satellite link involves the
transmission or uplinking of a signal from an Earth station to a satellite. The satellite then
receives and amplifies the signal and retransmits it back to Earth, where it is received
and re-amplified by Earth stations and terminals. Satellite receivers on the ground
include direct-to-home (DTH) satellite equipment,mobile reception equipment in
aircraft, satellite telephones, and hand held devices.
3.1 SATELLITE ORBITS:
a) GEOs = Geostationary Earth Orbits.
b) LEOs -= Low Earth Orbits. c) MEOs = Medium
Earth Orbits.
1. Geostationary orbit
A circular orbit 35,785 km (22,236 miles) above Earths Equator in which a satellites
orbital period is equal to Earths rotation period of 23 hours and 56 minutes. A
spacecraft in this orbit appears to an observer on Earth to be stationary in the sky. This
particular orbit is used for meteorological and communications satellites. The
geostationary orbit is a special case of the geosynchronous orbit, which is any orbit with
a period equal to Earths rotation period.
2. Low- Earth-orbiting satellites
A Low Earth Orbit (LEO) typically is a circular orbit about 400 kilometers above the
earths surface and, correspondingly, a period (time to revolve around the earth) of
about 90 minutes. Because of their low altitude, these satellites are only visible from within
a radius of roughly 1000 kilometers from the sub-satellite point. In addition, satellites in
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low earth orbit change their position relative to the ground position quickly. So even for
local applications, a large number of satellites are needed if the mission requires
uninterrupted connectivity.
Satellite communication
Started in 1960.
Uses Geo Stationary Satellite.
Operates in C-Band & Ku-Band.
Started in India in 1975.
First Indian Satellite INSAT launched in 1982.
Gulf War brought satellite television to prominence
3.2-Antennas:-
Antenna (or aerial) is a transducer that transmits or receives electromagnetic waves. In
other words,antennas convert electromagnetic radiation into electrical current, or vice
versa. Antennas generally deal in the transmission and reception of radio waves.
Types of antenna:
Isotropic antenna (idealized)
Radiates power equally in all directions
Dipole antennas
Half-wave dipole antenna (or Hertz antenna)
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Quarter-wave vertical antenna (or Marconi antenna)
Parabolic Reflective Antenna
A parabolic antenna is a high-gain reflector antenna used for radio, television and
datacommunications, and also for radio location (radar),on the UHF and SHF parts of
the electromagnetic spectrum. The relatively short wavelength of electromagnetic
radiation at these frequencies allows reasonably sized reflectors to exhibit the
desired highly directional response for both receiving and transmitting. A
typical parabolic antenna consists of a parabolic reflector with a small feed
antenna a tits focus. To find the focus, reflect the light of a flashlight off of the
dish. When the reflected beam is parallel, the flashlight is at the focus. The
reflector is a metallic surface formed into a paraboloid of revolution and
(usually) truncated in a circular rim that forms
the diameter of the antenna. This paraboloid possesses adistinct focal point
by virtue of having the reflective property of parabolas in that a point light
source at this focus produces a parallel light beam aligned with the axis of
revolution. The feed antenna at the reflector's focus is typically a low-gain
type such as a half-wave dipole or a small waveguide horn.
Electronics
& Communication
Chapter 4 PROPAGATION
MODEDS
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Ground-wave propagation
Sky-wave propagation
Line-of-sight propagation
Electronics &
Communication
Chapter 5 - TV
STUDIO
Doordarshan has two studio halls. One is used as News Room and the other
one is used for shooting various programs. Artificial sets are created in the
studio hall according tor equirements of the program to be shooted.
5.1-PROCEDURE IN REORDING
Set is designed in studio as per conceptual thought of program
producer.
Floor plan is envisaged. Lighting, Audio and placement of the cameras is arranged as per floor
plan.
Pre testing of cameras, microphones, VCRs etc. is done before
recording.
Recording begins and desired camera / mike are selected through VM/
Audio console as per command of producer. Program is recorded on
VCR.
5.2-PROCEDURE IN TRANSMISSION
The programs are transmitted as per the daily cue sheet.
Normal transmission hours are 1600-2000 Hrs.
Cue sheet is discussed daily by program and technical staff for details
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in it and for any last moment changes if any.
After getting D-link caption from Delhi end program is played from
VCR /Server. The program is uplinked by Earth Station.
The program is also transmitted to transmitter at HPT Nahargarh via
MW link.
During our slot, both live as well as recorded programs are transmitted.
Around 2000 Hrs after getting linking caption from DD# 1, the signal
from DD#1 is selected and accordingly transmitted by HPT/ ES.
5.3-Video signal generation
Video is nothing but a sequence of pictures. The image we see is maintained in our eye
for 1/16sec. So if we see images at the rate more than 16 pictures/sec, our eyes cannot
recognize the difference and we see the continuous motion. In movies camera and movie
projector it is found that 24 fps is better for human eyes. TV system could also use this
rate but in PAL system 25fpm is selected. In TV cameras image is converted in
electrical signal using photosensitive material. Whole image is divided into many micro
particles known as pixels. These pixels are small enough so that our eyes cannot
recognize pixels and we see continuous image. Thus, at any particular instance there are
almost infinite numbers of pixels that need to be converted in electrical signal
simultaneously for transmitting picture details. How ever this is not possible practical
because it is no feasible to provide a separate path for each pixel. In practice this
problem is solved by method known as Scanning in which information is converted
one by one pixel, line by line and frame by frame.
5.4-COLOUR COMPOSITE VIDEO SIGNAL
Active waveform comprises of 2 signals:
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Luminance(Y)-black and white
Chrominance(C)- colour signal
5.5-COMPONENTS OF TV STUDIO
Camera
Lighting
Microphones
Vision mixer and Audio consoles
MSR
VCR /Servers
Acoustics
Post production and video effects
supporting services like AC, UPS
Chapter 6- TV
CAMERA
A TV Camera consists of three sections:
a) A Camera lens and optical block
b) A transducer or pick up device
c) Electronics
6.1-CAMERA LENS
The purpose of the camera lens is to focus the optical energy at the
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face plate of a pickup device i.e. to form an optical image. The lens
has following sections:
1.Main focus section
2. Zoom section with manual or servo mode operation.
3.Servo drive assembly for Zoom and iris control.
4. Aperture section with manual or auto mode.
5. Back focus section with adjustment facilities for back and micro
focus.
6.2- TRANSDUCER PICK UP DEVICE
R, G & B signals, as separated by the optical block are converted to electrical signal in
the transducer section of the camera. It is then processed in camera electronics to give CCVS
(color composite video signal) output.
Chapter 7-
LIGHTING
Lighting for television is very exciting and needs creative talent. There is always a
tremendous scope for doing experiments to achieve the required effect. Light is a kind
of electro magnetic radiation with a visible spectrum from red to violet i.e. wavelength
from 700 nm to 380
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Nm respectively.
Basic three pointing lighting
Key light:- It gives shape and modeling by a casting shadow. It is treatedas a sun in
the sky and should cast only one shadow.
Fill light:- Controls the lighting contrast by filling in shadows.It can also provide catchlights in the eyes.
Back light:-Separates the body from the background, gives roundness to the subject
and reveals texture.
Background lights:- Separates person from the background and reveals
background interest and shape.
Lighting equipments:-
HMI lights compared to standard incandescent lights deliver five times the light output
per watt. They generate less heat, which is an important consideration when shooting
inside in a confined space. (HMI stands for Hydrargyrum Medium Arc-length Iodide).
The light on the left side of this picture is a HMI light; the one on the right a standard
quartz light.
Cycs (large, seamless, neutral backgrounds) can be lit from the top and bottom with
cyclights.The one here sits on the studio floor and is directed up at the background.
Chapter 8-
MICROPHONES
A microphone is an acoustic-to-electric transducer or sensor that converts sound in to
an electrical signal.
8.1- TYPES OF MICROPHONES
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1.CONDENSER MICROPHONE:-
In a condenser microphone also called a capacitor microphone or electrostatic
microphone, the diaphragm acts as one plate of a capacitor, and the vibrations produce
changes in the distance between the plates.
2. ELECTRET CONDENSER MICROPHONE
An electret microphone is a relatively new type of capacitor microphone invented at Bell
laboratories in 1962 by Gerhard Sessler and Jim West. An electret is a ferroelectric
material that has been permanently electrically charged or polarized. The name comes
from electrostatic and magnet; a static charge is embedded in an electret by alignment of
the static charges in the material, much the way a magnet is made by aligning the
magnetic domains in a piece of iron.
3. DYNAMIC MICROPHONE:-
Dynamic microphones work via electromagnetic induction. They are robust, relatively in
expensive and resistant to moisture. This coupled with their potentially high gain before
feedback makes them ideal for on-stage use. Moving-coil microphones use same
dynamic principle as in loudspeaker, only reversed.
4. RIBBON MICROPHONE:-
Ribbon microphones use a thin, usually corrugated metal ribbon suspended in a
magnetic field. The ribbon is electrically connected to the microphone's output, and its
vibration within the magnetic field generates the electrical signal. Ribbon microphones
are similar to moving coil microphones in the sense that both produce sound by means
of magnetic induction.
5. PIEZO ELECTRIC MICROPHONE:-
A crystal microphone or piezo microphone uses the phenomenon of piezoelectricity -
the ability of some materials to produce a voltage when subjected to pressure
- to convert vibrations into an electrical signal.
6. LASER MICROPHONE:-
Laser microphones are often portrayed in movies as spy gadgets. A laser beam is aimed
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at the surface of a window or other plane surface that is affected by sound. The slight
vibrations of this surface displace the returned beam, causing it to trace the sound wave.
The vibrating laser spot is then converted back to sound. In a more robust and
expensive implementation, the returned light is split and fed to an interferometer, which
detects movement of the surface.
7. FIBER OPTIC MICROPHONE:-
A fiber optic microphone converts acoustic waves into electrical signals by sensing
changes in light intensity, instead of sensing changes in capacitance or magnetic fields as
with conventional microphones.
Chapter 9-
VIDEO CHAIN
The video we see at our home is either pre-recorded in studio or live telecasted. Block
diagram shown in fig illustrates different chains of video recording, video playback,
news, and live broadcasting. In First chain we will understand studio program recording.
Camera output from the studio hall is sent to CCU where many parameters of videosignals are controlled. Output signal of CCU after making all corrections is sent to VM
in PCR-1 (production control room).Output of 3 to 4 cameras comes here and final
signal is selected here using VM according to a directors choice.
The final signal from VM is sent to VTR. VTR uses both analog and digital tape
recording system. At the time transmitting this pre recorded program cassettes is played
in to respective in VTR room. Signal from VTR is sent to PCR-2. PCR-2 has one VM,
video monitoring system, and CG (Computer Graphics). From PCR-2, signal travels
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CUT
The cut is an instantaneous switch from one picture to another. It avoids the frame roll &
flash evident, on picture at the moment of cutting.
MIX
It uses additive mixing. The transitions here are less pronounced. As the faders are
operated, the established picture fades away, while the new picture progressively.
Chapter 12- MASTER
SWITCHING ROOMMaster switching room (MSR) is used for transmission media. It is the engineering co-
ordination center of activity for selecting & routing the signal from various sources to
transmitter and earth station. It is a room where all different sources from the outsidestudio comes first here and enroots transmission to different destination like transmitter
& earth station. This room comprises of Routine switcher, Stab amplifier, Video/Audio
distribution amplifier etc.
It is the heart of the studio. Most of the switching electronics are kept here e.g. camera
base stations, switcher mainframe, SPG, Satellite receivers, MW link, DDA & most of
the patch panels. Signal is routed through MSR. Signal can be monitored at various
stages.
AUDIO CONSOLE
It has many input sources such as microphones, VCR/server, IRDs, tone generators.
Out of these i/p, any source can be taken on o/p Audio level of Sources can be
adjusted and audio effects can be added.
Chapter 13- EARTH
STATION
The digital earth station operates in the frequency range of 5.85 GHz to 6.425 GHz
for transmission and 3.625 to 4.24 GHz for reception of signals. The whole system
operates with DVB/MPEG2 Standards. The base band processor subsystem and base
band monitoring subsystem operates in fully digital domain. An OFC carries digital base
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band signal from studio to earth station site to minimize the noise and interference. It is
controlled by a PC called NMS PC. The compression segment has an
MPEG encoder, digital multiplexer and digital modulator. The monitoring and receiving
segment comprises of two digital receivers for receiving and decoding program. The
output of modulator (70 MHz) is sent to an up converter. The up converted signals are
sent to an HPA. Then this signal is given to a PDA (parabolic dish antenna) for up
linking to satellite. The uplinked signal is received again by the same PDA for monitoring
purposes. The signal between earth station and satellite are given along line of sight
which means there must be a clear path from earth to satellite. The uplink signal is fed
from the earth station by a large PDA. The satellite is equipped with its own dish
antenna which receives the uplink signals and feeds them to a receiver. The signal is then
amplified and changed to a different frequency which is downlink frequency. This is
done to prevent interference between uplink and downlink signals. The down linked
signal is then again sent to the transmitter which again retransmits it. Each satellite has a
transponder and a single antenna receives all signals and another one transmits all signals
back. A satellite transmits signals towards earth in pattern called the satellite footprint of
the satellite. The footprint is strongest at centre and the footprint is used to see if the
earth station will be suitable for the reception of the desired signal. Converts The parts
of the DES are Antenna subsystem including LNA Antenna control unit, beacon
tracking unit, beacon tracking receiver and up converter system high power
amplifier and power system. The system operates in 2 +1mode and is compliant with
DVBMPEG 2standards. The base band processor subsystem and base band
monitoring system operates in digital domain. An OFC contains the digital base band
signal for studio to earth station to minimize noise interference The network management
system or NMS monitors and controls baseband equipments compression equipments
and test instruments like video audio generation and video audio analyzer. They are
provided to ensure quality of transmission and help trouble shoot.The base band
segment comprises of baseband subsystems at studio site and base band subsystem at
earth station site. This baseband segment processes two video Programmes. The base
band segment is monitored and controlled using a PC placed near the base band earth
station equipments called base band NMS PC. The compression segments comprises
of Mpeg encoders in 2 +1 configuration for providing redundancy. It also comprises of
digital multiplexers and digital modulators in 1 +1 configuration. The compression
segment is monitored and controlled by compression NMS PC. The receive and
monitoring segment consists of two digital receivers for receiving and decoding of the
video programs and one ASI to SDI decoder for decoding of the transport stream for
monitoring video programs at the multiplexers output. RF NMS PC is placed near the
receive monitoring segment and video audio generator placed in the base band segment.
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For monitoring of video programs professional video monitor, LCD video monitor and
audio level monitor are provided in the base band segment. An operator console has
one 14 professional video monitor a video audio monitor unit for quantitative monitor
of video programs and a personal computer for centralized merit and contention of earth
station sub system.
13.1 COMPONENTS
PDA(parabolic dish antenna)
IRD(Integrator receiver decoder)
Multiplexer
Encoder
FEED
LNA(Low noise amplifier)/LNBC(low noise block converter)
Waveguide
HPA(TWTA, SSTA, Klystron)
Up Converter
Digital Earth Station
Earth station is the main part which communicates with satellite in which up linking and
downlinking of the signal into/ from the satellite takes place for TV transmission. Earth
station is a purely digitization version. The signal is uplinked from the earth station and
received by many downlink centers in TV broadcasting. It is a very important part of
satellite communication system for broadcasting of signals. A ground-based receiving or
transmitting/ receiving station in a satellite communications system. The counterpart to
the earth station is the satellite in orbit, which is the "space station." Earth stations usedish-shaped antennas, the diameters of which can be under two feet for satellite TV to
as large as fifty feet for satellite operators. Antennas for space exploration have
diameters reaching a hundred feet.
Multiplex, Modulate and Up convert
An earth station is generally made up of a multiplexor, a modem, up and down
converters, a high power amplifier (HPA) and a low noise amplifier (LNA). Almost all
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transmission to satellites is digital, and the digital data streams are combined in a
multiplexor and fed to a modem that modulates a carrier frequency in the 50 to 180
MHz range. An up converter bumps the carrier into the gigahertz range, which goes to
the HPA and dish. Down convert,
Demodulate and De multiplex
For receiving, the LNA boosts the signals to the down converter, which lowers thefrequency and sends it to the modem. The modem demodulates the carrier, and the
digital output goes to the demultiplexing device and then to its destinations.
Earth Station classification
Analog Earth Station
Digital Earth Station
ASNG
DSNG
C-band or Ku-band
Problems of Analog
One programme per channel/transponder
Comparatively noisy
Ghosts in Terrestrial Transmission
Lower quality with respect to VCD, DVD digital medium
Fixed reception
Why Digital?
More programmes per channel/Transponder i.e. spectrum efficient.
Noise-Free Reception.
Ghost elimination.
CD quality sound & better than DVD quality picture.
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Reduced transmission power.
Flexibility in service planning.
Process involved in transmission of signal
Up-Conversion
High power amplification
Transmission
Reception Up-Converters
The up-conversion is required to raise the frequency of the signal in desired band:
C- band, Extended C-band or Ku-band before transmission. The input to up converteris 70 MHz (output of modulator) and output of Up-converter is fed to HPA. The up-
conversion may be done in stages or in one stage directly. The 70 MHz signal is first
converted into L band and then L band signal raised to desired frequency band.
High power amplification
The high power amplifier is used for the final power amplification of the digital RF signal
in C-band/Ku band that is fed to the antenna. The important parameters of HPAs are:
1. Frequency range
2. Output power at flange
3. Bandwidth
4. Gain variation (1.0db (max.) for 40 MHz (narrow band)
5. 2.50db for full bandwidth.
The different types of HPAs are
1. KHPA - Klystron High Power Amplifier
2. TWTA -Traveling Wave Tube Amplifier
3. SSPA- Solid state Power Amplifier
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Chapter 14-
TRANSMITTER
The most widely used narrow beam antennas are reflector antennas. The shape is
generally a paraboloid of revolution.
For full earth coverage from a geostationary satellite, a horn antenna is used. Horns are
also used as feeds for reflector antennas.
A small earth terminal, the feed horn is located at the focus or may be offset to one side
of the focus.
Large earth station antennas have a sub reflector at the focus. In the Cassegrain design,
the sub reflector is convex with an hyperboloid surface, while in the Gregorian design it
is concave with an ellipsoidal surface.
These antennas are used to transmit signal from earth station to satellite.
Chapter 15-
RECEIVER
The most widely used narrow beam antennas are reflector antennas. The shape is
generally a paraboloid of revolution.
1.
For full earth coverage from a geostationary satellite, a horn antenna is used. Horns arealso used as feeds for reflector antennas.
2. They are basically used to receive signals from the satellite which were transmitted by
transmitter.
3. All the waves which fall on receiver are being focused on the feeder which is placed at
the center of receiver antenna.
4. This feeder collects all the waves and sends to master switching room through cable
sand wires.
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5. After that again down conversion and decoding of signals takes place and in this manner
we receive our information.
Chapter 16 ELECTRONIC NEWS
GATHERING
ENG gather news from different outside locations.
Its components:
1. Camera
2. Tripods
3. Mikes
4. Lights
5. Camera battery
6. Camera charger
7. Camera adapter
8. Headphone
9. Camera cassette
The job of journalists is fulfilled only when their news reaches the viewers, this is why
they long for great challenge ability to be present anywhere, anything. This means
faster news from anywhere anytime to everywhere. Further there is a need to send news
footages in the shortest possible time and practically from any location. Technologically,
Doordarshan has always been far ahead of its competitors. When it came to remote
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newsgathering, Doordarshan has set precedence by using innovative and cost effective
methods.
Chapter
17- OB Van
Outside broadcasting is the production of television or radio programmes (typically to
cover news and sports events) from a mobile television studio. This mobile control room
is known as an "Outside Broadcasting Van", "OB Van", "Scanner" (a BBC term),
"mobile unit", "remote truck", "live truck", or "production truck". Signals from cameras
and microphones come in to the OB Van for processing and transmission. A typical OB
Van is usually divided into 5 parts:
The 1st and largest part is the production area where the director, technical director,
assistant director, character generator operator and producers usually sit in front of a
wall of monitors. This area is very similar to a Production control room. The technical
director sits in front of the video switcher. The monitors show all the video feeds from
various sources, including computer graphics, cameras, video tapes, video servers and
slow motion replay machines. The wall of monitors also contains a preview
monitor showing what could be the next source on air and a program monitor that
shows the feed currently going to air or being recorded. Behind the directors there is
usually a desk with monitors for the editors to operate. It is essential that the directorsand editor are in connection with each other during events, so that replays and slow-
motion shot scan be selected and aired.
The 2nd part of a van is for the audio engineer; it has a sound mixer. The audio
engineer can control which channels are added to the output and will follow instructions
from the director.
The 3rd part of van is video tape. The tape area has a collection of VTRs and may also
house additional power supplies or computer equipment.
The 4th part is the video control area where the cameras are controlled by 1 or 2
people to make sure that the iris is at the correct exposure and that all the cameras look
the same.
The 5th part is transmission where the signal is monitored by and
engineered for qualitycontrol purposes and is transmitted or sent to other
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trucks.
Chapter 18- DD
Direct+ DTH
DD Direct:
Carries all channels of DD directly to homes.
Also carries few private channels and radio channels of AIR.
Features:-
Cost effective alternate to cable TV.
One time expenditure for procuring receive system by viewer.
No monthly/activation charges from subscriber.
No smart card/CAM module required for reception.
Receive Eqpt. consists of a 60/90cm Dish Antenna, a Block converter
and a Set Top Box (STB). STB readily available in the open market.
Dealers of the equipment available all over the country.
Indicative cost of the receive system Rs 3000 to Rs 3500.
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Cost likely to come down further with volumes.
Doordarshan, the national television service of India, is devoted to public
service broadcasting. It is one of the largest terrestrial networks in the world. In
my Industrial training at Doordarshan Kendra, Jaipur, I have gained useful
knowledge which will surely be of great help in future. This training gave me
an opportunity to learn the practical aspects of the knowledge of my field ofinterest, Electronics and communication.
Chapter 19 :
Fututre scope
Doordarshan, the national television service of India, is devoted to public service
broadcasting. It is one of the largest terrestrial networks in the world. Doordarshan is
the first ISO certified channel in India. The largest viewer of India ,watching
Doordarshan. It has good future scope in communication world. Because largest
network covered by the doordarshan only.
As now a days there is a huge competition and everything is getting digitized there is a
wide scope for electronics and communication engineers to show their skills and keep
the technology up to date.
In Doordarshan, all the electronic devices used are to be operated by skilled engineers.
It provides with good pay scales.
The selection for the posts is through UPSC examinations.
Chapter
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20 conclusion
Doordarshan, the national television service of India, is devoted to public service
broadcasting.
It is one of the largest terrestrial networks in the world. In my Industrial training at
Doordarshan Kendra, muzaffarpur, I have gained useful knowledge which will surely be
of great help in future.
This training gave me an opportunity to learn the practical aspects of the knowledge of
my field of interest, Electronics and communication.
Posted 9th July 2013by Kunal Kishor
Location: Jalandhar, Punjab, India
0 Add a comment
9th July 2013
Training Report
On
DOORDARSHAN KENDRA
Submitted in the partial fulfillment of the requirement for the award of
degree of
Bachelors of Technology
http://reportsummertraining.blogspot.com/2013/07/v-behaviorurldefaultvmlo.htmlhttp://maps.google.com/maps?q=Jalandhar%2C%20Punjab%2C%[email protected],75.57618290000005&z=10https://plus.google.com/112273954873096052071 -
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in
Electronics & Communication Engineering
Submitted by:
Name: KUNAL KISHOR
Name and Location of Company: DOORDARSHAN KENDRAMUZAFFARPUR
ACKNOWLEDGEMENT
I want to thanks to Mr. R. sahni sir and Mr. B.S. chaudhary sir because he give me right
concept to complete this training .Also I want to thanks doordarshan Kendra because
different types of metterials are present there help me a lot .
Doordarshan Kendra has provided such a big support in marking this training work
because it would be possible without the books available in the industry
INDEX
Chapter
1. Introduction.
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2. History.
3. Satellite Communication.
3.1 Satellite orbits.
3.2Antenna.
4. Propagation modes.
5. TV studio .
5.1 Procedure in recording.
5.2 Procedure in transmission.
5.3 Video Signal Generation.
5.4 CCVS.
5.5 Components of TV studio.
6. TV Camera.
6.1 Camera lens.
6.2 Transducer.
7. Lighting.
8. Microphone.
8.1 Types of microphone.
9. Video chain.
10. Audio chain.
11. Vision Mixer.
11.1 switchin .
12. MSR.
13. Earth Station.
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13.1 componenet.
14. Transmitter.
15. Receiver.
16. ENG.
17. OB Van.
18. DD Direct+ DTH.
19. Future scope.
20. Conclusion.
Abbreviation CCVS COLOR COMPOSITE VIDEO CHAIN
ENG ELECTRONICS NEWS GATHERING
LOS LINE OF SIGHT
MSR MASTER SWITCHING ROOM
VM VIDEO MIXER
CG COMPUTER GRAPHICS
PDA PARABOLIC DISH ANTENNA
IRD INTEGRATOR RECEIVER
DECODER
LNA LOW NOISE AMPLIFIER
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LNBC LOW NOISE BLOCK
CONVERTER
Electronics &
Communication
Chapter 1-
INTRODUCTION
Doordarshan is the public television broadcaster of India and a division of Prasar Bharti,
and nominated by the Government of India. It is one of the largest broadcasting
organizations in the world in terms of the infrastructure of studios and transmitters.
Doordarshan Kendra is amilestone in the field of entertainment and education media
source. Doordarshan, muzaffarpur is the Program Production Center and transmition ..
The studios are housed at same campus and the transmitter is located at the
muzaffarpur.
AIR and Doordarshan aims to provide information, education and entertainment for
the public. Its network of 1400 terrestrial transmitters cover more than 90.7% of
India's population.
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Electronics &
Communication
Chapter 2-
HISTORY
The birth of broadcasting in India has started on an experimental basis in year 1921
whenTimes of India in collaboration with P&T department broadcasts a musical
programme. In the year 1930 radio broadcasting started operating under the Indian
broadcasting company. Government took over the charge of broadcasting in March
1935, a separate office of the controller of broadcasting was created. The land mark in
the history of broadcasting is change of name of the Indian broadcasting to AIR in 1936
and in same year Delhi station was formed. From 1936 onwards the development of
AIR was very slow, nine stations were opened up in different places like Delhi,
Calcutta, Bombay, madras, lucknow and tiruchi. From 1956 onwards AIR was
popularly known as akashwani.
On 12thNovember 1947 the voice of Gandhi ji was broadcasted in AIR and since then
it is celebrated as broadcasting day. Television (Doordarshan) started in India in the
year 1959 with black and white transmission. The black & white transmission was
converted fully into colour in 1982 during Asian games.
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Electronics &
Communication
Chapter 3- SATELLITE
COMMUNICATION
In telecommunications, the use of artificial satellites to provide communication links
between various points on Earth. Satellite communications play a vital role in the global
telecommunications system. Approximately 2,000 artificial satellites orbiting Earth relay
analog and digital signals carrying voice, video, and data to and from one or many
locations worldwide.
Satellite communication has two main components: the ground segment, which consists
of fixed or mobile transmission, reception, and ancillary equipment, and the space
segment, which primarily is the satellite itself. A typical satellite link involves the
transmission or uplinking of a signal from an Earth station to a satellite. The satellite then
receives and amplifies the signal and retransmits it back to Earth, where it is received
and re-amplified by Earth stations and terminals. Satellite receivers on the ground
include direct-to-home (DTH) satellite equipment,mobile reception equipment in
aircraft, satellite telephones, and hand held devices.
3.1 SATELLITE ORBITS:
a) GEOs = Geostationary Earth Orbits.
b) LEOs -= Low Earth Orbits. c) MEOs = Medium
Earth Orbits.
1. Geostationary orbit
A circular orbit 35,785 km (22,236 miles) above Earths Equator in which a satellites
orbital period is equal to Earths rotation period of 23 hours and 56 minutes. A
spacecraft in this orbit appears to an observer on Earth to be stationary in the sky. This
particular orbit is used for meteorological and communications satellites. The
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geostationary orbit is a special case of the geosynchronous orbit, which is any orbit with
a period equal to Earths rotation period.
2. Low- Earth-orbiting satellites
A Low Earth Orbit (LEO) typically is a circular orbit about 400 kilometers above the
earths surface and, correspondingly, a period (time to revolve around the earth) of
about 90 minutes. Because of their low altitude, these satellites are only visible from within
a radius of roughly 1000 kilometers from the sub-satellite point. In addition, satellites in
low earth orbit change their position relative to the ground position quickly. So even for
local applications, a large number of satellites are needed if the mission requires
uninterrupted connectivity.
Satellite communication
Started in 1960.
Uses Geo Stationary Satellite.
Operates in C-Band & Ku-Band.
Started in India in 1975.
First Indian Satellite INSAT launched in 1982.
Gulf War brought satellite television to prominence
3.2-Antennas:-
Antenna (or aerial) is a transducer that transmits or receives electromagnetic waves. In
other words,antennas convert electromagnetic radiation into electrical current, or vice
versa. Antennas generally deal in the transmission and reception of radio waves.
Types of antenna:
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Isotropic antenna (idealized)
Radiates power equally in all directions
Dipole antennas
Half-wave dipole antenna (or Hertz antenna)
Quarter-wave vertical antenna (or Marconi antenna)
Parabolic Reflective Antenna
A parabolic antenna is a high-gain reflector antenna used for radio, television and
datacommunications, and also for radio location (radar),on the UHF and SHF parts of
the electromagnetic spectrum. The relatively short wavelength of electromagnetic
radiation at these frequencies allows reasonably sized reflectors to exhibit the
desired highly directional response for both receiving and transmitting. A
typical parabolic antenna consists of a parabolic reflector with a small feed
antenna a tits focus. To find the focus, reflect the light of a flashlight off of the
dish. When the reflected beam is parallel, the flashlight is at the focus. Thereflector is a metallic surface formed into a paraboloid of revolution and
(usually) truncated in a circular rim that forms
the diameter of the antenna. This paraboloid possesses adistinct focal point
by virtue of having the reflective property of parabolas in that a point light
source at this focus produces a parallel light beam aligned with the axis of
revolution. The feed antenna at the reflector's focus is typically a low-gain
type such as a half-wave dipole or a small waveguide horn.
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Electronics
& Communication Chapter 4 PROPAGATION
MODEDS
Ground-wave propagation
Sky-wave propagation
Line-of-sight propagation
Electronics &
Communication
Chapter 5 - TV
STUDIO
Doordarshan has two studio halls. One is used as News Room and the other
one is used for shooting various programs. Artificial sets are created in the
studio hall according tor equirements of the program to be shooted.
5.1-PROCEDURE IN REORDING
Set is designed in studio as per conceptual thought of program
producer.
Floor plan is envisaged.
Lighting, Audio and placement of the cameras is arranged as per floor
plan.
Pre testing of cameras, microphones, VCRs etc. is done before
recording.
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Recording begins and desired camera / mike are selected through VM/
Audio console as per command of producer. Program is recorded on
VCR.
5.2-PROCEDURE IN TRANSMISSION
The programs are transmitted as per the daily cue sheet.
Normal transmission hours are 1600-2000 Hrs.
Cue sheet is discussed daily by program and technical staff for details
in it and for any last moment changes if any.
After getting D-link caption from Delhi end program is played from
VCR /Server. The program is uplinked by Earth Station.
The program is also transmitted to transmitter at HPT Nahargarh via
MW link.
During our slot, both live as well as recorded programs are transmitted.
Around 2000 Hrs after getting linking caption from DD# 1, the signal
from DD#1 is selected and accordingly transmitted by HPT/ ES.
5.3-Video signal generation
Video is nothing but a sequence of pictures. The image we see is maintained in our eye
for 1/16sec. So if we see images at the rate more than 16 pictures/sec, our eyes cannot
recognize the difference and we see the continuous motion. In movies camera and movie
projector it is found that 24 fps is better for human eyes. TV system could also use this
rate but in PAL system 25fpm is selected. In TV cameras image is converted inelectrical signal using photosensitive material. Whole image is divided into many micro
particles known as pixels. These pixels are small enough so that our eyes cannot
recognize pixels and we see continuous image. Thus, at any particular instance there are
almost infinite numbers of pixels that need to be converted in electrical signal
simultaneously for transmitting picture details. How ever this is not possible practical
because it is no feasible to provide a separate path for each pixel. In practice this
problem is solved by method known as Scanning in which information is converted
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one by one pixel, line by line and frame by frame.
5.4-COLOUR COMPOSITE VIDEO SIGNAL
Active waveform comprises of 2 signals:
Luminance(Y)-black and white
Chrominance(C)- colour signal
5.5-COMPONENTS OF TV STUDIO
Camera
Lighting
Microphones
Vision mixer and Audio consoles
MSR
VCR /Servers
Acoustics
Post production and video effects
supporting services like AC, UPS
Chapter 6- TV
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CAMERA
A TV Camera consists of three sections:
a) A Camera lens and optical block
b) A transducer or pick up device
c) Electronics
6.1-CAMERA LENS
The purpose of the camera lens is to focus the optical energy at the
face plate of a pickup device i.e. to form an optical image. The lens
has following sections:
1.Main focus section
2. Zoom section with manual or servo mode operation.
3.Servo drive assembly for Zoom and iris control.
4. Aperture section with manual or auto mode.
5. Back focus section with adjustment facilities for back and microfocus.
6.2- TRANSDUCER PICK UP DEVICE
R, G & B signals, as separated by the optical block are converted to electrical signal in
the transducer section of the camera. It is then processed in camera electronics to give CCVS
(color composite video signal) output.
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Chapter 7-
LIGHTING
Lighting for television is very exciting and needs creative talent. There is always a
tremendous scope for doing experiments to achieve the required effect. Light is a kind
of electro magnetic radiation with a visible spectrum from red to violet i.e. wavelength
from 700 nm to 380
Nm respectively.
Basic three pointing lighting
Key light:- It gives shape and modeling by a casting shadow. It is treatedas a sun in
the sky and should cast only one shadow.
Fill light:- Controls the lighting contrast by filling in shadows.It can also provide catch
lights in the eyes.
Back light:-Separates the body from the background, gives roundness to the subject
and reveals texture.
Background lights:- Separates person from the background and reveals
background interest and shape.
Lighting equipments:-
HMI lights compared to standard incandescent lights deliver five times the light output
per watt. They generate less heat, which is an important consideration when shootinginside in a confined space. (HMI stands for Hydrargyrum Medium Arc-length Iodide).
The light on the left side of this picture is a HMI light; the one on the right a standard
quartz light.
Cycs (large, seamless, neutral backgrounds) can be lit from the top and bottom with
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cyclights.The one here sits on the studio floor and is directed up at the background.
Chapter 8-
MICROPHONES
A microphone is an acoustic-to-electric transducer or sensor that converts sound in to
an electrical signal.
8.1- TYPES OF MICROPHONES
1.CONDENSER MICROPHONE:-
In a condenser microphone also called a capacitor microphone or electrostatic
microphone, the diaphragm acts as one plate of a capacitor, and the vibrations producechanges in the distance between the plates.
2. ELECTRET CONDENSER MICROPHONE
An electret microphone is a relatively new type of capacitor microphone invented at Bell
laboratories in 1962 by Gerhard Sessler and Jim West. An electret is a ferroelectric
material that has been permanently electrically charged or polarized. The name comes
from electrostatic and magnet; a static charge is embedded in an electret by alignment of
the static charges in the material, much the way a magnet is made by aligning the
magnetic domains in a piece of iron.
3. DYNAMIC MICROPHONE:-
Dynamic microphones work via electromagnetic induction. They are robust, relatively in
expensive and resistant to moisture. This coupled with their potentially high gain before
feedback makes them ideal for on-stage use. Moving-coil microphones use same
dynamic principle as in loudspeaker, only reversed.
4. RIBBON MICROPHONE:-
Ribbon microphones use a thin, usually corrugated metal ribbon suspended in a
magnetic field. The ribbon is electrically connected to the microphone's output, and its
vibration within the magnetic field generates the electrical signal. Ribbon microphones
are similar to moving coil microphones in the sense that both produce sound by means
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of magnetic induction.
5. PIEZO ELECTRIC MICROPHONE:-
A crystal microphone or piezo microphone uses the phenomenon of piezoelectricity -
the ability of some materials to produce a voltage when subjected to pressure
- to convert vibrations into an electrical signal.
6. LASER MICROPHONE:-
Laser microphones are often portrayed in movies as spy gadgets. A laser beam is aimed
at the surface of a window or other plane surface that is affected by sound. The slight
vibrations of this surface displace the returned beam, causing it to trace the sound wave.
The vibrating laser spot is then converted back to sound. In a more robust and
expensive implementation, the returned light is split and fed to an interferometer, whichdetects movement of the surface.
7. FIBER OPTIC MICROPHONE:-
A fiber optic microphone converts acoustic waves into electrical signals by sensing
changes in light intensity, instead of sensing changes in capacitance or magnetic fields as
with conventional microphones.
Chapter 9-
VIDEO CHAIN
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The video we see at our home is either pre-recorded in studio or live telecasted. Block
diagram shown in fig illustrates different chains of video recording, video playback,
news, and live broadcasting. In First chain we will understand studio program recording.
Camera output from the studio hall is sent to CCU where many parameters of video
signals are controlled. Output signal of CCU after making all corrections is sent to VM
in PCR-1 (production control room).Output of 3 to 4 cameras comes here and final
signal is selected here using VM according to a directors choice.
The final signal from VM is sent to VTR. VTR uses both analog and digital tape
recording system. At the time transmitting this pre recorded program cassettes is played
in to respective in VTR room. Signal from VTR is sent to PCR-2. PCR-2 has one VM,
video monitoring system, and CG (Computer Graphics). From PCR-2, signal travels
from MSR to Transmitter or Earth-station for terrestrial and satellite transmission.
MSR is the main control room between studio and transmitter or receiver.
Chapter 10-
AUDIO CHAIN
In studio program, audio from studio microphones is directly fed to the AUDIO
CONSOLE place in PCR-1. It is used to mix audio from different sources and
maintain its output. From AC, signal is directly recorded on tape with video signal in
VTR. While playing back audio is extracted from tape and fed to another audio console
placed in PCR-2 and then travels with the video signal.
Chapter 11- VISION
MIXER
Vision mixer is the almost final equipment in programme (video) production and its
output is used either for recording or transmission.
Vision mixing is the process of providing a composite signal from various input sources.
It has many input sources such as cameras, VCR/server, Graphics, IRDs. Out of these
i/p, any source can be taken on o/p. It is used to switch or cut between 2 video sources,
or to combine them in a variety of ways.
11.1 TRANSIT ION/SWITCHING
It involves:
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Cut
Mix
Wipe
Fade
Keying
Special effects
CUT
The cut is an instantaneous switch from one picture to another. It avoids the frame roll &
flash evident, on picture at the moment of cutting.
MIX
It uses additive mixing. The transitions here are less pronounced. As the faders are
operated, the established picture fades away, while the new picture progressively.
Chapter 12- MASTER
SWITCHING ROOMMaster switching room (MSR) is used for transmission media. It is the engineering co-
ordination center of activity for selecting & routing the signal from various sources to
transmitter and earth station. It is a room where all different sources from the outside
studio comes first here and enroots transmission to different destination like transmitter
& earth station. This room comprises of Routine switcher, Stab amplifier, Video/Audio
distribution amplifier etc.
It is the heart of the studio. Most of the switching electronics are kept here e.g. camera
base stations, switcher mainframe, SPG, Satellite receivers, MW link, DDA & most of
the patch panels. Signal is routed through MSR. Signal can be monitored at various
stages.
AUDIO CONSOLE
It has many input sources such as microphones, VCR/server, IRDs, tone generators.
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Out of these i/p, any source can be taken on o/p Audio level of Sources can be
adjusted and audio effects can be added.
Chapter 13- EARTH
STATION
The digital earth station operates in the frequency range of 5.85 GHz to 6.425 GHz
for transmission and 3.625 to 4.24 GHz for reception of signals. The whole system
operates with DVB/MPEG2 Standards. The base band processor subsystem and base
band monitoring subsystem operates in fully digital domain. An OFC carries digital base
band signal from studio to earth station site to minimize the noise and interference. It is
controlled by a PC called NMS PC. The compression segment has an
MPEG encoder, digital multiplexer and digital modulator. The monitoring and receivingsegment comprises of two digital receivers for receiving and decoding program. The
output of modulator (70 MHz) is sent to an up converter. The up converted signals are
sent to an HPA. Then this signal is given to a PDA (parabolic dish antenna) for up
linking to satellite. The uplinked signal is received again by the same PDA for monitoring
purposes. The signal between earth station and satellite are given along line of sight
which means there must be a clear path from earth to satellite. The uplink signal is fed
from the earth station by a large PDA. The satellite is equipped with its own dish
antenna which receives the uplink signals and feeds them to a receiver. The signal is thenamplified and changed to a different frequency which is downlink frequency. This is
done to prevent interference between uplink and downlink signals. The down linked
signal is then again sent to the transmitter which again retransmits it. Each satellite has a
transponder and a single antenna receives all signals and another one transmits all signals
back. A satellite transmits signals towards earth in pattern called the satellite footprint of
the satellite. The footprint is strongest at centre and the footprint is used to see if the
earth station will be suitable for the reception of the desired signal. Converts The parts
of the DES are Antenna subsystem including LNA Antenna control unit, beacontracking unit, beacon tracking receiver and up converter system high power
amplifier and power system. The system operates in 2 +1mode and is compliant with
DVBMPEG 2standards. The base band processor subsystem and base band
monitoring system operates in digital domain. An OFC contains the digital base band
signal for studio to earth station to minimize noise interference The network management
system or NMS monitors and controls baseband equipments compression equipments
and test instruments like video audio generation and video audio analyzer. They are
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provided to ensure quality of transmission and help trouble shoot.The base band
segment comprises of baseband subsystems at studio site and base band subsystem at
earth station site. This baseband segment processes two video Programmes. The base
band segment is monitored and controlled using a PC placed near the base band earth
station equipments called base band NMS PC. The compression segments comprises
of Mpeg encoders in 2 +1 configuration for providing redundancy. It also comprises of
digital multiplexers and digital modulators in 1 +1 configuration. The compression
segment is monitored and controlled by compression NMS PC. The receive and
monitoring segment consists of two digital receivers for receiving and decoding of the
video programs and one ASI to SDI decoder for decoding of the transport stream for
monitoring video programs at the multiplexers output. RF NMS PC is placed near the
receive monitoring segment and video audio generator placed in the base band segment.
For monitoring of video programs professional video monitor, LCD video monitor and
audio level monitor are provided in the base band segment. An operator console has
one 14 professional video monitor a video audio monitor unit for quantitative monitor
of video programs and a personal computer for centralized merit and contention of earth
station sub system.
13.1 COMPONENTS
PDA(parabolic dish antenna)
IRD(Integrator receiver decoder)
Multiplexer
Encoder
FEED
LNA(Low noise amplifier)/LNBC(low noise block converter)
Waveguide
HPA(TWTA, SSTA, Klystron)
Up Converter
Digital Earth Station
Earth station is the main part which communicates with satellite in which up linking and
downlinking of the signal into/ from the satellite takes place for TV transmission. Earth
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station is a purely digitization version. The signal is uplinked from the earth station and
received by many downlink centers in TV broadcasting. It is a very important part of
satellite communication system for broadcasting of signals. A ground-based receiving or
transmitting/ receiving station in a satellite communications system. The counterpart to
the earth station is the satellite in orbit, which is the "space station." Earth stations use
dish-shaped antennas, the diameters of which can be under two feet for satellite TV to
as large as fifty feet for satellite operators. Antennas for space exploration have
diameters reaching a hundred feet.
Multiplex, Modulate and Up convert
An earth station is generally made up of a multiplexor, a modem, up and down
converters, a high power amplifier (HPA) and a low noise amplifier (LNA). Almost all
transmission to satellites is digital, and the digital data streams are combined in a
multiplexor and fed to a modem that modulates a carrier frequency in the 50 to 180
MHz range. An up converter bumps the carrier into the gigahertz range, which goes to
the HPA and dish. Down convert,
Demodulate and De multiplex
For receiving, the LNA boosts the signals to the down converter, which lowers the
frequency and sends it to the modem. The modem demodulates the carrier, and the
digital output goes to the demultiplexing device and then to its destinations.
Earth Station classification
Analog Earth Station
Digital Earth Station
ASNG
DSNG
C-band or Ku-band
Problems of Analog
One programme per channel/transponder
Comparatively noisy
Ghosts in Terrestrial Transmission
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Lower quality with respect to VCD, DVD digital medium
Fixed reception
Why Digital?
More programmes per channel/Transponder i.e. spectrum efficient.
Noise-Free Reception.
Ghost elimination.
CD quality sound & better than DVD quality picture.
Reduced transmission power.
Flexibility in service planning.
Process involved in transmission of signal
Up-Conversion
High power amplification
Transmission
Reception Up-Converters
The up-conversion is required to raise the frequency of the signal in desired band:
C- band, Extended C-band or Ku-band before transmission. The input to up converter
is 70 MHz (output of modulator) and output of Up-converter is fed to HPA. The up-
conversion may be done in stages or in one stage directly. The 70 MHz signal is first
converted into L band and then L band signal raised to desired frequency band.
High power amplification
The high power amplifier is used for the final power amplification of the digital RF signal
in C-band/Ku band that is fed to the antenna. The important parameters of HPAs are:
1. Frequency range
2. Output power at flange
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3. Bandwidth
4. Gain variation (1.0db (max.) for 40 MHz (narrow band)
5. 2.50db for full bandwidth.
The different types of HPAs are
1. KHPA - Klystron High Power Amplifier
2. TWTA -Traveling Wave Tube Amplifier
3. SSPA- Solid state Power Amplifier
Chapter 14-TRANSMITTER
The most widely used narrow beam antennas are reflector antennas. The shape is
generally a paraboloid of revolution.
For full earth coverage from a geostationary satellite, a horn antenna is used. Horns are
also used as feeds for reflector antennas.
A small earth terminal, the feed horn is located at the focus or may be offset to one side
of the focus.
Large earth station antennas have a sub reflector at the focus. In the Cassegrain design,
the sub reflector is convex with an hyperboloid surface, while in the Gregorian design it
is concave with an ellipsoidal surface.
These antennas are used to transmit signal from earth station to satellite.
Chapter 15-
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RECEIVER
The most widely used narrow beam antennas are reflector antennas. The shape is
generally a paraboloid of revolution.
1. For full earth coverage from a geostationary satellite, a horn antenna is used. Horns are
also used as feeds for reflector antennas.
2. They are basically used to receive signals from the satellite which were transmitted by
transmitter.
3. All the waves which fall on receiver are being focused on the feeder which is placed at
the center of receiver antenna.
4. This feeder collects all the waves and sends to master switching room through cable
sand wires.
5. After that again down conversion and decoding of signals takes place and in this manner
we receive our information.
Chapter 16 ELECTRONIC NEWS
GATHERING
ENG gather news from different outside locations.
Its components:
1. Camera
2. Tripods
3. Mikes
4. Lights
5. Camera battery
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6. Camera charger
7. Camera adapter
8. Headphone
9. Camera cassette
The job of journalists is fulfilled only when their news reaches the viewers, this is why
they long for great challenge ability to be present anywhere, anything. This means
faster news from anywhere anytime to everywhere. Further there is a need to send news
footages in the shortest possible time and practically from any location. Technologically,
Doordarshan has always been far ahead of its competitors. When it came to remote
newsgathering, Doordarshan has set precedence by using innovative and cost effective
methods.
Chapter
17- OB Van
Outside broadcasting is the production of television or radio programmes (typically to
cover news and sports events) from a mobile television studio. This mobile control room
is known as an "Outside Broadcasting Van", "OB Van", "Scanner" (a BBC term),
"mobile unit", "remote truck", "live truck", or "production truck". Signals from cameras
and microphones come in to the OB Van for processing and transmission. A typical OB
Van is usually divided into 5 parts:
The 1st and largest part is the production area where the director, technical director,
assistant director, character generator operator and producers usually sit in front of a
wall of monitors. This area is very similar to a Production control room. The technical
director sits in front of the video switcher. The monitors show all the video feeds from
various sources, including computer graphics, cameras, video tapes, video servers and
slow motion replay machines. The wall of monitors also contains a preview
monitor showing what could be the next source on air and a program monitor that
shows the feed currently going to air or being recorded. Behind the directors there is
usually a desk with monitors for the editors to operate. It is essential that the directors
and editor are in connection with each other during events, so that replays and slow-
motion shot scan be selected and aired.
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The 2nd part of a van is for the audio engineer; it has a sound mixer. The audio
engineer can control which channels are added to the output and will follow instructions
from the director.
The 3rd part of van is video tape. The tape area has a collection of VTRs and may also
house additional power supplies or computer equipment.
The 4th part is the video control area where the cameras are controlled by 1 or 2
people to make sure that the iris is at the correct exposure and that all the cameras look
the same.
The 5th part is transmission where the signal is monitored by and
engineered for qualitycontrol purposes and is transmitted or sent to other
trucks.
Chapter 18- DD
Direct+ DTH
DD Direct:
Carries all channels of DD directly to homes.
Also carries few private channels and radio channels of AIR.
Features:-
Cost effective alternate to cable TV.
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One time expenditure for procuring receive system by viewer.
No monthly/activation charges from subscriber.
No smart card/CAM module required for reception.
Receive Eqpt. consists of a 60/90cm Dish Antenna, a Block converterand a Set Top Box (STB). STB readily available in the open market.
Dealers of the equipment available all over the country.
Indicative cost of the receive system Rs 3000 to Rs 3500.
Cost likely to come down further with volumes.
Doordarshan, the national television service of India, is devoted to publicservice broadcasting. It is one of the largest terrestrial networks in the world. In
my Industrial training at Doordarshan Kendra, Jaipur, I have gained useful
knowledge which will surely be of great help in future. This training gave me
an opportunity to learn the practical aspects of the knowledge of my field of
interest, Electronics and communication.
Chapter 19 :Fututre scope
Doordarshan, the national television service of India, is devoted to public service
broadcasting. It is one of the largest terrestrial networks in the world. Doordarshan is
the first ISO certified channel in India. The largest viewer of India ,watching
Doordarshan. It has good future scope in communication world. Because largest
network covered by the doordarshan only.
As now a days there is a huge competition and everything is getting digitized there is a
wide scope for electronics and communication engineers to show their skills and keep
the technology up to date.
In Doordarshan, all the electronic devices used are to be operated by skilled engineers.
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It provides with good pay scales.
The selection for the posts is through UPSC examinations.
Chapter
20 conclusion
Doordarshan, the national television service of India, is devoted to public service
broadcasting.
It is one of the largest terrestrial networks in the world. In my Industrial training at
Doordarshan Kendra, muzaffarpur, I have gained useful knowledge which will surely be
of great help in future.
This training gave me an opportunity to learn the practical aspects of the knowledge of
my field of interest, Electronics and communication.
Posted 9th July 2013by Kunal Kishor
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