108600389 dd-report

ELECTRONICS & COMMUNICATION

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click here for freelancing tutoring sitesCHAPTER 1

TV STUDIO Doordarshan have their own shooting studio. Shooting hall is used to shoot various TV Programs. Artificial set is created in the studio hall according to requirements to the program to be shooted. Studio hall contains nos of lights live natural effects to artificial set. Jall is big enough to build the set of about 4 rooms.Studio hall contains many devices for shooting and for creating natural sets also.Like….

Lighting winches & control board. Cvclorama. Many mic. Connection Makeup room Furniture Camera Sound absorbers

Doordarshan produce programs in their own studios. Lights are hanged over the lighting winches are arranged in row. Types and purpose for studio lighting will be explained under title “Studio lighting”

Cvclorama is nothing but a special type of white curtain hanged with the wall in three dimensions. Cvclorama works as the light and color absorbers to maintain original color

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tone or video output because of it’s white color it is also used to create background of various color paper on lighting.

Many microphone connection hanged on between winces are used to attach the microphones during dialog delivery in play.

White colored tiles of sound absorber material are used on walls to reduce echo.Whole studio is central air conditioned and all the doors kept air tight for preventing

outer voices coming into studio.Studio is known as main action area. This place requires very large place compared to

other sections. Action in this area includes staging , lighting ,performance and arrangement to pick up sound and pictures.

Requirements of TV studio.

Very efficient air conditioning. Uniform and smooth floor for smooth movement of cameras. Efficient sound absorber. Effective communication with other sections. 3 to 4 studio cameras with telepromoter. Cvclorama and curtain. Audio and video monitors. Warning lights and safty devices like fire alarm , fire fighting equipments. Digital clock display.



CHAPTER 2

STUDIO LIGHTING Doordarshan uses various direct lights an dimmers hanged on winches in main recording studio. WHY LIGHTING IS DONE? When we shoot outdoor program the source of light is SUN. the natural effect we see in outdoor is greatly depends on the proper lighting. There are two main reasons to use light technique in studio. First is when we prepare artificial set to look like natural. We have to give the proper lighting effect as of it was outdoor. Lighting also depends on the mood of the scene. Secondly the output picture of the camera is 2D. while natural scene we see are in 3D. On TV screen to differentiate the main object from the background & to give 3D effect lighting is must.

Types of Lights In doordarshan 1KW , 2KW and Cool day lights are used to create artificial moon in night scene. Lighting Techniques



To understand lighting technique we should know all the parameters of lights are…. Quantity Quality Color temperature Contrast ratio

Quantity means the amount of light or amount of radiated energy by the source of light and quality means the type of light source used.Contrast ratio is the difference between highly lighted and darkest part of scene.Different lights and colors have their own temperature known as color temperature. When a black body is heated it may be noted that color of body changes from black to red and then towards white as temperature increase. Some nos. of color temperature for different light source are listed below.

Sun light 5600 K Studio lamp 3200 K Domestic lamp 2780 K Fire 1930 K Fluorescent 6500 K HMI 5600 K Cloudy day 6500 K Clear blue sky 12000K

Nature has provided us two types of lights hard and soft. Hard light is a point source light so the shadow of the object looks sharper. In nature sun is the hard light source and other reflecting clouds , hills and buildings are soft sources. The shadow of the object under soft light source looks feathered and soft.In studio mainly THREE POINT LIGHTING technique is used. These three points are..

Key light Fill light Back light

Key Light : is the main light used to highlight any object or to give attention towards the person. This is full intensive light used to highlight the depth of the object or human face.



Key light is usually a hard source at an angle of 15-30 degree to camera axis at an elevation of about 40 degree.

Fill light : is the 805 intensity of the key light and at the opposite side of the camera axis. Fill light is used to suppress the shadow made by key light. It is soft light and also used to fill in whole room.

Back light : is used to separate artist from the background and so to produce 3D visualization by rim lighting he head and shoulders. It is hard source located at 180 degree of camera axis.

The three point lighting ratio 3:2:1 (back: key: fill) in monochrome and 3:2:2 in color provide good portrait lighting.

The last is the background light used to highlight the background of the scene or to create color background on white cvclorama.

Fig 2.1:Lighting Set up



Balance of lightKey light 100%Fill light 85%Back light 110%Back around light 50-60%

The motors attached with winches by metal belts controlled by the height of light. Movement of winches is controlled from control panel which also contains the connection for talkback system. Intensity and power on/off of lights are controlled from the LCU (Light Controlled Unit). In doordarshan LCU is merged with CCU.

CHAPTER 3

VIDEO CHAIN We all know that video we see at our home is either pre-recorded in studio or live telecast. But we don’t know the path of this video signal from studio to our home or from cricket ground to our home.Here the simple chain of video from studio to our home is explained in brief.



Fig 3.1: Video chain Block diagram in fig. illustrate different chains of video playback , news and live broadcasting.

First chain we will understand is for studio program recording. Camera output from the studio hall is sent to CCU. CCU is the camera control unit. Many parameters of video signal like black level , gamma correction, voltage level, color correction are controlled from CCU after making all the correction is then sent to VM (Vision Mixer) in PCR-1 (Production Control Room). Output of 3 to 4 camera comes here and final signal that we see at home is selected here using VM according to a director’s choice. VM is the computer based system for ‘Pinnacle’ used to add transmission and many other effects like croma keying between two selected camera outputs. The final signal from VM is sent to VTR. VTR uses both analog and digital recording system. For digital recording signal is converted in to digital form using A/D converter.

At the time of transmitting this pre recorded program cassettes is played in to respective player in VTR room. Signal from VTR is sent to PCR-2 has one VM. Video monitoring system & CG(Computer Graphics). In PCR-2 CG is used to add computer graphics or onscreen moving messages. From PCR-2 signal travels from MSR (Master Switching Room) is the main control room between studio and transmitter or receiver.For live news the camera output from news room comes to PCR-2 containing small CCU



for news camera. After CCU the path is same as playback of program. Here MSR also sends signal to VTR for recording NEWS.The chain for live outdoor program like cricket will be explained under title “MSR”.AUDIO CHAIN As we understood video chain audio chain is also interesting to know and easier than video chain. In studio program audio from studio microphones is directly fed to the “AUDIO CONSOLE” place in PCR-1. Audio console offers a range of multi track mixing system with exceptional flexibility. Audio console used to mix audio from different source and maintain output. From AC signal is directly recorded on tape with video signal in VTR.While playing back audio is extracted from the tape and fed to another audio console placed in PCR-2 and then travels with video signal. News audio chain is same as play back chain.VIDEO SIGNAL GENERATION

Video is nothing but a sequence of pictures. The images we see is maintained in our eye for a 1/16 sec. so if we see images at the rate more than 16 picture/sec. our eyes cannot recognize the difference and we see the continuous motion.In movie camera and movie projector it is found that 24 fps is better for human eyes. TV system could also use this rate but in PAL system 25 fps is selected.Let’s begin from camera. We know about still cameras and movie cameras. In still camera and movie camera image is directly focused on directly focused on chemical based film. But in TV camera electronic signal processing is used rather then chemical processing. The advantage of electronic signal processing over chemical processing is that a user can modify some parameters and bring changes in the image quality at the time of taking shot. In TV cameras images is converted in electric signal using photosensitive material. Whole image is divided into many micro particles known as pixels. These pixels are small enough so that our eyes cannot recognize pixels and we see continuous images. Thus at any instant there are almost an infinite number of pixels that need to be converted in electric signal simultaneously for transmitting picture detail. However this is not practical because it is no fesiable to provide a separate path for each

CHAPTER 4

VTR(VIDEO TAPE RECORDING)



INTRODUCTIONVideo tape recorder is a most complex piece of studio equipment with analog and

digital processing servo system microprocessors, memories, logic circuits and mechanical devices etc. Also these recorders have been the main limitation so far as the quality output from studio is concerned.Requires higher writing speed and lower head gap along with reduction in number of octaves.

VIDEO TAPE FORMATSIntroduction:Format of Video tape recorder defines the arrangement of magnetic information of the tape. It specifies:The width of tapeNumber of tracks for Video, Audio, Control, Time Code and Cue,Width of tracksTheir electrical characteristics and orientation.Classification TELECINE:

It is used for telecast purpose. It converts the motion picture signal into video signal. This allows the use of old movies, documentaries educational & commercial films of various kinds as a source of program material Continuous transport by microcomputer controlled wrap capstan drive. Silent and film saving.BCN-3:Composite Analog FormatsBETACAM:Component analog formats 3(A) BETACAM SP

Updated models, Betacam-SP and M-II formats are using metal particle tapes and higher carrier frequency for FM. These machines have performance equal to the one inch type B or C formats. Introduced in 1986 as an improvement over Betacam with 60 min/90 min Cassette, it uses higher specification metal tape which increases overall performance particularly in bandwidth and multi-generation. It offers two high specification Fm audio channels in addition to two linear audio tracks.Types :



Studio Version (All with built in TBC and Time code).BVW 10 P – Non-SP, Player only.BVW 40 P – Non-SP, Recorder cum player.BVW 60 P – SP player only, compatible. BVW 65 P – SP player with DT head, compatible.BVW 70 P – SP Recorder cum player, No DT head.BVW 75 P – SP Audio Recorder cum player, with DT head, 4 Audio track,Compatible with non-SPPVW 2800 P – PRO SERIES, Recorder cum Player, SP only.PVW 2600 P – PRO SERIES, player only, SP only.3(B). BETACAM SYSTEMFig 2: Betacam Tape Path around the head drumHeads

Video head (two)Audio head (two for ch-1 & ch-2)Video erase headAudio erase headAll erase headTime code head (TC head)Control track head (CTL head)The R-Y and B-Y are clocked into separate one line duration stores. Similarly

during the second line, a second pair of stores receivers the next R-Y & B-Y.Meanwhile, R-Y is clocked out of its first store at twice the clock speed, compressed it to 32 µ sec. Then B-Y is clocked from its first store to fill the next 32 µ sec period. This is called CTDM.The first pair of stores is now empty, ready to receive new R-Y & B-Y from the input signal. While this is going on souble speed clock are used to empty the second pair of stores in a sequence of R-Y first and then B-Y.



Fig 4.1: Betacam Track layout

Fig 4.2:DVC Proffesional



Fig 4.3: tape construction

These are the ultimate in video recording as the information is recorded in digital form and multi-generation dubbing is no longer a problem. The various digital formats in use as under.

a) D1: It is the very first digital standard and uses component system (i.e. CCIR 601 yuv, 4:2:2 format) using ¾” tape with writing speed of about 30 cm/s and helical drum running at 150 rps with segmented tracks. Digital coding is in 8-bits words with a raw picture data at the speed of 216 M bits/sec. The 601 standard is now provides the option for 10-bit coding but it is not implemented in D1 machines. Each field is made of six segments. Each segment records 50 lines and 12.5 lines are not recorded so that 12 tracks must be scanned per frame. The video is laid down in non-azimuth tracks with guard bands using a randomize NRZ (non return to zero) code. The four channel of digital audio (sampled at 48 kHz using 16 bits) have data shuffled, interleaved and recorded twice in data bursts at the centre of video tracks with full time code facility. In all there are 16 heads, 6 pairs for video and 2 pairs of audio. Even though it is expensive , it has limited slow motion facilities and consumes lot of tape with linear speed around 29 cm/s. it provides excellent bandwidth and SNR (Y 5.75 MHz, C 2.075 MHz and 56 dB respectively). Luminancer sampling is at

13.5 MHz and chrominance is at 6.75 MHz (both U and V respectively).

b) D2: To reduces cost, D2 system was introduced by Ampex. D2 uses D1 cassette of high coercivity ¾” metal tape with two pairs of heads scanning 8 tacks per



fields D2 uses composite video signal for sampling, with writing speed of about 28 cm/s using helical drum running at 100 rps. Data rate is around 150 Mb/s. It has 4 digital audio tracks to aid in slow motion cueing. It has full variable speed range, cheaper than D1 and has bandwidth and SNR of 5.5 MHz and 54 dB respectively.

c) D3: it was developed by NHK and Panasonic using composite signal ½ “ metal particle VHS sized cassette thus saving cost. It records 8 bit digital video at a sampling rate of 4 fsc (17.73 MHz ) in 8 tracks per field. Data rate is similar to D2. It too 4 digital audio 16-20 bit and 48 kHz and cue track with comprehensive slow motion. Head drum rates at 100 rps with a writing speed of 21.4 cm/s. the signal recorded on ½ “ metal tape is more than twice recording density of any other existing formats. Because of its compact size it is suitable for camcorders. D3 cassette can record 4 hours of continuous recording. Multi-generation suffers in quality in comparision top component machine.

d) D4: It does not exists.

e) D5: Panasonic now has a new component system called D5 using ½ “ tape. It is successor to D3. It is digital component using same cassette as D3 but running at double speed. In addition to all the usual facilities, D5 can playback existing D3 tapes. It gives just two hours from a long size cassette. Coding is 10 bits with luminance sampling at 13.5 MHz. D5 can handle 4:3 or 16:9 aspect ratio is 18 MHz with 8 bit coding.



Fig 4.4: Magnetic Principle

Causing a magnetic field proportional to current.Fig.1 (b) shows current carrying conductor when wound like a coil acts like a bar magnet.Fig.1 (c) shows current carrying coil when bent to form a ring, inner field remains homogeneous but the outer field vanishes i.e. field lines inside are able to close.Fig.1 (d) shows ferromagnetic material inserted in side the ring with a narrow air gap causing a flux bubble because of magnetic potential difference across the gap.

Associated equations, which we already know, are:Magnetic field intensity H = NI / LMagnetic flux density B = µHMagnetic Flux Ǿ = BA

(µ Is of the order of 100 to few 10,000 for ferromagnetic materials.)Property of the ferromagnetic materials to retain magnetism even after the current or the H is removed is called retentivity and is used for recording electrical signals in magnetic form on magnetic tapes. This relationship can also be represented by a curve called BH curve. Magnetic tapes are made of ferromagnetic materials with broader BH curve than the material used recording process with reference to figure 1(d) when a tape is passed over the magnetic flux bubble, the electrical signal in the coil will cause the electric lines of force from the head gap to pass through the magnetic material of the tape producing small magnets depending upon the strength of the current. Polarity of the magnetic field which causes these bar magnets depends on the change of current. Decreasing current will cause NS magnet and vice versa. Power of these magnets is as per BH curve. Thus the magnetic flux strenghtents the unarranged magnetic particles as per the signal and they stay in that condition after the tape has already passed the magnetic head (Fig.2). Length of the magnet thus formed is directly proportional to writing speed



of the head v, and inversely proportional the frequency of the signal to be recorded, i.e.Recorded wavelength for one cycle of signal = speed x timeOr wave length of the magnetic signal tape = v/f

During play back when the recorded tape is passed over the head gap at the same speed at which it was recorded, flux lines emerging from the tape on crossing the head gap induce voltage in the coil proportional to the rate of change of flux, i.e. dѲ/dt and this in turn depends on the frequency causes voltage to increase by 6 dB. This accounts for the well known 6 dB/octave playback characteristics of the recording medium. This holds good only up to a certain limit thereafter at very high frequencies, lot of losses take place during

Fig. 4.5: Recording Process Play back process Playback and recordings process causing noise to be more than the signal itself. It may be noted that when the gap becomes equal to the wavelength of the recorded signal, two adjoining bar magnets may produce opposite current during playback and the output becomes zero. Similar thing happens when the gap equals 2,3 …n. times the wavelength. First extinction frequency occurs when gap becomes equal to wavelength. For getting maximum output, head gap has to be one half of wavelength. Frequency at which zero output occurs is called extinction frequency (Fig. 3). Thus the maximum



usable frequency becomes half of the extinction frequency. These parameters are related by :

So in order to record the higher frequencies we must increase the writing speed for a minimum value of wave length recorded on tape i.e. λ tape. This minimum value of λ tape is again restricted by the minimum practically possible head gap. Now the ratio of video and audio frequencies is approx matly 300, so we must increase the writing speed or reduce the gap by the same factor of 300 to get the desired results. Perhaps a speed of 60 mph will be required to cope with the higher video frequencies. Keeping in mind the practical limitations a gap of the order of 0.025 mil and writing speed of 600 ips or 15 mtrs/sec approx. (The requirement of portable machines demands resuction in writing speed to achieve lower tape consumption.

So it is always a compromise or balance between various parameters involved. For most of the present day portable machines, higher performance specification even at lower writing speed has beam possible because of development of better quality metal tape and improvement in video hands) for VTRS (compared to 0.5 mil and 7.5 ips for audio recorders) has been found practical and tried successfully. If we insert these figures in the above-mentioned relationship we get MUF or the order of 16.

MHz. This means that with these parameters we can obtain a usable parameters we can obtain a usable bandwidth for video tape recorders up to 8 MHz. Besides the requirement of attaining higher writing speed and reduced gap the range, during which the extracted signal is more than noise. This range is only 10 octaves. Thus the system can no longer be used for recording/reproduction after this dynamic range of 60 db, because of 6 dB/octave playback response characteristics. Beyond this range the low frequencies becomes inaudible and the higher frequencies become distorted.



During the initial stages it was tried to record video signal with stationary video heads and longitudinal tracks using tape speed of the order of 9 m/s which was very difficult to control besides very high tape consumption i.e. miles of tape for 3 to 4 minuts of recording and this was coupled with breaking of video signal frequencies into 10 [arts recorded by 10 different video heads and then switched during playback to retrieve the signal. The quality of the reproduced signal was also compromised up to the resolution of 1.7 MHz or so. Around 1956 the ‘AMPEX’ company of USA then came out with Quarruplex machines having two revolutionary ideas which laid the foundation of present day VTRs/VCRs.

Fig 4.6: Header WorkingThese ideas were:

1. Rotating Video Heads and Frequency Modulation before recordingIncrease in writing speed by rotating head when a video head mounted on a rotating head wheel writes on a tape moving across it, will lay a track of length which will depend not only on the speed of the tape but also on the rotating speed of the head. Single head with diameter d number of rotation per sec as r and full omega wrap or two heads in ½ omega wrap i.e. little over 180 degree, which most of the present day VCR are using, will have a writing speed of πdr minus or plus the linear tape speed (which is negligible as compared to the rotating speed). This avoids the requirement of miles of tape for few minuts of recording in a stationary head type of recorders tried earlier.



Fig 4.7: General Audio Cassets

Fig 4.8:Recording of cassets



Speed and AccuracyTiming accuracy, as pointed out earlier is especially important for VTRs as our eyes are very sensitive to these errors compared to our ears which may not detect these errors in audio tape recorders. In order to reduce these timing errors it is important to create same conditions for the capstan and drum motors of video tape recorders at the time of recording. To achieve this, the status of these motors during recording is written on the tape itself along with the signal, and is used during playback as one of inputs to the servo system. Servo systems are employed to control carious motor, ensure constant tape tension and minimize timing errors. These timing errors are further reduced to about 5 n sec. by using additional electronics called Digital Time Base Correctors (DTBC) to make it synchronous with other video signals like studio cameras etc.

Monitoring During Recording Most of the video tape recorders provide Electronics to Electronics monitoring at the time of recording. The video signal is monitored after routing it through all the signals systems electronics of the recorders excluding the video heads and preamplifiers etc. Some of the recorders also provide simultaneous playback for the off tape monitoring by using additional heads during recording called confidence heads.

Thus the VTRs could achieve wider frequency range with:a) Faster writing speedb) Smaller gap , and c) Ocatave band comparision with frequency modulation.

Also achieving accurate speed for motors with servo system reduces the timing errors.



CHAPTER 5

OUTDOOR BROADCASTING

For live broadcasting like any match or any event, out door broadcasting van is used. Out door broadcasting van consists of all the equipment that is prevent in the studio for telecasting.

It is referring to as mini Studio. It I constructed on four wheels.O.B. van is mainly divided into three part by partition:

Power supply unitProduction Control Rom(P.C.R.)Audio console and VTR

Main application of O.B. van is gathering news from different places, functiona or cricket match in stadium. In O.B. van there and microphones in broadcasting. All the nikes and camera out put to the van out side the stadium.Doordarshan have their own OB van which used to cover news and different programs, festivals held in different areas in Gujrat.

OB VAN has 15 monitoring system in it. It contains whole studio inside the van. Means CCU, MSR, PCR, AUDIO CONSOLE, etc.. thus the van is also called Studio on wheels.

OB Van uses special software and hardware for showing slow motion and replays while covering live programs.

Another small carriage van for microwave transmitter is attached with the main



van and also diesel generator is taken wherever van goes.

If there is live program to be telecast it has to option to transmission.

Microwave linkD.S.N.G.(Digital Satellite News Gathering)

Microwave link:

Audio and video signals are feed to microwave transmitter Input video is processed and up converted 12.25 and 12.30 GHz Approx. tranmit power is 600mWatts Transmit/Receive antenna size 1.1m diameter

Digital satellite news gathering (D.S.N.G.)

Audio/video input is respectively processed by audio/video encoder as per the MPEG-2 standards.

The audio and video along with other data are multiplied. Multiplied data is forward error corrected using convictioal coding

techniques. Error corrected codes are QPSK modulated at 70MHz. The modulated signal is up convert to the power amplifiers. Amplifiers signal is coupled to up link dish.



Fig 5.1: OB Van Chain

CHAPTER 6

Camera Control Unit (CCU) The television cameras which include camera head with its optical focusing lens, pan and tilt head, video signal pre-amplifier view finder and other associated electronic circuitry are mounted on cameras trolleys and operate inside the studios. The output of cameras is pre-amplified in the head and then connected to the camera control unit (CCU) through long multi-core cable (35 to 40 cores), or triax cable.

All the camera control voltages are fed from the CCU to the camera head over the multi-core camera cable. The view-finder signal is also sent over the camera cable to the camera head view-finder for helping the cameraman in proper focusing, adjusting and composing the shots.

The video signals so obtained is amplified, H.F. corrected, equalized for cable



delays, D.C. clamped, horizontal, and vertical blanking pulses are added to it. The peak white level is also clipped to avoid overloading of the following stages and avoiding over modulation in the transmitter. The composite sync signals are then added and these video signals are fed to a distribution amplifier, which normally gives multiple outputs for monitoring etc.

All the correction regarding video camera is applied here in CCU. In fig shown the control desk for the video signal of DDk. Parameter like average brightness, contrast ratio, gamma correction, voltage level, etc.. observed here and if varies it can be controlled automatically by the machine shown in fig. video output voltage should be 1 V peak to peak, if any difference occurs, we can control it manually as well as automatically by putting machine in auto control mode.

Fig 6.1:View of CCUCHAPTER 7

PRODUCTION CONTROL ROOM One of important parts of the DDK is the PCR, which is the second step of the Video chain.

The generated signals in the studio are controlled and with some effects and characters are added here.

So signals come firstly to the PCR and go for the further processing.

There are three main parts of the PCR i.e. (1) Base station equipment (2) Vision Mixer (3) Audio Console



BASE STATION: The video signals generated at the camera situated at studios, all VTR are transmitted to the base station for the further processing.

The base station consists of BASE STATION VIDEO MODULE, BASE STATION MPU MASTER PROCESSING UNIT MODULE BASE STATION DIGITAL PROCESSOR MODULE BASE STATION MODULE.

BS VIDEO MODULE: The video signal fed from the camera head to y, cb & cr signals amplified to a suitable level & then sent to BS MPU module.BS MPU MODULE: The video signals fed from BS VIDEO MODULE are first subjected to level adjustment & then they undergo analog clamp. They are filtered by low pass filter to limit the bandwidth. Then the signals pass through the white/black clip circuit & then converted in to digital data.

BS Digital PROC. MODULE: The BS D PROC. MODULE performs various processing omn digitized y, cb, cr video signals & outputs the followings signals.

1) Encoder signal2) Component signal3) 4:2:2 digital component signals.

Encoder Signal: The Y, Cb & Cr signals are encoded by the digital processing like Black STTRECH/PRESS, blanking sync addition & color brust addition and are output for analog composite signals.

Component signal: The encoder signals output are also branched off & passed through digital delay and are converted into analog signal for analog component signal.



Digital component signals: An another branched Y, Cr & Cb signals are used as digital signal output. The Y, Cb, Cr signals output are sampled. The Y signal is sampled at sampling frequency of 27.0 MHz & Cr, Cb are sampled at 13.5 MHz & Cr, Cb signal are converted to 6.25. The Y, Cr, and Cb whose frequency ratio is 4:2:2 are encoded.

BASE PULSE MODULE: The base station pulse module receives two analog video signals from BS D PROC MODULE, which are the encoder signal, & component signal of Y, Cr, and Cb.

The Y, Cr, Cb signal are converted to R, G & B signal by DE-MATRIX circuit.The camera videos after the treatment at the CCU are fed to the vision mixer panel in the production control room (PCR).

CHAPTER 8

VISION MIXER The vision mixer is the destination point for all the pictures sources in the studio. The output of all studio cameras, video tape recorder, caption scanners, character generator etc. are fed to the vision-mixing unit.

The vision mixing involves basically 3 type’s transition between the above sources. These transitions are mixing wiping & keying.



The output of the mixer desk is fed to transmission monitor, transmission chain etc. in production control area.

The vision-mixing panel offers a lot visual effects that requires time, skill & costly auxiliary equipments.

Some of the facilities of the vision mixer are explain here.

The CUT:

The cut is an instantaneous switch from one picture to another. It avoids the frame roll & flash evident, on picture at the moment of cutting. It is illustrated in fig. (1) & (2).

The MIX:

The transition here is less pronounced. As the faders are operated, the established picture fades away, while the new picture progressively appear on screen simultaneously while transition. The mixing is illustrated in fig. (3) & (4).

The FADE UP/FADE OUT:

A selected channel can be fade up or fade out with help of moving a fader up & down. The picture can be fade to black or from black.

TheSUPERIMPOSITION:

Superimposition can be obtained by fading up two or more picture together. This may be used to add tilling to an existing picture or special montage effects.

PREVIEW:Vision mixers also have a preview bank & its output connected to a monitor. It

enables us to check any selected no studio pictures source before its transition.

The WIPE:



The wipe is common special effects. It can be described as one picture chasing the original picture.

The direction of the entry of the picture in original picture can be horizontal, vertical, diagonal, circular & so on.

This is illustrated in the fig. below.

KEYING:The keying signal can be generated either by the luminance, hue or chrominance of

the source input. The kyed portin can be filled with the same or with matte or external source. Matte means internally generated BG with choice of color from the vision mixer itself.

Chroma keying:



Fig 8.1: Vision Mixing

This fig shows the result of the chroma keying. Computer graphics is super imposed on blue back ground in studio scene. In this effect a selected portion of the background video source is replaced with foreground video source. The FG portion to be inserted is determined from a keying waveform, which may be derived from the foreground picture. Some time this is also called as color separation ovelay (CSO).

Principal of Chroma keying



Chroma key is concerned with HUE, SATURATION AND LUMINANCE. Chroma key is produced by the use of a processing unit, which is adjustable to a specific hue, saturation & luminance combination in a source signal.

Hue select: It is used to adjust the keyer to a specific hue. Clip control: It allows rejection of lower luminance levels of the specified color. Gain Control: it reduces the contrast between high and low levels of the output key signal, softening the transition edges of the resultant composite. Comb filter: this feature found on some encoded key units. Its function is to eliminate high frequency luminance signals approaching the chroma sub carrier frequency, which, when present on the keyer’e input may cause the keyed to trigger falsely. This result in poor chroma keying.

Another feature provided by the VM is to superimpose the characters, program titles with DVE.

CHARCTER GENERATOR: For this superimpose process, the generated CG is provided by the one special S/W MOVECG2001 is used here with all the facilities like, font, size, regional language etc.

AUDIO CONSOLE: Like Vision Mixer, this is the instrument for the audio in which the audio is controlled. PCR-1 and PCR-2 have 16-line consoke, 12 monos and 4 stereos with control effect like gain, attenuation, filtering and switching for the different input. The video after the treatment on the vision mixer is sent to VTR & suitable conversion

Fig 8.2: Audio Consle



For the recording or to the MSR for the transmission through the transmitter or the earth station.

Fig 8.3 :Audio Panel

PHONE IN CONSOLE: Phone in console is the simple telephone device attached with the audio console. This device is used at the time of live studio program to have live presence of home viewer.TAL BACK SYSTEM.

Fig 8.4 : Talk Back System

This is one audio loop attached to all the sections of doordarshan to communicate with different sections. This is just like intercome.



CHAPTER 9

MASTER SWITCHING ROOM MSR is the Master Switching Room used for transmission media. It is the engineering co-ordination center for a TV station. This room is the center of activity for selecting & routing the signal from various sources to transmitter and earth station.

The master switching room is centrally room where all different sources from the outside studio are comes first here & enroots like Transmitter & Earth station. The different incoming sources are TVRO signal (DD-1,DD-NEWS) from transmitter, any microwave signals during LIVE coverage’s downlink monitoring signals of earth station & simulcast, Telecine, and any other sources. The output signals are fed to Transmitter & Earth station/SIMULCAST for transmission purpose and also some signals are distributed and given to various PCR, VTR or any other appropriate places.

This room comprises of Routine Switcher, Stab amplifier, Video/ Audio distribution amplifier, frame synchcronizr, digital/satellite clock monitoring system, logo generator vector scope, video monitor. The programmers from TVRO & OB program are also taken to MSR switcher unit to from part of the 16 inputs. On 16x8 switcher is used for its activity like on air transmission, networking monitoring etc.

The control console panel consisting of controls Routing switcher, stab amplifier, Frame synchronizer etc are stored here & also Wave form monitors, Vectroscope, Video monitors, Logo generator, Patch panel are placed at convenient place for final monitoring. The switcher unit and other video equipments are put in a standard rack.

16x8 AUDIO/VIDEO SWITCHER



16x8 switcher has max of 16 i/ps & up to 8 independent o/ps any one of the i/ps signals can be switched to any one or to all the channels at the same time. Using a common control panel can use it as an audio follow video switcher.

HUM SUPPRESSORIt is used for reducing the superious signals of different potential at the sending & receiving ends of the transmission line.

VIDEO EQUILISER It is used to compensate for in cables of length up to 300 mts.

COLOR STABILIZING AMPLIFIER This is employed in the video chain for regenerating noise free sync & blanking components from an incoming video signal. It is also use to provide controls for adjusting various component in a video signal so that the composite color signal can be adjust to the standard value.

VIDEO DISTRIBUTER It is used to distribute video signals to a number of units. It contains independent distributing amplifier each providing fine o/ps.

5x1 VIDEO SWITCHER It is used to select one video signal from 5 different sources. It can be controlled from a remote location.

SYNC GENERATOR It generates synchronizing & blanking signal.

PULSE DISTRIBUTER It is used to obtain no. of synchronizing & blanking signals



from an o/p of a sync generator. With only one SPG centrally located a mechanism of pulse distribution is required. With each and every 75 ohm destination requires a dedicated 75 ohm source. If this is not done then cables will be incorrectly terminated, signals will have the wrong amplitude and will suffer from reflection. Use of PDA provides multiple feeds to various destinations.

CHANGE OVER UNIT It is used to provide facilities for selecting video signals from one of the two sources. The change over of all the i/ps can be done from panel or from a remote point.

FRAME SYNCHRONIZER It is used to synchronies the different i/p signals. The synchronizer is one of thw many television units to use digital storage techniques. The signals to be synchronized is written in to the store as its own rate and timings. It is read from the store with respect to stations sync. At the timing and rate of the studio center, thus making it synchronous. If there are too many outstation feeds a synchronizer with each will allow mixing them with the other studio sources.

SIGMA ROUTER Every i/p & every output is given a specific code. The selected i/p & the corresponding o/p code can be checked on the sigma router.

VECTROMETER Every color has specific amplitude & phase relations. This should be maintained to get correct o/p on the screen.This can be checked on vectrometer, which shows the amplitude & phase of R.G.B. colors.It looks like RADAR screen. It gives the idea about amplitude & phase of different colors.

WAVEFORM MONITOR Waveform monitor is used to check & monitor the video



level at exactly 1 Vpp * to monitor the audio level at 0dB. The audio level should be kept less than 0dB. This is then amplified at LPT.

In MSR, 16x8 matrix is used in router such that any input can be given to any output.

16 inputs & 5 output are listed below;



Fig 9.1: Block Diagram Description of MSR



CHAPTER 10

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

Table 10.1: Comparision of S and C band Transmitter

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.

Fig 10.1: Transmission of signal

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 El74.0

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 programs 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 color burst which controls the color 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 color stability amplifier is used at this stage to regenerate synch color 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 color 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

Fig 10.2: Generation of vision and sound signals

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. Max Output 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.

CHAPTER 11

DIGITAL EARTH STATION

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 programs and one ASI to SDI decoder for decoding of the transport stream for monitoring video programs 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 programs 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 programs 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 color 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 symmetrial

Fig 11.1: Set-up of Digital E/S

CHAPTER 12

SATELLITE COMMUNICATION



In telecommunication, the use of artificial satellites to provide communications links between various points on Earth. Communications satellites relay voice, video, and data signals between widely separated fixed locations (e.g., between the switching offices of two different national telephone networks), between a fixed location and numerous small fixed or mobile receivers in a designated area (e.g., direct satellite broadcasting of television programming), and between individual mobile users (e.g., aircraft, ships, motor vehicles, and personal handheld units). The technique involves transmitting signals from an Earth station to a satellite. Equipment onboard the satellite receives the signals, amplifies them, and retransmits them to a region of Earth. Receiving stations within this region pick up the signals, thus completing the link.

Fig 12.1: Satellite Comm.

Satellite Communication

Started in 1960.



Uses Geo Stationary Satellite (36000 km).

Operates in C-Band & Ku-Band

Started in India in 1975

First Indian Satellite INSAT launched in 1982

Gulf War brought satellite television to prominence.

Satellite Orbits

1) Low Earth orbit: A low Earth orbit (LEO) is generally defined as an orbit within the locus

extending from the Earth’s surface up to an altitude of 2,000 km. Given the rapid orbital decay of objects below approximately 200 km, the commonly accepted definition for LEO is in between 160 - 2,000 km (100 - 1,240 miles) above the Earth's surface.

2) Medium Earth orbit:Medium Earth orbit (MEO) sometimes called intermediate circular orbit (ICO), is

the region of space around the Earth above low Earth orbit (altitude of 2,000 kilometers (1,243 mi)) and below geostationary orbit (altitude of 35,786 kilometers (22,236 mi)

3)Geostationary orbit:A geostationary orbit (GEO) is a geosynchronous orbit directly above the Earth's

equator (0° latitude), with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero.



Fig 12.2 : Satellite Orbits Purpose Of Satellite Communication

A single satellite can provide coverage to over 30% of Earth’s surface.

It is often the only solution for developing areas.

It is ideal for broadcast applications.

It can be rapidly deployed.

It is scalable. Depending on application, there is no need for the local loop.

Transmission cost is independent on distance

Wide bandwidths (155 Mbps) are available now.

Satellite Transmission Frequency bands Frequency Band Up Link Down Link

C-band 6 GHz 4 GHz X-band 8 GHz 7 GHz Ku-band 14 GHz 11 GHz



Ka-band 30 GHz 20 GHz Satellite Transmission: C-Band

Frequency band 4000 to 8000 MHz

Large sized dish required for reception

Useful to System Providers / Cable Operators

Mainly used for contribution & distribution

Satellite Transmission: Ku Band

Frequency Band 12.5 to 18 GHz

Smaller dish ( 60 – 90 Cms) needed for reception

Most useful for DTH application

Suitable for fly away terminals

Coverage limited as compared to C band due to narrow beam

Reception susceptible to failure during heavy rain



ADVANTAGES OF SATELLITE COMMUNICATION

Cost Effectiveness - Cost of satellite capacity does not increase with the number of users/receive sites, or with the distance from two communications points.

Global Availability - Communications satellites cover all land masses and there is growing capacity to serve maritime and even aeronautical markets. Customers in rural and remote regions around the world who cannot obtain high speed Internet access from a terrestrial provider are increasingly relying on satellite communications.

Superior Reliability - Satellite communications can operate independently from terrestrial infrastructure. The fact is that terrestrial outages do occur from man-made and natural events, but when they do, satellite connections remain operational.

Superior Performance - Satellite is unmatched for broadcast applications like television. For two-way IP networks, the speed, uniformity and end-to-end control of today's advanced satellite solutions are resulting in greater use of satellite by corporations, governments and consumers.

Immediacy and Scalability - Additional receive sites, or nodes on a network, can readily be added, sometimes within hours. All it takes is ground-based equipment.

Versatility and More - Satellites effectively support on a global basis all forms of communications ranging from simple point-of-sale validation to bandwidth intensive multimedia applications. Satellite solutions are highly flexible and can operate independently or as part of a larger network.



CHAPTER 13

CONCLUSIONS

The practical work done in college during B.E.is not sufficient and therefore it is required to go more about it & so it is necessary to take training in doordarshan .The aim of such a training is to learn the various aspect of the theoretical studies in practical field. It helped me to gain a knowledge in practical aspect of engineering studies. In doordarshan I saw processing of various instrument practically which are use in study .Setup of studio where shooting performed lighting ,different features of camera and all film making process ,recording is done by video tape recording .We know about the different type of transmission of audio and video signal.

Difference of transmission in live telecast and record telecast outdoor broadcasting van used for live telecast. Idea about production control room, vision mixer and master switching room. Proper steps of transmission how can reach signal at our television signal. Digital earth station which is the most important part of doodarshan and satellite communication how can both are interect and downlink and uplink frequency and advantage of satellite communication over terrestrial communication and Knowledge about band and satellite orbit is the important points which we are study in our complete tranning session.


http://B.E.is/


CHAPTER 14

REFERENCES

K.D.Prsad “Antenna & Wave Propagation”

http://en.wikipedia.org/wiki/Transmitter

http://www.ddindia.gov.in/

http://en.wikipedia.org/wiki/Communications_satellite

http://ctd.grc.nasa.gov/rleonard/

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http://ctd.grc.nasa.gov/rleonard/

http://en.wikipedia.org/wiki/Communications_satellite

http://www.ddindia.gov.in/

http://en.wikipedia.org/wiki/Transmitter


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