AREPORT ON

INDUSTRIAL TRAINING(13th June 2011- 22nd July 2011)

ATDOORDARSHAN KENDRA , Lucknow

Submitted In Partial Fulfilment Of B.Tech Degree

InElectronics & Comm. Engg.

Of F.E.T R.B.S COLLEGE

Bichpuri,Agra

BY

RAHUL KUMAR SHUKLA

Preface

This report is a brief introduction about Doordarshan, enclosing the topics that deal with all types of applications & with various aspects related to new researches.

I hope, this report will be extremely expedient for grasping the basic knowledge of various fields of communication. The suggestions and constructive criticism for the improvement of the report will be greatly acknowledge and appreciated for further improvements.

About DDK

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 a milestone in the field of entertainment and education media source.DDK, Delhi has the Largest Programmes recording Studio in the Asia. They Broadcast 30 channels in 22 languages over the country.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.

Acknowledgement

The happiness that accompanies the successful completion of any task would not be completed without the expression of thanks to all those who helped me throughout my training.

So, with reverence honour. I acknowledge those whose guidance and encouragement has made it possible. I wish to express my unlimited gratitude and thanks to all the respected members of DOORDARSHAN KENDRA, Lucknow for teaching and guiding us.

IndexSections 1. Earth station

2. TV Studio

Procedure in recording Procedure in Transmission TV Camera Lightening Microphones Video Chain Audio Chain

Vision Mixer 3. PAL System

Color television Delay line PAL-PAL Demodulator

4. MSR

Introduction

Audio Console

5. OB/DSNG Van Introduction OB Van DSNG Van

Parts Description

EARTH STATION

INTRODUCTION

An earth station, ground station, or earth terminal is a terrestrial terminal station designed for extraplanetary telecommunication with spacecraft, and/or reception of radio waves from an astronomical radio source. Earth stations are located either on the surface of the Earth, or within Earth's atmosphere. Earth stations communicate with spacecraft by transmitting and receiving radio waves in the super high frequency or extremely high frequency bands (e.g., microwaves). When an earth station successfully transmits radio waves to a spacecraft (or vice versa), it establishes a telecommunications link.

When a satellite is within an earth station's line of sight, the earth station is said to have a view of the satellite. It is possible for a satellite to communicate with more than one earth station at a time. A pair of earth stations are said to have a satellite in mutual view when the stations share simultaneous, unobstructed, line-of-sight contact with the satellite.

Earth station involves the two terms which are basically the important parameters of the communication i.e. UPLINK & DOWNLINK.

UPLINK: The process of gathering any informative part & sending it to the satellite, running on specified frequency is termed as UPLINK. The uplink frequency is 5950MHz.

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DOWNLINK: The process by which satellite sends the received signals to the controlling stations is termed as DOWNLINK. The downlink frequency is 3725MHz.

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TV Studios

Doordarshan-Delhi has four studio halls. One is used as News Room and the others are used for shooting various programs. Artificial sets are created in the studio hall according to requirements of the program to be shooted. The four studios are named as:>Studio Big > Studio Small > Studio Medium > Studio Large 

Procedure in recording 1. Set is designed in studio as per conceptual thought of program producer. 2. Floor plan is envisaged. 3. Lighting, Audio and placement of the cameras is arranged as per floor plan. 4. Pre testing of cameras, microphones, VCRs etc. is done before recording. 5. Recording begins and desired camera/mike are selected through VM/Audio console as per command of producer. Program is recorded on VCR. Procedure in Transmission �

1. The programs are transmitted as per the daily cue sheet.2. Normal transmission hours are 1600-2000Hrs.�3. Cue sheet is discussed daily by program and technical staff for details in it and for any last �moment changes if any.4. After getting D-link caption from Delhi end program is played from VCR/Server. The program is �uplinked by Earth Station.5. The program is also transmitted to transmitter at Pitampura via MW link. Then DD channels are �taken on air.6. During our slot, both live as well as recorded programs are transmitted.�

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. 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 ³Scanning´ in which information is converted one by one pixel, line by line and frame by frame.

Color Composite Video Signals

Active waveform comprises of 2 signals:

Luminance (Y)-black and white Chrominance (C)-colour signal

TV CameraA TV Camera consists of three sections :a) A Camera lens and optical block b) A transducer or pick up devicec) Electronics

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 section2. Zoom section with manual or servo mode operation3. Servo drive assembly for Zoom and iris control4. Aperture section with manual or auto mode5. Back focus section with adjustment facilities for back and micro focus.

Object Side Camera Side 12

3 4 5

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 electromagnetic radiation with a visible spectrum from red to violet i.e. wavelength from 700nm to 3800nm respectively.

• Basic three pointing lighting:

• Key light: It gives shape and modelling by a casting shadow. It is treated as 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.

• Lightening 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.

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 CCUwhere many parameters of video signals are controlled. Output signal of CCUafter 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 VMaccording to a director’s choice.

Studio 1(video camera)

CCU PCR 1

Studio 2(video camera)

PCR 2(vision mixer)

MSR

VTR

Earth Station

Transmitter

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.

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.

Pre-

Pre-

Pre-

VTR

CD/VCD

Outside

Satellite

MW link

Audioconsole

Program Audio distan.Ampl.

MSR

MSR

MW

FEEDVTR FOR

Program Ampl. ADA

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.

There are two types of mixing:

> Additive mixing &> Non additive mixing

PAL System

(Phase Alternating Line)

The Colour Television

It is possible to obtain any desired colour by mixing three primary colours i.e., red, blue and green in suitable proportion. Thus it is only required to convert optical information of these three colours to electrical signals and transmit it on different carriers to be decoded by the receiver. This can then be converted back to the optical image at the picture tube. The phosphors for all the three colours i.e. R, G and B are easily available to the manufacturers of the picture tube. So the pick up from the cameras and output for the picture tube should consists of three signals i.e. R, G and B. It is only in between the camera and the picture tube of the receiver we need a system to transmit this information.

PAL ENCODER

PAL encoder instead of reversing the phase of V component on every alternating line, it has been found much easier to change the phase of carrier modulating the R-Y component by 180 degree every alternate line. This switching is controlled by the H/2 oscillator i.e., by a 7.80 kHz PAL Indent pulse. The block diagram of PAL encoder explains a system having the following steps:- 1) Add R G B to generate Y, R-Y & B-Y 2) Modulate R-Y by SC at 90o for line n and 270 o for line n+1. Switching of SC phase is controlled by 7.80 kHz, switching pulse. 3) Modulate B-Y by SC at 0o phase. 4) To generate SC with V switching information i.e. either at 135/225o (burst) each alternate line. (Swinging burst) 5) Generation of pulse called PAL-indent signal of 7.80 kHz. 6) Generating of burst gate or K pulse to define the parking space for burst at the back porch. 7) Adding of 2, 3, 4, Y and sync to generate CCVS i.e., colour composite Video signal as Encoder output.

PAL - Decoder

PAL decoder is a reverse of encoding process. The objectives of recovering R G & B from the received signal is achieved in the following steps:

1) Y & S is recovered by decoding video & using LPF and Sync separator circuit of receiver. 2) Chroma is separated by using BPF ( centre at 4.43 MHz) 3) Chrome is keyed or gated to get back the burst i.e. SC by using K - Pulse. 4) L.O. 4.43 MHz is phase locked with the recovered burst to make it of same phase as that of the transmitted one. 5) 4.43 MHz SC is processed further to get the same pulse at 90 degree phase as well. 6) Modulated chroma is demodulated by these two SC at 0 & 90 degree. This will retrieve U & V components. 7) Phase of the V component is restored back to normal by using the concerned information from the transmitted burst. 8) U & V are demodulated back to R-Y & B-Y. 9) Y, R-Y & B-Y are mixed to retrieve R G B which will control the three grids of picture tube.

Master Switching Room

(MSR )

Master switching room (MSR) is used for transmission media. It is the engineering co-ordination centre 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.This section is equipped with a 64X64 Digital Routing Switcher where all the signals from Studio-A, Studio-B, Transmitter, Earth Station, OB Van signal, DSNG etc are routed to various areas as per requirements for recording/transmission. One OFC link between MSR and Earth Station has also been installed.

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.

OB / DSNG VAN

IntroductionOutside 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 into the OB Van for processing and transmission

OB VAN

OB Van is equipped with 8 numbers of Thomson TTV 1657 Digital CCD cameras, 16 input versatile vision mixer ROSS Synergy with various special effects. 16 channel Sound Craft make audio mixer with facility of individual channel equalization and limited. In addition to the above, one computerized MOVE CG for supering titles. Two nos. of broadcast quality VCR having slow motion (TTV3575p), two nos. of Recording VCRs and one EVS make Live slow motion hard disc recording system is also installed. One Long haul microwave link is also available with OB Van.

 DSNG VAN

The mobile DSNG Van is equipped with 400 W TWT of Xycom and Tandberg E5500 encoder in 1+1 mode along with up convertors / down convertors of ADVENT and base band equipments. The DSNG van can be operated in both C or Ku band and it has the unique dual band waveguide in it. The system is operational since November 2002 The 2 meter antenna system is of advent make having the auto tracking facility controlled through laptop computer and can track any satellite in very short period automatically. It has a GPS system with flux gate compass etc used for auto tracking of satellites. The vehicle mounted DSNG Van supplied through BECIL is used in live coverage’s for up linking.