An

Industrial Tour Report on Industrial visit

At

All India Radio Jodhpur

Submitted In partial fulfillment For the award of the Degree of

Bachelor of Technology In Department of Electronics and Communication Engineering

Submitted To: Submitted By:

R. K. Sharma Parikshit Kuldiya(Deputy Director, Engineering) (11ejiec739)

JODHPUR INSTITUTE OF ENGINEERING AND TECHNOLOGY

MOGRA N.H. 65, PALI ROAD,

JODHPUR-342001

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Preface

Practical training is an important constituent of any curriculum and the B.Tech course is no exception to this general rule. Practical training helps a Student in getting acquainted with the manner in which knowledge is being practically used outside his institute and this normally different from what he has learnt from books. Hence, when he switches from the process of learning to that of implementing his knowledge, he finds an abstract change. This is exactly why practical training session during the curriculum becomes all the more important. This report describes in detail my training after third year of engineering session which I have completed atALL INDIA RADIO JODHPUR. The training was in the form of practical study. The training was in the form of practical study. The report gives an introduction of AlR and its different section this complete chain is divided in different segment for clear understanding.

SCOPE OF TRAINING

The main aim of training is to put over practical knowledge into use. This training puts us in the actual field and to overcome practical situations faced in real life and to interact with people keeping our calm and patience in case of difficulties. This practical training will be very useful for further respects and offer a very useful for calm and patience in case of difficulties

This practical training provides us introductory knowledge about Radio communication. This training will be very useful for further aspects and offer a very bright scope in field of communication (especially RADIO broadcasting) and satellite communication.

Therefore the knowledge gained in the training will be very helpful while applying in various communication fields.

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Introduction

ALL India RADIO is a premier institute in the field of broadcasting and communication. It is a branch of PRASAR BHARTI CORPORATION OF India which broadcasts educative, informative and entertaining programs throughout the country by its wide network of AIR and DOORDARSHAN" the country's first broadcasting station was established on July 23, !927,Mumbai. AIR had a network of six stations and a complement of 1B transmitters covering to area of country. Today AIR has a network of 208 broadcasting centers with 150 MW transmitter, L28 FM transmitters and 4BHF (SW) transmitters

AIR JODHPUR is a major center in field of rural, cultural, informative programs, at poata c road is broadcasting two channels:

1. Primary channel2. FM carrying Vividh Bharti Commercial broadcast service.

It is having two separate transmitters for both channels. AIR JODHPUR was established on August 15, l-965. The first transmitters were 1KW medium wave transmitter which aired only Vividh Bharti. The studio set up was inaugurated by SHRI H.K.L.Bhagat. The FM transmitter was inaugurated by SHRI Pramod Mahajan on B July 1999. The new medium wave (3O0KW)Transmitter was commissioned on April, 2002.

Since then this institution is working efficiency to play the role of a national broadcaster utilizing all its available resources. It is being supported by a sufficient number of programs and it also has an efficient technical staff to maintain the whole setup and production work.

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COMPANY PROFILE

AIR one of the largest radio networks in the world. The head quarter is at the AKASHWANI BHAWAN, NEWDELHI. Akashwani bhawan house the drama section and the national service.

The broadcasting in India with the formation of private service in Chennai in 1924.in year of 1936 government of India controls the radio broadcasting in India on 1957 AIR was renamed as Akashwani. There are five regional headquarters for AlR. In north zone New Delhi, the east zone in Guwahati, the west zone in Mumbai and the south zone in Chennai. The commercial radio service in India was started in the year 1967 by vividh bharti with its headquarters at Mumbai.

Radio Broadcasting

AIR broadcasting international, regional and local channels in all genres (music, current affairs, and news, general entertainment etc.), AIR has network of 229 broadcasting center with 148 MW frequency 54 high frequency (SW) and 168 FM transmitters.

A national service planned, developed and operated by the prasar bharti broadcasting started in India in 1927 with the proliferation of private radio clubs. The operation of air begins formally in l956 as a government organization with clear objective to inform educates andEntertains the masses the first radio programmed in India was broad cast by radio club ofMumbai in June 1923.

Radio frequency spectrum

In radio communication system, carriers of wide range of frequency are used for different types of services, ln fact, sometime, communications system also categorized in terms of frequency of carrier. Radio frequency spectrum may be defined as a portion of electromagnetic spectrum which is used for electronic communication.

Radio frequency spectrum

S.NO. Frequency range Destination Abbreviation1 30-300Hz Extremely low

frequencyElf

2 300-3000 Hz Voice freq. Vf3 3-30 kHz Very low freq. Vlf4 30-300kHz Low freq. Lf5 300-3000kHz Medium freq. Mf6 3-30 MHz High freq. Hf7 30-300 MHz Very high freq. Vhf8 300-3000 MHz Ultra high freq. Uhf9 3-30 GHz Super high freq. Shf10 30-300 GHz Extra high freq. Ehf

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During last few years, an increasingly bigger portion of the electromagnetic spectrum has been used for transmitting from one place to other place. This due to fact that, in electronic communication system, message signal into high frequency carrier signal. According to information theory, the amount of information which can be transmitted is directly related to the frequency range of carrier signal.

Communication

Communication is the process of establishing connection or link between two points for information exchange. In communication system to communicate with audio frequency waveAudio frequencies are modulate with higher frequencies wave. These wave travel long distance with help of transmitter.

Satellite Communication

Earth station create info signal (such as drama, music, etc.) and it’s retransmitted by parabolic antenna to satellite studio receive the signal by parabolic antenna.

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Some specification of satellite communication-

Gain of satellite uplink channel 67db

Gain of satellite downlink channel 70db

Gain of uplink antenna 47db

Receiving antenna gain 41db

Uplink of loss -200db

Download link path loss -193db

Up link frequency 6 to 7 GHz

Down link frequency 2 to 4, 5 GHz

Distance of satellite from earth station 36000km

Transponder gain 100db

For transmit and receive signal from parabolic antenna, two angle two be set called elevation and azimuthal angle.

ELEVATTO N (ZEINTH)

Elevation refers to the angle between the dish pointing direction, directly towards the satellite, and the local horizontal plane. It is the up-clown angle.

AZIMUTH

Azimuth refers to the rotation of the whole antenna around a vertical axis, it is the side to size angle. Typically you loosen the main mount bracket. And swing the whole dish all the way around in a 360 degree circle.

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We can calculate azimuth angle and elevation angle by these parameters

Az = 180` + [tan-1(cos D / tan ψ)

EI = [tan-1 (cos ψ .cos D -r/R)/(I –cos ψ .cos D)

Where:-R = synchronized orbit radiusr = earth radiusD = αa-αb

Studio receive signal by satellite and signal is regenerated in studio and then it's send it to transmitter by a microwave link.

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STUDIO

There are following studio in AIR JODHPUR: --_

1. DRAMA STUDIO: Recording of Drama, discussion, chat, phone in Program.

2 TALK STUDIO: For live program like talk and rural programs.

3. MUSIC STUDIO: Recording of musical programs and concerts.

4. CBS: Purely dedicated to commercial broadcasting service of Vividh Bharti

5. PLAYBACK STUDIO: For announcing and playback of songs and records.

6. DUBBTNG STUDIO: dubbing and editing of tapes.

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The multifunction stereo audio console of up to 12 input modules, two output modules, one monitor and a power supply module. The input module can be configured from mono mic/line inputs with or without equalizer and stereo line inputs with or without remote selection.

1. POWER SUPPLY

The power supply has output of +48V, +24V, +-l-8V, and (excite). The DC voltage through the motherboard to power supply (excite). The various module of the console the 4BV is used for exciting.

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2. TALK BACK MODULE (two way communication)

A. The oscillators generated sine wave signals at 100H2, lKHz,l-0KHz at 0db, -70db levels. The frequency is selectable.

B. The announcer can invited a talk with any one of the eight stations AUX1. AUX 2 or studio by pressing the talk switch of the corresponding Section.

C. The return signals from eight stations is mixed and level controlled before sending to due monitor module for listening.

3. MONITOR MODULEThis module of console contains the H/W for selection and monitoring of different

signals on the console.

Signals can be modulated in two modes.

a) Mono mode

b) Stereo mode

The stereo PFL signals from different modules are mixed in this module. he left and right signals are summed to obtain a mono signals for a console monitoring amplifiers.

4. INPUT MODULE

Mono mic/line:-Line level signals from mono source and mic level signals from announcer/ studio Mics are feed to the mic/line modules.

Stereo High level: - (two types)One with other remote source selector and the other without ..; source selection. These both are identical but different is the logical circuits used in the remote source selector.

5. REMOTE SOURCE SELECTOR

This standalone unit is capable of routing any one of eight mono sources to the output depending on the selection logic sent from the source selector input module of the console.

6. CONSOLE METER PANELThere are indications for READY, ON AlR, SI-UDIO LIVE, and OSC ON<PHASE L RROR and POWER Supply.

7. OUTPUT MODULESignals on Master l and Master 2 buses routed from the input modules as left and right channels are mixed in the modules.

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TECHNICAL SPECI FICATION OF CO NSOLE

1. INPUT IMPEDENCEMicrophone: > 2K ohmLine :> 10K ohm

2. INPUT LEVELSMicrophone: -7O/-6A/-50/-40/-30d8(Selectable)Line: 20d B

3. INPUT HEAD ROON1Microphone: 20 ciBLine: 20d B

4. OUTPUT LEVELSOutput impedance : < 50OFrequency response: 40Hz +0.5dB

5. Cross TALKMaster: better then 75dBStereo: better then 60dB

6. NoiseSignal to noise ratio: better then -80dB

PHONE IN PROGRAIU CONSOLE

THIS CONSOLE IS GEENRALLY USED FOR THE PRODUCTION OF LISTENER INTERACTTVE RADTO/TV PROG RAM.

This is used to interface telephone line with the broadcast mixing console which is turn interfaces with the experts sitting in the studio.

This unit has provision for receiving 3 telephone line at a time. This system gives a new dimension and proves to be valuable medium to disseminate listener's information oriented live interactive program.

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SYSTEM FECILITIES

A. Interface with telephone lineB. Interface with telephone equipmentC. Optional facility for headset if requiredD. Optional facility for direct broadcast on air using headset/handset lf required.

FEATURES

1. Conversion with the remote participant in the live program.2. Feed responses from the expert in the studio to the listeners through telephone line.3. Facilitate live broadcast of both the listen enquiry and expert's responses.4. Provide music on hold5. Provide signaling facilities for indicating incoming calls.

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STUDIO TRANSMITTER LINK

Studio transmitter link equipment in 1.5 GHz frequency band can be used for transmission of signal music channel (STL-O1). STL link consist of two terminal i.e. one receiver and one transmit the music program from AIR.

Receiver terminal consist of only receiver modules required to receive the studio program and then this music is given to AIR transmitter. Both transmitter and receiver terminals are with standby modules the switch over operation to standing module is automatic without any time Delay.

CHARACTERISTICS

The studio transmitter link equipment satisfy highly specific requirement such as....1. High operation reliability.2. High quality transmission.3. Use of synthesizer for selection of oscillator frequency. Integrated operation and faults

diagnosis.4. Transmitter and receiver local monitoring facilities. Simple Direct and easy access to

channel signal easy replacement of subunits on site.5. No periodically maintenance necessary.

PROGRAMME INPUT RACK

It has following component 15 in different rack

1. Cathode ray oscilloscope to see the audio signal which is received From the studio and is now modulated by transmitter. (model of Tektronix tds 3032 300 mhz).

2. Monitoring amplifier to amplify the signal received.3. Hooter to alert before starting the transmission.4. Modulations monitor to monitor the modulated signal. There is a Small receiver located

at hpt soorsagar which receives the Modulated signal which is to be transmitted and fed to the program Input rack's modulation monitor.

5. Patch panel to terminate circuits and facilities provided for Interconnecting between circuits by means of jacks and plugs. It Consists of receptacles into which jumpers can be inserted.

6. Limiters to limit the modulated signal.7. Dual output regulated power supply. 8. Equalizer a network usually adjustable, which corrects the Transmission frequency

characteristics of a circuit.

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Antenna

The stl uses a parabolic dish antenna and line of sight transmission And reception is used (uhf range).

The entire incident is reflected back at the focus of the parabolic Dish. At its focus a low noise balloon is there which means balanced to Unbalanced it is a matching tuner with a certain impedance say 30 ohm Balanced antenna terminal to say 75 ohms coaxial lines or wave guide. At Air jodhpur circular wave guides are used since losses are less in it. The Directional pattern of parabolic reflector has 3 very sharp main lobe Surrounded by a number of minor lobes which are much smaller.

The fm operating in vhf range uses yagi Broadcasting, mounted on high mast and broadcast the Distances. Lt used space waver propagation. The high power transmitter at soorsagar lises a Having considerable height (186 m) and an impedance Ground wave propagation.

TRANSMITTTR

In electronics and Telecommunications a Transmitter or radio transmitter is an electronics device which, with the aid of antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, the antenna radiates. When excited by this alternating current, the antenna radiates Radio waves. In addition to their use in broadcasting, transmitters are necessary component parts of many electronics device that communicate by radio. The terms, transmitter is usually limited to equipment that generates radio waves f or communications purposes.

A radio transmitter is an electronic circuit which transforms electric power from a battery or electrical mains into a Radio frequency alternating current.

FM TRANSMITTER

INTRODUCTION

The VHF FM transmitter is design to meet the high performance standards required for mono stereo sound broadcasting applications over band-II channel frequencies (87.5 to 108 N4Hz). The transmitters adopts the advance trends in design such as use of solid state VHF power amplifier, VHF exciter with synthesizer technique permitting fast frequency section in 10kHz steps, with stereo coder for mono as well as stereo transmission. A simple automatic switch over operation in passive VHF exciter standby is incorporated GCEL 3 VHF FM has been designed for use.

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Features

1. The system is fully solid state design conforming to the state of art technology in the field of sound broadcasting equipment’s.

2. The vhf exciter equipped with stereo coder sends a frequency modulated mono or stereo signal in the frequency range 87.5 MHz to 108 MHz

3. The transmitter frequency is crystal controlled and can be set up in steps of 10 kHz over the entire frequency range using synthesizer.

4. The switch on the control board is equipped with simple automatic switchover for operation in passive VHF exciter standby.

5. The solid state VHF power amplifier connected with suitable power couplers. ln case of testing or failure, it can be suitable patched to dummy antenna, manually.

6. Overall efficiency of total transmitter is high to economize the power requirement.7. Plug-in RF Power transistor and the use of -strip line circuits provide increase servicing

ease.

COMBINING SYSTEM

The combining system is composed of;1. Monitoring and metering panel2. Patch panel (U link panel)3. 3 dB, 90 degree 2 way hybrid combiner4. Reject load 5. Dummy load6. Directional couplers, tuning and detectors

The overall insertion loss of combining system should be within 0.4dB. The VSWR between transmitter output and combiner input to be within 1.15. Under normal conditions, the RF power to reject load should be within 75 WATTS. If VSWR between transmitter and combiner input become worse than 1.5 the transmitter automatically taken care to bring down the RF power.

Phase errors are minimized by providing optimum line length to combine at a center frequency of 97 MHz's Rigid lines, elbows, straight couplings etc.

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Patch panel has the provision for connecting transmitter A and B output in different configuration.

In normal mode 2x3 KW outputs are combined at 3dB hybrid combiner and combined output power is connected to the antenna.

Transmitter A connected to antenna, transmitter B connected to dummy load in case of failure of transmitter B.

2*3 KW output are connected in 3db hybrid combiner and combined output power is connected to dummy load for testing the transmitter as whole.

Forward power or reflected power in the combined out coaxial line RF Power into reject load.

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Composition of system

The VHF FM transmitter system comprises of following sub system:-

A. VHF FM TRANSMITTER RACK

The 2*3 KV transmitters are made up of the following rack mounts and modules accommodated in a common rack:-

1. VHF exciter (main and standby)2. 4 VHF power amplifiers3. Harmonic filter modules provided with two harmonic filters each.4. Power divider and power coupler5. Switch on control unit6. FM monitoring demodulator, FKDL7. Adaptor unit8. Transformer carriage (transformer, recti-fier, filter')9. Power distribution panel10. Blower set

VHF POWER AMPLIFIER

The RF output power of the exciter is distributed in phase to the amplifiers via power divider. The amplifier unit is composed of a driver (30W), two pre-amplifiers (120W) and eight parallel connected amplifiers (200W) stages decoupled via coupling networks. The output power of these amplifiers stages are combined to an overall power of 1,5 kW via coupling networks. The overall power is routed to the power coupler via a harmonic filter".

RF power transistor used in power amplifiers in the transmitters assembly contain Beryllium oxide material which is not properly handle can constitute a serious hazard to health.

Two amplifiers of 1.5 kW power each, supply power to the dual power coupler with harmonic filter. The absorbers with corresponding feed liner and provided on the heat sink.

SWITCH ON CONTROL UNIT

The switch on control unit carries out switch On of the operating voltage as well as carrier enable according to the selection. Also, switch on control unit companies a simple automatic switch over permitting operation as selectable passive exciter standby.

Moreover, it can be used for adjusting the transmitter output power!' which can be read from a built in meter,. The operating state of the system is indicated by LEDs.

THE TRANSFORMER CARRIAGE

The FM monitoring demodulator FKDL, continuously tunable within frequency range 87,5 to 108 MHz is used for monitoring carriers signals modulated with !-!1ono and stereo signals in

accordance with the relevant CCIR recommendation. It is connected to transmitter via

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directional couplers or voltage dividers and delivers demodulated mono, multiplexed L and R signals for the usual performance checks on FM transmitter

The FM monitoring demodulator FKDL (transformers, rectifiers, tilters) provides the smoothened DC voltage for the amplifier. Power relays energize the transformers tapings whenever the AC power supply deviates from the nominal values.

POWER DISTRIBUTIONFor regulating, monitoring and isolation facilities from the line

B. Combining rackThe 5.5 KW combing rack is made up of the following rack mounts and components accommodated in a common rack.1. Metering and monitoring panel2. Patch panel3. 3 dB 6Kw RF combiner4. Reject load, 3 KW5. Elbows, straight coupling

Metering and Monitoring Panel

In metering and monitoring panel, meters are provided for measuring and monitoring forward and reflected RF output power from 3 dts combiner going to transmitter antenna. Also power going to dummy local and reject load is monitored.For metering, combined output power directional coupler GD-412 and RF detector GD-013 are provided. Directional coupler. Provides 40 db DOWN RF signal. For operating RF detector, +12 v supplies are taken from RF transmitter rack connector X22A. Output of transmitter A (TX-A) output of transmitter B (Tx-B), input to antenna and dummy load are brought a patch panel. interconnection can be made manually connecting u links.

Micro switches are provided to ensure that:-1. All outputs are terminated.2. No wrong connections is grade (which may be lead to failure) 3dB RF combiner and reject load is provided to combiner RF output power of TX-A and Tx-B to get 5.5 KW output power.

C. 3-0 VOLTAGE STABLTZER, 25 KVA

The 3-cf ,4t5v, voltage stabilizer is supplied along with the VHF FM transmitter system. The unit supplies very stable line AC (415t1%l voltage to transmitter rack and automatic dehydrator.

D. AIJTOMATTCDEHYDRATOR/PRESSURING UNIT

This unit is mainly used for pressuring the RF feeder cable and to dehydrate moisture, collected inside the feeder cable after some time. Pressurization and dehydration of feeder cable help to maintain the low VSWR and low RF feeder cable power loss.

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E. DUMMY LOAD

The dummy local with 10 KW power capacities is supplied along with VHF FM transmitter system to serve as a dummy antenna at the of installation and maintenance to divert total or partial power. This load is provided with thermal protection. In case of dummy load, this switch will cut off the RF loop up the transmitter and the power will be automatic cut off.

POWIR DISTRIBUTION PANEL

Power distribution panel has to be well mounted. ln this panel 3-ϕ wires and neutral wire are connected on 60 amp terminal blocks. Subsequently, these wires get connected through the 3-0 MCB and again get terminated on another terminal block. Red, blue and yellow colored neon lamps are provided to indicate the availability of three phases. To monitor the individual phase voltages and voltages between various phases, voltmeter is provider with selector switches.

For monitoring current drawn from various phases, current transformers inside the distribution panel in each phase line are provided on front panel. Form line distribution panel,3 phase supply goes to 25 KVA voltages stabilizer, from which stabilized supply return to this panel and form here three phase and single phase power line connections are distributed. Various terminal blocks are provided with the two 40 amp circuit breakers and 6 amp circuit breakers inside the power distributor panel. From this panel, wires are run to voltage stabilizer, automatic dehydrator/pressuring unit and dummy load blower. For any extra three phase or single phase connections, extra blocks with circuit breakers are also provided.

SPECIFICATIONS OF SYSTEM

1. Transmission system recommendation As per CCIR2. Class of emission F3E (F3)3. Frequency range band 87.5 MHz to 108 MHz4. RF output power 5.5 KW5. Input impedance 600 ohm (balanced)6. Shift of center frequency ≤ 2 KHz

M ODULATION

1. Stereo channel separation ≤40 dB between l-00 Hz and 15 kHz2. FM noise dB (stereo) ≥ 60 dB (mono) and 54 dB (stereo)3. Asynchronous Am noise ≥ 46 dB down4. Power factor ≥ 0.95. Operating temperature -10 to 50ºC6. AC input line voltage 3-ϕ + neutral, 415 v at 47 to 63 Hz,7. Power consumption 11.5 KVA8. Cooling air cooling with built in blowers

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9. Permissible electric stray field ≤ 10 v/m Strength10. Permissible magnetic stray field ≥4 amp/meter Strength11. Dimensions Transmitting rack 582x2026x1000mm Combing rack. 587x2060x1000mm

KW VHF AMPLIFIER

This amplifier is the basic module in the transmitter. It has a broad band design so that no tuning is required for operation over the entire FM broadcast band. RF power transistor of its output stages is of; lug in type which are easy to replace and no adjustment are required afterReplacement. Each power amplifier gives an output of 1.5 kW. Depending on the required configuration of the transmitter, output of several such amplifiers is combined to get the desired output of the transmitter, For instance, for a 3 kW setup two power amplifiers are used whereas for a 2*3 kw setup, 4 of 1.5 kW power such amplifiers are needed. The simplified block diagramAmplifiers is given in fig...

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This amplifier requires an output power of 2.3 to 3 W and consists of a driver stage (output 30 W) followed by a pre amplifier stage (1,20 W). The amplification from 120 W to L500 W in the final stage is achieved with the help of eight 200 W stages. Each 200 W stage consist of two output transistors (TP 9383, SD 1460 or FM 150) operating in parallel. These RF transistors operate in wide band class C mode and are fitted to the PCB by means of large gold plated spring contacts to obviate the need for soldering. The output of all these stages is combined via coupling networks to give the final output of 1.5 kW, a monitor in each amplifier controls the power of the deriver stage deepening on the reference voltage produced by the switch on control by the switch on control unit. Since the reference voltage is same for all the VHF amplifiers being used, all of them will have the same output power.

Each amplifier has a meter for indicating the forward and reflected voltages and transistor currents. Also a fault is signaled if the heat sink temperature of the VSWR exceeds the prescribed limits. In both cases, the amplifier power is automatically reduced to protect the transistors.

HIGH POWER TRANSMTTTER {300KW)

INTRODUCTION

The purpose of the transmitter is to broadcast an audio frequency signal by amplitude modulation of a carrier in the medium waver range. Carrier modulation is achieved by digital processing of audio signal. Use of transmitter is simple and entirely automated. The equipment,Control systems and transmit parameters are automatically controlled by the system; operation and maintenance are controlled by through a man machine interface (MMI).

The equipment is designed to ensure optimum service availability and functional reliability. The modular architecture of the transmitter is design to compensate for failures in certain modules. Incidents, faults and cutouts on the network are acknowledge and managed.

The transmitter is design to ensure personal safety. The amplifier block is autonomous and self-protected. A locking system prevents access inside the block when the latter is in operation.

Features

Fully solid state Plug in design Interchangeable Modules, No returning at module levels. Less maintenance cost. Minimum inventory cost, Easy to operate. Optimum service availability. Redundant modular architecture.

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At RF level transmitter used efficient N-1 active redundancy strategy where automatic switching in the transmitter combiner connects all operational blocks in parallel and adjusts the combine impedances of the system to operating value. During fault in one of the transmitter gets connected to the dummy load for preventive or corrective maintenance and working TX remains connected to the antenna.

Highest overall efficiency Overall efficiency is 80% (MW) Module efficiency is 94%

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Description of transmitter (TMW 2400Tx)

Company: Thom cast (France)Model: S7H P

The transmitter comprises of the following sub-assemblies:

One autonomous amplifier block comprising two amplification line (left and right lines) and is composed of-1. 4 amplification racks containing 64 amplifiers modules associated with RF Transformers

grouped in central cabinet of the block, in each amplifier block 8 MOSFET are there and each of it contributes 2.4 KW.

2. One adoption unit ensuring coupling of the amplification line.3. One management and control rack ensuring management of the redundant crystal pilots

and modulation of the RF signal.4. One electro technical rack constraining the power supply, protection circuits and relays.5. One man machine interface (MMI) dedicated to operation and maintenance.6. One power supply enclosure comprising the 25V DC (Vint) auxiliary

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Power for the amplifiers modules.7. The 330 v power supply rectifier supply by a power transformer. The rectifier supplies

the main 330V DC power supply for the amplifier modules and pre charge 330V DC power supply for the filtering capacitors, the amplifier block locking and grounding circuits.

One power transformer associated with amplifier block, converting a high voltage input power into 330V power supply.

One RF filter associated with the amplifier block, composed mainly of the RF filtering signal components.

One power input system ensuring- Distribution of the HT energy to the power transformer associated with amplifier blocks Distribution of LV supplies (410V AC)" One ventilation system comprising one independent ventilation caisson associated with the

amplifier block. One cooling system.

PRINCIPLES

RF generation principle

The signal to be transmitted is generated by a crystal master oscillator. This signal is controlled by a digital modulator (encoder) which modulates the amplitude of the carrier signal according to audio signal.

Each module forms a switch producing a rectangular RF signal with in times the amplitude of an elementary module. The rectangular RF signal is filtered so that only the fundamental frequency of the signal passes at transmitter output.

Principle of operation of an amplifier module

Due to limited power capacity of the transistors, the amplifier blocks contains several' medium power (about 2.4kw) amplification sub-assemblies. Each model forms a switch producing a rectangular RF signal" Modulation is obtained by digitally processing of the audio input signal.

MOSFECT act like switches and are connected in a h-bridge to work as full QUAD configuration to give rectangular RF signal with amplitude equal to the twice the power supply voltage. The phase of RF drive signals to gates of n.-channels MOSFETs is such that only two configurations are possible for operation of switches unless MOSFET IS SHORTED.

During positive half cycle of input RF S1, 54 are saturated, and S2, 53 are driven to cut off. This switching action of half QUAD at a time delivers rectangular RF to toroidal transformer as shown in fig. The output of no. of active module is coupled to get required FR output.

DISTRIBUTION OF RF SIGNAL AND COMMAND TO AMPLIFIRE MODULES

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The amplifier block has 255 RF amplifier modules. The modules are physically distributed among four 64 modules rack (two racks on the left coupling line and two on the right coupling line).

From the management point of view 255 modules are organized into 4 assemblies comprising 64 modules each. An amplifier assembly comprises two sets of 32 modules, one on right line and one on left line.

Each of the amplifier assemblies has two remote distribution ckts. Each remote distribution ckt distribution the RF signals from the exciter to a 32 module group (including one dedicated module). The module control information generated by the encoder is carried through remote distribution ckts.

Modulation processing principle

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The amplitude modulation principle applied here consists in, varying the no. of amplifier modules active with amplitude and thus the rate of modulation on the signal to be transmitted. This result in stepped variation of the amplitude of the signal transmitted. The encoder determines, at each moment of RF half period (sampling period) the no. of modules to be activated.

To reproduce the audio signal wave shape, a sufficiently high no" of elementary steps (amplified- modules) is required. However for various technical reasons it is better to limit the no. of modules coupled in series.

Principle of Fine Modulation

The purpose of fine modulator system is lo supplement the main modulation system by correcting the error amplitude of the Modulation RF signal envelope generated by the main modulation system. The fine modulation system instantly corrects this amplitude for each half cycle of RF signal.

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Coupling principle

The various amplification sub-assemblies of the transmitter are connected is series or in parallel. The amplification sub-assemblies N-2 (amplifier modules) are associated in series while the sub-assemblies N-1 (amplifier modules line) are associated parallel in series coupling arrangement, RF transformers associated to the amplifiers modules are used to….

A. Transfer to the coupling line, the energy generated to the modules.B. Match the impedance on the line with that required for correct operation of the amplifiers

modules. Parallel coupling of the lines requires impedance matching by means of an LC Circuit.

The resultant signal of n modules is a rectangular wave with amplitude of an elementary module.

Vo = nxvWhere is the output voltage of an elementary module.

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Power Supply principal

The energy required for operation of the transmitter is supplied by the power input assembly comprising:

A Three phase HV power supply (HTA): This circuit supplies the transformer associated with amplifier block, enabling the amplifier to generate its own 330V DC power supply by rectification of 260V AC coming from the secondary coil of the transformer in the power supply enclosure. A 330V Dc main power supply is generated using a power transformer. Its voltage is rectified by a water cooled. Semiconductor diodes. Then smoothened by a board of RF amplifier modules. To avoid surges on the closure of circuit due to changes in the smoothing capacitors. The capacitors are pre charged prior to start up by a low power 330V DC auxiliary power supply. The power transformer is a three phase dry encapsulated transformer. The. Low voltage output windings are combined into two secondary circuits, each with a delta connection. Each circuits drives a bridge rectifier located in the power supply enclosure.

A three phase 400 V AC low voltage power Supply: This supply is used for all the transmitter sub-assemblies requiring an electrical power supply source.

Cooling System

Two types of cooling is arranged in HPT:

1. AIR COOLING: for PA component, toridal TX, LT power supply.2. WATER COLLING: for MOSFET, H I rectifiers, vint rectifiers (driver circuit).

AIR CONDITIONING

ITNTRODUCTION

The primary function of an air conditioning system is to maintain conductive condition for human comfort. Comfort air condition system is defined as the process by which simultaneously the temperature, moisture contents, movement and quality of all in enclosed space, intended forHuman occupancy many by within required limits.

In order to satisfy the requirements a complete air-conditioning system is to perform the following functions:-A. Cooling and dehumidification for summer conditioning.B. Heating and dehumidification for winter conditioning.C. Air filtration and proper ventilation the year round.

REFRIGERANT CYCLE Mechanical refrigeration is achieved by alternately compressing and expanding the

refrigerant with the help of a compressor and pressure reducing device (such as expansion valve).

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Compressor serves two purposes; first it draws the refrigerant from evaporator (cooling coil) and forces it into the condenser and secondly it increases the pressure of the refrigerant.By sucking the refrigerant, the compressor reduces the pressure in the cooling coil and maintains it at a level it at a level low enough to permit the refrigerant to boil the vaporize and consequently absorb the heat in the process, (refrigerant boils at a relatively low temperature when pressure is reduces).

By discharging refrigerant vapor into the condenser the pressure and temperatures. The hot vapor flows to the condenser, where it condensed into liquid at high pressure. Giving up heat to atmospheric air or water depending on whether the condenser [s air cooled or water cooled.

System components

Compressor:This equipment used for compression of the refrigerant from the heart of the refrigerant unit. Condenser:It is heat exchanger and it is in the condenser that the refrigerant must give up heat absorbed in the evaporator plus the heat added by compressor.

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Cooling tower and spray ponds: cooling towers may be classified as atmospheric draft/draught of natural and as mechanical draft draught.

Evaporator (cooling coil):This is a component that is common to both the air cycle and refrigeration. It cycle it is the cooling coil where heat from circulating air is absorbed by the refrigerant.

Expansion Valve:The expansion value reduces the pressure of the refrigerant liquid and in doing so, cools the liquid.

1. Distribution strategy

The module pairs to be activated are distributed in an equal number (to within one) on the four amplifier assemblies of a block. By retaining the active modules (controlled by encoder). The work load in distributed over 31 pairs (3'2 less the dedicated module pair) of amplifier modules in an amplifier assembly, to equalize the average load of all modules, The list of valid module pairs sent by module fault management function is used to automatically disregard any faulty modules. The identification of modules to be activated is sent to remote distribution ckts which control the amplifier modules. When the status of a module needs to [e changed, the encoder. generates the status and no. of modules (encoded in binary) to the daughter board of remote distribution circuits. This board decodes the information and control the change of state of the module.

2. Fine modulation strategy

The overall modulation management function is performed by encoder board. It manages both of the main and dedicated modules. This output amplitude of modulated RF signal is obtained by vector summing of the main and of dedicated module output signals. For each 2 MHz the encoder determines the no. of main and dedicated modules to be activated. The no. of dedicated modules to be activated is calculated from the no. of main and dedicated modules activated at time in relation to value to be reached at time t+1.

The time interval between two calculations is too closed to 0.5 µsec. and no. of dedicated modules to be activated can range from 1. To 7 these dedicated are placed at position no. 32, 64,96, 1-28 and224. These seven are not having any rotation these are always ON.

3. Man machine interface

A. MMI of amplifier block is used to:

Monitor overall protection of the block Modify certain block adjustment Control, in test mode only, tests within the block or relates to its cooling system

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B. Transmitter local MMI (Optional):

The transmitter is designed to be operated locally and also supports a remote control capability.The optional MMI is used to:

Control transmitter operation Switch the amplifier block to local control operations using the block MMI Report on all the transmitter multi functions. Display the information and operating indications.

RF filter architecture

A low pass filter made of 1.2 inductive resisters and two capacitor assays, C2 and C3. Discharger placed at each capacitor assay. A feed earthing. Photocells located opposite the discharges to inform the control and management

(GESMOD) of electric is formed in cession.

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CONCLUSIONS

The training at RADIO broadcasting station indeed adds knowledge of wide concept of wireless communication especially for broadcasting purpose. The study of operation and maintenance of studio consoles and the medium wave high power transmitter as well as FM low power transmitter help in relating theoretical concept of communication with the practical.Also, the measuring instrument used there give better understanding of the monitoring and control of audio signal as well as modulated signal" It was very satisfactory period of training where I gained very useful overall training. It also provided me an opportunity to develop myself as an engineer with Competitive edge.

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REFERENCES

[1] http://prasarbharati.gov.in [2] http://en.wikipedia.org/wiki/Mast_radiator [3] http://en.wikipedia.org/wiki/Antenna_(radio) [4] www.allindiaradio.org [5] http://india.gov.in/knowindia/radio.php [6] Electronics Measurements and Instruments A.K. Sawhney [7] Electronic Communication systems in advance by Wayne Tomasi[8] Taub’s Principles of communication by Herbert Taub, Donald L Schilling [9] www.howstuffworks.com

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