complete training report ddk kerala
TRANSCRIPT
PROJECT REPORT
PRODUCTION & BROADCASTINGOF TV PROGRAMMES
DOORDARSHAN KENDRATHIRUVANATHAPURAM
KUDAPPANAKKUNNUKERALA
Submitted By:
ABRAHAM RENN S159/05Ec-4Electronics & Communication EngineeringNIT 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 SRoll No 159/05Electronics & 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 Kendra Thiruvananthapuram 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 the country. 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 terrestrial transmitters 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 MHzDD-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
DDK, Thiruvananthapuram programmes (DD-KERALAM & DD-MALAYALAM) can also be received from DD-DIRECT PLUS, the Doordarshan DTH Service.
SATELLITEINSAT-3A
LOOKING ANGLE 93.5 Degree East
DOWNLINK FREQUENCY 3811.5 MHz
SYMBOL RATE 6.25 MSPS
FEC ¾
POLARISATION VERTICAL
DOWNLINK PARAMETERS OF DD-KERALAM/DD MALAYALAM DTH SERVICE
SATELLITEINSAT-4B
LOOKING ANGLE 93.3 Degree East
DOWNLINK FREQUENCIES
10990 MHz Vertical
11150 MHz Vertical
11490 MHz Vertical
11570 MHz Vertical
SYMBOL RATE 27500 KSPS or 27.5 MSPS
FEC¾
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. STUDIO2. 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 production of 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 angles sound 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 and compatible 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 the first 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, is an 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 Format
NTSC PAL HDTV/SDTV
Description
Television Format for
North America and
Japan
Television Format for
Most of Europe and
South America.
Used in India
High Definition/ Standard
Definition Digital Television Format
Vertical Resolution Format (visible lines per frame)
Approx 480 (525 total
lines)
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 Frame Rate (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. Commonly
found 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 from the 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 rising edge 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.
Luma
The 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 in computer 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 systemii) Video system
iii) Monitor system
iv) Pulse system
v) Control system
vi) 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 man handles 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 photodiodes and 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 crystal filter 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 discharging excessive 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 BS MPV, 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, budget microphones 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 is recorded 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, delaying it, 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 tape recording 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 interactively while 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 done to prevent interference between uplink and downlink signals. The down linked signal is then again sent to the transmitter which again retransmits it. Each satellite has a transponder and a single antenna receives all signals and another one transmits all signals back. A satellite transmits signals towards earth in pattern called the satellite footprint of the satellite. The footprint is strongest at centre and the footprint is used to see if the earth station will be suitable for the reception of the desired signal. Converts
The parts of the DES are Antenna subsystem including LNA Antenna control unit, beacon tracking unit, beacon tracking receiver and up converter system high power amplifier and power system. The system operates in 2 + 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 baseband equipments compression equipments and test instruments like video audio generation and video audio analyzer. They are provided to ensure quality of transmission and help trouble shoot.
The base band segment comprises of baseband subsystems at studio site and base band subsystem at earth station site. This baseband segment processes two video Programmes.
The base band segment is monitored and controlled using a PC placed near the base band earth station equipments called base band NMS PC. The compression segments comprises of Mpeg encoders in 2 + 1 configuration for providing redundancy. It also comprises of digital multiplexers and digital modulators in 1 + 1 configuration. The compression segment is monitored and controlled by compression NMS PC. The receive and monitoring segment consists of two digital receivers for receiving and decoding of the video 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 panel depending 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 processing through 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-going signal on output.ANALOG AUDIO INPUTConfiguration: Left and RightImpedance: 600 ohms or 10k ohms load impedance, electronically balanced, jumper selectable Common Mode Rejection: Greater than 70dB, 50-60Hz. Greater than 45dB, 60Hz-15 kHzSensitivity: -40dBu to +20dBu to produce 10dB gain reduction at 1kHzMaximum Input Level: +27dBuConnector: XLR-type, female, EMI-suppressed. Pin 1 Chassis, Pins 2 and 3 electronically balanced, floating and symmetrical
ANALOG AUDIO OUTPUTConfiguration: Left and right, flat or pre-emphasizedSource Impedance: 30 ohms, ±5%, electronically balanced and floatingLoad 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 3 electronically 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
Reflector diameter
Drive
Sky coverage
X axis (EL)
Y axis (cross EL)
Surface accuracy
Wind resistivity
Limited steer able X-Y type
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 100
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 for circular polarization greater than 20 dB
24.4/db/0k at 4 GHz at 250
elevation
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 mesh strengthened 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 is connected 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. Many characteristics 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 sound and 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 50ohm coaxial 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 the filtered 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 be replaced 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 sys automatically 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 surge2. 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 600C 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.