7117469 Complete Training Report

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PROJECT REPORT

PRODUCTION & BROADCASTING

OF TV PROGRAMMES

DOORDARSHAN KENDRA

THIRUVANATHAPURAM

KUDAPPANAKKUNNU

KERALA

Submitted By:

ABRAHAM RENN S

159/05

Ec-4

Electronics & Communication Engineering

NIT Kurukshetra



ACKNOWLEDGEMENT

Words often fail to express one’s feeling

towards others, still I express my sincere gratitude to

Shri. B Sudhakaran, Assistant Station Engineer

DOORDARSHAN KENDRA THIRUVANANTHAPURAM for his

valuable guidance without which it would have been difficult for me

to complete my training. I also express my gratitude to

Shri. Kesavan Namboodiri, Shri. Muraleedharan P and

Shri. Abraham John, who helped me a lot in understanding the

various processes and concepts involved. It was really a great

experience working in the DD Kendra and learning from such

experienced engineers with hands on experience on the subject.

Abraham Renn S

Roll No 159/05

Electronics & Communication Engg.

BTech, NIT Kurukshetra



The Doordarshan Kendra Thiruvananthapuram

An Overview

Doordarshan Kendra Thiruvananthapuram is part of the DD India, the

largest television network in the world. Doordarshan with over 35

Terrestrial Transmitters and 3 production centers serve Kerala, Lakshadweep

and Mahi regions. Inaugurated on 1st January 1985 by the then Chief Minster

of Kerala Shri. K. Karunakaran, Doordarshan Kendra Thiruvananthapuram

currently produces and telecasts 168 hrs of Malayalam programmes per

week. 27 transmitters in Kerala, 7 in Lakshadweep and one in Mahi relay

these programmes. Now more than 90 per cent of the 35 million populations

of Kerala, Lakshadweep and Mahi can receive Doordarshan KendraThiruvananthapuram programmes through a network of terrestrial

transmitters. With the introduction of DTH almost cent percent of the

population can now receive DDK Thiruvananthapuram programmes

without cable connection. Doordarshan studios have been established at

Thiruvananthapuram, Thrichur and Calicut to foster regional diversity.

People all over India are watching Doordarshan’s Malayalam programmes.

It is also received in 64 countries spread over the continents of Asia, Africa,

Europe, Australia and America.

TV Scenario in Kerala

As per the 2001 census there are 65,95206 (6.6 million) house holds in

Kerala. 74.9 per cent of them are in the rural sector (49,42550) the

remaining 25.1 per cent (16,52656) are in the urban sector. In 2001, 38.8 per

cent of the households owned TV sets (25,60686). Of these 62.3 per cent

were in rural areas and the remaining 37.7 per cent in urban areas. The

percentage of TV ownership in the rural areas in Kerala is the highest in thecountry. Even if we estimate 10 – 15 per cent growth per annum, total

number of TV households in Kerala will not be more than 40 million. Of

these estimated 40 million TV households 40 – 45 per cent is estimated to

have cable connection i.e., 17.5 million and the remaining 22.5 million are

without cable connection, and totally depend on DDK Thiruvananthapuram

for their TV viewing. The introduction of DTH, DD Direct Plus has



considerably increased DD viewership in Kerala. From the available sales

estimates of set top boxes and receivers it is estimated that Kerala has 3 to 4

lakh DTH households.

Universal Reach

Doordarshan Kendra Thiruvananthapuram programmes reaches each and

every TV household in Kerala. It has universal reach and viewing. As per

the TAM Media Research Data DD Malayalam Programmes have very good

reach in all the metro cities and other regions of the country. Viewers in the

Gulf and some countries in the west are regularly demanding for more

programmes for them.



TECHNICAL INFORMATION OF TRANSMITTING

FACILITIES AT DDK, THIRUVANANTHAPURAM:

Doordarshan Kendra, Thiruvananthapuram is equipped with two studios,

two terrestrial transmitters and one digital up-link station. The two terrestrialtransmitters are of 10 KW power each. One is for DD-National and the

other is for DD-News telecasting.

TERRESTRIAL TRANSMITTER PARAMETERS:

DD-NATIONAL:CH#9 (VHF-Band-III) Picture IF: 203.25 MHz, Sound IF: 208.75 MHz

DD-NEWS :CH #11 (VHF-Band-III) Pictures IF: 217.25 MHz, Sound IF: 222.75 MHz

DOWNLINK PARAMETERS OF DD-KERALAM/DD MALAYALAM SATELLITE

PROGRAMMES

SATELLITEINSAT-3A

LOOKING ANGLE 93.5 Degree East

DOWNLINK FREQUENCY 3811.5 MHz

SYMBOL RATE 6.25 MSPS

FEC ¾

POLARISATION VERTICAL



DDK, Thiruvananthapuram programmes (DD-KERALAM & DD-

MALAYALAM) can also be received from DD-DIRECT PLUS, the

Doordarshan DTH Service.

DOWNLINK PARAMETERS OF DD-KERALAM/DD MALAYALAM

DTH SERVICE

Technical Overview



DDK Trivandrum has the following main departments which manage the

production, storage transmission and maintenance of the two DD National

channels and the DD Malayalam channel.

1. STUDIO

2. PRODUCTION CONTROL ROOM (PCR)

3. VIDEO STORAGE AND TRANSMISSION ROOM(VTR)

4. MAIN SWITCHING ROOM(MSR)

5. DIGITAL EARTH LINK STATION

6. TRANSMITTER

Each of these departments are discussed in detail with due stress to the

relevant engineering aspects. The studio has

•Camera and lights and other equipment required for productionof a feed.

• Camera control unit or CCU

It is in the studio that all aspects related to the production of a video takes

place. The DDK has two large studios and a small studio for news

production.

The PCR is where the post production activities like minor editing and

management of feed during a live program takes place. The production

manager sits in the PCR and directs the camera men and selects the anglessound parameters etc during the production stage in the PCR. It is in the

PCR that we can control all the studio lights and all the microphones and

other aspects. The PCR has a vision mixer and an audio mixer. Its working

and other aspects are discussed in detail in the following pages. The PCR is

where the phone in console and other systems are also kept.

The VTR is the next section where copies of all programs are stored. All the

programs shot in the camera are simultaneously recorded in the VTR. Also

the VTR plays back all the videos as and when required. Videos of pre-recorded events are queued up in the VTR and are played back without a

break. Videos of famous people and important events are stored in the

central film pool.

The MSR stores all the circuitry of the DDK. All the camera base units, all

the vision mixer base units and all the audio processor base units are kept in

MSR. The audio chain and video chain of MSR is explained in detail. The



monitoring and control of all activities takes place in MSR. It is the MSR

which decides what is to go in air. The MSR also performs some additional

functions like logo addition etc.

The next station is the earth station which has an uplink chain, simulcast

transmitters, audio processors video processors, up converters, modulators

etc. The earth station is in fully digital domain.

The last stage is the transmitter which has the antenna and facilities for

terrestrial transmission.

Picture Basics



A television creates a continuous series of moving pictures on the screen.

This section will describe in detail how pictures are created in a television. A

camera works exactly on the same principle applied the other way round.

A picture is "drawn" on a television or computer display screen by sweeping

an electrical signal horizontally across the display one line at a time. The

amplitude of this signal versus time represents the instantaneous brightness

at that physical point on the display.

At the end of each line, there is a portion of the waveform (horizontal

blanking interval) that tells the scanning circuit in the display to retrace to

the left edge of the display and then start scanning the next line. Starting at

the top, all of the lines on the display are scanned in this way. One complete

set of lines makes a picture. This is called a frame. Once the first complete

picture is scanned, there is another portion of the waveform (vertical blanking interval, not shown) that tells the scanning circuit to retrace to the

top of the display and start scanning the next frame, or picture. This

sequence is repeated at a fast enough rate so that the displayed images are

perceived to have continuous motion. This is the same principle as that

behind the "flip books" that you rapidly flip through to see a moving picture

or cartoons that are drawn and rapidly displayed one picture at a time.

Interlaced versus Progressive Scans

These are two different types of scanning systems. They differ in the

technique used to cover the area of the screen. Television signals andcompatible displays are typically interlaced, and computer signals and

compatible displays are typically progressive (non-interlaced). These two

formats are incompatible with each other; one would need to be converted to

the other before any common processing could be done. Interlaced scanning

is where each picture, referred to as a frame, is divided into two separate

sub-pictures, and referred to as fields. Two fields make up a frame. An

interlaced picture is painted on the screen in two passes, by first scanning the

horizontal lines of the first field and then retracing to the top of the screen

and then scanning the horizontal lines for the second field in-between thefirst set. Field 1 consists of lines 1 through 262 1/2, and field 2 consists of

lines 262 1/2 through 525. The interlaced principle is illustrated in Figure

2. Only a few lines at the top and the bottom of each field are shown.



There are many different kinds of video signals, which can be divided into

either television or computer types. The format of television signals varies

from country to country. In the United States and Japan, the NTSC format is

used. NTSC stands for National Television Systems Committee, which is the

name of the organization that developed the standard. In Europe, the PAL

format is common. PAL (phase alternating line), developed after NTSC, isan improvement over NTSC. SECAM is used in France and stands for

sequential coleur avec memoire (with memory). It should be noted that there

is a total of about 15 different sub-formats contained within these three

general formats. Each of the formats is generally not compatible with the

others. Although they all utilize the same basic scanning system and

represent color with a type of phase modulation, they differ in specific

scanning frequencies, number of scan lines, and color modulation

techniques, among others. The various computer formats (such as VGA,

XGA, and UXGA) also differ substantially, with the primary difference in

the scan frequencies. These differences do not cause as much concern, because most computer equipment is now designed to handle variable scan

rates. This compatibility is a major advantage for computer formats in that

media, and content can be interchanged on a global basis.

In India we use the PAL system. It has 625 lines in each frame and

uses interlaced scanning.



Typical Frequencies for Common TV and Computer Video Formats

Video FormatNTSC PAL HDTV/SDTV

Description

Television

Format for

North

America and

Japan

Television

Format forMost of

Europe and

South

America.

Used in India

High Definition/

Standard

Definition Digital

Television Format

Vertical

Resolution

Format (visiblelines per

frame)

Approx 480

(525 totallines)

Approx 575

(625 total lines)

1080 or 720 or 480;

18 different formats

Horizontal

Resolution

Format (visible

pixels per line)

Determined by

bandwidth,

ranges from

320 to 650

Determined by

bandwidth,

ranges from

320 to 720

1920 or 704 or 640;

18 different formats

Horizontal

Rate (kHz)15.734 15.625 33.75-45

Vertical FrameRate (Hz)

29.97 25 30-60

Highest

Frequency

(MHz)

4.2 5.5 25

There are three basic levels of baseband signal interfaces. In order of

increasing quality, they are composite (or CVBS), which uses one wire pair;

Y/C (or S-video), which uses two wire pairs; and component, which uses

three wire pairs. Each wire pair consists of a signal and a ground. These

three interfaces differ in their level of information combination (or

encoding). More encoding typically degrades the quality but allows the



signal to be carried on fewer wires. Component has the least amount of

encoding, and composite the most.

Composite/CVBS Interface

Composite signals are the most commonly used analog video interface.

Composite video is also referred to as CVBS, which stands for color,

video, blanking, and sync, or composite video baseband signal. It

combines the brightness information (luma), the color information

(chroma), and the synchronizing signals on just one cable. The connector is

typically an RCA jack. This is the same connector as that used for standard

line level audio connections. A typical waveform of an all-white

NTSC composite video signal is shown in Figure.

This figure depicts the portion of the signal that represents one horizontal

scan line. Each line is made up of the active video portion and the horizontal

blanking portion. The active video portion contains the picture brightness

(luma) and color (chroma) information. The brightness information is the

instantaneous amplitude at any point in time. From the figure, it can be

see that the voltage during the active video portion would yield a bright-

white picture for this horizontal scan line, whereas the horizontal blanking

portion would be displayed as black and therefore not beseen on the screen.



Color information is added on top of the luma signal and is a sine wave with

the colors identified by a specific phase difference between it and the color-

burst reference phase.

The amplitude of the modulation is proportional to the amount of color (or saturation), and the phase information denotes the tint (or hue) of the color.

The horizontal blanking portion contains the horizontal synchronizing pulse

(sync pulse) as well as the color reference (color burst) located just after the

rising edge of the sync pulse (called the "back porch"). It is important to note

here that the horizontal blanking portion of the signal is positioned in time

such that it is not visible on the display screen.

Y/C Interfaces

The Y/C signal is a video signal with less encoding. Brightness (luma),which is the Y signal, and the color (chroma), the C signal, are carried on

two separate sets of wires.

Component Interfaces

Component signal interfaces are the highest performance, because they have

the least encoding. The signals exist in a nearly native format. They always

utilize three pairs of wires that are typically in either a luma (Y) and two-

color-difference-signals format or a red, green, blue (RGB) format. RGB

formats are almost always used in computer applications, whereas color-

difference formats are generally used in television applications. The Y signal

contains the brightness (luma) and synchronizing information, and the color-

difference signals contain the red (R) minus the Y signal and the blue (B)

minus the Y signal. The theory behind this combination is that each of the

base R, G, and B components can be derived from these difference signals.

Common variations of these signals are as follows:

• Y, B-Y, R-Y: Luma and color-difference signals.

•

Y, Pr, Pb: Pr and Pb are scaled versions of B-Y and R-Y. Commonlyfound in high-end consumer equipment.

• Y, Cr, Cb: Digital-signal equivalent to Y, Pr, Pb. Sometimes

incorrectly used in place of Y, Pr, Pb.

• Y, U, V: Not an interface standard. These are intermediate, quadrature

signals used in the formation of composite and Y/C signals.

Sometimes incorrectly referred to as a "component interface."



Some important terms and their meanings in this context are listed below

Aspect Ratio

Aspect ratio is the ratio of the visible-picture width to the height. Standard

television and computers have an aspect ratio of 4:3(1.33). HDTV has

aspects ratios of either 4:3 or 16:9(1.78). Additional aspect ratios like 1.85:1

or 2.35:1 are used in cinema.

Blanking Interval

There are horizontal and vertical blanking intervals. Horizontal blanking

interval is the time period allocated for retrace of the signal from the right

edge of the display back to the left edge to start another scan line. Vertical

blanking interval is the time period allocated for retrace of the signal fromthe bottom back to the top to start another field or frame. Synchronizing

signals occupy a portion of the blanking interval.

Blanking Level

Used to describe a voltage level (blanking level). The blanking level is the

nominal voltage of a video waveform during the horizontal and vertical

periods, excluding the more negative voltage sync tips.

Chroma

The color portion of a video signal. This term is sometimes incorrectly

referred to as "chrominance," which is the actual displayed color

information.

Color Burst

The color burst, also commonly called the "color subcarrier," is 8 to 10

cycles of the color reference frequency. It is positioned between the risingedge of sync and the start of active video for a composite video signal.

Fields and Frames



A frame is one complete scan of a picture. In NTSC it consists of 525

horizontal scan lines. In interlaced scanning systems, a field is half of a

frame; thus, two fields make a frame.

LumaThe monochrome or black-and-white portion of a video signal. This term is

sometimes incorrectly called "luminance," which refers to the actual

displayed brightness.

Monochrome

The luma (brightness) portion of a video signal without the color

information. Monochrome, commonly known as black-and-white, predates

current color television.

PAL

Phase alternate line. PAL is used to refer to systems and signals that are

compatible with this specific modulation technique. Similar to NTSC but

uses subcarrier phase alternation to reduce the sensitivity to phase errors that

would be displayed as color errors. Commonly used with 626-line, 50Hz

scanning systems with a subcarrier frequency of 4.43362MHz.

Pixel

Picture element. A pixel is the smallest piece of display detail that has a

unique brightness and color. In a digital image, a pixel is an individual point

in the image, represented by a certain number of bits to indicate the

brightness.

RGB

Stands for red, green, and blue. It is a component interface typically used incomputer graphics systems.

Sync Signals/Pulses

Sync signals, also known as sync pulses, are negative-going timing pulses in

video signals that are used by video-processing or display devices to

synchronize the horizontal and vertical portions of the display.



Y Cr Cb

A digital component video interface. Y is the luma (brightness) portion, and

Cr and Cb are the color-difference portions of the signal.

Y/C

An analog video interface in which the chroma (color) information is carried

separately from the luma (brightness) and sync information. Two wire pairs

are used, denoted Y and C or Y/C. Often incorrectly referred to as "S-

video."

CAMERA AND ITS BASE STATION

The camera system in DDK Trivandrum has the following main components



i) Optical system

ii) Video system

iii) Monitor system

iv) Pulse system

v) Control systemvi) Auto setup system

vii) Power system

viii) Intercommunication system and tally system

ix) Transmission system

Camera has a head unit as well as a base unit. The head unit is located in the

studio and the base unit is located in the MSR. Also there is a Camera

Control Unit (CCU) which is a separate unit in itself which is used to control

the camera. The base station of the camera houses all the electronics related

to the camera. The head unit of the camera is the part which the camera manhandles in the studio. The head unit of the camera is connected to other parts

of the system through a triax cable alone. This reduces the clutter in the

studio. The triax cable carries power for the camera. Signals of the pictures

to from the camera and also carries the communications in RF to and from

the camera. The head unit of the camera houses the charge coupled devices

(CCD) which take in the light from the viewing area and convert them to

electrical signals. Before the light hits the CCDs in a colour camera, a

dichroic prism is used to split the three primary colours RGB into three and

cause them to be absorbed by different CCDs which are kept at the focus of

the lens system. They absorb light from each part of the screen pixel after

pixel and for a moving picture frame after frame. The CCDs improve the

apparent limit resolution with the help of spatial pixel shifting. There are 3

types of CCDs available

Interline transfer (IT)

Frame Transfer (FT)

Frame Interline Transfer (FIT)

The DDK Trivandrum studio uses 4 IKEGAMI (HK 399W) cameras in

studio 1 and an Ikegami camera and a SONY camera in Studio 2.The



Ikegami camera and Sony both uses FIT type CCDs. The sonny camera

gives a digital output where as the Ikegami gives out an analog output.

The FIT type CCD has photodiodes, vertical transfer CCDs and Horizontal

transfer CCDs , all of which but photodiodes are covered with metallic film

to prevent any kind of exposure to light. The residual charges in vertical

transfer CCD is swept out. If it is not swept out smearing occurs (light leaks

into vertical transfer CCD and is seen as light above and below a bright

object).The charges, the result of light converted by photodiodes are

transferred to vertical transfer CCDs during vertical blanking. Then the

charges are transferred to the storage CCD’s at high speed. This reduces

smear.FIT is complex but has very little smear.

Light entering sections is covered with metallic film do not cause

photoelectric conversion. But light which is reflected enters the photodiodesand may generate false signals called moiré (faded distortion). An optical

low pass filter is used for reducing this moiré phenomenon

ON CHIP LENS

It is mounted on the CCD to collect light which is not contributing to photo

electric conversion. This improves CCD sensitivity. Most CCDs have on

chip lens.

OPTICAL LOW PASS FILTER



Unlike pickup tubes the CCD does not have a continuous surface but

discrete photodiodes. This lowers spatial frequencies that are higher than

half the sampling frequency on the basis of sampling theorem. These

frequently cause spurious signals which cause moiré. The optical low pass

filter is used to attenuate and surpass high pass spatial frequencies. A crystalfilter with the effect of double refraction is used in this.

SPATIAL PIXEL SHIFTING

This is a method of improving horizontal resolution such that the light

receiving element of channel G is shifted by half pitch compared to that of R

and B. This effectively doubles the sampling points and theoretically

doubles the upper band resolution if luminance signal Y= .25R + .50G + .

25B holds true. In reality however Y= .25R + .50G + .25B is required and

that does not result in double resolution but can achieve a satisfactory effect.

An inner sampling point also reduces moiré.

OVERFLOW DRIVES(OFD) of CCDs are responsible for dischargingexcessive charges when a large volume of light falls on the photo diodes

Without OFD the charges will overflow to the adjacent pixels and a

phenomenon called blooming occurs. In blooming the ambient are of a spot

image extensively in white.



Appropriate control of OFD allows signal charges to discharge by force

midway through the charge storage process thus performing same role as a

shutter.

Standards of shutter

Preset shutter 1/60th of a second for NTSC and 1/60th of a second to 1/200th

of a second for PAL

CVSS or continuous variable shutter speed is 1/30.3th to 1/ 57.6th for NTSC

and again 1/61.4 to 1/1996 for NTSC. For PAL 1/25.4 to 1/47.6 and from

1/50.4 to 1/1953.

In particular 1/100 seconds make it possible to eliminate flicker caused

between NTSC field and 50Hz commercial power supply.

New Super V is technology incorporated to improve vertical resolution. It

gives a vertical resolution of 480 TV lines against a normal or 400 TV lines.

Video System

It has a CCD multimodule, a PROC -1 module a PROC-2 module, a Head D

PROC and Head pulse modules. The video system of BS/CCU contains BSMPV, BS DF PROC and BS Pulse modules

The electric signal that has undergone photoelectric conversion in the CCD

element are transferred to the sample hold circuit in the CCD multi module

and output to the A PROC -1 module, undergo video processing by a A



PROC-2 Head D Proc and Head Pulse module and are transmitted to

BS/CCU via the triax cable adaptor as component (Y, Cr, Cb) signals

In self contained mode they are converted into encoder signals by the digital

encoder ASIC in the Head D PROC module for Output.

Monitoring System

The monitoring System generates various signals to be output to VF, PF and

WFM. It is separate from the main, the system can actually switch R, G and

B video signal or display signal requirements for monitoring the maker or

characters.

Pulse System

The pulse system is installed in department of camera head and BS/CCU,

and is designed to operate in conjunction with the CCU operation connected

to BS/CCU and in the self contained mode operated by the camera head

alone, in either way the system can be operated in internal or external

synchronization mode.

Control System

The camera is normally controlled through the CPUs of the HEAD MPU

and BS MPU modules to keep watching each unit and module.

Soundcraft Audio Processor

Sound mixer is a unit used in the production control room (PCR) to control

all the audio of the incoming sound from the studio or other source. It is the

single most important component used to control audio in an audio chain.

The sound mixer used in DDK Trivandrum is a Soundcraft sound mixer. It is

located in both the PCRs with a standby arrangement for each.



All mixers carry out the same basic function - to blend and control the

volume of a number of input signals, add effects and processing where

required and route the resulting mix to the appropriate destination, which

could be power amplifiers, the tracks of a recording device - or both. A

mixer is the nerve centre of these sources, and therefore the most vital part

of any audio system. A mixer performs a variety of functions and effects

some are detailed below.

Equalization

Equalization is useful for making both corrective and creative changes to a

sound, but it need to be used with care. Corrective applications include

making tonal changes to compensate for imperfect room acoustics, budgetmicrophones or inaccurate loudspeaker systems. While every effort is to be

made to get the sound right at the source, this is less easily achieved live

than in the more controlled conditions of the recording studio. Indeed, the

use of equalization is often the only way to reach a workable compromise in

live situations. Creative applications, on the other hand, are equally as valid

in the recording studio as they are live, and an equalizer with a swept

midrange control is infinitely more versatile than one that has simple high

and low controls. The only rule of creative equalization is - 'If it sounds

good, it is good!'

Fixed Equalization

Most people will be familiar with the operation of high and low frequency

controls; they work in a similar manner to the tone controls on a domestic

stereo system. In the centre position the controls have no effect, but rotate

them clockwise and they will provide boost, or rotate them anticlockwise

and they provide cut. Despite their apparent simplicity, however, high and

low controls should be used with caution as overuse can make things worse.

Adding a small amount of high or low boost should be enough to add a



touch of brightness or warmth to a sound, but a quarter of a turn should be

sufficient, especially where the low control is concerned.

The drawback with fixed controls often lies in the fact that you may want to

boost just a particular sound such as the punch of a bass drum or the ring of

a cymbal, whereas a fixed control influences a relatively large section of the

audio spectrum. Apply too much bass boost and you could find the bass

guitar, bass drum and any other bass sounds take on a flabby, uncontrolled

characteristic which makes the mix sound muddy and badly defined. This is

because sounds occupying the lower mid part of the spectrum are also

affected. Similarly, use too much top boost and the sound becomes edgy

with any noise or tape hiss being emphasized quite considerably.

In a PA situation, excessive EQ boost in any part of the audio spectrum will

increase the risk of acoustic feedback via the vocal microphones.

Using Effects Units

Reverb

Reverberation is the most commonly used studio effect, and also the most

necessary. Western music is invariably performed indoors where a degree of

room reverberation is part of the sound. Conversely, most pop music isrecorded in a relatively small, dry-sounding studio, so artificial reverberation

has to be added to create a sense of space and reality. Reverberation is

created naturally when a sound is reflected and re-reflected from the surfaces

within a room, hall or other large structure

Delay

Often used to make a sound 'thicker' by taking the original sound, delayingit, then mixing it back with the original sound. This short delay added to the

original sound has the effect of doubling the signal.

Echo



Echo is a popular effect that was used extensively on guitars and vocals in

the 60s and 70s. It is not used on vocals so much nowadays, but quite

effective on guitars and keyboards. A neat trick is to set the echo delay time

so that the repeats coincide with the tempo of the song.

Chorus & Flanging

Both chorus and flangers are based on a short delay, combined with pitch

modulation to create the effect of two or more instruments playing the same

part. Flanging also employs feedback and is a much stronger effect. Both

these treatments work well on synth pad sounds such as strings and are best

used in stereo where they create a sense of movement as well as width.

Pitch Shifters

These change the pitch of the original signal, usually by upto one octave in

either direction and sometimes by two. Small pitch shifts are useful for

creating de-tuning or doubling effects. Which can make a single voice or

instrument sound like two or three, while larger shifts can be used to create

octaves or parallel harmonies.

All these effects will be added in the audio processor and the final output

will be sent to VTR along with video in case of a recording or will be

telecast live through MSR as is required.

Production Control Room (PCR)

A major objective of TV program control facilities is to maintain a smooth

continuous flow of program material. The overall control of program is done

in production control room by the producer with the help of a production



assistant, a CCU engineer and an engineer at vision mixer. They have in

front of them, the switching panel of the vision mixer console and a stack of

monitors for the individual cameras, preview monitors of VTRs and

transmission monitor for displaying the switched output, with the aid of

which the program is edited.

The PCR usually of the various equipments like:-

• Camera Control Unit(CCU)

• Vision Mixer(VM)

• Video Tape Recorder(VTR)

• Audio Mixer(AM)

• Camera Control Unit (CCU)

The CCU contains control for

• Aperture

• Optical Focus

• Zoom of the lens system

• Beam Focus

• Selecting Gain

• Color Temperature

• Contours (Camera Details)

• Gamma

Vision Mixer (VM)

A vision mixer or video switcher enables the program producer to select the

desired sources or a combination of the sources in order to compose the

program. The vision mixer is typically 10x6 or 20x10 crossbar switcher

selecting any one of the 10 or 20 input sources to 6 to10 different output

lines. The input sources include: Camera-1, Camera-2, Camera-3, Telecine-

1, Telcine-2, VTR-1, VTR-2, Test Signal etc.

The vision mixer provides the following operational facilities for the editing

of the TV programs.



• Take –selection of any input source, or cut-switching cleanly from

one source to another.

• Dissolve-fading in or fading out.

• Lap Dissolve-dissolving from one source to another with an overlap

mixing.• Superposition of two sources-keyed caption when the selected inlay is

superposed on the background picture

Video Tape Recorder (VTR)

The standardized two inch tape quadrupled head recording machines are

called the video tape recorder and are used for the high quality video taperecording one or half inch helical scan tape recorders have been used for

outdoor field recording. This multi purpose studio digital video cassette

tapes, and is designed to record, play back and edit interlace signals

(6251/5251) as well as record, playback and edit existing DVCPRO signals

(25Mbps). Its 625/525 switching functions makes this studio video cassette

recorder which can be used any where in the world. In addition, it corporate

digital compression technology so that the deterioration in picture quality

and sound quality resulting from dubbing is significantly minimized. The

compact, light weight 4U size makes carry easier, even when mounted in a

19 inch rack. The settings for the units set up can be performed interactivelywhile viewing the screen menus on the monitor, and editing functions

include both assemble and insert editing.

DIGITAL EARTH STATION SIMULCAST

Frequency range - 5.85 GHz to 6.425 GHz for transmission

3.625 GHz to 4.2 GHz for reception

The digital earth station operates in the frequency range of 5.85 GHz to

6.425 GHz for transmission and 3.625 to 4.24 GHz for reception of signals.

The whole system operates with DVB/MPEG2 Standards. The base band

processor subsystem and base band monitoring subsystem operates in fully

digital domain. An OFC carries digital base band signal from studio to earth



station site to minimize the noise and interference. It is controlled by a PC

called NMS PC.

The compression segment has an MPEG encoder, digital multiplexer and

digital modulator. The monitoring and receiving segment comprises of two

digital receivers for receiving and decoding program. The output of

modulator (70MHz) is sent to an up converter. The up converted signals are

sent to an HPA. Then this signal is given to a PDA (parabolic dish antenna)

for up linking to satellite. The uplinked signal is received again by the same

PDA for monitoring purposes. The signal between earth station and satellite

are given along line of sight which means there must be a clear path from

earth to satellite. The uplink signal is fed from the earth station by a large

PDA. The satellite is equipped with its own dish antenna which receives the

uplink signals and feeds them to a receiver. The signal is then amplified and

changed to a different frequency which is downlink frequency. This is doneto prevent interference between uplink and downlink signals. The down

linked signal is then again sent to the transmitter which again retransmits it.

Each satellite has a transponder and a single antenna receives all signals and

another one transmits all signals back. A satellite transmits signals towards

earth in pattern called the satellite footprint of the satellite. The footprint is

strongest at centre and the footprint is used to see if the earth station will be

suitable for the reception of the desired signal. Converts

The parts of the DES are Antenna subsystem including LNA Antenna

control unit, beacon tracking unit, beacon tracking receiver and up converter

system high power amplifier and power system. The system operates in 2 +

1 mode and is compliant with DVB MPEG 2 standards. The base band

processor subsystem and base band monitoring system operates in digital

domain. An OFC contains the digital base band signal for studio to earth

station to minimize noise interference

The network management system or NMS monitors and controls basebandequipments compression equipments and test instruments like video audio

generation and video audio analyzer. They are provided to ensure quality of

transmission and help trouble shoot.



The base band segment comprises of baseband subsystems at studio site and

base band subsystem at earth station site. This baseband segment processes

two video Programmes.

The base band segment is monitored and controlled using a PC placed near

the base band earth station equipments called base band NMS PC. The

compression segments comprises of Mpeg encoders in 2 + 1 configuration

for providing redundancy. It also comprises of digital multiplexers and

digital modulators in 1 + 1 configuration. The compression segment is

monitored and controlled by compression NMS PC. The receive and

monitoring segment consists of two digital receivers for receiving and

decoding of the video programmes and one ASI to SDI decoder for decoding

of the transport stream for monitoring video programmes at the multiplexers

output. RF NMS PC is placed near the receive monitoring segment and

video audio generator placed in the base band segment. For monitoring of video programmes professional video monitor, LCD video monitor and

audio level monitor are provided in the base band segment. An operator

console has one 14” professional video monitor a video audio monitor unit

for quantitative monitor of video programmes and a personal computer for

centralized merit and contention of earth station sub system.

Features of ES

• All major sub systems operate in redundant mode and takes over

immediately without any noticeable break in the service in the event

of failure of the main chain

• A fiber optic connectivity to transport two SDI video and two AES

audio signals from a studio to the earth station separated by a distance

of approximately 200m

• System configuration in MCPc in 2+1 mode

• Base band process in fully digital domain. In case input video and

audio are analog A/D counter in first and converts analog signal in to

digital signal to ensure operation in fully digital domain

• Digital encoding system compliant to MPEG2/DVB standards

• On line trouble shooting with the help of converter, IRD and other

associated test and measuring equipment

• Exhaustive professional quality measuring of video and audio

• Control and monitoring using NMS

• Single point remote monitoring and control on the console



The physical configuration of the racks in the digital earth station is as

follows

• Base band Rack(studio)

•

Base band rack (earth station)• Compression rack

• Receive and monitoring rack

• Console

• NMS

• System Layout

All the above systems are located in the station as per the typical station

layout to have smooth flow of all signals mainly video audio RF and control

so as to reduce cabling length between racks. An OFC of 200m length with

NMS control cable (RG 5A) is provided for base band between the studio

and the earth station.

Specifications:

Electrical specifications:

System Voltage 230V AC, Single phase

Satellite communication systems

System configuration: (2 +1) mode with full redundancy

Transmitter

Video audio input parameter

No of program input: 2

Type of input format: Analog or digital, 75ohm

Input format (analog): 625 line PAL- B CCIR standard



Input level (analog): 1VPP+-5%

A to D converter: 10 Bits

Video Bandwidth: 5.5MHz

Input format (digital): SMTPE 259M, 270Mbps

Input level (digital): 800mVPP+-10%

No of audio input: Analog dual mono/normal stereo/joint stereo

per program

Input Frequency Range: 20 Hz to 20 kHz

Input Standard: Balanced analog 600ohm

Input Level: 0dB with +-10dB adjustment

No of audio Input Digital: Single at specified program

Input Standard: 110 ohm

Sampling rate: 32/44.1/48 kHz (selectable)

Data Rate: 32-384kBPS

Video/ Audio Compression Parameter

Video compression: MPEG-2 4:2:2@ML

4:2:0@ML

Bit Range: 1.0 To 15Mbps for 4:2:0

1.0 To 50Mbps for 4:2:2

Resolution: 704X576/720X576(selectable)

Audio Coding: MPEG layer2

Multiplexer O/P rate: 1-80Mbps



Modulation Type: QPSK selectable

FEC Rate: ½ 2/3 ¾ 5/6 7/8

Receiver

Domain Concession receiver frequency: 3.6 to 4.2 GHz

C to L o/p frequency: 950 to 1750 MHz

Video/Audio Decoder and Receiver: L Band

Monitoring

RF Monitoring

IF (70 MHz monitoring): using 70 to L converter

L Band monitoring: Using IRD

C Band monitoring: Using downlink through satellite

Base Band monitoring: Video and Audio monitoring in transmit or

receive path through router

RF Measurement

RF Parameters: Spectrum Analyzer

Video Generation and Monitoring

Video Monitoring(digital): one 14” professional colour monitor, one

5.6” LCD monitor in the base band rack for high quality monitoring

and one 14” professional and one 4” LCD in console for confidence

monitoring

Video analyzer (SDI/Analog): Waveform Monitor (wfm-601M) and

VM-700

Video Generator (SDI/Analog): TG-700



Environmental specifications

Temperature

Operation – 00C to 450C

Storage – -200C to 800C

Humidity – 0% to 95% non condensing

Altitude – 0 to 3000msl

NMS Functions

•

monitoring all the subsystems• control of the subsystems

• configuration of all the subsystems

• separate monitor and control computer for baseband and compression

system

• monitor and control of the earth station subsystem for a remote

computer wanted in the console

• interface between the computer and equipment is RS 232

Base Band Rack (studio)

The base band system is divided into two parts of Video /Audio compression

system at studio site and further audio and video base processing at the earth

station site

It has the following parts

• Audio Patch panel

• Video Patch panel



• Base band frame which as

• Video ADC

• Dual Audio embedder

• Dual Audio ADC

• Fiber optic transmitter

• Line interface unit for fiber input/output termination

• Video audio termination panel

The base band segment of the system carries two programs from the studio

to the earth stations equipment separated by a distance of about 200m. To

cater to these needs two video and two audio signals each one stereo are

processed. The video signals are handled in the digital domains in SDI

(serial 4:2:2@ 270 Mbps data rate) and the audio signals in AES/EBU as per

the AES 2- 1992 standards. If all the input signals are analog, A/D

converters will have to be used in the transmitter end, which give SDI and

AES outputs for operation in fully digital domain. One A/D card is mounted

in the frame and wired up to the patch panel so that in case of failure of main

video A/D card this spare A/D card can take over.

The analog or digital input from the camera or VTR and from live events are

fed to the suitable connectors on video and audio termination paneldepending upon whether the type of signal is analog or digital.

If the signal is analog, then the video ADC cards perform the analog to

digital conversion of the incoming video and audio signals. The serial digital

video and audio outputs are further fed to the audio embedder through a

patch panel.

If the input video and audio signals are digital, suitable patching is to be

done and the video patch panel and audio patch panel for routing these

inputs to the embedder

The dual channel audio embedder can embed up to two AES/EBU streams

in to a serial 4:2:2 video streams. In the earth station, one AES/EBU stream

embeds one digital video signal so that the cards are used for two program

channels. The embedder is fed to the fiber optic transmitter.



The OFC takes two inputs of SDI at 270Mbps for the two embedder and

provides multimode operation option for each input in accordance with

SMPTE 297M.

The O/P signal from the optional transmitter is in the opt form so it protects

the signal from EM interference and cross talk. The OFC loss is less than co

axial loss and so signal can travel longer distances. In earth station an OFC

is used to handle two embedded SDI signals. The channel A and channel B

optical output from the unit are made available via a SC connector with

shutters.

These two optical outputs are fed to the line interface unit; they are

transported back to earth station base band rack for further processingthrough the optical link.

The video patch panel (2x24 way) employed in the system is 2u unit suitable

for the digital video. The two patch cords are used for making connection

through on the patch panel either for analog or digital video input. The audio

patch panel (2x24 ways) is a 1u unit. Two patch cords are used for making

connection through on the patch panel either for analog or for digital input.

Both the patch panels are configured through for analog input in normal

condition for video as well as audio. All the IQ modules from the Sand W

are incorporated in the IQH3A enclosure. It can accommodate 8 double or 16 single width modules or every combination fitted with a roll call gateway

for roll net 2.5Mbps network. The enclosure consists of dual PSU for

redundancy. The max power consumption of the unit is 225VA.The BNC

connector on the near panel of the connector allows it to be connected to the

roll call network. The bicolor LED’s V1 and V2 indicate positive and

negative supplies. They are green if PSU supplies power and is red

otherwise.

UP CONVERTER (1+1)

The UPC will add in any frequency within stated transmission BW in 125

kHz stepped increments. The IF bandwidth is indented for operation within

an 80Mhz BW centered at 70MHz (for +/- 40 MHz) Due to its low phase

noise and HF stability the model UC6M2D5 (satellite networks) meets



INTELSAT, DOMSAT, EUTELSAT and regional requirements. It can stand

alone up converter or in a 1:1 protection switch option. The uplink frequency

for Trivandrum is 6036.5 MHz and downlink is 3811.5MHz.

AUDIO PROCESSOR

Designed specifically for the demands of television audio, the programmable

OPTIMOD-TV 8282 digital audio processor meets all requirements of the

various systems in use around the world. It is impossible to characterize the

listening quality of even the simplest limiter or compressor on the basis of

the usual specifications, because such specifications cannot adequately

describe the crucial dynamic processes that occur under program conditions.

Therefore, the only way to meaningfully evaluate the sound of an audio processor is by subjective listening tests. Certain specifications are presented

here to assure the engineer that they are reasonable, to help plan the

installation, and to help make certain comparisons with other processing

equipment. Some of the specifications are for features that are optional. The

TX’s sampling rate can be synchronized with that of audio processors or can

be allowed a free run of 32 kHz, 44.1 kHz or 48 kHz. The audio signal is

sent to the digital I/O cards and analog cards separately. These cards provide

pre emphasis truncations required and attenuation on the digital signal

before transmission.

PERFORMANCE :Specifications for measurements from analog left/right input to analog

left/right output are as follows:

Frequency Response (all structures, measured below gain reduction and

clipping thresholds, high-pass filter off): Follows standard 50 microseconds.

Or 75 microseconds. Pre-emphasis curve ±0.20dB, 5Hz-15 kHz. Analog and

digital left/right outputs can be independently user-configured for flat or pre-emphasized output.

Noise: Output noise floor will depend upon how much gain reduction the

processor is set for (AGC and/or DENSITY), gating level, equalization,

noise reduction, etc. It is primarily governed by the dynamic range of the

A/D Converter. The dynamic range of the digital signal processing is 144dB.

Total System Distortion (de-emphasized 100% modulation): Less than



0.01% THD, 20Hz-1 kHz rising to less than .05% at 15 kHz. Less than

0.02% SMPTE I MHz Distortion.

Total System Separation: Greater than 80dB, 20Hz-15 kHz.

Polarity: (PROTECTION or BYPASS structure) Absolute polarity

maintained. Positive-going signal on input will result in positive-goingsignal on output.

ANALOG AUDIO INPUTConfiguration: Left and Right

Impedance: 600 ohms or 10k ohms load impedance, electronically balanced,

jumper selectable Common Mode Rejection: Greater than 70dB, 50-60Hz.

Greater than 45dB, 60Hz-15 kHz

Sensitivity: -40dBu to +20dBu to produce 10dB gain reduction at 1kHz

Maximum Input Level: +27dBu

Connector: XLR-type, female, EMI-suppressed. Pin 1 Chassis, Pins 2 and 3

electronically balanced, floating and symmetrical

ANALOG AUDIO OUTPUT

Configuration: Left and right, flat or pre-emphasized

Source Impedance: 30 ohms, ±5%, electronically balanced and floating

Load Impedance: 600 ohms or greater, balanced or unbalanced. Termination

not required

Maximum Output Level: +23.7dBu into 600 ohm or greater balanced load

Connector: XLR-type, male, EMI-suppressed. Pin 1 Chassis, Pins 2 and 3electronically balanced, floating and symmetrical

Transmitter

Antenna

A 6.3m diameter antenna with a simplified manual track device features

ready erection, ease of maintenance and high reliability.

Antenna parameters

Antenna type Limited steer able X-Y type



Reflector diameter

Drive

Sky coverage

X axis (EL)

Y axis (cross EL)

Surface accuracy

Wind resistivity

6.3m

Manual hand operation only

450 to 900 in steps, continuous mount up to 10 only

+ 40 at any given position in steps, continuous up to

only

2.00mm rms for winds up to 60 kmph

Operation up to 60 kmph

Survival up to 200 kmph

Frequency range

Polarization

Antenna gain

VSWR

Volt axial ratio

Receiver system G/T

S - band

2555 MHz to 2635 MHz

left hand circular

41.8dbi at 2.6 GHz

1.25 max

better than 3 dB

14/db/0k at 2600 MHz

C - band

3700 MHz to 4200 MHz

linear and changeable

44.8dbi at 4 GHz

1.30 max

less than 3 dB and

circular polarization gr

than 20 dB

24.4/db/0k at 4 GHz atelevation



Reflector structure

The 6.3 m diameter antenna is made up of 4 quarter segment. Each and

every quarter is made up of 10 segments fixed on five trusses. Panels which

are fixed to the trusses are made up of fine aluminium expanded meshstrengthened with the help of channel sections and tee sections whose ends

are fixed to the backup structure. Trusses are composed of aluminium square

tubes and the welded back up made up of hub and 20 trusses. The hubs and

trusses are constructed in such a way that they constitute to the high level of

surface accuracy.

Mount structure

A simple tubular steel space frame makes up most of the mount structure. It

allows rotation about x-axis as well as y axis. The x axis drive rod isconnected between the top of the mounted structure and the concrete

foundation. The y axis drive rod is connected between the base of the x axis

bearing mount and the reflector back up structure on the left hand side as

viewed from the rear of the antenna. The mount is rigidly attached to the

concrete base which is facing north such that it can survive even in wind

speeds up to 200 kmph.

Drive mechanism

It has a telescopic pipe arrangement and a screw rod within it along with

manual handle. There are mechanical angle indicators along the screw rod

which indicate the exact position and angle of the antenna with respect to

both the axes.

Material

Most of the parts of the panel and antenna structure are made up of

aluminium alloy which has corrosion resistance and yield strength.



Finish

The reflector is treated in the following order before installation

(A) Etch primer is applied after caustic soda acid treatment

(b) Painted with white matt paint

The mount is treated with the following

(a) A hot dip which galvanizes all steel parts

(b) Etch primer treatment

(c) White enamel paint is applied as a last coating

Fixing the feed onto the antenna

The feed is supported by a set of four pipes called as a quadripod. It is fixed

before the whole antenna structure is hoisted, that is, it is fixed on the

ground itself before the whole antenna structure is fixed. Care should be

taken that the feed is at the exact focus of the reflector. A maximum

tolerance of +3mm is allowed for the separation between the actual focus

and feed position. Also the feed entrances and cable output ports are covered

with waterproof Teflon sheet to prevent the entry of moisture into the

arrangement.

The LNBC (Low Noise Block Converter) and cables are connected to the

feed output. The x-y adjustment is then done and fixed. The bolts are

tightened with care and the arrangement is set. Care should be taken while

lifting and fixing of the whole apparatus to prevent any damage.

The Trivandrum station has the following specifications which are used for

signal reception

Sat long lat Y angle Y length X angle X length Az El

74.

0

93.5

6.95

"

8.55

"

-3.46

19.37

2778.37

2424.36

-10.0

-10.13

3269.0

3265.4

119.12

116.58

79.37

68.23



The signals which are received by the antenna are given to the feed and from

there it goes to the LNB from where the signals are given to the receiver.

The receiver changes the frequency bandwidth of the signal so as to decrease

the losses through noise. These signals can now be observed on a TV screen.And this is the principle which is used in home dish antennas and by cable

operators for broadcasting in a small area. For transmitting these signals

back to air there are some changes which are to be made to these signals.

I.e., these signals have to be properly set according to the specifications

given. So the signal is next fed to a control console. From here the different

programmes or channels have to be selected first and then each channels

visual and aural property can be set properly before transmission to air. The

visual properties can be seen in the video waveform screen

Video waveform modifications

In the video waveform as can be observed, 625 vertical lines make up one

frame of the video which appears on the TV screen. It is divided into odd

lines and even lines on either side of the video waveform. In this video

waveform, the peak to peak voltage is 1 volt. The synchronizer or the synch

voltage which extends below the other parts of the graph and in the middle

has a voltage of .3V.this is the standard level for horizontal as well as for

vertical synch. The next part is colour burst which controls the colour

characteristics of the video. The remaining 0.7V is the video level. Manycharacteristics of the video signal like its brightness its chroma etc can be

modified here at this stage before transmission. A colour stability amplifier

is used at this stage to regenerate synch colour burst and brightness level of

the signal. Many times the signal which is received from the antenna do not

confirm to the standards. Hence it might need modifications before

transmission so that it can be received uniformly by all the viewers.

The 5KW and 10 KW TX of TW200 HP series com band 1 on band 3 and

are equipped with two dims operating in a passive reserve mode. The soundand vision channels are amplified separately.

It is designed to operate in all the negative modulation standards with PAL,

NTSC and SECAM colour systems. Each transmitter is designed for a

precise output power and a specific frequency but is built using a series of

common modules based on the same technology the standardization has



following advantages like the maintenance personnel of one type can work

with the other type as well and spare parts can be shared.

All amplifiers are WB devices (170 to 230 MHz in B3 and 44 and 88 MHz

in B1) and can operate in band 3 and band 1 of both sound and vision.

In the driver Audio and video I/P signals are connected to vision and sound

IF signals. These IF proceed prior to concession to RF output frequencies

and amplified.

The attenuated 5 and 10 KW sideband pattern is obtained through the use of

a lithium niobate ground wave filter. Each amplifier is equipped with AGC.

The driver also consists of a vision synchronization detection circuit used to

automatically switch the transmitter on and off. Also the transmitter can be

controlled locally and remotely. All IF and RF interconnections use 50ohmcoaxial links to simplify maintenance.

By the use of redundant of the ampliform and power supplies, briefently can

estimated reduced power levels in the event of a failure in several transistors

amplifiers or a power supply.

This man machine interface ensures high user friendliness both in terms of

operation and maintenance. System info and controls are accessed through a

touch screen controlled by a microprocessor.

Description of TX

The TX is in a single cabinet which the diplexer and filter assembly is

associated. The TX as discussed above has two drivers’ two RF

amplification channels, power supplies and associated co-ordination and

control system, a diplexer and a RF filter. All amps power supplies and their

driver components are plug-in drawers and sub assemblies are designed for

easy access and removal. The main switch is designed for use with all types

of 3phiW/W with or without neutral 208V or 480V.

Driver



This subassembly is used to generate vision and sound signals corresponding

to the selected standard using input video and audio signals. This sub

assembly performs the processing and conversion required to generate thefiltered and vision and sound signals in the selected RF band.

The dent also provides phase and amplitude corrections to ensure that the

linearity specifications comply with various standards.

The driver acknowledges s the presence or absence of the video and audio

signals that are applied to the driver.

The driver consists of plug-in mounted in a single PCB rack, 6 units high.

Each driver has 5 modules connected to the mother board. Each can bereplaced separately without changing the entire assembly. MaxOutput power

is 19ddBm for vision signals and 13dBm for sound signals.

Local driver controls are on the local freq and interface board. In the

maintenance mode of the TX these controls are active. The 2 drivers and

associated passive resonance relays are directly controlled by the control

system. (Each driver has +_ 12V power supply).Each driver has its own

internal oscillator. However they can be made to work with an external

frequency synthesizer. In case of synthesizer failure the change into internal

oscillator takes place automatically. In this dual drive configuration the sysautomatically switches over to the reserve driver.

Power amplification

The driver generates a low power vision RF signal and a low power sound

RF signal. They are applied to the vision and sound amplification chains



consisting of identical parallel wired high gain amplifier decreases. These

drivers are used for the 10Kw sys. They are distributed as follows

Each high gain amplifier provides a power of 1600 W at peak and has

An interface safety board for gain and phase adjustments, SWR,

and power surge protection

Class A preamplifier mode.

Class AB Driver amplifier generating 30 to 80 W to the 3

channel input distribution.

Three 2X300 W amplifiers grouped by a empty system

diagonal power in the high generator amplifier drawer to

1600W peak

A power supply distribution board.

Each amplifier has its own protection devices for

1. Power surge

2. SWR

3. Temperature rise

The LCD screen provides control system monitoring and analysis. The

amplifier drivers are provided by plug in high power supplies. (1power

supply for 2 amplifiers.)These highly reliable units generate 50V with 120A.

Each RF O/P of amplifier is coupled with a balanced WILKINSON

COMBINER. Ensuring insulation of approximately 18dB between O/P. This

drive makes it possible to remove an amplifier driver when on the air

without disrupting broadcast. This way a faulty amplifier can be replaced

with a spare drawer and also a sound amplifier can be used in case of a

vision amplifier.

CPU or Control System

It is a microprocessor board and with a LCD screen coupled to it with a

command and control facility. Safety is achieved through hardwired systems

to maintain operations and safety precautions and optimum performance.

The CPU can in fact control



Sound to vision ratio

System power

Type of pilot wave

Synthesizer frequency

Single drive or dual drive

Filtering assembly

It is formed by a diplexer reflecting sound signal and an RF pass band filter

introducing 2 rejecters. A wave counter reset signal is sent to sample vision

and output signal

Tx Cooling

The amplifiers are cooled with pressurized air through an external vertical

system that lets filtered air.

Protection systems

Thermal protection: the Tx is protected against excess temperature increase.

For air if T> 450C then the output power is reduced and when outside

temperature is greater than 600

C the Tx is shut down.

SWR protection: it is independent for each high gain amplifier. If a faulted

amplifier is detected it can be restarted. If the failure causes power rise then

the TX is cut off

Power surge protection: the amplifier has a fast protection circuit in the

event of a power surge at amplifier locations.

Power distribution system

The network is directly connected to I/P of main breaker. And the power

distribution is as shown in figure.



Why is an LNB needed?

The dish antenna does one amplification by concentrating the signals at the

focus. The LNB mounted exactly at the focus amplifies this signal again.

This signal cannot be sent through a coaxial cable because of high frequency

attenuation. So the LNB converts it to a lower frequency between .950MHz

to2.150MHz as that is the frequency required by the IRD.

The IRD used is a Scopus IRD. it has a demultiplexer, an MPEG-2 video

and audio decoder as well as data and VBI insertion functions. It can also

handle high seed and low speed data input functions. And has an on board

DVB descrambling with BISS mode1 and BISS-E support.

It can be used to descramble Scopus CAS 5000 encryption system and a

DSNG CA fixed key encryption system

The DVB deciphers by means of a smart card and conditional access module

CA method- Multicrypt, Simulcrypt

CAS Method – Irdeto, Via access, Crypto works, Covax, Aston, Nagra

Vision, On Digital, Codi Crypt, Beta Crypt, NDS Video Guard.

Documents

7117469 Complete Training Report