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“DOORDARSHAN”

Industrial Training Report

Submitted in the partial fulfillment of requirement for the award of degree of 

Bachelor of Engineering

In

Electronics and Communication Engineering

Submitted By

Rachit Sharma (En. No 291 /07)

Submitted to

M/s.Arpanjeet Kour

Lect. ECE Deptt.

Department of Electronics And Communication Engineering

MAHANT BACHITTAR SINGH COLLEGE OF ENGINEERING

&TECHNOLOGY JAMMU. (J&K)

2010

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COMPANY CERTIFICATE

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DECLARATION

I hereby declare that the I.T. report entitled “DOORDARSHAN” is a

record of my own work carried out as per requirements for the award of 

degree of B.E (E&CE) at Mahant Bachittar Singh College of Engineering &

 Technology Jammu, during a period from June 15, 2010 to July 15, 2010 at

DDK, Jammu.

Date: 21/10/2010 Rachit Sharma (En.

No291/07)

Certified that the above statement made by student is correct to the

best of my knowledge and belief.

Mr. Jamini Sharma

Ms.Arpanjeet Kour

(H.O.D. E&CE) (Seminar Coordinator/Teacher Incharge)

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ACKNOWLEDGEMENT

First and foremost, I would like to thank my respected parents, who always encouraged me

and taught me to think and workout innovatively what so ever be the field of life. My sincere

thanks goes to Mr.Balbir Singh (ASE Doordarshan) for his prodigious guidance,

 persuasion, and painstaking attitude, reformative and prudential suggestion throughout my

industrial training schedule.

Special thanks go to Mr. T.K Koul . Who helped me a lot in giving various information

about DDK Jammu and enlightened me with the knowledge of Transmission equipments.

Last but not the least, my sincere thanks to all the staff members and friends for instilling in

me a sense of self-confidence and encouraging me be the best in whatever I opt to do.

Rachit Sharma (En. No 291/07)

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ABSTRACT

The vocational training provides an essential step towards making future engineers familiar 

with the practical aspects of their field work. During the training a trainee gets an opportunity

to relate the theoretical knowledge with practical operation.

I feel privileged for the opportunity of undergoing the training at Doordarshan Jammu. This

report is an attempt to put in words our study of various steps that are followed in video

signal processing and transmission in the three basic departments of Doordarshan, that is

Studio, Earth Station, Transmitter.

This report also includes the description of satellite communication along with the various

methods like PAL-D and HD mechanisms 

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LIST OF FIGURES

S.No. Figure Page No.

1. Television 1

2. Typical modern plasma modern screen T.V. 3

3. Logo of doordarshan 4

4. Schematic of vidicon 7

5. Actual vidicon tube 76. Parabolic reflector 10

7. Terrestrial Antenna 11

8. Block diagram of T.V. transmitter 13

9. Pal Video Transmitter 14

10. Spectrum of a system I television channel with PAL color 16

11.Oscillogram of composite PAL signal 16

12.Blanking signal 17

13. Visual level diagram 20

14. Oral level diagram 21

15. Satellite communication 24

16. Satellite network 2517. Inside OB van 25

18.OB van 26

19. Block diagram of OB van 26

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LIST OF TABLES

S.No. Table Page No.

 

1. PAL signal details 17

2. Vertical timings 18

3. Standard HD video modes 27

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CONTENTS

TITLE PAGE NO

Certificate i

Declaration ii

Acknowledgement iii

Abstract iv

List of figure v

List of tables vi

CHAPTER 1 INTRODUCTION TO TELEVISION 1

1.1 HISTORY 2

1.2 DOORDARSHAN 4

1.2.1 BEGINNING 4

1.2.2 NATIONWIDE TRANSMISSION 5

CHAPTER 2 PROGRAMMER CONTROL ROOM (PCR) 6

2.1 STUDIO (CAMERA SECTION) 6

2.2 VIDEO TAPE RECORDER (VTR) 7

2.3 STUDIO SECTION 8

2.3.1 AUDIO SUB CARRIER FREQUENCY 8

2.4 EARTH STATION 9

2.4.1 MICROWAVE PARABOLIC REFLECTOR 9

CHAPTER 3 TRANSMITTER 12

3.1 GENERAL FEATURES OF A TV TRANSMITTER 12

3.2 CHARACTERISTICS 13

3.3 FORWARD ERROR CORRECTION 14

3.4 CONSTRUCTION 15

3.5 PAL 15

3.5.1 COLOUR ENCODING 17

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3.5.2 PAL SIGNAL DETAILS 19

3.5.3 PAL B/G/D/K/I 19

3.6 DESCRIPTION 19

3.7 EXCITER SECTION 19

3.7.1 VISUAL EXCITER SECTION 19

3.7.2 WORKING 20

3.7.3 AURAL EXCITER SECTION 20

CHAPTER 4 SATELLITE COMMUNICATION 22

4.1 POLARIZATION 25

4.2 DOWNLINK FREQUENCY IN GHZ (GIGA HERTZ) 254.3 O.B. VAN (OUTSIDE BROADCASTING VAN) 27

CHAPTER 5 FUTURE SCOPE

5.1 HIGH-DEFINITION VIDEO

5.2 HD CONTENT

REFERENCE/BIBLIOGRAPHY

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CHAPTER 1

INTRODUCTION TO TELEVISION

.

Fig. 1.1 Television

Television (TV) is a widely used telecommunication medium for transmitting and receiving

moving  images that are either   monochromatic ("black and white") or  color , usually

accompanied by sound. "Television" may also refer specifically to a television set, television

 programming or  television transmission. The word is derived from mixed Latin and Greek  

roots, meaning "far sight": Greek tele, far, and Latin visio, sight.

Commercially available since the late 1920s, the television set has become common in

homes, businesses and institutions, particularly as a source of entertainment and news. Since

the 1970s the availability of  video cassettes, laserdiscs, DVDs and now Blu-ray Discs, have

resulted in the television set frequently being used for viewing recorded as well as broadcast

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material. In recent years  Internet television has seen the rise of television available via the

Internet, eg iPlayer and Hulu.

1.1 HISTORY

In its early stages of development, television employed a combination of  optical, mechanical

and electronic technologies to capture, transmit and display a visual image. By the late 1920s,

however, those employing only optical and electronic technologies were being explored. All

modern television systems rely on the latter, although the knowledge gained from the work 

on electromechanical systems was crucial in the development of fully electronic television.

The first images transmitted electrically were sent by early mechanical fax machines,

including the  pantelegraph, developed in the late nineteenth century. The concept of 

electrically powered transmission of television images in motion was first sketched in 1878

as the  telephonoscope, shortly after the invention of the telephone. At the time, it was

imagined by early science fiction authors, that someday that light could be transmitted over 

wires, as sounds were.

The idea of using scanning to transmit images was put to actual practical use in 1881 in the

 pantelegraph, through the use of a  pendulum-based scanning mechanism. From this period

forward, scanning in one form or another has been used in nearly every image transmission

technology to date, including television. This is the concept of "rasterization", the process of 

converting a visual image into a stream of electrical pulses.

In 1884 Paul Gottlieb Nipkow, a 23-year-old university student in Germany, patented the first

electromechanical television system which employed a scanning disk , a spinning disk with a

series of holes spiraling toward the center, for rasterization. The holes were spaced at equal

angular intervals such that in a single rotation the disk would allow light to pass through each

hole and onto a light-sensitive  selenium sensor which produced the electrical pulses. As an

image was focused on the rotating disk, each hole captured a horizontal "slice" of the whole

image.

 Nipkow's design would not be practical until advances in amplifier  tube technology became

available. The device was only useful for transmitting still "halftone" images—represented by

equally spaced dots of varying size—over  telegraph or telephone lines. Later designs would

use a rotating mirror-drum scanner to capture the image and a cathode ray tube (CRT) as a

display device, but moving images were still not possible, due to the poor sensitivity of theselenium sensors. In 1907 Russian scientist Boris Rosing became the first inventor to use a

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CRT in the receiver of an experimental television system. He used mirror-drum scanning to

transmit simple geometric shapes to the CRT.

Fig. 1.2 Typical modern plasma-screen television set.

Scottish inventor  John Logie Baird demonstrated the transmission of moving silhouette

images in London in 1925, and of moving, monochromatic images in 1926. Baird's scanning

disk produced an image of 30 lines resolution, just enough to discern a human face, from a

double spiral of lenses. This demonstration by Baird is generally agreed to be the world's first

true demonstration of television, albeit a mechanical form of television no longer in use.

Remarkably, in 1927 Baird also invented the world's first video recording system,

"Phonovision": by modulating the output signal of his TV camera down to the audio range,

he was able to capture the signal on a 10-inch wax audio disc using conventional audio

recording technology. A handful of Baird's 'Phonovision' recordings survive and these were

finally decoded and rendered into viewable images in the 1990s using modern digital signal-

 processing technology.

In 1926, Hungarian engineer  Kálmán Tihanyi designed a television system utilizing fully

electronic scanning and display elements, and employing the principle of "charge storage"

within the scanning (or "camera") tube.

By 1927, Russian inventor Léon Theremin developed a mirror-drum-based television system

which used interlacing to achieve an image resolution of 100 lines.

Also in 1927,  Herbert E. Ives of  Bell Labs transmitted moving images from a 50-aperture 

disk producing 16 frames per minute over a cable from Washington, DC to New York City,

and via  radio from Whippany, New Jersey. Ives used viewing screens as large as 24 by

30 inches (60 by 75 centimeters). His subjects included Secretary of Commerce  Herbert

Hoover .

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In 1927, Philo Farnsworth made the world's first working television system with electronic

scanning of both the pickup and display devices, which he first demonstrated to the press on

1 September 1928.

The first practical use of television was in Germany. Regular television broadcasts began in

Germany in 1929 and in 1936 the Olympic Games in Berlin were broadcast to television

stations in Berlin and Leipzig where the public could view the games live.

In 1936, Kálmán Tihanyi described the principle of   plasma television, the first flat panel

system.

Mexican inventor  Guillermo González Camarena also played an important role in early

television. His experiments with television (known as telectroescopía at first) began in 1931

and led to a patent for the "trichromatic field sequential system" color television in 1940, as

well as the remote control.

1.2 DOORDARSHAN

Fig. 1.3 Logo of Doordarshan

Doordarshan is the public television  broadcaster  of India and a division of Prasar Bharati, a

 public service broadcaster 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. Recently, it has also started Digital Terrestrial Transmitters. On September 152009, Doordarshan celebrated its 50th anniversary.

1.2.1 BEGINNING

Doordarshan had a modest beginning with the experimental telecast starting in Delhi on 15

September 1959 with a small transmitter and a makeshift studio. The regular daily

transmission started in 1965 as a part of All India Radio. The television service was extended

to Bombay (now Mumbai) and Amritsar in 1972. Up until 1975, only seven Indian cities had

a television service and Doordarshan remained the sole provider of television in India.

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Television services were separated from radio in 1976. Each office of All India Radio and

Doordarshan were placed under the management of two separate Director Generals in New

Delhi. Finally Doordarshan as a National Broadcaster came into existence.

1.2.2 NATIONWIDE TRANSMISSION

 National telecasts were introduced in 1982. In the same year, colour TV was introduced in

the Indian market with the live telecast of the Independence Day speech by the then prime

minister Indira Gandhi on 15 August 1982, followed by the 1982 Asian Games which were

held in Delhi. Now more than 90 percent of the Indian population can receive Doordarshan

(DD National) programmes through a network of nearly 1,400 terrestrial transmitters. There

are about 46 Doordarshan studios producing TV programs today.

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CHAPTER 2

PROGRAMMER CONTROL ROOM (PCR)

The programmer control room is one of the essential blocks of DDK. It can be termed asrecording Centre for the programmer. The live telecast of the programmer such as news,

interviews etc. also take place here. This is one among the major sections of DDK and

involves a number of technical and non- technical persons. Recording takes place according

to a predetermined schedule called programed schedule. The PCR of DDK Jammu is double

storied building having in it three studios and their control rooms. It lies just opposite to

Administration and has constructed 30 years ago.

The PCR consists of following three sections:

1. Studio.

2. Video Tape Recorder.

3. Audio Section.

2.1 STUDIO (CAMERA SECTION)

Studio is the room where a program is performed and recorded using cameras. The studio

number of these lights may reach 50 in order to cover the whole of the studio usually the no.

of cameras used is three. A typical camera is shown on the following page. Various set are

made. The selection of particular set depends on the type of program that cameras are

assigned the numbers i.e. camera 1, camera 2 etc. The position of camera is so adjusted that

we get different views from each camera. It is he who adjusts the settings of the camera and

 people who perform as per the instructions of the program producer instructions to start,

silent atmosphere is created and every body prepares for the final go. The video signal sent to

VTR via Optical fiber cables.

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Fig 2.1 Schematic of Vidicon

Fig 2.2 Actual Vidicon Tube

2.2 VIDEO TAPE RECORDER (VTR)

It stands for videotape recorder. VTR is an essential section of PCR. This is in fact the main

recording room having co-ordination with both the studio as well as Audio section. Thissection is controlled by producer and his assistant. Here the output of all the cameras is

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 provided to producer to make the selection of the shots. It is there from where the producer 

can communicate with every person involved in recording.

VTR mainly consists of a video console, which is used for shot selection and a recording's

apparatus used for recording of the final program. Different control knobs on video-console

are output of different cameras. A particular shot that has to be selected and recorded out of 

various cameras is decided by the producer himself and accordingly he gives instructions to

his assistants for the same.

A summary of the program that is to be recorded is lying with the producer. He prepares in

advance a list of shots that are to be inserted at different positions and as the program runs it

is up to him to make the shot selection by going through his summary. The making and the

final shape of a program depends on how effectively the producer shots selection on VTR.

There is a fixed time period allowed for recording each program. Weekly schedule of 

  programs is framed in advance and recording proceeds according to that schedule. In

Doordarshan Kendra Jammu usually four programs are recorded each day by protective

 producers.

2.3 STUDIO SECTION

2.3.1 AUDIO SUB CARRIER FREQUENCY

These are for analog channels.The column shows the audio frequencies. The video signal of 

vision channel is transmitted on the channel.The frequency given in the "GHZ" column

accompanying sound signal is transmitted at a sub carrier of that video (main) frequency. The

sub carrier frequency is given in MHz (Megahertz). A single frequency entry in this column

represents Mono sound, while two frequencies separated by "& ", represent Stereo sound.

Two or frequencies without "&", represent different Mono sound carriers. For digital

channels this column gives the Tele text PID Audio section as the name indicates is the part

of the PCR that produces noise free 'Q signals to the VTR for recording. This section is

controlled by two technicians. It consists of audio console and echo inserter. The use of echo

inserter is optional and depends on the nature program. Audio console in it contains the

control knob of gains of various mikes that are present studio. Out of the various mikes

 present in studio the no. of mikes and there nature is selected in section. The audio signal

from the studio is given to is a maintaining section and no recording takes place of amplifiers

and then finally to console where it is checked for the noise. The gain meters on audio

console gives an idea of the noise level present in the signal. The reading should not cross the

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zero db. if does, it brought back by control knobs on the console. There is a matrix of 

connections and a particular choice activates a particular set of connections. The coordination

of various persons involved in the recording of a program is done e help of head phones and

mikes.

2.4 EARTH STATION

An Earth Station is actually a Satellite linker which forms an essential block of DDK ar. The

 programs that are recorded at PCR are played in this block at their respective s. These

  programs are up linked to a particular satellite after passing-them through a series of 

amplifiers and multipliers.

The Earth Station in a sense is a transmitter however; it differs from the terrestrial in terms of 

frequency and operation. While the function terrestrial transmitter is to signals into

ionosphere for their reception by local areas, the Earth Station uplinks the satellite for their 

reception by large area. The frequency band is isn MHz for terrestrial Transmitter while as

it's in GHz for the Earth Station. The transmission system for DDK Kashir’s both the Digital

as well as Analog. The frequency analysis of DD Jammu is given below. The difference n

uplink and downlink frequency is 2225MHz. There are both digital as well as analog

available for DD Kashir.

Analog Uplink Frequency = 6006MHz.

Analog Downlink Frequency = 6006 -2225 = 3781MHz.

Digital Uplink Frequency = 6025MHz.

Digital Downlink Frequency = 6025 -2225 = 3800MHz.

Difference between downlink frequencies for Analog and Digital = 3800-3781 = 19 MHZ.

Difference of 19 MHZ. is responsible for the early reception of analog signal rather than

digital signal. But it is well known the clearness of reception of digital over analog signal.

Our country is using the service of this satellite on the rental basis and has to pay lacks of 

rupees same.

2.4.1 MICROWAVE PARABOLIC REFLECTOR 

Radio Frequency Systems offers the most comprehensive line of highest quality microwave

antennas in the industry. Antennas are available in all the common frequency bands ranging

from 3GHz to 60GHz. They are available in diameters from 1 feet (0.3 m) to 15 feet (4.60

m). System design becomes easy and efficient with such a comprehensive antenna offering.

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The antennas are available in four performance classes offering complete flexibility when

designing a network.

The antennas meet the pattern requirements according to EN 302 217 and FCC depending on

the frequency range.

In addition to the different electrical classes of antennas Radio Frequency Systems offers the

system design engineers different options of survival wind speeds. This allows the use of 

antennas in areas where extreme wind conditions are normal.

Fig 2.3 parabolic reflector 

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• Fig 2.4 Terrestrial antenna

 

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CHAPTER 3

TRANSMITTER 

3.1 GENERAL FEATURES OF A TV TRANSMITTER 

1. TYPE: -PCN-810 AL.

2. RATING: -10 KW.

3. STATUS: -VHF.

All of the visual modulator and visual exciter of the visual transmitter and the aural ulator and

aural exciter of the aural transmitter are composed of transistors and ICs. They use no tubes

at all. As compared with the conventional transmitter, therefore, it features easier 

maintenance and higher reliability. Unlike the conventional Grid modulation system, the

video carrier is modulated by Diode balanced modulator while the audio carrier is modulated

  by Varactor Reactance modulator at intermediate Frequency (IF). This gives lowest

modulating level as well as lower nonlinear distortion. This results in excellent color.

3.2 CHARACTERISTICS

1. 'The video carrier is modulated in IF band by the VSB filter in built in the visual

modulator. It is compact in nature. A typical NEC VSB filter section is of the

dimensions 120(W) x70(D) x80(H).

2. The VSB filter section has a built in phase compensator which compensates phase

distortion in AF region of the VSB filter.

3. In a conventional TV transmitter a phase compensator is inserted in the video signal

input distortion of the phase.

4. However, even if the phase compensation is even if the phase compensation is

accomplished in the frequency band of the video signal it is impossible to compensate

the non linearity of the phase completely. Therefore, in a demodulated video signal,

discreteness occurs near 1 MHz.

5. Circulators are used between cascaded visual power amplifier stages for impedance

matching ensures maximum and safe power transmission between two stages

6. Aural transmitter is capable of double broadcasting. The aural modulation is of the

reactance FM modulation system so that it has excellent frequency deviation

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characteristics, requires less multiple stages. It has excellent distortion factor and AF

characteristics

7. Cooling is maintained using blowers. This can be led via floor surface or top of the

transmitter.

8. The devices have protective relays and are also protected by an inter lock circuit

which s the transmitter to be started only according to a predetermined sequence

3.3 FORWARD ERROR CORRECTION

It is only applicable for digital transmissions. The FEC (Forward Error Correction) indicates

how are used for the actual signal, and how many for correction of errors. A FEC of 1 Byte

out of 2 is used for error correction, while a ratio of 7/8 means 7 Bytes are used for actualsignal, and only one for error correction. A FEC of 1/2 gives as perfect as reception, since

every Byte containing actual signal is controlled by another Byte en a provider chooses a

FEC of 7/8 it means he is not wasting any bandwidth at the cost of delivering a signal. The

lower amount of error correction means that more sophisticated equipment receiving end (for 

example a more stable and sensitive LNB, or higher reserves e needed compared to the same

transmission using a FEC of ½.

Fig. 3.1 Block Diagram of TV Transmitter 

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Fig. 3.2 Pal Video Transmitter 

3.4 CONSTRUCTION

The transmitter consists of two frames as shown facing the front. The left frame

accommodates the s and P A panel while the right frame accommodates Visual Last Stage

 power amplifiers In addition plate voltage transformer, silicon rectifier and blower are

installed outside the frame.

DIMENSIONS

WIDTH: 2450 mm.

DEPTH: 800 mm.

HEIGHT: 2100 mm

WEIGHT: 1500 kg (app.)

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3.5 PAL

Television encoding systems by nation; countries using the PAL system is shown in blue.

PAL, short for Phase Alternate Line, is an analogue television encoding system used in

 broadcast television systems in many countries. Other common analogue television systems

are SECAM and  NTSC.

3.5.1 COLOUR ENCODING

The basics of PAL and the NTSC system are very similar; a quadrature amplitude modulated 

subcarrier  carrying the chrominance information is added to the luminance video signal to

form a composite video baseband signal. The frequency of this subcarrier is 4.43361875

MHz for PAL, compared to 3.579545 MHz for NTSC. The SECAM system, on the other hand, uses a frequency modulation scheme on its two line alternate colour subcarriers

4.25000 and 4.40625 MHz.

The name "Phase Alternating Line" describes the way that the phase of part of the colour 

information on the video signal is reversed with each line, which automatically corrects phase

errors in the transmission of the signal by cancelling them out, at the expense of vertical

frame colour resolution. Lines where the colour phase is reversed compared to NTSC are

often called PAL or phase-alternation lines, which justifies one of the expansions of theacronym, while the other lines are called NTSC lines. Early PAL receivers relied on the

imperfections of the human eye to do that cancelling; however this resulted in a comblike

effect known as  Hanover bars on larger phase errors. Thus, most receivers now use a

chrominance delay line, which stores the received colour information on each line of display;

an average of the colour information from the previous line and the current line is then used

to drive the picture tube. The effect is that phase errors result in saturation changes, which are

less objectionable than the equivalent hue changes of NTSC. A minor drawback is that the

vertical colour resolution is poorer than the NTSC system's, but since the human eye also has

a colour resolution that is much lower than its brightness resolution, this effect is not visible.

In any case, NTSC, PAL and SECAM all have chrominance bandwidth (horizontal colour 

detail) reduced greatly compared to the luminance signal.

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Fig. 3.3 Spectrum of a System I television channel with PAL colour.

Fig. 3.4 Oscillogram of composite PAL signals - several lines.

The 4.43361875 MHz frequency of the colour carrier is a result of 283.75 colour clock cycles

 per line plus a 25 Hz offset to avoid interferences. Since the line frequency is 15625 Hz, the

colour carrier frequency calculates as follows: 4.43361875 MHz = 283.75 * 15625 Hz + 25

Hz.

The original colour  carrier is required by the colour decoder to recreate the colour difference 

signals. Since the carrier is not transmitted with the video information it has to be generated

locally in the receiver. In order that the  phase of this locally generated signal can match the

transmitted information, a 10 cycle burst of colour  subcarrier  is added to the video signal

shortly after the line sync pulse but before the picture information, during the so called back 

 porch. This colour burst is not actually in phase with the original colour subcarrier but leads it

 by 45 degrees on the odd lines and lags it by 45 degrees on the even lines. This swinging

 burst enables the colour decoder circuitry to distinguish the phase of the R-Y vector which

reverses every line.

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3.5.2 PAL SIGNAL DETAILS

Table 1: PAL-B/G signal has following features.

Parameter Value

Clock frequency* 14.8 MHz

Bandwidth 5.0 MHz

Horizontal sync polarity Negative

Total time for each line 64.000 µs 

Front porch (A) 1.65+0.4−0.1 µs

Sync pulse length (B) 4.7±0.20 µs

Back porch (C) 5.7±0.20 µs

Active video (D) 51.95+0.4−0.1 µs

*(Total horizontal sync time 12.05 µs)

After 0.9 µs a 2.25±0.23 µs colourburst of 10±1 cycles is sent. Most rise/fall times are in

250±50 ns  range. Amplitude is 100% for white level (white colour on a monochrome

receiver), 30% for black, and 0% for sync. The CVBS electrical amplitude is Vpp 1.0 V and

impedance of 75 Ω.

Fig. 3.5 Blanking Signal

The composite video (CVBS) signal used in analogue television systems M and N before

combination with a sound carrier and modulation onto an RF carrier .

Table 2 Vertical timings

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Parameter Value

Vertical lines 313 (625 total)

Vertical lines visible 288 (576 total)

Vertical sync polarity Negative (burst)

Vertical frequency 50 Hz

Sync pulse length (F)* 0.576 ms (burst)

Active video (H) 18.4 ms

*(Total vertical sync time 1.6 ms)

As PAL is interlaced, every two fields are summed to make a complete picture frame.

Luminance, Y, is derived from red, green, and blue (R'G'B') signals.

• Y = 0.299R' + 0.587G' + 0.114B'

U and V are used to transmit chrominance. Each has a typical bandwidth of 1.3 MHz.

• U = 0.492(B' − Y)

• V = 0.877(R' − Y)

Composite PAL signal = Y + Usin(ωt) + Vcos(ωt) + timing where ω = 2πFSC.

Subcarrier frequency FSC is 4.43361875 MHz (±5 Hz) for PAL-B/D/G/H/I/N.

An interesting comparison can be made with the VGA signal, the most notable differences

 being the double horizontal sweep time and interlace mode.

3.5.3 PAL B/G/D/K/I

The majority of countries using PAL have television standards with 625 lines and 25 frames

  per second, differences concern the audio carrier frequency and channel bandwidths.

Standards B/G are used in most of Western Europe, standard I in the UK, Ireland, Hong

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Kong and Macau, standards D/K in most of Central and Eastern Europe and Standard D in

mainland China. Most analogue CCTV cameras are Standard D.

7-MHz channels are used in VHF (B, D) and 8-MHz channels in UHF (G, K, I), although

Australia used 7-MHz channels in UHF and Ireland uses 8-MHz channels in VHF.

3.6 DESCRIPTION

This TV transmitter consists of an exciter section consists, Visual and Aural Power Amplifier 

section(A), Visual Last stage P A section (B) and external devices. It delivers 1.0KW output

and 2-2.5KW aural output. The power supply and control Circuits of this transmitter are

common to both visual and aural transmitters.

Parts of power supply:

1. Main Power Supply AC 200V (3-P) 50/60 Hz.

2. Internal illumination & receptacle Power Supply AC IOOV (I-P) 50/60 Hz.

3.7 EXCITER SECTION

The exciter section consists of fully solid-state visual and aural exciters and s the subsequent-

stage vacuum Power Amplifier section.

3.7.1 VISUAL EXCITER SECTION

The main components in the construction of visual exciter section are as below:

1. Visual Modulator.

2. IF Attenuator.

3. VSB Filters Phase-Compensator.

4. Mixer.

5. Output Filter.

6. Local Crystal Oscillator.

7. Visual Transistor P A & Power Supply.

3.7.2 WORKING

The input video signal is Amplitude Modulated (AM) by the visual modulator to obtain the

wave {Video Intermediate Frequency- VIF). The modulated wave is level adjusted by r andis passed through a VSB filter to reduce unwanted LSB. Phase changes in cutoff of the VSB

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filter is compensated at the phase compensator. This output is fed to them with the local

crystal oscillator output, (frequency) for conversion into the required frequency. After the

reduction of the spurious components by the next output filter, it is applied to the Visual

 power Amplifier to obtain sufficient output for excitation of the next stage power amplifier.

3.7.3 AURAL EXCITER SECTION

The main components in the construction of Aural Exciter Section are as below:

1. Aural Modulator.

2. Aural Transistor.

3. Local Crystal Oscillator & Power Supply.

Modulated wave (aural IF, f IAF), frequency modulated with audio signal, is obtained by the

aural This modulated wave is applied to aural P A for multiplication by n to obtain sufficient

output for exciting the next stage Power Amplifier System

Fig 3.6 visual level diagram

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Fig. 3.4 Aural Level Diagram

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CHAPTER 4

SATELLITE COMMUNICATION

In satellite communications, the use of orbiting satellites is to provide communication links invarious points on earth. Communication satellites provide telephone, television, and data s

 between widely separated fixed locations. The technique basically involves transmitting from

an earth station to a satellite. Equipment’s on board of the satellite receive the signals, them,

and transmit them to a region of the earth. Receiving stations within this region pick signals,

thus providing the communication link.

Satellites provide communication links via microwave radio, most commonly in the super 

high frequency band of 3 to 30 GHz. (3 billion to 30 billion hertz, or cycles per second).

These frequencies correspond to wavelengths ranging from 10 cm to 1 cm (4 inches to 0.4

inches). Radio this short diverges along straight lines in narrow beams, rather than

 propagating in an in spherical wave front in the manner of longer wavelengths. In order to

communicate via radio, therefore, transmitters and receivers must be situated within line of 

sight of one another. On land, this can be achieved by using towers on hilltop locations, but

microwave communication across oceans is not possible without use of satellites.

The specific frequency bands open to civilian satellite communications are assigned by the,

International Telecommunication Union, based in Geneva, Switzerland. Each band consists

of an (Earth-to-satellite) frequency and a Downlink (satellite-to-Earth) frequency. The two

 bands that have been in use longest, and still carry the most traffic, are the C band, with

uplink frequencies centered on 6 GHz and downlink frequencies centered on 4 GHz, and the

Ku band, uplink/downlink frequencies centered on 14/11 GHz. In order to relay signals in

these frequencies, a typical communication satellite is equipped with a number of 

transponders. Each transponder consists of a receiver tuned to the uplink band, a frequency

shifter to the received signals to the downlink band, and a power amplifier to produce an

adequate sitting power.

4.1 POLARIZATION

One frequency can be used twice by using two opposing polarizations, so that the two signals

on the two identical frequencies do not interfere with each other  doubles the actual number 

of channels that can be transmitted in the satellite's frequency range. One way of transmitting

a signal is in linear polarization, the other way by rotating circular polarization. For the latter 

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The satellite used by DDK is Insat2-E. This satellite does not belong to India itself; therefore,

the service is n contract basis. May be in near future we may be using our own satellites for 

the above thus making our country self-reliant in this aspect.

Currently India uses the European Meteosat-5 for its forecasting requirements. India's failed

INSAT originally provided this service. INSAT satellites are equipped with Very High

Resolution Radiometers (VHRR) in addition to their primary communication payload.

However, Most developed problems, and the only one working is on the aging Insat ID. The

Geo-sync birds, with a much higher orbit, compared to the Polar orbited Insat. India uses the

European weather Satellite INSAT which unfortunately was expected de-orbited by end

2001. Hence India has set up a new Insats program, & its launch, on a carsh, to ensure we

have a GEO Insats before Insats gets decommissioned. The number of Indian satellites to belaunched over the next two years is seven. The Indian metrological satellite insat will not be

launched into a polar orbit. Despite its rather name, India's Polar Satellite Launch Vehicle

(PSL V) will actually put Met sat into any Transfer Orbit. If successful, this will bring India

into the elite league of countries launch Geo-sync Satellites. The Indian government has

approved plans by the Indian Space Research Organization (ISRO) to advanced remote

sensing satellite, Cartosat 2, which will have an optical resolution of 1 meter. Cartosat 2 was

to be put in orbit by India's Polar Satellite Launch Vehicle (PSL V) in 2003 or 2004. Cartosat

1 (IRS-P5,) to be launched in 2002, will offer a resolution of 2.5 meters. Earlier Indian

Satellites offered a resolution of only 5.8 meters. Cartosat 2 will cost Rs 230 Crores, which is

about Rs 20 Crores less than the technically inferior Cartosat's cost of Rs 250 Cores.

Fig 4.1 satellite communications

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Fig 4.2 Satellite network 

4.2 DOWNLINK FREQUENCY IN GHZ (GIGA HERTZ)

The frequency the satellite uses to beam the transmission down to Earth. This is known as

link" frequency -as opposed to the frequency used to send the transmission to the first report

 place, which is known as the "uplink" frequency. There are two main frequency se; the C-

Band with downlink frequencies in the 3 and 4 GHz range, and the Ku-Band frequencies in

the 10, 11 and 12 GHz range.

1 GHZ =1000 MHz = 1000000 kHz = 1000000000 Hz. (Hz = Hertz). Example: 3.456 GHz =

3456 MHZ

4.3 O.B. VAN (OUTSIDE BROADCASTING VAN) 

Fig 4.3 Inside O.B. Van

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Fig 4.4 O.B. VAN

Fig 4.5 Block Diagram of O.B. VAN

The mobile vans can be used for direct news gathering from anywhere. It can uplink or 

downlink the signal from satellite from anywhere, so they provide live telecast of any event.

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CHAPTER 5

FUTURE SCOPE

Till now Doordarshan was using PAL-D system for colour TV transmission. But nowrecently it has planned to introduce high definition technology with starting of Common

Wealth Games, Delhi 2010.

5.1 HIGH-DEFINITION VIDEO

High-definition video or HD video refers to any video system of higher  resolution than

standard-definition (SD) video, and most commonly involves display resolutions of 

1,280×720 pixels (720p) or 1,920×1,080 pixels (1080i/1080p). This article discusses the

general concepts of high-definition video, as opposed to its specific applications in television

 broadcast (HDTV), video recording formats (HDCAM,  HDCAM-SR ,  DVCPRO HD,  D5

HD, AVC-Intra, XDCAM HD, HDV and AVCHD), the optical disc delivery system Blu-ray

Disc and the video tape format D-VHS.

Table 3 Standard high-definition video modes

Video mode Frame size in

pixels (W×H)

Pixels per

image

Scanning

type

Frame rate (Hz)

720p 1,280×720 921,600 Progressive 23.976, 24, 25, 29.97, 30, 50,

59.94, 60, 72

1080i 1,920×1,080 2,073,600 Interlaced 25 (50 fields/s), 29.97 (59.94

fields/s), 30 (60 fields/s)

1080p 1,920×1,080 2,073,600 Progressive 23.976, 24, 25, 29.97, 30, 50,

59.94, 60

5.2 HD CONTENT

High-definition image sources include terrestrial broadcast, direct broadcast satellite, digital

cable, high definition disc (BD), internet downloads and the latest generation of video game

consoles.

1. Most computers are capable of HD or higher resolutions over VGA, DVI, and/or 

HDMI.The optical disc standard Blu-ray Disc can provide enough digital storage to

store hours of HD video content. DVDs look best on screens that are smaller than

36 inches (91 cm), so they are not always up to the challenge of today's high-definition

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(HD) sets. Storing and playing HD movies requires a disc that holds more information,

like a Blu-ray Disc.

Although, it is a very expensive technology but, with technical progress in this field it is

 becoming cheaper day by day and easily accessible.

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REFERENCE/BIBLIOGRAPHY

•http://www.antennasdirect.com/

• http://electroschematics.com/46/simple-tv-transmitter-schematic

• http://en.wikipedia.org/wiki/PAL