doordarshan summer traning

8/11/2019 doordarshan summer traning

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PREFACE

Training is important phase of student life. During this period student gets both

theoretical as well as practical knowledge of the subject. Training also

impresses a student overall approaches to life and impress his personality andconfidence.

Our training was in Doordarshan Kendra lucknow . This report contains a

detailed study of Doordarshan Kendra lucknow . There are 3 division here :-

Studio

Transmitter

Earth Station

1) Studio :-Doordarshan is a leading broadcasting service provider in india. DD Lucknow is

full-flathead broadcast set up. Many serials &program are being made here like

"HATIM TAI" etc. recorded in studio.

2) Transmitter:-Here the transmission of both audio and video has been made. The transmission

section does the function of modulation of signal. Power amplification of the

signal & mixing of audio and video signal is done here.

3) Earth Station :-The main function of earth station is to make contact with satellite or

communicate with it. The signals from other transmitter are down linked here.

Also the signals here are uplinked to send it to larger distance.


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Introduction of Doordarshan lucknow

Lucknow Doordarshan started functioning on 27th Nov. 1975 with an interim

setup at 22, Ashok Marg, Lucknow. The colour transmission service of NationalChannel (only with Transmitter) started from 15-8-82. While the regular colour

transmission service from studio was started in 1984 with ENG gadgets.

During Reliance Cup, OB Van came to Kendra for outdoor telecast having 4

colour camera chain, recording equipments, portable microwave link. In March

1989 new studio complex started functioning. EFP Van came to DDK Lucknow in1989 with compliment of 3 colour camera chain and recording setup for outdoor

telecast. The entire recording of studio/van have been replaced to Beta formatHigh Band edit VCR and still in use as the old recording are on H.B.

UP Regional Service telecast with up linking facility from studio (DDK,

Lucknow) started in January 1998 on INSAT-2B. This service was changed to

INSAT-2D (T) ARAB SAT. on 14-7-98. The news feeds are up-linked to Delhioccasionally from Lucknow Earth Station.

Studio program is transmitted from 10 KW-TV transmitter installed at Hardoi

Road through Studio Transmitter Microwave Link. Besides this, one 16 feet PDA

is being installed at TV Transmitter site to receive the down link signal of

Regional Service telecast from studio via ARAB SAT. on INSAT-2D (T).

Site of 22 Ashok Marg, Lucknow is being utilized by Doordarshan Training

Institute (for staff training) having one studio (12m x 6m) and colour camera

chain. The DTI Lucknow was inaugurated in September 1995.

In the beginning, only the development programmes were telecast but later on to

enlighten the viewers as per their needs, expectations, many more informative,

educative and entertaining programmes have been introduced from time to time.

Lucknow Doordarshan produced some of the best programmes in the country. To

entertain cross section of the society.


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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 to requirements of the program to be shooted.

PROCEDURE IN RECORDING:-

Set is designed in studio as per conceptual thought of program producer.

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.

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 MWlink.

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.


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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 wesee 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. However 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.

COLOUR COMPOSITE VIDEO SIGNAL:-

A signal that contain all three component i.e intensity information, horizontal-

retrace signal and vertical-retrace signals these type of signal is known as

composite video signal or we can say that colour composite video signal. The

video carrier is demodulated to give acomposite video signal; this contains

luminance, chrominance and synchronization signals; this is identical to thevideo signal format used byanalog video devices such asVCRs orCCTV

cameras.Colour Composite Video Signal is formed with Video, sync and

blanking signals. Note that the RF signal modulation is inverted compared to

the conventional AM: the minimum video signal level corresponds to maximum

carrier amplitude, and vice versa. The carrier is never shut off all together ; this

is to ensure that inter carrier sound demodulation can still occur.
http://en.wikipedia.org/wiki/Composite_videohttp://en.wikipedia.org/wiki/Analog_videohttp://en.wikipedia.org/wiki/VCRshttp://en.wikipedia.org/wiki/Closed-circuit_televisionhttp://en.wikipedia.org/wiki/Closed-circuit_televisionhttp://en.wikipedia.org/wiki/Closed-circuit_televisionhttp://en.wikipedia.org/wiki/Closed-circuit_televisionhttp://en.wikipedia.org/wiki/VCRshttp://en.wikipedia.org/wiki/Analog_videohttp://en.wikipedia.org/wiki/Composite_video


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Active waveform comprises of 2 signals:

Luminance(Y)-black and white

Chrominance(C)- colour signal

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


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TV CAMERA

INTRODUCTION:

A TV Camera consists of three sections:

a) A Camera lens & Optics:To form optical image on the face plate of a pick up

device.b) A transducer or pick up device: To convert optical image into a electrical

signal.

c) Electronics:To process output of a transducer to get a CCVS signal.

TYPES OF PICK - UP DEVICES:-

There are three types of pick up devices based on :

a) Photoemissive material: These material emits electrons when the light falls on

them. Amount of emitted electrons depends on the light . Monochrome cameras

used in Doordarshan were based on this material. These cameras were called

Image Orticon Cameras. These cameras were bulky and needed lot of light. These

are no longer in use at present.


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b) Photo conductive material: The conductivity of these material changes with

amount of light falling on them. Such material with variable conductivity is made

part of a electrical circuit. Voltage developed across this material is thus recovered

as electrical signal.

c) Charge coupled devices: These are semiconductor devices which convert light

into a charge image which is then collected at a high speed to form a signal. Most

of the TV Studios are now using CCD cameras instead of Tube cameras. Tube

cameras have become obsolete & are not in use .The CCD is a solid-state device

using special integrated circuitry technology, hence it is often referred to as a chip

camera. The complete CCD sensor or chip has at least 450000 picture elements or

pixels, each pixel being basically an isolated (insulated) photodiode. The action of

the light on each pixel is to cause electrons to be released which are held by theaction of a positive voltage.

The Charge held under electrode can be moved to electrode by changing the

potential on the second electrodes. The electrons (negative charges) follow the

most positive attraction. A repeat of this process would move the charges to

next electrode, hence charge-coupled device. A system of transfer clock pulses

is used to move the charges in CCDs to achieve scanning.

There are three types of CCD device:

frame transfer (FT).

interline transfer (IT).

frame interline transfer (FIT).

Size of the chip used for broadcast cameras varies from inch to 2/3inch.

Development in CCD technology has seen the introduction of :

The hole accumulated Diode (HAD) sensor which enabled upto 750

pixels/line, with increased sensitivity and a reduction in vertical smear.


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The hyper HAD sensor, which included a microlens on each pixel to

collect the light more efficiently (this gave a one stop increase in

sensitivity over the HAD sensor).

The power HAD sensor with improved signal-to- noise ratio which has

resulted in at least half an -stop gain in sensitivity; in some cases a full

-stop of extra sensitivity has been realized.

The built in sync pulse generator provides all the pulses required for the encoder

and colour bar generator of the camera. The signal system is described below:

The signal system in most of the cameras consists of processing of the signalfrom red, blue and green CCD respectively. The processing of red and blue

channel is exactly similar. Green channel which also called a reference channel

has slightly different electronic concerning aperture correction. The signal

picked up from the respective CCD is amplified in a stage called pre-pre

amplifier. Most of the cameras also provide gain setting of 6 dB, 9dB and 18dB

at the pre amplifier. Shading compensator provides H and V shading

adjustments in static mode and dynamic mode by readjusting the gain.All the

three signals namely R, G and B are then fed to the encoder section of thecamera via a colour bar/camera switch. This switch can select R, G and B from

the camera or from the R, G, B Signal from colour bar generator. In the encoder

section these R, G, B signals are modulated with SC to get V and U signals.

These signals are then mixed with luminance, sync, burst, & blanking etc. to

provide colour composite video signal (CCVS Signal). Power supply board

provides regulated voltages to various sections.


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TV LIGHTING

GENERAL PRINCIPLES:-

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 electromagnetic radiation with a visible spectrum from red to

violet i.e, wave length from 700 nm to 380 nm respectively. However to

effectively use the hardware and software connected with lighting it is important

to know more about this energy.

Light Source: Any light source has a Luminance intensity (I) which is

measured in Candelas. One Candela is equivalent to an intensity released by

standard one candle source of light.

Luminance flux (F): It is a radiant energy weighted by the photonic curve and

is measured in Lumens. One Lumen is the luminous flux emitted by a pointsource of 1 Candela.

Illumination (E): It is a Luminous Flux incident onto a surface. It is measured

in LUMENS/m2, which is also called as LUX. A point source of 1 candela at a

uniform distance of 1 meter from a surface of 1 square meter gives illumination

of 1 LUX.

Luminance (L): It is a measure of the reflected light from a surface. Measured

in Apostilbs . A surface which reflects a total flux of 1 lumen/m2 has a

luminance of 1 Aposilbs .


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DIFFERENT LIGHTING TECHNIQUES: -

Eye light, Low intensity light on camera itself to get extra sparkle to an actor's

eye.

Rim light, to highlight actor's outline, it is an extra back on entire body at

camera level.

Kickkar light, Extra light on shadow side of the face at an angle behind and to

the side of the actor.

Limbo Lighting, Only subject is visible, no back ground light.

Sillhoutt lighting,No light on subject, BG is highly lit.

LIGHTING CONSOLE:-

In a television production, each scene will require its own lighting plan to give

the desired effect. In order to assist in setting up a particular lighting plon, aconsole should provide :-

a) One man operation and a centralised control desk with ability to switch any

circuit.

b) Facilities to obtain good balance with flexibility to have dimming on any

circuit.

c) With all controls for power at low voltage and current.

Modern lighting consoles also provide file & memory to enable the console

operator to store and recall the appropriate luminaries used for a particular

lighting plot. These console also provide Mimic panelsto show which channels

are in use and which memories or files have been recalled.


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DIMMERS:-

Dimmers are devices used to vary the brightness of alight. By decreasing or

increasing theRMS voltage and hence themean power to the lamp, it ispossible to vary the intensity of the light output.

In the professional lighting industry, changes in intensity are called fades.

Modern dimmers are built from silicon-controlled rectifiers (SCR) instead of

variable resistors, because they have higherefficiency. A variable resistor

would dissipate power as heat and acts as avoltage divider. Since a silicon

controlled rectifier switches between a low resistance "on" state and a high

resistance "off" state, it dissipates very little power compared with the

controlled load.

Three basic methods for dimming are :-

Resistance :- This is the simplest and cheapest form of dimmer. It consists of a

wire wound resistor with a wiper .It is used in series with the load.

The basic principle of the saturable reactor is to connect an iron cored choke in

series with the lamp.

Capacitor :-The capacitor are used to stored energy or power.In the case of

dimmers the capacitor can store an aequate amount of power to redused the

intensity of light.

LIGHTING THE SET FOR DRAMA:-

The top of the set should be darkened off by using the barndoors, this puts a

"ceiling" on the set by giving the feeling of a roof. If more than the top of the set

is darkened, that gives enclosed feeling.
http://en.wikipedia.org/wiki/Light_fixturehttp://en.wikipedia.org/wiki/Root_mean_squarehttp://en.wikipedia.org/wiki/Arithmetic_meanhttp://en.wikipedia.org/wiki/Silicon-controlled_rectifierhttp://en.wikipedia.org/wiki/Electrical_efficiencyhttp://en.wikipedia.org/wiki/Voltage_dividerhttp://en.wikipedia.org/wiki/Voltage_dividerhttp://en.wikipedia.org/wiki/Electrical_efficiencyhttp://en.wikipedia.org/wiki/Silicon-controlled_rectifierhttp://en.wikipedia.org/wiki/Arithmetic_meanhttp://en.wikipedia.org/wiki/Root_mean_squarehttp://en.wikipedia.org/wiki/Light_fixture


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Indoor day time:

- If there is a choice in the direction of the 'sun'(Key) take the shortest route

inside the set to a wall, and if possible throw the shadow of window bars onto a

door - it usually is in shot.

-A patch of light on the floor inside the set, backlight from outside using a soft

source at steep elevation adds realism.

- When a set does not have a window, a window pattern can be projected onto a

wall to produce a suitable window effect.

-Roof and Ceiling Pieces - if they make lighting impossible, check if they can

be removed at the planning state. Light any ceiling pieces from outside, use a

soft source at ground level. If the ceiling has plaster a hard source may be used.

Indoor night time:

- The outside of the window should be dark, except for a possible dim skyline if

the room is well above adjacent streets, or lit by an outside practical lamp i.e.

street lighting.

- The wall with the window in it should be lit at night to be brighter than for the

day condition. Subjectively the walls appear brighter at night than at daytime. .

- General for night effects it is not a good plan to just simply dim the set

lighting when changing from day to night.

Outdoor daylight and Moonlight:

The direction of the light is dictated by the position of the 'sun' or 'moon'. As a

general principle one should remember that sunlight (hard source) is

accompanied by the reflected "skylight" (soft source) whereas moonlight is a

single hard source. One of the biggest problems when lighting exteriors is the

maintenance of single shadow" philosophy - double shadows on a long shot

will quickly destroy the apparent realism created in the set. Very large area filler

light is ideal for exterior daylight scenes. This can be achieved by using a

suspended white screen 12' x 8' where the filler would be positioned then

lighting it with hard light.


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VISION MIXING

Introduction

Vision mixing is a process of creating composite pictures from various sources.

Vision mixing involves basically three types of switching or transitions between

various sources. These are mixing, wiping and keying. These transitions can

also be accompanied by special effects in some of the vision mixers.

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.

Wipe :-

In this case the control for the two input sources is generated by the wipe

pattern generator (WPG), which can either be saw tooth or parabola at H, V or

both H & V rate. Unlike in MIX, during WIPE, one source is present in one side

of the wipe and the second source on other side of the wipe. A very simple to

very complex wipe patterns can be generated from the WPG.

Key :-

In the Key position between two sources i.e. foreground (FG) and background

(BG) the control derived from one of the source itself (overlay), or by the third

source (external key). This keying signal can be generated either by the

luminance, or chrominance of the source input.


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MASTER SWITCHING ROOM

Master 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. 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.


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TV TRANSMITTER ANTENNA SYSTEM

Antenna System is that part of the Broadcasting Network which accepts RF

Energy from transmitter and launches electromagnetic waves in space. The

polarization of the radiation as adopted by Doordarshan is linear horizontal. The

system is installed on a supporting tower and consists of antenna panels, power

dividers, baluns, branch feeder cable, junction boxes and main feeder cables.

Dipole antenna elements, in one or the other form are common at VHFfrequencies where as slot antennae are mostly used at UHF frequencies. Omni

directional radiation pattern is obtained by arranging the dipoles in the form of

turnstile and exciting the same in quadrature phase.

Here the transmission of both audio as well as video signals is being made. The

transmission section does the function of modulation of signals, power

amplification of the signal & mixing of the audio & video signals.


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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.

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.


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EARTH STATION

Digital Earth Station:-

Earth station is the main part which communicates with satellite in which

uplinking and downlinking of the signal into and 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 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.

The earth station is supposed to convey the information from the user to

the satellite and from satellite back to the user.

The earth station can be located on land,ships,aircraft etc.


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Process involved in transmission of signal:-

Up-Conversion.

High power amplification.

Transmission.

SATELLITE COMMUNICATION:-

Satellite Communication is the outcome of the desire of man to achieve the

concept of global village. Penetration of frequencies beyond 30 Mega Hertz

through ionosphere force people to think that if an object (Reflector) could be

placed in the space above ionosphere then it could be possible to use complete

spectrum for communication purpose. It is simply the communication of the

satellite in space with large number of earth stations on the ground.The function

of the satellite is to receive a high frequency signal (uplink) , processes it and

resend back to the earth station at a lower frequency signal (downlink).

Intelsat-I (nick named as Early Bird) was launched on 2 April 1965. This was

parked in geosynchronous orbit in Atlantic ocean and providedtelecommunication or television service between USA and Europe. It had


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capacity for 240 one way telephone channels or one television channel.

Subsequently Intelsat-II generation satellites were launched and parked in

Atlantic ocean and Pacific Ocean.

ANIK : Canadian satellite system.

INSAT : Indian Satellites.

AUSSAT : Australian Satellites.

BRAZILSAT : Brazilian Satellites.

FRENCH TELECOM : French Satellites.

ITALSAT : Italian Satellites.

CHINASAT : Chinese Satellites.

STATSIONAR, GORIZONT, Russian Satellites.

Architecture of a Satellite Communication System:-


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The Space Segment

The space segment contains the Satellite and all terrestrial facilities for the

control and monitoring of the Satellite. This includes the tracking, telemetry and

command stations (TT&C) together with the Satellite control centre where allthe operations associated with station-keeping and checking the vital functions

of the satellite are performed.The quality of a radio link is specified by its

carrier-to-noise ratio. The important factor is the quality of the total link, from

station to station, and this is determined by the quality of the uplink and that of

the down link .uplink frequency always greater than downlink frequency due to

the interference between transmittion and reception.

Uplink frequency :- The frequency at which the signal are transmitted from

earth station to satellite.

Downlink frequency :-The frequency at which the signal are send to satellite

back to earth station.

The Ground Segment:

The ground segment consists of all the earth stations ; these are most often

connected to the end-users equipment by a terrestrial network or, in the case of

small stations (Very Small Aperture Terminal, VSAT), directly connected to the

end-users equipment. The largest are equipped with antenna of 30 m diameter

(Standard A of the INTELSAT network). The smallest have 0.6 m

antenna(direct television receiving stations).

Space Geometry:

Types of Orbit:

The orbit is the trajectory followed by the satellite in equilibrium between two

opposing forces. These are the force of attraction, due to the earths gravitation,

directed towards the centre of the earth and the centrifugal force associated with

the curvature of the satellites trajectory. The trajectory is within a plane and

shaped as an ellipse with a maximum extension at the apogee and a minimum at


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the perigee. The satellite moves more slowly in its trajectory as the distance

from the earth increases .

Most favourable Orbits:

Elliptical orbits:

Elliptical orbitsinclined at an angle of 64o with respect to the equatorial plane.

This orbit enables the satellite to cover regions of high latitude for a large

fraction of the orbital period as it passes to the apogee.

Circular inclined orbits :

The altitude of the satellite is constant and equal to several hundreds of

kilometers. The period is of the order of one and a half hours. With near 90%

inclination this type of orbit guarantees that the satellite will pass over every

region of the earth.

Circular orbits:

Circular orbitswith zero inclination (Equatorial orbits). The most popular is thegeo stationary satellite orbits ; the satellite orbits around the earth at an altitude

of 35786 km, and in the same direction as the earth. The period is equal to that

of the rotation of the earth and in the same direction.

Factors deciding the selection of Orbit:

The choice of orbit depends on the nature of the mission, the acceptable

interference and the performance of the launchers :

The extent and latitude of the area to be covered.

The elevation angle of earth stations

Transmission duration and delay.


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Interference.

The performance of launchers.

Advantages of satellite communication:

Mobile/Wireless Communication, independent of location.

Wide area coverage:country,continent,or globe.

Wide bandwidth available throughout.

Independence from terrestrial infrastructure.

Rapid installation of ground network.

Low cost per added site.

Small Fading margin (3dB).

Disadvantages of satellite communication:

Launching satellites into orbit is costly.

Short life time maximum of 15 years.

Redundancy in component!

There is a larger propagation delay in satellite communication than in

terrestrial communication.

Satellite bandwidth is gradually becoming used up.


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TVRO SYSTEM

Presently Doordarshan is up linking its national, metro and regional services to

INSAT-2A (74o E) and INSAT-2B (93.5o E) and INSAT 2E (83o E). Down

link frequency bands being used are C-Band (3.7-4.2 GHz) and Ex-C Band

(4.5-4.8 GHz).

Satellite Earth Station Uplink / Downlink Chain

Transmission of base band to Satellite:

The base band signal consists of video (5 MHz), two audio subcarriers (5.5

MHz & 5.75 MHz) and energy dispersal signal (25 Hz). After modulation (70

MHz) and upconversion (6 GHz) the carrier is amplified and uplinked through

Solid Parabolic Dish Antenna (PDA). Down link signal can be received through

same PDA using Trans-Receive Filter (TRF) and Low Noise Amplifier (LNA).

After down conversion, it is demodulated(70 MHz) to get audio and video.

Satellite Transponder:

As shown in fig, the uplinked signal (6 GHz) at satellite is received, amplified

and down converted to 4 GHz band and sent back through filter and power


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amplifier (TWT). The local oscillator frequency of down converter is 2225

MHz for C band and Ex-C band transponders.

Block diagram of Satellite Transponder

Receiving Satellite Signal:- For receiving a satellite signal we need following

equipment :

Satellite receiving antenna (PDA).

Feed with low noise block converter (LNBC).

Indoor unit consisting of satellite system unit and a Synthesised satellite

receiver.

Parallels of Latitudes Latitude as angular distance


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Indoor Units:-

The indoor unit contains two units. They are :

System unit

Satellite Receiver Unit

System unit:

The system unit contains a passive power divider and power supply for the

LNBC. The power divider divides the IF into two equal parts to be applied to

the two receivers. The power supply is fed through same cable to the LNBC.

Satellite Receiver Unit:

The satellite receiver contains the down converter, video/audio demodulators

and processing circuits. Finally we get two video/audio output. is the

distribution of television signals from high powered geo-stationary satellites to a

small dish antenna and satellite receivers in homes across the country. The cost

of DTH receiving equipments is now gradually declining and can be afforded

by common man. Since DTH services are fully digital, it can offer value added

services, video-on-demand, Internet, e-mail and lot more in addition to

entertainment. DTH reception requires a small dish antenna (Dia 60 cm), easily

be mounted on the roof top, feed along with Low Noise Block Converter

(LNBC), Set-up Box (Integrated Receiver Decoder, IRD) with CAS

(Conditional Access System). A bouquet of 40 to 50 video programs can

simultaneously be received in DTH mode.

UPLINK CHAIN :

DTH broadcasting is basically satellite broadcasting in Ku-Band (14/12 GHz).

The main advantage of Ku-Band satellite broadcasting is that it requires

physically manageable smaller size of dish antenna compared to that of C-Band

satellite broadcasting.


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DOWN-LINK CHAIN :

Down-Link or receiving chain of DTH signal is depicted in Fig. below. There

are mainly three sizes of receiving antenna, 0.6m, 0.9m, and 1.2m. Any of thesizes can easily be mounted on rooftop of a building or house. RF waves

(12.534GHz, 12.647GHz, 12.729 GHz) from satellite are picked up by a feed

converting it into electrical signal. The electrical signal is amplified and further

down converted to L-Band (950-1450) signal. Feed and LNBC are now

combined in single unit called LNBF. The L-Band signal goes to indoor unit,

consisting a set-top box and television through coaxial cable. The set-top box or

Integrated Receiver Decoder (IRD) down converts the L-Band first IF signal to

70 MHz second IF signal, perform digital demodulation, de-multiplexing,

decoding and finally gives audio/video output to TV for viewing.


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OUTDOOR BROADCASTING VAN

O B Van (Outdoor Broadcasting van ):

OB van is used for live broadcasting like any match or any event. It consist all

the equipments that is present in the studio for telecasting. It also referring as

mini studio . 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 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 thatall the cameras look the same.

The 5th part is transmission where the signal is monitored by and

engineered for quality control purposes and is transmitted or sent to other

trucks.


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Inner View of OB van

Inner View of OB van


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FUTURE 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.


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BIBLIOGRAPHY

Satellite communication book by dennis roddy

Technologyinterface.nmsu.edu

www.cosmic.ucar.edu

www.slashdocs.com
http://www.cosmic.ucar.edu/http://www.cosmic.ucar.edu/http://www.cosmic.ucar.edu/

doordarshan summer traning

Documents