Air India-ece Project Report

ACKNOWLEDGEMENT This report is outcome of "On the Practical training which I received at Prasar Bharti Doordarshan Kendra Shimla (H.P.)". It includes the organizational Structure, Procedure, function & performance of the station. First of all I would like to express deep sense of gratitude towards Mr.AMIT SHARMA (S.E.(engineering head)) who permitted us to undergo training in the Prasar Bharti Doordarshan Kendra (B.C.!.) Shimla. I would like to express my special thanks to Mr. OM PRAKSH (A.E. (training coordinator)) who prepared our training schedule &helped us to complete our training. I would also like to express my thanks to Mr. S.K. BHARDWAJ (A.E.), Mrs. Champa (A.E.) to give me full support to prepare this report / also thanks to Mr.SURIENDER KUMAR (A.E) for guiding me.

GROUP 2 Electronics & Communication Engineering

6th Sem 3rd Year.

CONTENTS 1.

STUDIO :

•

INTRODUCTION -------------------------------------------------------

•

STUDIO CHAIN -------------------------------------------------------

•

ACTIVITY IN STUDIO -----------------------------------------------▪ ACTION AREA -------------------------------------------------▪ CENTRAL APPARATUS ROOM ----------------------------▪ PRODUCTION CONTROL ROOM -------------------------▪ VIDEO TAPE RECORDER ------------------------------------

2.

EARTH STATION :

•

INTRODUCTION -------------------------------------------------------

• 3.

SIMULCAST EARTH STATION ------------------------------------

TRANSMITTER :

•

INTRODUCTION -------------------------------------------------------

•

TECHNICAL DATA ---------------------------------------------------

•

PRINCIPAL FEATURES OF 1KW TV TRANSMITTER -------

•

GENERAL TECHNICAL DESCRIPTION -------------------------

•

TRANSMITTER BLOCK DIAGRAM ------------------------------

•

POWER SUPPLY -------------------------------------------------------

INTRODUCTION A TV studio is an acoustically treated compact anechoic room. It is suitably furnished and equipped with flood light for proper light effected. The use of dimmer states with flood lights enables suitable illumination level of any particular area of the studio depending on the scene to be televised Several cameras are used to telecast the scene from different angles. Similarly a large number of microphones are provided at different locations to pick up sound associated with programme. The camera and microphone outputs are fed into the control room by coaxial cables. The control room has several monitors to view picture picked up by different cameras. A monitor is

a TV receiver that contains no provisions for receiving bradcast signals but operates on a direct input of unpopulated signal. A large number of such monitors are used to keep a check on ht contest and quality of pictures being telecast. In addition to live studio. Video tape recording and telecine machine rooms are located close to the control room. In most cases, programmes as enacted in the studio are recorded on video tape recorder (VTR) through the control. These are later broadcast with VTR output passing through the same control room. All these rooms are interconnected by co-axial cables and shielding wires.

VIDEO CHAIN IN A TYPICAL DOORDARSHAN STUDIO STUDIO CENTRE: A studio chain of Doordarshan has the following objectives: 1. To originate programs from studio either for live telecast of for recording on a video tape. 2. To knit various other source of programs available at the production

desk i.e. camera output from pre-recording tape, film based programs slides, video graphics and characters generator etc. this knitting or live editing includes generation of special effects and desired transition between various sources. 3. Processing/distribution of different source to various destination in technical areas. 4. Routing of mixed program for recording/transmission via central apparatus room and Earth station to the transmission or any other desire destination.

ACTIVITIES IN A TV STUDIO CAN BE DIVIDED INTO THREE MAJOR AREAS SUCH AS : • Action Area • Central Apparatus Room • Production Control Room

ACTION AREA: This place requires large space and ceiling as compared to any other technical area. Action in this area includes staging, lighting performance by artists and arrangement to pick up picture and sound. This place requires large space and coiling as compared to any other

technical data. Very efficient air conditioning because of lot of heat dissipation bay studio light and presence of large number of persons including invited audience performing artists and operational crew. Uniform and even flooring for smooth operation of camera trollies and microphone etc. Acoustic treatment keeping in mind that a TV studio is a multipurpose studio with lot of moving person and equipment during production. Supporting facilities like properties, makeup and wardrobe etc. • Digital clock display. • Audio and video monitoring facilities. • Pick up wall sockets for audio operations. • Luminaries and suspension system having grids or battens. • Tie lines box for video and audio from control room. • Cyclorama and curtain tracks for blue and black curtain for chrome keying and limbo lighting respectively. Camera Chain: A typical three tube camera chain is described in the block diagram. Tube power supply section provides all the voltages required grids of electron gun. Horizontal and vertical deflection section supplies the saw tooth current to the deflection coils of scanning the positive image formed on the target. The built in synchronous pulse generator provides all the pulses required for the encoder and colours bar generator of the camera. The signal system in most of the camera consists of processing of the signal form red, blue and green tube. Some of the camera us-e white, blue and red tubes instead of R,G, B system. the processing of red and blue channel is exactly similar. Green Channel, which also called a reference channel, has slightly different electronics concerning aperture correction. So if we understand a particular channel, the other channels can be followed easily. In each camera signal are given to generate synchronous pulse and black burst pulse for a good picture in television.

CAR (CENTRAL APPARATUS ROOM) In small broadcasting, houses the PCR has a master switches for routing the composite video signal and allied audio output directly to the transmitter. The ancillary equipment is mostly located in the central apparatus room. However to bigger establishments which have a large number of studios and production control rooms, all output from various sources are routed through the master control room. This room houses Centralized video equipment like:-

•

• • • •

Sync puse generators special effects generators test equipment video routing switcher and audio monitors Besides a master, in the master control room the composite video signal is raised to about one volt P-P level before feeding it to the level that connects the control room to the transmitter. Though the transmitter is located close to the studios, often in the same building, matching networks are provided at both ends of the connecting cable to avoid unnecessary attenuation and frequency distortion. This is nerve centre for a television station. Authorities in this area include: 1. Distribution of stabilized power supply to different areas with protection devices. 2. Synchronous pulse generation and distribution. Distribution of source to various destinations. 3. Video processing and routing. 4 Electronics for camera chain, 5. video switchers 6 .special effect generator and test signal and pattern generator. Monitoring facilities. 7. Patch panel for video and audio lines. Electronics for micro wave links.

Control Apparatus Room consists of sync pulse generator, logo generator, electronic control of PCR and other controlling instruments. Sync pulse generator act as a heart of studio and its description is given as below: Sync Pulse Generator : SPG Without the Sync Pulse Generator the picture is not stable. The sync pulse generator used in doordarshan Kendra is controlled by two groups of four push button switches. The right hand group controls the generator operating mode, and are interlocked, care should be taken not to operate more than one switch at a time. The four operating modes are as follows crystals. This is a free running mode of operation in which the generator output are under control of master sub carrier oscillator (MSO). Gen lock: This is the Hard Genlock mode of operation,which is designed to work with stable video sources. VTR lock: This mode of operation is similar to the generator lock mode, but is designed to operate with unstable signals such as those obtained from a helical scan VTR. Remote: With remote selected, operation of the front panel switches is disabled and is assigned to the remote control unit.

Advance: This is non-locking switch, operating only in the crystal mode, which subtracts one line per field of the internally generated pulses to perform the field phasing operation. Retard: This non-locking switch adds one line per field for field phasing operation. Crash lock enables: This is a locking switch which enables the manual crash lock mode. Crash lock resets the internal field counter in order to synchronise to the incoming video signal. Crash lock: This is the momentary push switch, which perform the field reset operation, when enabled by the crash lock enable switch. Pulse generation ► Mixed blanking, line drive and field drive are generated. ► Mixed sync are generated. ► Burst gate timing is generated. ► PAL square wave is generated ► PAL ident wave is generated. ► 8 field, field1 ident is generated. * Auxiliary reference voltage: the auxiliary reference voltage is generated by the circuit.

# Pattern generation (video): Horizontal component: The horizontal component is generated at 15 line interval in each field. The provision is made to position the horizontal component anywhere within the 15line grid. Vertical component: The vertical component are adjusted at 2.25 it all interval to give 23 interval. Video generation: The horizontal and vertical components are combined. Colour Bar Generation: RGB Generation: The colour bar outputs are generated using standard encoding techniques from R, G and B signals.

Luminance, Sync and 1 Flag generation: The luminance component is generated by resistively adding the R,G and B components in the appropriate proportion. The luminance and sync components are then resistively summed. The Field 1 Flag is added to the sync waveform before filtering. Sub carrier Phase-Shifting: Sub carriers is fed to the edge connector. A phase shift network allows adjustment of the processed sub carrier to be varied by >360◦ Sub carrier Quadrature signal generation Colour difference signal generation and modulation. Block and burst outputs: Sub carrier processing: the sub carrier feed for block and burst generation is passed through a phase shifting network identical to that used for the color bar output. Burst generation: The logic burst gate is processed.

Camera control unit: The TV camera which includes camera head with its optical focusing lens. pan and tilt head, video. Single pre- amplifier view finder and other associated electronic circuiting and mounted on cameras trolley and operate inside the studio. he output of camera of cameras in preamplifier in the head and then connected to the camera control unit through long multi-core cable. In this room shot can be decided to which camera can be taken. Camera position can also be control in this room. CCU can control three colour RGR= .10+.59+.11=100% In CCU monitoring sources, monitoring facilities and pulse disribution amplifies are available. Vectroscope provides on overview of control and connection function. Monitor can detect any fault in the camera. The studio has three cameras. The camera control unit (CCU) consists of the control of these three cameras. The camera system is designed for use in the studio and on location, providing top picture quality in any shooting conditions. The color camera chain comprises the following basic assembly: • color camera • Camera control unit

• • •

Connection unit Multiwire cable Camera view finder The color camera chain meets the ultimate requirement in the field of studio. It features easy handling, operational safety and good serviceability. It can be operated either with multiwire or with coax/triax camera cable. The color camera head, the camera control unit and remote control unit associated with the setup control console or remote control console are each equipped with a microcomputer. The color camera uses a 3-tube RGB system with high grade beam splitter. It is equipped with 1-inch plumbicon pickup tubes with dioxide gun system, bias light and ABC facilities. Various high grade lenses of different brands are available for camera. The camera control unit is of compact design. The connection between camera head and camera control unit can be established either via a multiwire camera cable or via a coax/triax camera cable.

DIMMER ROOM Dimmer Room consists of light control system which give the various lightening effects in the studio. General Description Of Light Control System : The light control system designed for television studio comprises of i. A light control desk. ii. Electronic dimmer rack. iii. Power distribution and control panel. iv. Studio lights. v. Talk back system. * The function of Light Control Desk is to enable the operator to remotely select the studio lamps, that need to be turned on for a particular scene & also enable control of intensity of some of the lamp, required for color matching.

* Using Electronic Dimmer, the operator is able to control the intensity of lamp remotely. The intensity of a group of the lamps can be adjusted individually or in one of the two scenes. *The system has been designed for large number of the loads, distributed on 415V,3 phase, 50Hz, 4 wire mains. The phase distribution both on the rack as well as on the light control desk are marked with dots. This helps to distribute high loads on the three phase more or less equally. * Any individual intensity control fader can be connected by the means of 3 position lever switch to any one of the three control in each present. Scene A OFF Scene B * Two electronic dimmer are wired as one plug in module, each rated at 2.5 KW where as one dimmer is wired in one plug in module of 5.0 KW. * The dimmer rack is interconnected with light control desk by means of multi core 0.2 sqmrs. Flexible copper PVC unarmored control cable.

Talk Back System : It is a in house communication system. This type of system is very useful for TV, Studio,Theaters etc. this system is based on duplex communication system & has 4 stations – one master and three slaves. Special advantages og this :(1) Any one can talk to any one. (2) Master can talk to all stations at a time. (3) It can hand off loud speaking type. Power Distribution and Control System (panel is helpful in distribution of power to different racks). Light Control: The scene to be television must be well illuminated to produce a clear and noise free picture. The lighting should also give the depth, the correct contrast and artistic display of various shades without multiple shadows. The lighting arrangements in a TV studio have to be very elaborate. A large number of lights are used to meet the need of "key" "fell" and "back"

lights etc. Lights are classified as spot and soft lights. These are suspended from motorized hoists and telescopes. The up and down movement is remote controlled. The switching ON and OFF is lights at the required time and their dimming is controlled from the light control room using SCR dimmer controls. These remotely control various lights inside the studios.

V. T .R. (Video tape recording): It is the most complex piece of studio equipment with analog and digital processor servo system, micro-processor, memory, logic circuits and mechanical devices etc. V.T.R room is provided at each studio center. It houses at least two console type 'A video tape recorders' (V.T.R.) and a few broadcast standard video cassette recorder (V.C.R.).Here recording is done on playback format CAM. Quality of recorded programme is tested immediately after recording is completed so that if there is any technical or any other problem the same could be rectified and the final recording is of good quality. During the original transmission the programme tapes are played back from the V.T.R The audio and video labels can also be adjusted from here. The format of programme from mini D.V.C to J3 is transferred in the V.T.R room, DD news, OTR(off telecast recording) is also recorded for the use in original news programme. Specifications: Sony Video Cassette Recorders Operational Environment 1. operating temperature 5deg C to 40deg C. 2. Storage temperature -20deg C to 60 deg C. 3. Location to avoid : *areas whose BVW-70P will be exposed to direct sunlight or any other strong light. *dustry areas or areas where it is subject to vibration. *areas with strong electric or magnetic fields *areas near heat sources Technical Information: General Specifications Power requirements Power consumption Operating temperature

AC 90 to 265V, 48 to 68 Hz 240W 5deg C to 40deg C

Storage temperature Humidity Weight Dimensions Tape speed Record & playback time Fast forward/rewind time Video cassette

-20deg C to 60deg C Less than 80% 30 Kg. 427*237*520 mm/w/h/o 101.51 mm/s 100 minutes max. less than 180 seconds ½ inches, Betacam & Betacam SP cassette for Beta format

PCR(PRODUCTION CONTROL ROOM):A video and audio outputs are routed through a production control room. This is necessary for a smooth flow and effective control. of the programme material. This room is called the production Control Room' (PCR) It is manned by the programme director, his assistant a camera control unit engineer a video mixer expert a sound engineer and a lighting engineer. The programme directors with the help of this staff effects overall control of the programme whole it is telecast live or recorded on a VTR. The video and audio outputs from different studios and other sources are terminated on separate panels in the control room. One panel contains the camera control unit and video mixer. In front of this panel are located a number of monitors for editing and previewing a incoming and outgoing programmes. Similarly another panel houses microphone controls. This panel is under control of the sound engineer who is consultation with the programme director selects and controls a available sound output. . The producer and the programme assistant have in front of them a talk back control panel for giving instruction to the camera man, audio engineer and floor manager. The producer can also talk over the intercom system to the VTR. The lighting is controlled by V

switches and faders from a dimmerf (A aA u,J$ console which in also located in the control room. II

PCR includes following two sections: • Vision mixer • Audio distribution amplifier-ADA MIKE-1 MIKE-2 MIKE-3

MATRIX

TAG

PATCH

AUDIO

BLOCK

PANEL

AMPLIFIE R

Audio Distribution Amplifier Mon. O/P Studio

AUDIO CONSOLE UNIT

VTR

VISION MIXER: It is used for mixing video signals, which are received from two sources like either from two cameras or from signals from Delhi. The cameras are located in studio at different positions. The control panel has following control switches: CAM1, CAM2, CAM3, VTR1, VTR2, CG, BAR CAM1, CAM2 and CAM3 are present in the studio room and their control is in the camera control unit. The three cameras are present at different positions and covering different portions of the scene. VTRs are Video Tape Recorder present in the VTR room. CG means character generator.

AUDIO DISTRIBUTION AMPLIFIER: Audio Distribution Amplifier, model ADA-6 acts as a professional grade isolation amplifier meant for the distribution of audio signal in broadcasting station. This amplifier can feed signals effectively to long lines without passing interference between the lines. All the outputs of this amplifier are coupled through dedicated output matching transformers. Using four selecting combination of integrated circuits and discrete devices achieve excellent frequency response and low distortion. Large individually adjustable channel gain control enables installation and adjustment very easy. SALIENT FEATURES: ▪ All output transformers are isolated. ▪ Short-circuit protected. ▪ Excellent frequency response. ▪ Very low noise. ▪ Excellent isolation. ▪ Stabilized power supply. ▪ Wide dynamic range. ▪ Single PCB design. ▪ Fully solid state. ▪ Very low distortion. ADA-6 model means that amplifier has six outputs and only one input. PRODUCTION CONTROL AREA:Activities in this area: 1. Direction to the production crew by the producer of the program. 2. Timing a production/telecast 3. Editing of different source available at the production desk. 4. Monitoring of output OFF air signal. 5. Direction to the production crew by the producer of the program. 6. Timing a production/telecast. . 7. Editing of different source available at the production desk. 8. Monitoring of output OFF air signal.

VISION MIXING AND SWITCHING :Unlike films, television media allows switching between different sources simultaneously at the video switcher in the PCR operated by the vision mixer on the direction of program producer. The producer directs the cameramen for proper shots on various camera through intercom and the vision mixed (VM) switches shots from the selected camera/cameras with split second accuracy, in close cooperation with the producer. The shots can be switched from one video source to another video source, superimposed cross faded, faded in or faded out electronically with actual switching being done during the vertical interval between the picture frames. Though the video switching is done by the VM at the remote panel three electronics is located in CAR. The vision mixer provided for the following operational facilities for fundamentals editing of tv programme 1. Selection of any input source. 2. fading out of one source of video. 3. Superposition of two sources: Keyed caption when selected in line in superimposed on the background picture. This signal is passed through a tuned amplifier (32 to 42 MHZ) band to remove unwanted frequency components. The resultant signal is a clean, video modulated IF waveform at 38.9 MHz (Vision IF Carrier).

VDA

Ref.

Ref.

CAM 1.

CCU

VDA VTR

Ref.

Ref.

CAM 2.

CAM 3.

CCU

Ref.

CCU

VDA

PCR Switch-er

VDA

Ref.

VTR

Ref.

Ref.

VTR

Ref.

VIDEO MIXER & SWITCHER

Video chain:The block diagram on facing page connects 4 these section and it can be observed that the CAR in the nodal area. Now let us follow a CAM-I signal. CAM-I first goes to a camera electronics in CAR via a multi-core cable the signal then like any other source it goes to video switcher via patch panel and respective VDAs (Video Distribution Amplifier) and optional HS (Hum Supressor) video equalizer. Output from the switcher goes to stabilizing amplifier via (PP) and (VDAs) Output from the stab. Is further distributed to various destinations. It may be noted that the use of VDAs helps to monitor the video signal at different location and the use of PP is very helpful for emergency arrangements during breakdowns and trouble shooting. A separate monitoring bus is provided in CCU, LCU and) end control also has a remote for the other source is similarly to this and can be understood from the block diagram

ENG-CAMERA Eng means Electronic News Gathering. This camera is used for news coverage. It does not contain vacuum tube, rather contain charged couple device CCD. CCD is compact and small in size. This camera is portable and movable. The features of camera are as follows: □ The camera contain three CCD. □ The camera is battery operated and battery used is 12V,SA and chargeable. □ The camera can be operated by AC supply and for that AC adapter is used. □ The camera has audio monitor. □ The camera has video recorder which is also compact. The video tape is of 30 minutes. □ The camera make use of lens assembly for focusing purposes. □ The different types of mikes used are as follows: • Gun mike • Lapel mike • RF mike The gun mike has high gain. The lapel mike is used by news readers.

RF mikes are cordless mikes. The ENG-camera is better than the camera which makes use of vacuum tube.

Fundamentals of Satellite Communication A satellite communication system basically consists of a satelite in space and many earth stations on the ground which is linked with each other through the satellite. Base band signal Vedio & station through a terrestrial network and is modulated by an from the user is transmitted to earth Audio RF carrier at the earth station and16×16 transmitted to the satellite. The satellite receives the modulated RF carrier in its uplink frequency spectrum from the earth stations and retransmits them to the earth in the downlink frequency spectrum, which is different from the uplink frequency spectrum. D I The satellites therefore can be G thought of large repeater stations inI space T A L

Rofc (core) Analog Vedio & Audio Studio Rack

RXr.

Studio Rack

Rxr.

R O U T E R

Video Proces sor

Encod er Enc Encod ode er r

M U X

M O D

UP/ C

Analog Vedio & Audio

Video Proces sor

Speaker

From

Div ider

A to D Convertr

Protect - ion switch

Dist. Amp.

M UX .

optimode VU meter

Router

A to D convertr VU= Volume Unit Meter

10 w Amp.

D/A-1 Audio Processo r limiter

Audio delay & dist. unit

UP C

UP link Detector

M O D

HDA Detector

Analog Mon.

waveguides

Analog Mon.

From LNA

D/A-2

Audio delay & dist. unit

C-L Conve rtor

Digital mon

Digital mon Audio delay & dist. unit

IRD

L- Band Divider

IRD To RF IRD

NMS system With PC

SIMULCAST EARTH STATION

SIMULCAST EARTH STATION Simulcast Earth Station is intended to uplinkJT.V signals (digital Vidio & stereo audio) in digital format compliant to MPEG-2 standard.

Rofc (core) Analog Vedio & Audio Studio Rack

Video Proces sor

RXr.

Analog Vedio & Audio Studio Rack

Video Proces sor

Rxr.

Speaker From

A to D Convertr

VU meter

Router

A to D convertr VU= Volume Unit Meter

10 w Amp.

Vedio & Audio 16×16

D I G I T A L

R O U T E R

Dist. Amp.

Encod er

M U X

M O D Protect - ion switch

Encod er Enc ode r

M UX .

optimode D/A-1 Audio Processo r limiter

Audio delay & dist. unit

Div ider

UP/ C UP C

UP link Detector

M O D

HDA Detector

Analog Mon.

waveguides

Analog Mon.

From LNA

D/A-2

Audio delay & dist. unit

C-L Conve rtor

Digital mon

Digital mon Audio delay & dist. unit

IRD

L- Band Divider

IRD To RF IRD

NMS system With PC

The analog video & audio signals from studio are terminated on the connector plate placed at rear side of the studio rack. The anolog signal is converted into SDX & AES/EBU stream with the help of convertors. After conversion the signals are fed to the fiber optic transmitter through video & audio patch panels. The digital video signals is transmitted by the fiber optic and received by fiber optic receiver at the earth station. Same is the case with the audio signal. The video & audio signals are then fed to the 16* 16 audio/video routing switcher. This enables the operator to switch the program of any desired channel. Further the video is processed by video processor & routed to the respective encode in compression rack. The other of video processor is also routed back to the If-p of the 16* 16 audio /video switcher unit for online

monitoring purpose. Similarly audio is processed by audio processor. Audio distributor & routed to the respective encoder in compression rack. The either 8/p of audio distributor is also routed back to 16* 16 audio /video switcher for online monitoring purpose. Compression system comprises of SDI video/ ASI router, AES/EBU audio router, encoders, modulators, multiplexers, channels, controller, IF protection switch ethernet hub & network management system. The encoders are wired in 2+ 1 configuration. SDI video & audio router controls the i/p to encoders the encoder O/P is being given to the multiplexer (mux). ASI router controls the input to the modulators, mux & modulators are wired for redundancy operation. Encoder excepts SDI video &AES/EBU audio signals. The O/P of encoder is an ASI stream. This forms the input to the mux. & the o/p of the mux. will be given be modulator through ASI router. The modulated o/p at 70MHZ will be fed to upconvertor system which already exist in the station. The received signal from LNA unit is given to a C-L band convertor. The C-L band convertor output is given to the 4-way divider which is used to feed different IRDs . The IRD demodulates the L-band RF signal & decodes to recover the audio &video in analog format or in digital format (SDI+AES/EBU) The o/p of IRD is routed to the input of '16* 16 audio/video router for online monitoring purpose.

LNA Low Noise Amplifier Typical LNA has the low phase noise. C-Band receive signal from antenna is fed to the LNA, which provides a conversion gain of 60 db. A LNA has noise temperature of 441< & has excellent frequency stability & phase noise performance. It can be use in low data rate digital video analog audio& any data applications.

C-L Band Convertor:

Signal received from LNA is in C-Band (3.7-4.2 GHZ) in order to provide suitable input to IRD, the C-Band signal is converted to L-Band convertor unit. Output of this unit is given to power divider to feed to other IRD & to monitor received signal.

Terms used here: IRD- Integrated Receiver Decoder SDI - Serial Digital Interface AES- Audio Engineering Society EBU- European Broadcast Unit ASI - Analog Signal Interface

Technical Data: Digital Simulcast (2+1) Satellite Look angle Uplink frequency Down link frequency SIR FEC

INSAT-3A 93.5° East 6156.5 MHZ 3931.5 MHZ 6.25MSPS 3/4

Modulator: Modulator accepts 2ASI input from the mux. Data passes through DVD framer buffer & a scrambler. Further outer encoding & convolutional encoding is carried out on the data stream finally the data is QPSK modulated amplified to provide the required IF output. Alarm closure contacts are provided for monitoring. the modulator can be configured by its front panel control or through a PC running the control software the i/p of the modulator is given to dividers & divider output will be given to dividers & divider output will be given to existing up convertor.

The 70 MHZ signal will be upconverted to required level at 6 GHZ freq. band & 6GMZ signal will be given to HPA for further amplification. The HPA will be given to antenna system through wave guide for up linking to the station.

INTRODUCTION TRANSMITTER:- The function of a transmitter is to perform modulation process and to raise the power level of the modulated signal to be desired extent for effective radiation.The 1KW transmitter houses the solid state exciter, exciter input, output selector, transmitter control unit,

corrector divider unit 130W solid state vision amplifier gain. RF monitoring unit, the 1 KW vision cavity and its associated voltage and filament power supplies. The transformer and rectifier assembly for generating the high voltage for the value is located external to the transmitter rack. The blower required to cool the value is positioned inside the rack itself. In addition the peak power measuring modules and the linear detector are also mounted in this rack. Signal is received from Delhi through satellite. After that Audio and Video signal are then separated out and demodulated and both signals are checked. After that the audio and video signal are again modulated. Audio is frequency modulated and Video is amplitude modulated. After that video and audio signals are combined and then transmitted by transmitter.

Reciever

Combiner

Separator (Audio + Video)

Modulato r

Demodula tor

Audio and video is checked

Transmitt er

TECHNICAL DATA OF TRANSMITTER VISUAL OUTPUT Type of emission------------------- C3F Output power ------------------------ 1 K W + 0.5 dB Different gain------------------------ 10% (P- P)max Video input impedence------------- 75 ohm Frequency Range------------------- 174.1MHZ to 230 MHZ

AURAL OUTPUT Type of emission ------------------ F3 RF output -----------------------------50 W Impedence audio input--------------600 Ohm + 40 ohm Frequency Response-----------------with in + dB (30 Hz to 15 KHz) ELECTRICAL DATA Input voltage---------------------------415 V + 10% 3 Phase Input Power-----------------------------7KV A (max) Ambient Temp. ------------------------ 0 C to + 45 C I

BASIC SOUND AND PICTURE STANDARDS ADOPTED BY INDIA. The picture and sound signal standards are specified by the International Radio Consultative Committee (C.C.I.R.) : 1. No. of lines per picture (frame) 2. Field Frequency 3. Interlaced Ratio

=625 =50Hz =2:1

4. 5. 6. 7.

Picture (Frame) Frequency Line Frequency Aspect Ratio Scanning Sequence

8. Channel Bandwidth 9. Sound Carrier Relative to Vision Carrier 10. Picture IF Frequency 11. Sound IF Frequency = 12. Type of Sound Modulation 13. Type of Vision Modulation

=25Hz =15625Hz =4:3 (i) Line : left to right (ii) Field : top to bottom =7MHz =5.5MHz =38.9MHz 33.4MHz =F.M =A.M (negative)

STANDARDS FOR CHANNELS DD-1 & DD-news Diameter ofDD1 dish antenna

=6.3m

Diameter of DD news dish antenna

=7.5m

Uplink Frequency

=6GHz

Downlink Frequency

=3.7GHz-4.2GHz(C-Band)

DD 1 Channel Frequency

=195-202MHz(8th Channel)

Visual Frequency of DD 1

=195.25MHz

Aural Frequency of DD 1

=201.75MHz

DD news Channel Frequency

=216-223MHz(11th Channel)

Visual Frequency of DD news

=216.25MHz

Aural Frequency of DD news

= 222.75MHz

THE PRINCIPAL FEATURES OF THE 1 KW TV TRANSMITTER. The transmitter is compact in construction and the design employs state of the art techniques and devices. The principle features of the I KW TV transmitter are explained in the following paragraphs. Solid State Exciter (with standby): The exciter is completely solid state ensuring case of servicing and reliability. A passive standby is provided, which can be selected through the keyboard of the transmitter control unit. IF Modulation:

The video signal is amplitude modulated on the vision intermediate frequency (It) of 28.9 MHz using diode balanced modulation system. The modulating level is kept low. This ensures low non-linear distortion and excellent colour characteristics. Low differential gain and phase are obtained. SAW VSBF (Surface Acoustic Wave Vestigial Side Band Filter) : Surface acoustic wave filter is used for vestigial side band shaping. The VSB SA W filter using inter digital transducer is characterized by flat group delay and response characteristics in the pass band with required attenuation outside the limits of the designated channel and a defined side band response. Thus, it eliminates the use of the all pass networks for group delay correction, which were used with conventional LC filters. Low Pass Filter: The low pass filter is included to limit the incoming video signal of 5 MHz. The LPF incorporates an active Delay Equalizer to correct the group delay introduced by LPF. Delay Equalizer: A receiver pre-corrector and a transmitter delay equalizer are used. The receiver precorrector pre-distorts the signal providing compensation of group delay which will occur in the domestic receiver. The transmitter delay equalizer enables the correction of group delay occurring in transmitter chain due the output band-pas filter. Both employ active circuits ensuring unity gain in the vision chain. Linearity Corrector: The inter modulation distortions introduced in the solid state vision power amplifiers are corrected by the VHF linearity corrector which is provide at the output of the Exciter. Varactor Modulation: The aural modulator employs varactor for frequency modulation of sound at the IF. The sound IF is maintained constant at 5.5 MHz below the vision of38.9 MHz by a phase lock loop.

GENERAL TECHNICAL DESCRIPTION 1. The 1 KW Transmitter comprises of a 130 w solid state exciter/amplifier which drives the valve-stage using BLLcx tube to obtain 1 KW (Sync peak) output. 2. The vision & Aural drives of the required channel frequency is derived from a solid state exciter. 3. The Tx. has a built in standby exciter in passive standby mode. The main exciter or the standby exciter can be brought into the line up by keyboard selection on the control panel. 4. The Tx. control system for safety interlocks overload protection and the switching on sequence and blower cooling off delays are carried out through microprocessor based control and monitoring circuits.

lKW TV Transmitter: The 1 KW TV Transmitter houses the solid state exciter, the standby

Exciter, input output selector, transmitter control unit, corrector/divider unit, 130 w solid state vision amplifier chain, the power supply for 130w amplifier chain, RF monitoring unit, the 1 KW vision cavity and its associated voltage and filament power supplies. The transformer and rectifier assembly for generating the high voltage plate power supply for the valve is located external to the transmitter rack. The blower required to cool the valve is positioned inside the rack itself. In addition, the peak power measuring modules and the linear detector are also mounted in this rack. Solid state exciter with standby actually comprises of the following plug in modules. : a) DP/DG Corrector b) Low Pass Filter c) Delay Equalizer d) Visual Modulator e) IF Oscillator f) Local Oscillator g) Combiner/Corrector h) VSBF & Mixer i) Aural Modulator j) Power Supply

240v

Video in 1v CCVS 75 ohms

+12v -12v

DPDG corrector

+12v -12v +16v

1v(P-P) LPF 75Ω

1v(P-P) 75Ω

+16v

+12v -12v +16v

Delay Equaliz er

+16v

+4dB sync Combiner/ pulse Corrector 50Ω

1v Visual (P-P) Modulator 75Ω

+10dBm +16V FIF 50 Ω 38.9MHz FIF Aural IF 38.9M Modulator Oscillator

Faif 33.4MHz 50Ω (-90dBm) VSBF/ Mixer

50Ω -5dBm

FIF 38.9MHz -10dBm 50Ω

Power Supply Unit

+16v(2.5A)

+12V + 16v

Local oscillator

Fvif,Faif

FV (+6dBm) sync pulse 50Ω

FA (-7dBm)

Audio in 600Ω+10dBm

50Ω +16v

Monitoring

AGC Vol (DC)

230 V AC in

+12v(1A)

-12v(500mA) 4-PIN +16v Hybrid Adjustable Regulator +12v,-12v → 3 pin Regulator

FLO = (Fv +38.9) MHz 50Ω + 5dBm

EXCITER LINE-UP

a) DP/DG Corrector: This unit is used for pre-correcting the differential gain of the final output of the transmitter. The pre-correction is achieved by introducing nonlinearity introduced in opposite tot hat of non-linearity existing in the demodulated video from the 1 Kilo watt output stays. b) Low Pass Filter: The Low Pass filter unit cuts off the video frequencies beyond 5 MHz so that video information beyond 5 MHz does not interfere with the sound signal which will be appearing as frequency modulated signal at 5.5 MHz and around in the RF spectrum. The resultant group delay is corrected in a delay equalizer circuit in this unit to preserve video characteristics. c) Delay Equalizer: This unit comprises of two sections namely the receiver pre-corrector and transmitter delay corrector section. The former, the later or both or none can be brought into the line up by selection on the front panel. The receiver pre-corrector required for achieving a god video wave form at the domestic receivers where in delays are introduced by use of nyquist filter in the demodulation stage for compensating for the vestigial side band characteristics of the t4ransmitted RG spectrum. "If receivers use linear SAW filter for achieving nyquist characteristics, then receiver pre-correction at the transmitter end is not required. The Tx. delay equalizer section is used for correcting the group, delay arising out of band shaping and the usage of the band pass filter at the output of the lKW stage. d) Visual Modulator: This unit provides the vision modulated IF signal at the intermediate

frequency of 38.9 MHz. The IF carrier is taken from the IF oscillator unit and the video signal from the delay equalizer output. The video signal is clamped to its pedestal level to stabilize the black level of the modulated IF signal and also to remove the hum present in the video waveform. The signal is first separated from the video signal, passed through pulse shaping circuits and then a clamping pulse is generated which will clamp the video signal at the back porch. The clamped video signal and the IF signal amplified in a two stage tuned amplifier, are fed to a ring modulator to achieve the modulated IF signal. This signal is passed through a tuned amplifier (32 to 42 MHz) band to remove unwanted Frequency components. The resultant signal is a clean, video modulated IF waveform at 38.9 MHz (vision IF carrier). e) IF Oscillator: This unit generates using a crystal oscillator the visual I frequency of 38.9 MHz. Four outputs are available in this unit of these four outputs are the first one goes to the Visual Modulator Unit., second one is used for monitoring third one is taken to the Local Oscillator and the fourth one to the Aural Modulator Unit.

f) Local Oscillator Unit: This unit generates the visual oscillator frequency (fc + 38.9 MHz) of the required channel. The basic oscillator is crystal oscillator at fc/4 frequency. The crystal is housed in a proportionately controlled over to maintain frequency stability. The fc/4 oscillator output is harmonic. the collector tuning gives the required channel vision carrier frequency (fc). This is passed through a combination of high pass filter and low pass filter to eliminate the unwanted components. the resultant signal is a clean channel frequency signal. this is fed to mixer. The mixer receives the IF oscillator signal also. The output of the mixer contains different components. The required frequency is (fc+ flF). The mixer output is passed through a combination of LPF and HPF to remove unwanted spurious components. This signal amplified and fed to a 4-way power divider. Out of these four outputs one is fed to VSBF and Mixer. The second one is terminated in 50 ohm resistor internally. g) Combiner/Corrector: The combiner/corrector receives signals from the visual modulator and the aural modulator unit. These two signals are combined to vet a composite output in the combiner output in the combiner section of the unit. The composite signals is next few to the corrector section of the unit.

The corrector is used for correcting the non-linearity introduced in the value state of the transmitter. h) VSBF & Mixer Unit: This nit mixes the modulated vision and aural signal at IF and local oscillator signal to derive the modulated RF signal at the required channel frequency. The input to this unit from the combiner/corrector is amplifier and fed to a SAW filter for VSBF. The SAW filter output is amplified and passed through a hybrid circuit containing PIN attenuator for level control. This again is fed to the balanced mixture. The Mixture output is passed through a helical filter (Band Pass) to eliminate the unwanted components. hten this signals amplified to get+6dbm sync peak output. This unit has front panel MGC/ AGC selection. i) Aural Modulator Unit: This unit consists of mainly the following stages: a) Audio Amplifier b) VCO c) Mixer d) Automatic Phase Control (APC) The audio amplifier receives an audio signal at a level of + 10dBm balanced input from the studio. The signal is passed through a balance to unbalance transformer and than to rotary radar for audio input amplifier which has the 50 micro second pre emphasis circuits. The output of the audio amplifier is applied to a VCO for frequency modulating. The VCO is a varactor tuned oscillator. The IF oscillator frequency at 38.9 MHz is also fed to this unit which is mixed with the VCO signal working at 33.4 MHz to derive a 5.5 MHz signal. This is divided get a square pulse at 537 Hz which is fed to the APC is a simple and hold circuit. A 1.1 MHz TCXO is used as reference which to the APC as reference. The de error signal from APC is used for correcting the VCO frequency locking at to a frequency 5.5 MHz below the vision IF frequency. Using an output variable attenuator, the frequency modulated aural IF signal level is set at 0dbm. j) Power Supply Units: This unit generates + 16V (2.5 A), + 12 V (lA),-I2 V (500A). The AC voltage at 240 single- phase is fed to the power transformer. The Secondary has 3 winding to feed the 3 full wave rectifiers. The + 16 V regulator is a 4- pin hybrid adjustable regulator. The +I2V and -I2V regulator are 3 pin regulators. Each output is provided with a over voltage protector. The front panel LEDs indicates the status of these 3 power supplies.

130w amplifier chain consist of a two-way combiner unit, 2 numbers of 80 w power amplifier units, one 10w units, dual driver unit, a vision monitoring unit and a linearity corrector and power divider unit. He 80 w units, dual driver and the vision monitoring unit are housed in a shelf and the linearity corrector and divider is a separate unit mounted on the rack. The output at approximately +2dbrn from the exciter is fed to the corrector/divider unit +6dbm signal from exciter after passing the 2 way divider into exciter input/output selector will be at a level +2dbm taking into account other insertion losses.

-6dBm

+49dBm SP,50Ω

RF in +2dBm +51.2dBm

50Ω Sync 130w Pulse 50Ω

VHF Linearity corrector

+51.7dBm,SP

80W power Amp.-1

Driver Amplifier1 50Ω(SP)

Power Combiner

Divider

(80W)

50Ω(148W) RF output

0dBm

(SP)

50Ω

-6dBm 50Ω(SP)

Driver Amplifier2

+37dBm 50Ω

80W power Amp.-2

+49 dBm (SP) 50Ω

Circulator 50Ω/150w

5W

SOLID STATE POWER AMPLIFIER

Corrector/Divider Unit: This unit comprises of 2 sections namely the linearity corrector unit and the 2 way hybrid divider. The output of the exciter is fed to the linearity corrector PCB the - input is split into 2 paths. One signal is fed to a liner amplifier and the other is passed though a non-linear section. These two are combined to produce the non-linearity required to compensate for the nonlinearity that will occur in the solid state power amplifier stages. It should be remembered

that this pre-corrector circuit is level sensitive and to the extent possible the level of +2dbm sync. Peak to be maintains at the input to the corrector unit to enable proper per-correction of linearity. The pre-corrected RF signal is fed to be 2-way hybrid divider gives 2 output which are at 90 degree phase difference and at an amplitude level of dbm down compared to the input level. Each divided path has a variable attenuator which serves as level control for the corresponding solid state power amplifier input. Dual driver Unit: This unit houses 2 independent chain of amplifiers capable of delivering 10 w output mounted on a single heat sink. Each amplifier is made to one state 4 W amplifier which si turn drives the 10W output state. The 4W state uses VTVO 75 transistor and 10W stages used VTV 150 transistor. Each output is passed through directional coupler to enables monitoring of RF signals. The amplifiers work in class A configuration. Each 10W line up consumes approximately 3 amps t + 28 V dc supply. 80 W amplifier Unit: This unit is driven by the output of dual driver. The 80 W amplifiers is made of 2 Numbers of 40 W amplifiers working in class A configuration and mounted on a single heat sink. The output of the dual driver which is fed into this unif in a 2 ways 90 degree hybrid divider. These 2 outputs fed the corresponding 40 w amplifiers. The output of the 40W amplifiers are combined in a 2 ways 90 degree hybrid combiner. The resultant output at 80W power level is in phase with respect to the input. Similarly, the other 80W P A unit is fed from the second output of the dual driver unit the current consumption of each 80W unit is approximately 8A. The dual driver and the 80 W units operate form a + 28 W power supply. The power supply for the driver is interlocked through the 80W units of prevents pumping in RF power into 80 W units without switching on the power supply to 80W units. 2 Way Combine Unit: The 2 ways combiner unit comprises of a 2 ways 90 degree hybrid combiner a dummy load, a directional couplers on aural band pass filter an aural notch filter a front panel meter and peak power circuits. The output form the exciter has been split into 2 paths with a 90 degree phase. Shift in the corrector/Divider unit and these are fed to 2 chain of amplifiers (10W and 80W) Hence the outputs of the two 80W units are 90 degree out of phase. The hybrid combiner in the 2 ways combiner unit combiners the 80 w units output to give round 130W

vision RW output. This signal is passed through a directional coupler to get a sample' RF signal for monitoring purpose. +25V

+26V 350Ma

-3dBm,50Ω RF in

R2

-10dBm 50Ω

CA 2870

Vtv

+22dBm

+32dBm

Vtv 150

50Ω

Hybrid Amplifier G=(32 db)

R 3

2A

675 50Ω

R 1

26.5V 1A

+40dBm RF out 50Ω

(G=10db)

(G=8db)

DRIVER AMPLIFIER 7db

pad

+28V 2×2A +36.7dBm RF in 50Ω 4.7W

SP

POWER 1n 0deg

+33.4dBm,50Ω 2.2W SP

-9odeg ISO SPLITTER

+33.4dBm,50Ω 2.2w SP

TPv 3100

TPv 3100

50Ω

+46.4dBm(SP),50Ω 43.7W G=13db

Power -90deg ISO

43.7w,50Ω+46.4dBm

0deg 1n COMBINER

G=13dB

50Ω

+49dBm SP RF out 50Ω (80W)

80W POWER AMPLIFIER

+28V Power Supply Unit The power supply unit for the vision solid state amplifier chain comprises of 2 independent section of switch mode power supply capable of supplying 17 A at 60C. The output voltage is +28 V. One section feeds the first 80 w chain and the other section the second 80 W chain. Each section of the PSU can be remotely switched ON+OFF using TTL logic level.

Txr.

The 10 KW TCD has two independent control systems, namely 1. Main control system (MCS) 2. Backup control system (BCS) The BCS has a limited capability & is provided to control the transmitter in the event of the failure of MCS. The MCS consists of mother board (MB) with 7 plugs in cards, transformers T1 & T2. The seven boards are as : 1. CPU Board 2. BIT I/O Board 3. I/O Board 4. Control interface Board (CIB) 5. Analog Receiver Board (ANRX) 6. Rectifier & Regulator Board Main control system (RRBMC) 7. Interlock interface Board (IIB).

6v to 6.2v Filament Supply

130w vision Sync peak 50Ω And 7w Aural

-50v to-70v grid supply

1Kw PA BEL 4000X

1⅝” Rigid Line 1.1Kw –vision (sync peak) 50Ω &55w Aural

CHANNEL BAND PASS

FILTER

1⅝” Rigid Line 1kW sync Peak 50Ω &50w –Aural

To antenna dummy load through v-link panel

Screen supply (700v to 750v)

H-T Plate supply (3kv to 3.4kv)

CAVITY POWER AMPLIFIER &OUTPUT FILTER

MCS: The digital I/P from the trx. 31I/P are fed to the TCU (transmitter control unit). These I/P are fed to the CPU & BIT I/O Board after isolating in the interlock interface board (IIB). This board has the optocouplers for isolating the I/P. The O/P of the IIB is fed to the I/O ports in CPU & Bit I/O Board. The TCU O/P control the contactors namely MS 1, MS2 & MS3. There are 8 TTL control output which controls the power supplies of the 130 solid state PA amplifier modules. In accordance with the program fused in the EPROM (residing in CPU Board) The TCU reads the digital I/P & control the output. The TCU O/P is connected to the I/O selector for exciter main or standby selection. The OIPs are also connected to the RF monitoring units to select one of the 7 RF monitoring OIP from PB' s. For controlling alP, I/O ports in BIT i/O Boards are fed to the CIB. This board has optocouplers for isolating the O/P & also has the interface circuit, to control contactors. For RF selection the I/O Ports alPs are fed to the 4:16 decoder in the CIB. The decoder OIP goes through a interface circuit & is connected to the coaxial switches in the RF monitoring unit. BCS: BCS consist of BCS board RRBBCS (Rectifier & Regular Board BCS ) & transformer T3. The BCS Boards has a single chip processor 8751 & opt& coupler for isolating I/P & O/P of the processor. The RRBBCS generates the power supply (+ 24V). The interlock & relay power supply generated in MCS & BCS are selected in the relay board & taken out of the TCU. This is done in order to have a totally independent BCS. The BCS is provided here in order to continue transmission in the event of failure to MCS, BCS performs limited functions of Txr. interlock & control. The part of keyboard is used to input command to BCS.

'Power Supply' There are four types of power supply which are .used in transmitter section. These are as follows:

i) Filament Supply ii) Bias supply iii) Plate Voltage Supply iv) Screen Grid Voltage Supply i) Fillament Supply:This supply for 1 KW PA (BEL 4000 Ix) is derived from a three phase full wave rectifier using silicon rectifier. The rectifier is followed by a single section LC filter for the reduction of ripples. The filament transformer is of the leakage type so as to limit the starting current drawn by the valve filament under initial switching condition. The transformer is provided with tapes to adjust the filament voltage precisely to the rated value. ii) Bias Power Supply: This supply feeds the grid of 1 KW valve stage. It consist of 2 independent sections of Dc power supply with a common ac input. The first section can deliver on O/P adjustable voltage between-50V to -80V dc, while the second section can deliver in O/P adjustable voltage between-80V to -120V dC each section has the capacity to supply current of 200 mA and operates at an ac input voltage 200 V single phase supply. During normal operation the first section only is used. The second section is used as stand by in event of failure of the first section. iii) Screen Grid Power Supply: This provides a regulated output at 1000V dc. A constant voltage transformer (CVT) Tl feeds a constant ac voltage through the magnetic amplifier. The O/P voltage V can be adjusted by changing the taps of the CVT. The screen voltages set between 700 V toI 750 V & the screen D dissipation is E limited to 100 W. O

. Line#1 from studio

Line#2 From

HS≠1

Vedio equalizer dd#2

VDA

VDA 2A 2B

250 1

HS#2

Console monitoring

251 2

252

253

VDA 1A

1n 1 11 12

IN2

S W I T C H E R U N I T

267

268

C S A

272 ↓

273

Studio

252 ↓

3

4

258

259

console monitoring NDS IRD 263

Vedio equalizer DD≠1

255

254 352

studio line#1

VDA

270 1.2

271 sk11

265

1B

261 console monitoring

287

264

IRD 283

Studio line#2 Console monitoring

274 275 CCVS IN12

In 11 276

Pattern

1

Generat-or

3

console monitoring

277

3k 12

I/P CHAIN TO 1KW BEL 4OOOX TXR

iv) HT 1 Power Supply: The plate supply for 1KQW PA (BEL 4000 x) is derived from this power supply. The HT Power supply is housed in a separate rack & is located outside the Txr. racks. + 28V SMPS : The +28V SMPS unit consists of two separate 28V modules. Each module feeds one 80W power amplifier & the corresponding dual driver section. Remote sensing & TTL ON/OFF facilities for each module are provided. 4 Fan Unit: This unit consists of 4 blowers used for cooling the solid state power amplifier. The cool air is sucked from the unit & blown vertically upward through the power amplifier heat sinks. The ac supply for all blowers are paralleled & fed through a power connector at the rear end of the unit. AGC Ckt : AGC ckt. is used for providing automatic gain control for the vision power of Txr. RF sample is fed to this unit. The DC O/P from AGC ckt. is

fed in parallel to the two VSBF (Vestigial Side Band Filter) & mixer units of solid state exciter, Both (Main & standby). This AGC voltage is intern fed to the voltage controlled alternator located internal to the VSBF & mixer of the exciter. Monitoring: The RF monitoring unit is used for the RF samples from different stage of the Txr. by the keyboard selection. A linear detector is used to broadly monitor the video from the RF sample fed to it.