10 KW TV Transmitter

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Front View of NEC 10 KW

VHF Transmitter

IRD

PDA

SWITCHER EXCITER PA

ANTENNA

BASIC TRANSMISSION SYSTEMBASIC TRANSMISSION SYSTEM

VHF TV TransmittersVHF TV Transmitters

DD-1 (CH-5)DD-1 (CH-5)Power Power 10 KW10 KWVid. FrequencyVid. Frequency 175.25 Mhz175.25 MhzAud. FrequencyAud. Frequency 180.75 Mhz180.75 Mhz

DD-News (CH-8)DD-News (CH-8)Power Power 10 KW10 KWVid. FrequencyVid. Frequency 196.26 Mhz196.26 MhzAud. FrequencyAud. Frequency 201.76 Mhz201.76 Mhz

Satellite Downlink ParametersSatellite Downlink Parameters

INSAT 3C (For DD-1)INSAT 3C (For DD-1)Location Location 74740 0 EastEastD/L FrequencyD/L Frequency 3778.5 Mhz3778.5 MhzSymbol RateSymbol Rate 6.25 Mbps6.25 MbpsFECFEC ¾¾PolarizationPolarization HorizontalHorizontal

INSAT 4B (For DD-1 & DD News)INSAT 4B (For DD-1 & DD News)Location Location 93.593.50 0 EastEastD/L FrequencyD/L Frequency 3725 Mhz3725 MhzSymbol RateSymbol Rate 27.500 Mbps27.500 MbpsFECFEC ¾¾PolarizationPolarization HorizontalHorizontal

Satellite Downlink ParametersSatellite Downlink Parameters

INSAT 3A (Regional Service)INSAT 3A (Regional Service)Location Location 93.593.50 0 EastEastD/L FrequencyD/L Frequency 3940.5 Mhz3940.5 MhzSymbol RateSymbol Rate 6.25 Mbps6.25 MbpsFECFEC ¾¾PolarizationPolarization VerticalVertical

Mast & AntennaMast & Antenna

MastMastTypeType Guyed WireGuyed WireHeightHeight 100 Mtrs.100 Mtrs.

AntennaAntennaTypeType BroadbandBroadbandFreq.Freq. 170-230 Mhz170-230 MhzMakeMake DielectricDielectricPatternPattern OmnidirectionalOmnidirectionalCoverage AreaCoverage Area 65 Km.65 Km.

Block Diagram of 10 KW VHF Transmitter (NEC)Block Diagram of 10 KW VHF Transmitter (NEC)

ExciterExciter

99

1010

Necessity of ExciterNecessity of Exciter

• To get highly linear base band signalTo get highly linear base band signal

• To get required IF modulation To get required IF modulation technique, i.e, IF AM modulation for technique, i.e, IF AM modulation for video and FM modulation for audio.video and FM modulation for audio.

• To get the required RF channelTo get the required RF channel

• To amplify the signal up to the such To amplify the signal up to the such extent which is required by the next extent which is required by the next stage.stage.

A-Mix

IM Corrector

Synthesizer

V-Mix

IF Corrector

V-Mod

A-Mod DVC AD-DA Power Supply

EXCITER

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Principle Feature of PCN-Principle Feature of PCN-1610SSPH/11610SSPH/1

• Overall Linearity Corrector :Overall Linearity Corrector : Most non-linear distortion cause in Most non-linear distortion cause in

power amplifier of the transmitter are power amplifier of the transmitter are corrected by the IF corrector unit.corrected by the IF corrector unit.

• In the DVC, ICPM correction or buzz In the DVC, ICPM correction or buzz correction is carried out.correction is carried out.

• Both DG and DP correction circuit in the Both DG and DP correction circuit in the DVC have circuits which maximize DVC have circuits which maximize isolation from the luminance linearity isolation from the luminance linearity circuit with consequent ease of overall circuit with consequent ease of overall adjustment.adjustment.

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• The most significance feature is digital The most significance feature is digital video correction in particular it can be video correction in particular it can be used to corrector automatically by using used to corrector automatically by using the output precision TV demodulatorthe output precision TV demodulator

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Mixer and AGCMixer and AGC• The mixer is built by combining a band The mixer is built by combining a band

pass filter, a notch filter, a white band pass filter, a notch filter, a white band amplifier with a double balanced mixer amplifier with a double balanced mixer using diodesusing diodes

• The IF stage of mixer is provided with The IF stage of mixer is provided with an AGC circuit. The AGC circuit is of an AGC circuit. The AGC circuit is of the pedestal type operating to hold the the pedestal type operating to hold the pedestal or black level constant when pedestal or black level constant when used for video signal.used for video signal.

• If there is no modulation presents the If there is no modulation presents the AGC is automatically switched off AGC is automatically switched off

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AD-DA UnitAD-DA Unit• The AD-DA unit has function that The AD-DA unit has function that

converts the video output signal supplied converts the video output signal supplied to exciter into PCM signal and sends the to exciter into PCM signal and sends the PCM signal to a unit for digital correction PCM signal to a unit for digital correction and which converts the video PCM and which converts the video PCM signal after the digital correction into signal after the digital correction into analog video signal, and supplies the analog video signal, and supplies the analog video signal to a visual modulator analog video signal to a visual modulator unitunit

• This unit also supply 4 fsc clock signal, This unit also supply 4 fsc clock signal, SC signal, H pulse signal and V pulse SC signal, H pulse signal and V pulse signal that a DVC unit needssignal that a DVC unit needs

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The Function Exercised By AD-The Function Exercised By AD-DA UnitDA Unit

• Allows, Switching between the input video signal Allows, Switching between the input video signal from the main line and that form feedback linefrom the main line and that form feedback line

• Converts the analog video signal fed to the Converts the analog video signal fed to the exciter into a 10 bit PCM signal, and supplies exciter into a 10 bit PCM signal, and supplies video data to DVC unit at the next stage.video data to DVC unit at the next stage.

• Converts he 12 bit video data from DVC unit Converts he 12 bit video data from DVC unit into an analog video signal, and supplies the into an analog video signal, and supplies the signal to the V.MOD Unit.signal to the V.MOD Unit.

• Clamps the pedestal potential of the video Clamps the pedestal potential of the video signal.signal.

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• Carries out synchronous separation of Carries out synchronous separation of the main input video signal, the feedback the main input video signal, the feedback video input video signal and that of video input video signal and that of synchronous signal when scrambling is synchronous signal when scrambling is used.used.

• Generates 4 fsc clock signal locked to Generates 4 fsc clock signal locked to the input video signal or F/B video signal the input video signal or F/B video signal (BCO circuit).(BCO circuit).

• Reconstruction the synch pulse of the Reconstruction the synch pulse of the main input video signal.main input video signal.

• Changes the clamp potential in the Changes the clamp potential in the visual blanking period corresponding to visual blanking period corresponding to video-level inversion scramble for the video-level inversion scramble for the visual period.visual period.

Block Diagram of 10 KW VHF NEC Transmitter (Mono Block Diagram of 10 KW VHF NEC Transmitter (Mono Sound)Sound)

2020

Power AmplifiersPower AmplifiersV1200GHII TR PAV1200GHII TR PA

Special FeaturesSpecial Features

• Wide Band Amplifier.Wide Band Amplifier.• VHF V1200GHII (170-230 MHz) VHF V1200GHII (170-230 MHz)

Channel 5-12Channel 5-12• V1000GUII V1000GUII

(470-570 MHz) Channel 21-32(470-570 MHz) Channel 21-32

(570-700 MHz) Channel 33-48 (570-700 MHz) Channel 33-48

(700-800 MHz) Channel 49-61(700-800 MHz) Channel 49-61

(800-860 MHz) Channel 62-69(800-860 MHz) Channel 62-69

• The amplifier can be used unmodified for The amplifier can be used unmodified for digital and analog T.V. transmitters.digital and analog T.V. transmitters.

2121

UHF

2222

2323

V1200GHII TR PA mainly V1200GHII TR PA mainly consists of six units.consists of six units.

• Driver PA1 Circuit.Driver PA1 Circuit.

• Driver PA2 Circuit.Driver PA2 Circuit.

• Wilkinson 3 Way Divider.Wilkinson 3 Way Divider.

• Final PA CircuitFinal PA Circuit

• 6 Way Combiner and Directional 6 Way Combiner and Directional Coupler.Coupler.

• Alarm Circuit.Alarm Circuit.

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Driver PA1 CircuitDriver PA1 Circuit

• The Drive PA1 circuit comprises 2 stages of The Drive PA1 circuit comprises 2 stages of power amplifier circuits containing, a PIN power amplifier circuits containing, a PIN attenuator, a phase shifter, RF limiter, hybrid IC attenuator, a phase shifter, RF limiter, hybrid IC MC5388, and FET 2SK1543.MC5388, and FET 2SK1543.

• The PIN attenuator is specifically used to adjust The PIN attenuator is specifically used to adjust the gain of the unit. the gain of the unit.

• The Phase Shifter adjusts the phase between 2 The Phase Shifter adjusts the phase between 2 units when the units run in parallel with the one units when the units run in parallel with the one another. The phase shifter can adjust the phase another. The phase shifter can adjust the phase in a range within approximately in a range within approximately

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• RF limiter protects the unit from over-RF limiter protects the unit from over-drive.drive.

• Hybrid IC MC5388 which is operated at Hybrid IC MC5388 which is operated at class A have the gain of approximately class A have the gain of approximately 1818dB. dB.

• The next stage amplifier comprise a The next stage amplifier comprise a MOSFET 2SK1543 which is in class AB MOSFET 2SK1543 which is in class AB operation has a gain of approximately 18 operation has a gain of approximately 18 dB.dB.

• The output from this MOSFET passes The output from this MOSFET passes through an isolator and then is to the through an isolator and then is to the driver PA2.driver PA2.

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Driver PA2 CircuitDriver PA2 Circuit

• Driver PA2 comprise of one stage of Driver PA2 comprise of one stage of power amplifier having a 2SK1543M.power amplifier having a 2SK1543M.

• Driver PA2 is operated in class AB Driver PA2 is operated in class AB operation with a gain of approximately 16 operation with a gain of approximately 16 dB.dB.

• The output from the driver PA2 circuit The output from the driver PA2 circuit passes through an isolator and then is to passes through an isolator and then is to the Wilkinson 3-way divider. the Wilkinson 3-way divider.

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Final PA CircuitFinal PA Circuit

• The Final PA Circuit is the final stage The Final PA Circuit is the final stage amplifier circuit supplied with 6 amplifier circuit supplied with 6 2SK1543MPs which use a pair of 2SK1543MPs which use a pair of characteristic matched 2SK1543M.characteristic matched 2SK1543M.

• The final stage amplifier circuit operated in The final stage amplifier circuit operated in optimum class AB push-pull design and optimum class AB push-pull design and has a gain of approximately 16 dB and has a gain of approximately 16 dB and Maximum output of 250 W .Maximum output of 250 W .

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C.I.B.D.C.I.B.D.((Constant Impedance Bandpass Diplexer)Constant Impedance Bandpass Diplexer)

• A simple explanation of the CIB diplexer is A simple explanation of the CIB diplexer is given below:given below:

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Antenna SystemsAntenna Systems

What is AntennaWhat is Antenna

An Antenna is a transducer which transmit or An Antenna is a transducer which transmit or

receive electromagnetic waves. receive electromagnetic waves.

oror

An antenna is a metallic object which used to An antenna is a metallic object which used to convert high frequency current into electro-convert high frequency current into electro-magnetic waves and vice versa.magnetic waves and vice versa.

RadiationRadiation• Antennas radiate electromagnetic waves, radiation Antennas radiate electromagnetic waves, radiation

will result from the flow of high-frequency will result from the flow of high-frequency current in a suitable circuit. This is predicted current in a suitable circuit. This is predicted mathematically by the Maxwell equations, which mathematically by the Maxwell equations, which show that current flowing in a wire is accompanied show that current flowing in a wire is accompanied by a magnetic field around it. If the magnetic field by a magnetic field around it. If the magnetic field is changing, as it does with alter-nating current, an is changing, as it does with alter-nating current, an electric field will also be present. A proportion of electric field will also be present. A proportion of the electric and magnetic field is capable of the electric and magnetic field is capable of leaving the current-carrying wire. How much of it leaving the current-carrying wire. How much of it leaves the conductor depends on the relation of leaves the conductor depends on the relation of its length to the wavelength of the current. its length to the wavelength of the current.

Radiation PatternRadiation Pattern

The radiation pattern of an antenna is a The radiation pattern of an antenna is a graphical representation of the radiation of graphical representation of the radiation of the antenna a function of direction. When the antenna a function of direction. When the radiation is expressed as the radiation is expressed as field strength field strength E Volt per meter ,the radiation pattern is a E Volt per meter ,the radiation pattern is a field strength pattern.field strength pattern. If the radiation If the radiation pattern is expressed is term of power per pattern is expressed is term of power per unit solid angle, the resultant pattern as unit solid angle, the resultant pattern as power pattern. power pattern. A power pattern is a A power pattern is a proportional to the square of the field proportional to the square of the field strength pattern. strength pattern.

ISOTROPIC ANTENNAISOTROPIC ANTENNA

• An Isotropic antenna is a standard An Isotropic antenna is a standard reference antenna radiating equally in all reference antenna radiating equally in all direction so that its radiation pattern is direction so that its radiation pattern is spherical. This is very useful property and spherical. This is very useful property and very easy to visualize but practically such very easy to visualize but practically such antenna does not exist. antenna does not exist.

Power densityPower density

Power density of an antenna is Power density of an antenna is defined as radiated power per unit defined as radiated power per unit area area

Standing Wave Ratio (SWR)Standing Wave Ratio (SWR)

• The ratio of maximum current to minimum The ratio of maximum current to minimum current along a transmission line is called current along a transmission line is called the standing-wave ratio, as is the ratio of the standing-wave ratio, as is the ratio of maximum to minimum voltage, which is maximum to minimum voltage, which is equal to the current ratio. The SWR is a equal to the current ratio. The SWR is a measure of the mismatch between the measure of the mismatch between the load and the line, and is the first and most load and the line, and is the first and most important quantity calculated for a important quantity calculated for a particular load. particular load.

PART-IIPART-II

Details of antennas used in TV Details of antennas used in TV

Transmission/ReceptionTransmission/Reception

CirculatorsCirculators

• A circulator is a ferrite device somewhat like a A circulator is a ferrite device somewhat like a rat race. It is very often a four-port (i.e. four-rat race. It is very often a four-port (i.e. four-terminal) device. It has the property that each terminal) device. It has the property that each terminal is connected only to the next clockwise terminal is connected only to the next clockwise terminal. Thus port 1 is connected to port 2, but terminal. Thus port 1 is connected to port 2, but not to 3 or 4 ; 2 is connected to 3, but not to 4 or not to 3 or 4 ; 2 is connected to 3, but not to 4 or 1; and so on. The main applications of such 1; and so on. The main applications of such circulators are either the isolation of transmitters circulators are either the isolation of transmitters and receivers connected to the same antenna or and receivers connected to the same antenna or isolation of input and output in two-terminal isolation of input and output in two-terminal amplifying devices such as parametric amplifying devices such as parametric amplifiers. amplifiers.

Coding SystemCoding System

• VHF TV Transmitter:

PCN-16 [a][a] SS [b][c]/[d][e]• UHF TV Transmitter:

PCN-11 [a][a] SS [b]/[d][e]• [a][a] : Output Power (kW)

e.g., 10 10 kW

R5 500 W

2R5 2.5 kW

• [b] : Configurationnon Basic Transmitter

(Single Exciter, Single Blower)PE Dual Exciter, Single BlowerPP Dual Exciter, Single Blower

Plural TR PAP Dual Exciter, Dual Blower

Plural TR PAW Active Reserve System

(Exciter Changeover)WX Active Reserve System

(OSC Changeover)

• [c] : L Band I H Band II

• [d] : Visual/Aural Power Ratio 1 10:1 4 4:1 5 5:1

• [e] : Rack Sizenon Standard RackS Small Rack