Telecommunication Complete PDF

Electronics and Telecommunication PART 1 Radio Wave Propagation: Radio Wave Propagation Principle, types of Propagation, Fading. What is Radio Wave Propagation? Radio Wave Propagation means how radio waves travel from one place to another (from the transmitt...

Electronics and Telecommunication PART 1 Radio Wave Propagation: Radio Wave Propagation Principle, types of Propagation, Fading. What is Radio Wave Propagation? Radio Wave Propagation means how radio waves travel from one place to another (from the transmitter to the receiver). Think of it like sound waves — if you shout, your voice travels through the air to someone else. Similarly, radio waves travel through different paths depending on the conditions. Types of Radio Wave Propagation A. Ground Wave Propagation How it works: Radio waves travel along the surface of the Earth. Frequency Range: Works for low and medium frequencies (below 3 MHz). Distance: Short to medium distances (up to 100-300 km). Used for: o AM Radio o Military and maritime communication Example: Just like rolling a ball on the ground, the waves "roll" along the Earth's surface. 1 B. Sky Wave Propagation How it works: Radio waves go up into the atmosphere, hit the ionosphere, and bounce back to Earth. This allows signals to travel much farther distances. Frequency Range: Works best with high frequencies (3 to 30 MHz). Distance: Long distances (up to thousands of kilometers). Used for: o Shortwave radio (international broadcasting) o Amateur radio (ham radio) Example: Imagine bouncing a ball off a wall and it comes back to you. Here, the ionosphere acts like the wall. C. Space Wave Propagation How it works: Waves travel in a straight line between the transmitter and the receiver. This type needs a clear line-of-sight (no big obstacles in between). 2  Frequency Range: Works best with very high frequencies (VHF) and ultra-high frequencies (UHF) (above 30 MHz). Distance: Line-of-sight distance (up to the horizon or further, depending on height). Used for: o FM radio o TV broadcasting o Mobile phone signals o Satellite communication Example: Think of a flashlight beam going straight. If something blocks the beam, the light can't reach the other side. Fading in Radio Wave Propagation Fading means that the strength of the radio signal weakens or fluctuates as it travels. This can happen due to: Multipath Fading: Signals take different paths (e.g., bouncing off buildings) and interfere with each other. Absorption Fading: Signals are absorbed by objects like buildings, trees, or the atmosphere. Interference Fading: Other signals or noise weaken the radio wave. Weather Fading: Weather conditions like rain, fog, or humidity weaken the signal. 3  Ionospheric Fading: Changes in the ionosphere can affect long-distance signals, especially during the day or night. Clear Summary 1. Radio Wave Propagation: How radio waves travel from one place to another. 2. Three Main Types: a. Ground Wave Propagation: Travels along the ground; used for AM radio. b. Sky Wave Propagation: Bounces off the ionosphere; used for long-distance communication. c. Space Wave Propagation: Travels straight in a line; used for FM, TV, and mobile communication. 3. Fading: The signal gets weaker or changes due to obstacles, interference, or weather. PART 2 MODULATION AND DEMODULATION: NEED FOR MODULATION, TYPES OF MODULATION AND D EMODULATION. INTRODUCTION TO AM, FM & PM, SSB-SC & DSB-SC. BLOCK DIAGRAM OF AM A ND FM TRANSMITTER. FM G ENERATION & DETECTION. AM, FM & PM COMPARISONS. What is Modulation? Modulation is the process of adding information (like your voice, music, or data) to a carrier signal. The carrier signal is a high-frequency wave that helps to carry the information over long distances. Example: Imagine you want to send a letter to someone far away. You can't throw the letter, so you use a mail service (the carrier) to carry the letter (information) to its destination. 4 Why Do We Need Modulation? Without modulation, signals like your voice would not travel far enough because voice frequencies are too low to travel long distances. So, we use a higher frequency (carrier signal) to "carry" the information farther. Types of Modulation There are different types of modulation, depending on how the carrier signal is modified: A. Amplitude Modulation (AM) What is it?: In AM, the amplitude (strength) of the carrier signal changes based on the information (message signal) you want to send. Example: Imagine you're adjusting the brightness of a light to send a message. The brightness (amplitude) goes up and down depending on the message. B. Frequency Modulation (FM) What is it?: In FM, the frequency (the number of waves per second) of the carrier signal changes with the message. Example: Instead of changing the brightness, you're changing how fast the light flickers. The faster it flickers (frequency), the more it’s saying. C. Phase Modulation (PM) What is it?: In PM, the phase (position) of the carrier signal changes to carry the information. Example: Imagine flipping a switch between two positions to send a message. The switch's position (phase) is what changes to communicate. 5 Need for Demodulation Demodulation is the reverse process of modulation. The receiver gets the modulated signal and extracts the original message (like voice or data) from the carrier wave. Without demodulation, the receiver can't understand the transmitted information. Example: If modulation is like putting a letter into an envelope for sending, then demodulation is like opening the envelope to read the letter. Introduction to AM, FM & PM AM (Amplitude Modulation): Changes the amplitude (strength) of the carrier wave. FM (Frequency Modulation): Changes the frequency (how fast the wave repeats) of the carrier wave. PM (Phase Modulation): Changes the phase (position) of the carrier wave. 6 Advanced Modulation Techniques There are other forms of amplitude modulation, including: A. SSB-SC (Single Sideband Suppressed Carrier) Only one sideband (the part of the signal carrying information) is transmitted, and the carrier is suppressed (not sent). Why?: This saves bandwidth and power, making communication more efficient. B. DSB-SC (Double Sideband Suppressed Carrier) Both sidebands are transmitted, but the carrier is suppressed. Why?: It uses less power than standard AM because the carrier isn't sent, but still transmits more information than SSB. Block Diagram of AM and FM Transmitter AM Transmitter Block Diagram: 1. Audio Input (like voice or music) 2. Modulator (modifies the amplitude of the carrier wave) 3. Amplifier (boosts the power of the modulated signal) 4. Antenna (sends the signal into the air) FM Transmitter Block Diagram: 1. Audio Input 2. Oscillator (generates the carrier wave) 7  3. Frequency Modulator (modifies the frequency based on the message) 4. Power Amplifier (increases the power of the signal) 5. Antenna 7. FM Generation & Detection FM Generation: An oscillator generates the carrier wave. The frequency of the wave is varied in response to the input signal (like voice or music). FM Detection: A demodulator extracts the original message (voice or data) from the frequency- modulated signal. 8. AM, FM, and PM Comparison Feature AM (Amplitude FM (Frequency PM (Phase Modulation) Modulation) Modulation) What Amplitude Frequency (how fast Phase (position of changes? (strength) wave repeats) the wave) 8  Sound Lower (affected Better sound quality, Similar to FM Quality by noise) less noise Bandwid Requires less Requires more Similar to FM th bandwidth bandwidth Power More power Less power for same Similar to FM Consumptio needed quality n Used In AM radio FM radio, TV, mobile Satellite, advanced communication communication Summary Modulation is used to send information (voice, data) over long distances. Demodulation is the process of extracting that information at the receiver's end. There are different types of modulation: o AM: Changes in amplitude. o FM: Changes in frequency. o PM: Changes in phase. AM and FM Transmitters have similar blocks, but FM offers better quality and less noise. Advanced techniques like SSB-SC and DSB-SC are used to save bandwidth and power. PART 3 Antenna: Fundamentals Of Antenna, Various Parameters, Types Of Antennas & Application 1. Fundamentals of Antennas An antenna is a device that converts electrical energy into radio waves and vice versa. It serves as a crucial component in wireless communication systems, allowing the transmission and reception of electromagnetic signals. 9 Key Functions of an Antenna: Transmission: Converts electrical signals into electromagnetic waves for transmission. Reception: Converts incoming electromagnetic waves back into electrical signals. Parameters of Antennas When evaluating antennas, several important parameters are considered: 1. Radiation Pattern Definition: A graphical representation of the radiation properties of the antenna as a function of space. Types: o Omnidirectional: Radiates equally in all directions (e.g., dipole antenna). o Directional: Concentrates energy in a specific direction (e.g., Yagi-Uda antenna). 2. Gain Definition: The measure of an antenna's ability to direct radio frequency energy in a particular direction compared to a standard (isotropic) antenna. Measured in: Decibels (dB). Importance: Higher gain means better signal strength and reach. 3. Directivity Definition: The measure of how focused the antenna's radiation pattern is in a particular direction. Difference from Gain: Gain includes efficiency, while directivity does not. 4. Bandwidth Definition: The range of frequencies over which the antenna operates effectively. Significance: Wider bandwidth allows the antenna to transmit and receive a range of signals. 10 5. Input Impedance Definition: The impedance at the antenna's feed point. Importance: It affects how efficiently the antenna transmits or receives signals. 6. Efficiency Definition: The ratio of the power radiated by the antenna to the power input to the antenna. Factors: Losses due to resistance, mismatch, and other factors affect efficiency. Types of Antennas There are several types of antennas, each suited for different applications: 1. Dipole Antenna Structure: Consists of two conductive elements (wires) oriented in a straight line. Characteristics: Omnidirectional radiation pattern in the horizontal plane. Applications: Used in radio and television broadcasting. 2. Monopole Antenna Structure: A single conductor mounted over a ground plane. Characteristics: Similar to a dipole, but typically shorter. Applications: Commonly used in mobile devices and car radios. 3. Yagi-Uda Antenna Structure: Consists of multiple elements (one driven, one reflector, and several directors). Characteristics: Highly directional with significant gain. Applications: Used in television reception and amateur radio. 4. Parabolic Reflector Antenna Structure: A parabolic dish that reflects signals to a focal point. 11  Characteristics: Very high gain and directivity. Applications: Used in satellite communications and radio telescopes. 5. Patch Antenna Structure: A flat rectangular or circular radiating element mounted above a ground plane. Characteristics: Low profile and lightweight. Applications: Used in mobile devices, GPS, and Wi-Fi. 6. Loop Antenna Structure: A loop of wire or other conductive material. Characteristics: Can be directional or omnidirectional, depending on design. Applications: Used in RFID systems and some communication systems. Applications of Antennas Antennas are used in various fields, including: 1. Communication Systems Mobile Phones: For voice and data transmission. Broadcasting: Radio and television broadcasting. 2. Satellite Communication Dish Antennas: For receiving signals from satellites. 3. Radar Systems Antenna Types: Used in aviation and military for detecting objects. 4. Wi-Fi and Networking Access Points: Antennas in routers for wireless networking. 12 5. RFID Systems Loop and Patch Antennas: For tracking and identification applications. 6. Scientific Research Radio Telescopes: Antennas for astronomical observations. Summary Antennas play a vital role in wireless communication systems, enabling the transmission and reception of signals. Understanding their fundamental concepts, parameters, types, and applications helps in designing and selecting the right antenna for specific needs. Each antenna type has unique characteristics that make it suitable for various applications, from broadcasting to satellite communications. MCQs on Antennas 1. What is the primary function of an antenna? a. A) Convert mechanical energy into electrical energy b. B) Convert electrical energy into electromagnetic waves c. C) Increase signal frequency d. D) Store electrical energy e. Answer: B) Convert electrical energy into electromagnetic waves 2. Which parameter measures the concentration of an antenna's radiation in a particular direction? a. A) Gain b. B) Directivity c. C) Impedance d. D) Efficiency e. Answer: B) Directivity 3. What does the term "bandwidth" refer to in antenna terminology? a. A) The range of power levels an antenna can handle b. B) The frequency range over which an antenna operates effectively c. C) The physical size of the antenna d. D) The material used to construct the antenna e. Answer: B) The frequency range over which an antenna operates effectively 13 4. What type of radiation pattern does a dipole antenna typically have? a. A) Unidirectional b. B) Omnidirectional c. C) Bidirectional d. D) Isotropic e. Answer: B) Omnidirectional 5. Which type of antenna consists of multiple elements, including a driven element, reflector, and directors? a. A) Dipole Antenna b. B) Monopole Antenna c. C) Yagi-Uda Antenna d. D) Parabolic Antenna e. Answer: C) Yagi-Uda Antenna 6. What is the main advantage of using a parabolic reflector antenna? a. A) Compact size b. B) Low cost c. C) High gain and directivity d. D) Easy to manufacture e. Answer: C) High gain and directivity 7. Which parameter describes how well an antenna converts input power to radiated power? a. A) Directivity b. B) Gain c. C) Input Impedance d. D) Efficiency e. Answer: D) Efficiency 8. What type of antenna is commonly used in mobile devices? a. A) Parabolic Antenna b. B) Yagi-Uda Antenna c. C) Patch Antenna d. D) Loop Antenna e. Answer: C) Patch Antenna 9. Which of the following is a characteristic of a monopole antenna? a. A) It has two conductive elements. b. B) It is mounted over a ground plane. c. C) It is purely directional. d. D) It is used only for television reception. 14  e. Answer: B) It is mounted over a ground plane. 10. What is the primary use of a loop antenna? a. A) Satellite communication b. B) RFID systems c. C) TV broadcasting d. D) Radio telescopes e. Answer: B) RFID systems 11. Which of the following statements about antenna gain is true? a. A) Gain is measured in Watts. b. B) Higher gain indicates better directivity. c. C) Gain is the same as efficiency. d. D) Gain is always positive. e. Answer: B) Higher gain indicates better directivity. 12. The input impedance of an antenna is important because it affects: a. A) The radiation pattern. b. B) The power transferred to the antenna. c. C) The bandwidth of the antenna. d. D) The antenna's weight. e. Answer: B) The power transferred to the antenna. 13. Which of the following is NOT a type of antenna? a. A) Yagi-Uda b. B) Parabolic c. C) Diode d. D) Dipole e. Answer: C) Diode 14. Which type of antenna is often used for television reception due to its directionality? a. A) Dipole Antenna b. B) Loop Antenna c. C) Yagi-Uda Antenna d. D) Patch Antenna e. Answer: C) Yagi-Uda Antenna 15. What is a common application for parabolic antennas? a. A) Mobile phones b. B) GPS systems c. C) Satellite communication d. D) RFID readers 15  e. Answer: C) Satellite communication 16. In which application would you typically find a patch antenna? a. A) Amateur radio b. B) Cellular phones c. C) Satellite dishes d. D) Shortwave radio e. Answer: B) Cellular phones 17. What does an omnidirectional antenna provide? a. A) Focused energy in one direction b. B) Equal radiation in all directions c. C) Variable radiation based on frequency d. D) Higher gain in specific directions e. Answer: B) Equal radiation in all directions 18. Which type of antenna is generally used for broadcasting at high frequencies? a. A) Loop Antenna b. B) Yagi-Uda Antenna c. C) Dipole Antenna d. D) Parabolic Antenna e. Answer: C) Dipole Antenna 19. What does the term "radiation pattern" describe? a. A) The physical shape of the antenna b. B) The relationship between input and output power c. C) The distribution of radiated energy in space d. D) The type of materials used in the antenna e. Answer: C) The distribution of radiated energy in space 20. Which parameter indicates how well an antenna can operate over a range of frequencies? a. A) Gain b. B) Directivity c. C) Bandwidth d. D) Radiation Pattern e. Answer: C) Bandwidth 16  PART 4 Digital Modulation and Demodulation: Techniques, Sampling. Quantization & Encoding, Concept of Multiplexing and De Multiplexing. PAM/PPM/PWM Signals and principles 1. Digital Modulation and Demodulation Digital modulation involves encoding information into a carrier signal using various techniques. It is essential for transmitting digital data efficiently over communication channels. Key Concepts in Digital Modulation: Modulation: The process of varying a carrier signal to encode information. Demodulation: The process of extracting the original information from the modulated signal. Imagine you want to send a message, like "HELLO." Instead of sending it as a simple wave, you modulate (change) a carrier wave. 2. Techniques of Digital Modulation Several techniques are used for digital modulation, including: 1. Amplitude Shift Keying (ASK) Definition: The amplitude of the carrier signal is varied in accordance with the digital signal. Advantages: Simple and easy to implement. Disadvantages: Sensitive to noise and interference. In Amplitude Shift Keying (ASK): You might represent "H" with a tall wave and "E" with a shorter wave. o Tall wave = "H" o Short wave = "E" 17 2. Frequency Shift Keying (FSK) Definition: The frequency of the carrier signal is changed based on the digital signal. Advantages: More robust against noise compared to ASK. Disadvantages: Requires more bandwidth. 3. Phase Shift Keying (PSK) Definition: The phase of the carrier signal is changed to represent the digital data. Types: o Binary PSK (BPSK): Two phases to represent binary digits. o Quadrature PSK (QPSK): Four phases to represent two bits per symbol. Advantages: More efficient use of bandwidth. 4. Quadrature Amplitude Modulation (QAM) Definition: Combines both amplitude and phase modulation to encode multiple bits per symbol. Applications: Used in digital television and data communication. 3. Sampling, Quantization, and Encoding 1. Sampling Definition: The process of measuring the amplitude of an analog signal at discrete intervals. Nyquist Theorem: To avoid aliasing, the sampling frequency must be at least twice the highest frequency present in the signal. Example: Imagine you're recording a sound wave (like music). If you sample the sound every 0.01 seconds: At 0.00s, you measure 0.8V At 0.01s, you measure 0.6V 18  At 0.02s, you measure 0.4V At 0.03s, you measure 0.7V These measurements represent the audio signal at those specific moments. 2. Quantization Definition: The process of mapping sampled values to discrete levels. It involves rounding each sampled value to the nearest available value. Types: o Uniform Quantization: Fixed intervals between quantization levels. o Non-Uniform Quantization: Variable intervals, often used to minimize distortion in audio signals. Example: Continuing with the sampled values: 0.8V might be rounded to 1.0V 0.6V might be rounded to 0.5V 0.4V might be rounded to 0.5V 0.7V might be rounded to 1.0V. 3. Encoding Definition: The conversion of quantized values into binary code for transmission. Various encoding schemes exist, such as: o Pulse Code Modulation (PCM): Represents the quantized values as binary numbers. o Delta Modulation (DM): Transmits the difference between successive samples rather than the actual sample values. Example: If your quantized values after rounding are: 1.0V → represented as 0001 (in 4-bit binary) 19  0.5V → represented as 0000 You now have binary representations that can be sent as digital data. 4. Multiplexing and Demultiplexing 1. Multiplexing Definition: The process of combining multiple signals into one signal over a shared medium. It allows multiple data streams to be transmitted simultaneously. Types: o Time Division Multiplexing (TDM): Divides the time into slots and allocates each slot to a different signal. o Frequency Division Multiplexing (FDM): Divides the frequency spectrum into sub-bands, each carrying a separate signal. Example: Imagine you have three audio streams (A, B, and C) from three different sources. Instead of sending each stream separately: Time Division Multiplexing (TDM) could be used: o For 0-2 seconds: Stream A is sent. o For 2-4 seconds: Stream B is sent. o For 4-6 seconds: Stream C is sent. At the receiver end, each stream is extracted based on timing 2. Demultiplexing Definition: The reverse process of multiplexing, where a single combined signal is separated back into its original components. Importance: Essential for retrieving individual signals at the receiving end. Example: Using the previous example, at the receiver: 20 The combined signal is split back into separate streams based on the timing: The data from 0-2 seconds goes to Stream A. The data from 2-4 seconds goes to Stream B. i The data from 4-6 seconds goes to Stream C 21  PAM, PPM, and PWM Signals Pulse Amplitude Modulation (PAM) Definition: The amplitude of each pulse in a series of pulses represents the sample value of the analog signal. Characteristics: Simple to implement but sensitive to noise. Applications: Used in applications like digital audio and video. Example: If you have sampled values of 2, 4, and 3, the pulse heights could be: Pulse 1 (2) = Medium height Pulse 2 (4) = Tall height Pulse 3 (3) = Slightly shorter than tall 22 Pulse Position Modulation (PPM) Definition: The position of each pulse in time represents the sample value of the analog signal. Characteristics: More robust against noise compared to PAM. Applications: Used in optical communication systems and infrared communication. Example: If you have signal values 1, 2, and 3: A pulse occurs at 1ms for "1" A pulse occurs at 3ms for "2" A pulse occurs at 5ms for "3" The timing of the pulse indicates the value. 23 Pulse Width Modulation (PWM) Definition: The width of each pulse is varied according to the sample value of the analog signal. Characteristics: Allows for efficient power delivery; used to control devices like motors and lights. Applications: Commonly used in audio signal processing and motor control. 24  Example: For values 1, 2, and 3: A pulse of width 1ms for "1" A pulse of width 2ms for "2" A pulse of width 3ms for "3" Summary Digital modulation and demodulation techniques are vital for modern communication systems, enabling efficient data transmission. Sampling, quantization, and encoding transform analog signals into digital form, while multiplexing allows multiple signals to share the same transmission medium. PAM, PPM, and PWM represent different ways to encode information in pulse signals, each with unique characteristics and applications. 25 Summary Table Concept Definition Example Digital High/low waves for "1" Encoding digital info into an analog signal Modulation and "0" Measuring voltage every Sampling Measuring an analog signal at intervals 0.01s Rounding sampled values to discrete Quantization Rounding 0.8V to 1.0V levels Converting values to binary for Encoding 1.0V becomes 0001 transmission Time slots for audio Multiplexing Combining multiple signals into one streams Demultiplexin Separating a combined signal back into Extracting audio streams g originals Pulse heights for values 2, PAM Modulating by varying pulse amplitude 4, 3 Pulses at 1ms, 3ms, and PM Modulating by varying pulse position 5ms Pulse widths of 1ms, 2ms, PWM Modulating by varying pulse width 3ms Here are 30 multiple-choice questions (MCQs) on digital modulation techniques, including Sampling, Quantization, Encoding, Multiplexing, Demultiplexing, and PAM/PPM/PWM signals: PART 5 MOBILE COMMUNICATION. BASICS OF MOBILE COMMUNICATION. CONCEPT CELL SITE, HAND OFF, FREQUENCY REUSE, BLOCK DIAGRAM AND WORKING OF CELL PHONES, CELL PHONE FEATURES. GSM AND CDMA TECHNOLOGY 26  Mobile Communication Basics of Mobile Communication Mobile communication refers to the transmission and reception of signals between a mobile device (e.g., smartphone, tablet) and a network infrastructure. This allows for communication while on the move. Key Concepts Cell Site: A base station that provides coverage for a specific geographical area (cell). Handoff: The process of transferring a call from one cell site to another as the user moves. Frequency Reuse: Using the same frequency band in different cells that are sufficiently far apart to avoid interference. EXPLAINATION Cell Site A cell site (or cell tower) is a fixed point of communication that serves a specific geographic area called a cell. Each cell site contains antennas and equipment to transmit and receive radio signals, connecting mobile devices to the network. The area around a cell site is divided into cells to manage the frequency spectrum effectively. Handoff Handoff (or handover) refers to the process of transferring an ongoing call or data session from one cell site to another as the user moves through the coverage area. There are two types of handoffs: o Hard Handoff: The connection to the current cell is broken before connecting to the new cell (break-before-make). 27  o Soft Handoff: The connection to the new cell is established before breaking the connection to the current cell (make-before-break). Frequency Reuse Frequency reuse is the concept of using the same frequency bands in different cells to maximize the efficient use of available spectrum. By separating cells using adequate distance, interference is minimized, allowing multiple users to share the same frequency without affecting each other. Block Diagram and Working of Cell Phones Block Diagram of a Cell Phone A basic block diagram of a cell phone includes the following components: 1. Antenna: For sending and receiving signals. 2. Transmitter: Converts audio signals into radio waves for transmission. 3. Receiver: Converts incoming radio waves back into audio signals. 4. Modulator/Demodulator (Modem): Modulates and demodulates signals for efficient transmission. 5. Microphone and Speaker: For input (speaking) and output (hearing) of audio. 6. Battery: Provides power to the device. 7. Control Unit: Manages all functions of the phone. 8. Display and User Interface: Allows users to interact with the device. 28 Working of Cell Phones 1. The user speaks into the microphone. 2. The audio signal is converted into an electrical signal and sent to the transmitter. 3. The transmitter modulates the signal and sends it via the antenna as radio waves. 4. The radio waves are picked up by a nearby cell site. 5. The cell site forwards the signal to the intended recipient through the mobile network. 6. The recipient's phone receives the signal through its receiver, demodulates it, and converts it back to audio, which is outputted through the speaker. 29 Cell Phone Features Voice Calling: Basic communication feature. Text Messaging: SMS (Short Message Service) and MMS (Multimedia Messaging Service). Internet Access: Browsing, streaming, and email services. Camera: For capturing photos and videos. GPS: Global Positioning System for location tracking. Apps: Applications for various functionalities like social media, gaming, and productivity. Bluetooth: Wireless technology for short-range data exchange. Wi-Fi: Enables wireless internet access. GSM and CDMA Technology GSM (Global System for Mobile Communications) GSM is a digital mobile communication standard used for transmitting mobile voice and data services. It operates on a time-division multiple access (TDMA) protocol, dividing each frequency into time slots for multiple calls. Key features: o SIM (Subscriber Identity Module) card for user identification. o Supports voice calls, SMS, and mobile internet. o Global compatibility and widespread adoption. CDMA (Code Division Multiple Access) CDMA is another digital mobile communication technology that uses spread- spectrum technology to allow multiple users to share the same frequency band. Each call is assigned a unique code, enabling simultaneous communication without interference. Key features: o More efficient use of bandwidth compared to GSM. o Enhanced voice quality and better call capacity. o Used primarily in the US and some regions for 3G networks. 30 Conclusion Mobile communication encompasses various technologies and concepts, enabling users to stay connected on the go. Understanding the basics, cell sites, handoffs, frequency reuse, and the differences between GSM and CDMA technologies is crucial for comprehending how mobile networks operate. PART 6TH AND 7TH 31 Communication equipment's. AM&FM RADIO Concept and Working, TELEVISION Concept and Working and Optical Fiber Equipments Electrical and Electronic Gadgets: UPS, Inverter, Stabilizer and SMPS working Communication Equipment AM & FM Radio: Concept and Working AM (Amplitude Modulation) Radio Concept: In AM radio, the amplitude (signal strength) of the carrier wave is varied in proportion to the information being sent (audio signals). The frequency remains constant. Working: o Audio Input: The audio signal is captured by the microphone. o Modulation: The audio signal is used to modulate the amplitude of the carrier wave, which remains at a fixed frequency. o Transmission: The modulated wave is transmitted through an antenna. o Reception: The receiver antenna captures the transmitted AM signals. o Demodulation: The radio receiver demodulates the signal, extracting the audio information. o Output: The audio signal is amplified and sent to the speaker for playback. FM (Frequency Modulation) Radio Concept: In FM radio, the frequency of the carrier wave is varied according to the amplitude of the audio signal. The amplitude remains constant. Working: o Audio Input: The audio signal is captured by the microphone. o Modulation: The frequency of the carrier wave is varied based on the amplitude of the audio signal. o Transmission: The modulated FM signal is transmitted via an antenna. o Reception: The FM receiver picks up the transmitted signals. o Demodulation: The receiver demodulates the signal to retrieve the audio information. o Output: The audio signal is amplified and sent to the speaker. 32 Television: Concept and Working Concept: Television is a communication medium that transmits moving images and sound over a distance, enabling broadcasting of video content. Working: o Video and Audio Capture: Cameras capture moving images, and microphones capture audio. o Encoding: The captured video and audio signals are encoded into a composite signal. o Modulation: The composite signal is modulated onto a carrier wave (using AM for audio and FM for video). o Transmission: The modulated signal is transmitted through antennas or cable systems. o Reception: The TV antenna or cable system receives the transmitted signals. o Demodulation: The TV set demodulates the signal to separate audio and video components. o Display: The video is displayed on the screen, and the audio is played through the speakers. Optical Fiber Equipment Concept: Optical fiber equipment uses glass or plastic fibers to transmit data as light signals, providing high-speed communication over long distances with minimal signal loss. Working: o Light Transmission: Data is converted into light signals using a laser or LED. o Propagation: The light travels through the optical fiber via total internal reflection, allowing it to bend around corners. o Reception: At the receiving end, a photodetector converts the light signals back into electrical signals. o Processing: The electrical signals are processed and used for communication. 33 Electrical and Electronic Gadgets Uninterruptible Power Supply (UPS) Concept: A UPS provides backup power to connected devices during a power outage or voltage fluctuations. Working: o Normal Operation: The UPS charges its internal battery while supplying power to connected devices. o Power Failure: In the event of a power outage, the UPS automatically switches to battery mode, providing power to the devices. o Output: The inverter within the UPS converts DC power from the battery to AC power for the devices. Inverter Concept: An inverter converts DC (Direct Current) power into AC (Alternating Current) power. Working: o DC Input: The inverter receives DC input from sources like batteries or solar panels. o Conversion: The inverter uses electronic circuits to switch the DC power, creating an AC output. o Output: The AC output can be used to power household appliances and electronic devices. Stabilizer Concept: A stabilizer regulates and stabilizes voltage to protect electrical appliances from voltage fluctuations. Working: o Voltage Sensing: The stabilizer senses the incoming voltage and compares it to a set reference level. o Regulation: If the voltage exceeds or drops below the set level, the stabilizer adjusts it using transformers or electronic circuits. 34  o Output: The stabilized voltage is supplied to connected appliances, ensuring their safe operation. Switched-Mode Power Supply (SMPS) Concept: SMPS is a power supply unit that converts electrical power efficiently using switching regulators. Working: o AC Input: The SMPS receives AC input from the mains supply. o Rectification: The AC is converted to DC using rectifiers. o Switching: The DC is switched on and off rapidly using transistors, creating a high-frequency signal. o Transforming: The high-frequency signal is transformed to the desired output voltage using a transformer. o Output: The output is filtered and regulated to provide a stable DC voltage for devices. PART 8TH E-Governance: Objectives. Origins In India, E-Governance Project In India. Work plan And Infrastructure. DBMS, ANTI-VIRUS. E-Governance: Objectives e-Governance aims to improve the efficiency and effectiveness of government operations and enhance service delivery to citizens. The main objectives include: Improving Service Delivery: Streamlining processes to provide quicker and more efficient services to citizens. Enhancing Transparency: Increasing government accountability by making information publicly accessible and reducing corruption. Empowering Citizens: Providing citizens with access to information and services, enabling informed participation in governance. Reducing Red Tape: Minimizing bureaucratic obstacles and paperwork, making government interactions smoother and faster. 35  Integrating Services: Connecting various government departments to provide seamless service delivery. Encouraging Participation: Involving citizens in the governance process through feedback and online platforms. Origins of e-Governance in India The origins of e-Governance in India can be traced back to several key developments: 1980s: Introduction of computer technology in government departments to enhance efficiency and administration. National Policy on Information Technology (2000): This policy aimed to promote IT usage in governance and laid the groundwork for e-Governance initiatives. 2006: The Government of India launched the e-Governance Mission, aiming to facilitate e-Governance across all sectors. Digital India Initiative (2015): A flagship program aimed at transforming India into a digitally empowered society and knowledge economy, with a focus on digital infrastructure and services. e-Governance Projects in India Several e-Governance projects have been launched in India to improve service delivery and transparency: National e-Governance Plan (NeGP): Launched to make all government services accessible to citizens electronically. e-District: A project that allows citizens to apply for various certificates (like birth, death, and caste) online. Mahatma Gandhi National Rural Employment Guarantee Act (MGNREGA) IT Project: Facilitates transparency in the rural employment guarantee scheme through online management of funds and work details. Digital India Land Records Modernization Programme (DILRMP): Aims to digitize land records to make them easily accessible and reduce disputes. Common Service Centers (CSCs): A network of physical centers providing various government services to citizens, especially in rural areas. 36 Work Plan and Infrastructure Work Plan: Needs Assessment: Understanding the requirements of citizens and the government. Technology Implementation: Integrating suitable ICT solutions for service delivery. Capacity Building: Training government officials and citizens in using e- Governance platforms. Monitoring and Evaluation: Continuously assessing the performance and impact of e-Governance initiatives. Infrastructure: Data Centers: Centralized facilities for hosting e-Governance applications and databases. Networking: Robust connectivity solutions to facilitate communication between government offices and citizens. Security Framework: Implementing cybersecurity measures to protect sensitive data and ensure privacy. Database Management Systems (DBMS) DBMS plays a crucial role in e-Governance by managing the large volumes of data generated by government services: Data Storage: Provides a structured way to store data efficiently. Data Retrieval: Facilitates quick access to information, allowing timely decision- making and service delivery. Data Integrity: Ensures the accuracy and consistency of data, critical for government operations. User Management: Controls access to data, ensuring that only authorized personnel can view or modify sensitive information. 37 6. Anti-Virus Software Anti-virus software is essential for maintaining the security of e-Governance infrastructure: Threat Detection: Identifies and removes viruses and malware that can compromise systems. Real-time Protection: Monitors system activity to prevent potential threats from executing. Data Security: Protects sensitive information from unauthorized access and cyberattacks. Compliance: Helps meet legal and regulatory requirements related to data protection and privacy. i 38  TELEVISION TRANSMITTERS Television transmitters are devices used to send television signals over the air to be received by televisions. They are a critical component in broadcast television systems and work by converting audio and video signals into radio frequency (RF) signals that can be broadcast over long distances. Here’s a basic breakdown of how television transmitters work: 1. Signal Input (Audio and Video) The television transmitter receives input signals, which include both video (picture) and audio (sound). These signals come from sources such as live TV studios or recorded content. 2. Modulation Video Modulation: The video signal is usually amplitude modulated (AM). In older analog TV systems, the video signal is converted into a radio wave using vestigial sideband (VSB) modulation, which is a variant of AM designed to use less bandwidth. Audio Modulation: The audio signal is typically frequency modulated (FM) to allow for better sound quality and noise resistance. 3. Combining Audio and Video After modulation, the audio and video signals are combined using a technique called frequency division multiplexing (FDM). The audio and video signals are carried on different frequencies within the same TV channel. 4. RF Amplification The combined modulated signal is then amplified to a high power level to ensure that it can be transmitted over long distances without significant loss of quality. 5. Transmission The amplified signal is fed to an antenna that broadcasts the signal as electromagnetic waves. The signal is transmitted over a specific frequency band assigned to the television channel. 6. Reception The signal is received by TV antennas on the viewer’s end, and the television’s tuner demodulates the audio and video signals, converting them back into sound and picture. Types of Television Transmission Analog Transmission: This was the original method of broadcasting TV signals, where audio and video signals were transmitted in an analog format. Analog systems like NTSC, PAL, and SECAM were widely used. Digital Transmission: Modern TV transmitters use digital transmission, where the video and audio are converted into digital data (binary format). This allows for better picture quality (HDTV), more efficient use of bandwidth, and the ability to broadcast multiple channels in the same frequency space. Technologies like DVB-T (Digital Video Broadcasting - Terrestrial) are commonly used for digital television. Important Components of Television Transmitters: Modulator: Handles the modulation of audio and video signals. Upconverter: Converts the baseband signal to the desired broadcast frequency. Power Amplifier: Amplifies the RF signal for transmission. Antenna: Broadcasts the signal to the viewers. In digital TV, additional components include: Digital Encoder: Compresses the video/audio data. Multiplexer (MUX): Combines multiple streams into one signal for transmission. Key Concepts: VSB (Vestigial Sideband): Used for efficient transmission in analog TV. OFDM (Orthogonal Frequency-Division Multiplexing): Often used in digital TV for better handling of multi-path interference. ANTENNA, TYPES-DIPOLE ANTENNA , TRANSMISSION LINES FEEDERS, COAXIAL CABLES. ANTENNA An antenna is a device that transmits or receives electromagnetic waves. In communication systems like radio and television broadcasting, antennas convert electrical signals into radio waves (for transmission) or radio waves back into electrical signals (for reception). Let’s break down the main concepts: 1. Antenna Basics An antenna works by creating electromagnetic waves when an alternating current is applied to it. These waves travel through the air and can be received by another antenna, where the waves are converted back into electrical signals. Antennas come in various shapes and sizes, depending on their application (TV, radio, mobile communication, etc.). 2. Dipole Antenna The dipole antenna is one of the simplest and most widely used antennas. It consists of two conductive elements (usually metal rods) placed end to end, with a gap in the middle where the feed line is connected. Key features of a dipole antenna: Half-Wave Dipole: The length of the dipole is typically half the wavelength of the signal being transmitted or received. Radiation Pattern: A dipole antenna radiates in all directions perpendicular to the antenna, creating an omnidirectional pattern in the horizontal plane. Types of Dipole Antennas: Half-Wave Dipole: The most common, with a total length equal to half the wavelength.  Folded Dipole: A modified version where the two rods are folded back parallel to each other, offering a wider bandwidth. Applications: Used in radio, television transmission, and reception, as well as in Wi-Fi and mobile communication systems. 3. Transmission Lines and Feeders Transmission lines and feeders are used to transfer the electrical signals from the transmitter or receiver to the antenna. Their primary role is to deliver the maximum amount of power with minimal losses. Types of Transmission Lines: Parallel Wire Line (Balanced Line): Consists of two parallel conductors, often used with dipole antennas. They are known for low loss but are susceptible to interference and noise. Coaxial Cable: A more common type of transmission line, consisting of a central conductor, an insulating layer, and an outer conductor (shield). It is widely used due to its superior shielding and reduced noise. 4. Coaxial Cables Coaxial cables are commonly used for connecting antennas to receivers or transmitters. They are favored because of their ability to minimize signal loss and interference.  Or Coaxial cable is a type of copper cable specially built with a metal shield and other components engineered to block signal interference. Structure of a Coaxial Cable: Inner Conductor: Carries the signal (usually copper). Dielectric Insulator: Surrounds the inner conductor and separates it from the outer conductor. Outer Conductor (Shielding): Usually made of braided metal or foil, it prevents interference from external sources. Outer Jacket: The outer insulating layer that protects the cable. Advantages of Coaxial Cables: Low Loss: Coaxial cables have lower losses compared to parallel wire lines, especially at high frequencies. Shielding: The outer conductor acts as a shield to block electromagnetic interference from external sources. Types of Coaxial Cables: RG-58: Common in radio systems. RG-6: Widely used for cable television. RG-213: Used in high-power applications such as transmitting antennas. 5. Transmission Line Matching To ensure that maximum power is transferred from the transmitter to the antenna, the transmission line and antenna impedance must match. If there is a mismatch, it results in standing waves along the transmission line, leading to power loss. Key Matching Concepts: Impedance Matching: Ensuring the impedance of the transmission line matches the impedance of the antenna (typically 50Ω or 75Ω). Standing Wave Ratio (SWR): A measure of the efficiency of power transmission. An SWR close to 1:1 indicates efficient power transfer. Summary of Components: 1. Dipole Antenna: a. Simple, widely used, particularly in radio and TV applications. b. Types include half-wave dipole and folded dipole. 2. Transmission Lines: a. Transfer signals from transmitter/receiver to antenna. b. Types: Parallel wire and coaxial cables. 3. Coaxial Cables: a. Highly shielded transmission lines that reduce interference. b. Used in applications like TV, radio, and data communication. Key Points: Antennas convert electromagnetic waves into electrical signals and vice versa. Dipole antennas are a basic type with two conductors. Transmission lines transport electromagnetic waves. Coaxial cables are a common type of transmission line with excellent shielding. Feeders are the transmission lines connecting antennas to equipment. PERSISTENCE OF VISION OF EYE , PICTURE TRANSMISSION, SCANNING IN PICTURE TUBE HOGRESSIVE SCANNING INTER LACED SCANNING -COMPOSITE VIDEO SIGNAL , NEGATIVE PICTURE PULSES, VIDEO SIGNAL BAND WIDTH, CHANNEL BAND , WIDTH, SSB (SINGLE SIDE BAND TRANSMISSION) VHF, UHF RANGES 1. Persistence of Vision in the Eye Persistence of vision is a phenomenon where the human eye retains an image for a brief moment after the object has been removed. This effect is responsible for the illusion of motion in film and television. If images are flashed rapidly in succession, the brain perceives them as continuous motion. Television relies on this by showing a series of still frames (called frames per second, or FPS) quickly enough that the viewer’s brain blends them into a smooth moving picture. Standard frame rates for TV are 25, 30, or 60 FPS. 2. Picture Transmission in TV Picture transmission in TV involves converting visual information into electrical signals and sending them over a communication channel (like radio waves) to a television receiver. In traditional analog TV, the video is amplitude modulated (AM), while the audio is frequency modulated (FM). For digital TV, the picture is digitized into binary data before transmission. 3. Scanning in Picture Tube In older analog televisions (CRT or picture tube TVs), the image is created by scanning an electron beam across the screen. This scanning happens line by line, from left to right and top to bottom. Types of Scanning: Progressive Scanning: In progressive scanning, the lines are scanned sequentially from top to bottom (1, 2, 3, 4, etc.). This method provides a smooth and high-quality image but requires higher bandwidth. Interlaced Scanning: In interlaced scanning, the odd-numbered lines are scanned first (1, 3, 5, etc.), followed by the even-numbered lines (2, 4, 6, etc.). This method reduces bandwidth but can cause flickering, especially in fast-moving scenes. It was widely used in analog TV (e.g., 480i, 1080i). 4. Composite Video Signal A composite video signal is a standard analog video signal that combines all the video information, including brightness (luminance), color (chrominance), and synchronization signals, into a single line-level signal. Composite video is often referred to as CVBS (Color, Video, Blanking, and Sync). It is used in older video transmission systems but has been replaced by digital systems (like HDMI) today. 5. Negative Picture Pulses Negative picture pulses refer to the synchronization signals in analog video systems. The sync pulses are transmitted in a "negative-going" direction to help synchronize the video display. In TV transmission, these pulses ensure that the receiver's scanning process is aligned with the transmitted video signal. 6. Video Signal Bandwidth The video signal bandwidth refers to the range of frequencies required to transmit the video signal. For analog television: o Standard Definition (SD): The video signal typically requires around 4-6 MHz of bandwidth. o High Definition (HD): Requires more bandwidth, usually in the range of 10-20 MHz depending on the resolution. 7. Channel Bandwidth The channel bandwidth refers to the total range of frequencies allocated for a television channel. For example, in analog TV: o In VHF (Very High Frequency) bands, channels are typically spaced 6 MHz apart. o In UHF (Ultra High Frequency) bands, channels may require 8 MHz or more bandwidth, especially for digital broadcasts. 8. SSB (Single-Sideband Transmission) Single Sideband (SSB) is a type of amplitude modulation (AM) that uses less bandwidth than standard AM by transmitting only one of the sidebands (upper or lower) and suppressing the carrier and the other sideband.  In TV transmission, SSB is used in a modified form known as Vestigial Sideband (VSB) modulation, where part of one sideband is retained to simplify receiver design and reduce bandwidth. 9. VHF and UHF Ranges VHF (Very High Frequency) and UHF (Ultra High Frequency) refer to frequency bands used for TV and radio communication. o VHF: Frequencies from 30 MHz to 300 MHz. In TV, this corresponds to channels 2 to 13 in most regions. o UHF: Frequencies from 300 MHz to 3 GHz. In TV, this corresponds to channels 14 and above. UHF is used for digital television broadcasting and mobile communications. Differences: VHF has better long-distance propagation and can penetrate buildings more effectively, but it has limited bandwidth and is prone to interference. UHF offers more bandwidth, which is useful for digital and HD broadcasting, but it doesn’t travel as far and is more easily blocked by obstacles. Summary: Persistence of vision enables us to perceive a series of still frames as continuous motion in TV. Picture transmission involves converting images into electrical signals for transmission. Progressive and interlaced scanning are methods to display images on a screen. Composite video signals combine luminance, chrominance, and sync pulses into a single signal. Negative picture pulses help with synchronization in analog TV systems. Video signal bandwidth and channel bandwidth are crucial in determining the quality and capacity of TV transmissions. SSB transmission is used to reduce bandwidth in TV systems. VHF and UHF ranges are frequency bands used for TV and radio broadcasting, with UHF being more common for modern digital TV.  Amplitude Modulation (AM) kya hai? Amplitude Modulation (AM) ek aisa tareeka hai jisme ek high-frequency signal (jo "carrier" hota hai) ki amplitude (signal ki height) ko message signal ke mutabiq badla jata hai. Matlab, jo bhi aapko bhejne wala signal hai (jaise aapki awaaz ya music), us signal ko high-frequency wave par chadhaya jata hai, aur us high-frequency wave ki amplitude us message ke according badalti hai. Carrier Signal: Ek high-frequency wave jo apne aap mein information carry nahi karti. Iska kaam bas message signal ko door tak pahunchana hota hai. Iska formula hai: c(t)=Ac sin(ωc t), jahan: o Ac = carrier ki amplitude (fixed hoti hai jab tak modulate nahi hota). o ωc = carrier ka angular frequency (high frequency wave ka frequency). Message Signal: Ye signal wo information hota hai jo aap bhejna chahte ho, jaise awaaz, music, ya data. Is signal ki frequency low hoti hai. Modulation ka kaam kya hai? Modulation ka matlab hai ki carrier signal ki amplitude ko message signal ke hisaab se badalna. Carrier wave ki height kabhi zyada, kabhi kam hoti hai, depending on message signal. Example se samjho: Agar aapki awaaz (message signal) soft hai, to carrier wave ki amplitude chhoti ho jayegi. Agar aapki awaaz loud hai, to carrier wave ki amplitude badh jayegi. Visual Example: Socho ki carrier wave ek regular sine wave jaisi hoti hai, jo same height ke up and down ja rahi hoti hai. Jab message signal aata hai, tab us wave ki height (amplitude) ko message ke upar base karke chhota ya bada kiya jata hai. Easy Analogy: Carrier wave ek gaadi hai. Message signal aapka load ya weight hai jo gaadi pe rakha gaya hai. Jab message signal (load) zyada heavy hota hai, gaadi (carrier wave) zyada neeche jhukti hai (amplitude zyada hoti hai). Jab load halka hota hai, to gaadi kam neeche jhukti hai (amplitude kam hoti hai). Aapke message ko modulate kar ke gaadi (carrier wave) ke through bheja jata hai, aur receiver par demodulate karke original message ko wapas nikala jata hai. Simple Terms mein Summary: AM mein aap ek high-frequency carrier wave ka height (amplitude) change karte ho, jo aapke message signal ke according hota hai. Carrier signal ka frequency aur phase constant rehta hai, sirf amplitude change hoti hai message signal ke hisaab se. Chalo, aur easy karte hain: Amplitude Modulation (AM) kya hai? Socho, ek carrier signal ek wave jaisa hota hai, jaise samundar ki lehr. Yeh lehr apni height (amplitude) ko barabar rakhte hue aage badhti hai. Ab socho ki aapko ek message bhejna hai, jaise aapki awaaz. Aapki awaaz ka volume kabhi zyada hota hai, kabhi kam. Amplitude Modulation (AM) mein hum kya karte hain? Hum is wave ki height ko (amplitude) badal dete hain, aapki awaaz ke upar depend karke. Carrier wave toh ek simple wave hai, jo barabar up-down hoti rehti hai. Message signal (aapki awaaz) ko carrier wave ke upar "rakhte" hain. Jab aapki awaaz zyada tez hoti hai, to carrier wave ki height zyada hoti hai. Jab aapki awaaz dheemi hoti hai, to carrier wave ki height kam ho jaati hai. Simple Example: Socho aap ek radio station ho aur awaaz (message) bhej rahe ho. Aapki awaaz ko hum ek wave par "ride" karwa dete hain. Ab ye wave (carrier signal) ka height (amplitude) aapki awaaz ke according kabhi zyada, kabhi kam hoti hai. Jab ye signal radio ke paas pahuchta hai, to radio us wave ki height ko padhta hai aur samajh jata hai ki aap kya bol rahe the. Aur Simple Samjhane ke Liye: 1. Carrier signal ek khali gaadi ki tarah hai, jo seedha chalti rehti hai. 2. Message signal aapka samaan hai, jo aap gaadi pe rakh rahe ho. 3. Jab gaadi pe zyada samaan hota hai (loud voice), to gaadi thodi neeche jhukti hai (height barh jaati hai). 4. Jab gaadi pe halka samaan hota hai (soft voice), to gaadi zyada neeche nahi jhukti (height kam hoti hai). AM ka matlab yeh hai ki hum gaadi (carrier signal) ki height ko aapke samaan (message signal) ke mutabiq adjust karte hain, taaki information door tak pahunc Bandwidth – Kitni "Space" chahiye signal ko? Socho ki ek highway hai, aur signal ek gaadi hai jo highway par chalti hai. Bandwidth ye batati hai ki gaadi ko kitni road chahiye: AM (Amplitude Modulation): Chhoti road chahiye, ek do lane wali. Kyunki AM mein signal ki "height" badalti hai, frequency toh same rehti hai. FM (Frequency Modulation): FM mein zyada road (badi highway) chahiye, kyunki FM mein signal ka frequency badal raha hota hai. Summary: AM ka signal chhoti bandwidth leta hai. FM ka signal badi bandwidth leta hai. AM Applications – AM kahan use hota hai? AM Radio: Jo aapko purani khabrein ya cricket commentary sunne ko milti thi, wo AM radio hota tha. Aawaz thodi si clear nahi hoti thi, lekin door tak signal pahunchta tha. Airplane Communication: Pilot aur air traffic control AM se baat karte hain, kyunki door tak signal bhejna hota hai, aur halka sa noise chalega. Walkie-Talkie: Walkie-talkies ya chhote communication devices mein AM use hota hai, taaki baat-cheet ho sake. Summary: AM zyada door tak signal bhejne ke liye use hota hai, lekin noise thoda zyada hota hai. FM Applications – FM kahan use hota hai? FM Radio: FM radio pe aap jo music sunte ho, wo FM technology use karta hai. Isme sound quality bahut acchi hoti hai, aur noise bilkul kam hota hai. TV Sound: TV ka purana sound system FM pe chal raha tha, jisme awaz bilkul clear aati thi. Police aur Emergency Services: FM ka signal noise se pareshaan nahi hota, isliye FM radios police aur emergency services mein bhi use hota hai. Summary: FM zyada clear sound ya high-quality music ke liye use hota hai, lekin signal door tak nahi pahunchta. AM Receiver – Superheterodyne Radio Receiver – Simple Explanation Socho tum ek radio sun rahe ho. AM receiver wo device hai jo tumhare liye signal ko samjhta hai aur awaz bana deta hai. 1. Antenna: Signal ko pakadta hai (jaise radio ki lehrain hawa mein hoti hain). 2. Tuning: Tum apne pasandida station ko tune karte ho (jaise 98.3 FM ya 720 AM). 3. Mixer: Signal ko ek aasan frequency mein badal deta hai, taaki radio usko samajh sake. 4. Demodulation: Original awaz ya message ko signal se nikalta hai. 5. Speaker: Awaz sunne ke liye speaker mein bajta hai.  Summary: AM receiver wo device hai jo signal ko samajh kar tumhe awaz sunata hai. FM Receiver – FM kaise sunte ho? FM receiver bhi waise hi kaam karta hai, bas yeh frequency changes ko samajh ke message nikalta hai. Isme noise kam hota hai aur sound quality acchi hoti hai. 1. Antenna: Signal ko pakadta hai. 2. Tuning: FM station ko tune karta hai. 3. Mixer: Signal ko badal kar ek manageable frequency mein lata hai. 4. FM Demodulator: Frequency ke changes ko samajh kar original awaz ya music nikalta hai. 5. Speaker: Clear awaz speaker mein bajti hai. Summary: FM receiver wo device hai jo frequency changes ko samajh ke clear awaz nikalta hai. Ek Dum Simple Example Socho tum apne friend ko door se sandesh bhejna chahte ho: AM (Amplitude Modulation): Aap apne friend ko zyada zor se bolte ho, "HELLO!" agar tumhe lagta hai wo door hai, aur dheemi awaz mein bolte ho "hello..." agar wo paas hai. Aapki awaz ki volume (amplitude) change ho rahi hai. FM (Frequency Modulation): Aap apne friend ko "HELLO!" bolte ho, lekin volume nahi badalte, bas speed change karte ho. Kabhi jaldi "HELLO!" bolte ho, kabhi dheere "HELLO..." Ye speed (frequency) change hoti hai, jo message ko bhejne ka tarika hota hai. AM receiver wo hai jo aapki volume change ko pakad ke samajhta hai, aur FM receiver speed change ko samajhta hai. Radio Wave Propagation Kya Hai? Radio wave propagation ka matlab hai ki radio waves kaise travel karte hain transmitter se receiver tak. Socho jaise aap kisi dost ko door se bulane ki koshish kar rahe ho. 1. Ground Wave Propagation Ground wave waise waves hain jo zamin ke saath-saath chalte hain. Kaisa hota hai: Jaise aap zameen par koi cheez fenk rahe ho, wo zameen ke saath saath chhoti doori tak ja rahi hai. Kahaan use hota hai: AM radio mein. Example: AM radio ka signal zameen ke saath chalta hai aur door tak sunai deta hai. Lekin agar koi barrier hai, toh signal kamjor ho sakta hai. Sky Wave Propagation Sky wave waise waves hain jo aasmaan ki taraf jaati hain aur phir wapas zameen par aati hain. Kaisa hota hai: Socho jaise aapne ek ball ko upar feka aur wo waapas aakar kisi aur jagah girti hai. Kahaan use hota hai: Shortwave radio mein. Example: Agar aap shortwave radio sun rahe ho, toh signal aasmaan se bounce karke door tak jaata hai. Isse aap duniya ke dusre kone ki khabrein sun sakte ho. Space Wave Propagation Space wave waise waves hain jo seedha chalte hain bina kisi bounce ke. Kaisa hota hai: Jaise aapne ek flashlight on kiya ho aur light seedhe chale. Kahaan use hota hai: FM radio aur TV signal mein. Example: FM radio aur TV mein, signal seedha transmitter se receiver tak jata hai. Isme direct line-of-sight hona chahiye, matlab beech mein koi rukawat nahi honi chahiye. Frequencies Kya Hain? AF (Audio Frequency) Kya hai: Ye wo frequency hai jise hum sun sakte hain, 20 Hz se lekar 20,000 Hz (20 kHz) tak. Kahan use hota hai: Ye music aur voice signals mein hota hai. IF (Intermediate Frequency) Kya hai: Ye ek middle frequency hai jo radio signals ko process karne ke liye use hoti hai. Example: Jab aap radio sunte ho, signal ko pehle IF mein badla jaata hai, taaki wo samajhne mein aasan ho. RF (Radio Frequency) Kya hai: Ye un frequencies ka range hai jo radio communication ke liye use hoti hain, 30 kHz se lekar 300 GHz tak. Kahan use hota hai: Isme sabhi wireless communication aata hai, jaise AM, FM, TV, aur Wi-Fi. Summary 1. Ground Wave: Zamin ke saath chalta hai, AM radio mein use hota hai. 2. Sky Wave: Aasmaan se bounce karke chalta hai, shortwave radio mein use hota hai. 3. Space Wave: Seedha line-of-sight mein chalta hai, FM radio aur TV mein use hota hai. 4. Frequencies: a. AF: Sunne ki frequency (20 Hz - 20 kHz). b. IF: Radio signal ke liye intermediate frequency. c. RF: Radio communication ki frequency range (30 kHz - 300 GHz).  ELECTRICITY Electrical units, Effects of electric current, conductors and insulators. Types of solder and flux. AC Circuits 1. Electrical Units Electrical units are the fundamental measurements used to describe electric quantities in circuits. Here are some of the key electrical units: Voltage (V): Measured in volts (V), it represents the electrical potential difference between two points in a circuit. It’s like the "pressure" pushing electrons through the conductor. Current (I): Measured in amperes (A), current represents the flow of electric charge through a conductor. It's the "flow rate" of electrons. Resistance (R): Measured in ohms (Ω), resistance quantifies how much a material opposes the flow of electric current. Power (P): Measured in watts (W), power represents the rate at which electrical energy is consumed or produced. The formula for power is: P=V×IP = V \times IP=V×I Capacitance (C): Measured in farads (F), capacitance is the ability of a component (like a capacitor) to store electric charge. Inductance (L): Measured in henries (H), inductance quantifies a coil’s ability to store energy in a magnetic field when current flows through it. 2. Effects of Electric Current Electric current can produce various effects when it flows through a conductor: Heating Effect: When current passes through a conductor, it generates heat. This effect is the basis of devices like electric heaters and incandescent light bulbs. The heat produced is proportional to the square of the current (I2×RI^2 \times RI2×R). Magnetic Effect: Electric current flowing through a conductor creates a magnetic field around it. This is the principle behind electromagnets and transformers. Chemical Effect: When current flows through an electrolyte (a solution of ions), it can cause chemical reactions, such as in electroplating or electrolysis. Luminous Effect: In certain materials, electric current causes light to be emitted. This is how light-emitting diodes (LEDs) and fluorescent lamps work. 3. Conductors and Insulators Conductors are materials that allow electric current to flow freely because they have a large number of free electrons. Examples include: o Copper: Widely used in wiring due to its excellent conductivity. o Aluminum: Lighter and cheaper than copper but slightly less conductive. Insulators are materials that do not allow electric current to flow freely. They have very few free electrons, making them good at resisting the flow of current. Examples include: o Rubber: Used in insulating gloves and wires. o Plastic: Used as an outer covering in electrical cables. o Glass and ceramics are also excellent insulators, often used in high-voltage systems. 4. Types of Solder and Flux Soldering is the process of joining two metal components by melting solder between them. Solder and flux are crucial for making strong, reliable electrical connections. Types of Solder: Lead-based Solder: This is a mixture of tin and lead (commonly 60% tin and 40% lead, or 63/37 for better precision). It melts at a lower temperature and is easy to work with, but lead-based solders are being phased out due to health and environmental concerns. Lead-free Solder: Used in modern electronics to comply with environmental regulations (e.g., RoHS). It's typically made from tin, silver, and copper (e.g., SnAgCu or SAC). It requires a higher melting temperature and is harder to work with than lead -based solder. Silver Solder: Contains a higher percentage of silver, offering stronger joints, higher melting points, and better conductivity. It's commonly used in sensitive electronics or applications requiring high strength. Types of Flux: Flux is a chemical cleaning agent used during soldering to prevent oxidation of metals and improve the flow of solder. Rosin Flux: Commonly used in electronics, it is a resin-based flux that cleans the metal surfaces and allows solder to bond better. It can be cleaned off afterward using isopropyl alcohol. No-Clean Flux: Does not require cleaning after soldering, leaving minimal residue behind. Often used in mass production.  Water-Soluble Flux: Requires cleaning with water after soldering, but it offers strong cleaning action for surfaces. 5. AC Circuits AC (Alternating Current) circuits use current that reverses direction periodically, unlike DC (Direct Current), where the flow of current is constant in one direction. AC is the form of electricity commonly used in households and industries because it can be easily transformed to different voltages and transmitted over long distances with low losses. Key Concepts in AC Circuits: Frequency (f): In AC circuits, the current reverses direction at a specific frequency, measured in hertz (Hz). In many countries, the standard frequency is 50 Hz or 60 Hz. Peak and RMS Values: The voltage and current in an AC circuit vary sinusoidally. The peak value is the maximum value reached by the waveform, while the RMS (Root Mean Square) value is the effective or average value used for practical calculations. Impedance (Z): In an AC circuit, impedance is the total opposition to the current flow, considering resistance RRR, capacitance CCC, and inductance LLL. Unlike resistance, impedance has both magnitude and phase (since voltage and current may not be in phase in AC circuits). Power in AC Circuits: Power in AC circuits can be a bit more complex due to the phase difference between voltage and current. The real power (P), reactive power (Q), and apparent power (S) are key measures: o Real Power (P): Power that actually performs work, measured in watts (W). o Reactive Power (Q): Power stored in the magnetic or electric fields, measured in VAR (volt-amp reactive). o Apparent Power (S): Combination of real and reactive power, measured in VA (volt-amperes). 1. Magnetic Terms and Units Magnetic concepts are fundamental to understanding how electromagnets, motors, generators, and transformers work. Below are the essential magnetic terms and units: a. Magnetic Field (B): The magnetic field represents the region around a magnetic material or a current- carrying conductor where a magnetic force can be felt. It is measured in teslas (T). b. Magnetic Flux (Φ): Magnetic flux refers to the total number of magnetic field lines passing through a given area. It is measured in webers (Wb). 2. Magnetic Materials Magnetic materials are categorized based on their magnetic properties. There are three main types of magnetic materials: a. Ferromagnetic Materials: These materials exhibit strong magnetic properties. They have high magnetic permeability and can be magnetized easily. Examples include iron, nickel, cobalt, and alloys like steel. o Domains: In ferromagnetic materials, small regions called domains are magnetized in random directions. When an external magnetic field is applied, these domains align, resulting in a strong magnetic effect. o Hysteresis: Ferromagnetic materials show hysteresis, meaning that once they are magnetized, they tend to retain some of their magnetization even after the external field is removed. This is important in materials like permanent magnets. b. Paramagnetic Materials: These materials are weakly attracted to magnetic fields. They have small, positive magnetic susceptibility, meaning they are slightly magnetized in the presence of an external magnetic field but do not retain magnetism when the field is removed. Examples include aluminum, platinum, and magnesium. c. Diamagnetic Materials: Diamagnetic materials are weakly repelled by magnetic fields. They create an opposing magnetic field when exposed to a magnetic field. Examples include copper, bismuth, lead, and water. 3. Properties of a Magnet A magnet exhibits several key properties: a. Attraction and Repulsion: A magnet attracts ferromagnetic materials like iron, cobalt, and nickel. Like poles repel each other (north repels north, south repels south), while unlike poles attract (north attracts south). b. Magnetic Poles: Every magnet has two poles: north and south. The magnetic field lines flow from the north pole to the south pole outside the magnet and within the magnet from south to north. c. Magnetic Induction: When a non-magnetized piece of ferromagnetic material is brought near a magnet, it temporarily becomes magnetized by the external field. This is called magnetic induction. d. Retentivity: Retentivity is the ability of a material to retain magnetization after the external magnetic field is removed. This property is crucial for making permanent magnets. e. Coercivity: Coercivity is the amount of reverse magnetic field required to demagnetize a material. Materials with high coercivity are used for permanent magnets, while those with low coercivity are used for electromagnets. 4. Laws of Electromagnetism Electromagnetism describes the interaction between electric currents and magnetic fields. There are several key laws governing electromagnetism: a. Ampere’s Law: Ampere's Law states that the magnetic field generated by a current-carrying conductor is proportional to the current and inversely proportional to the distance from the conductor. Wiring, IE rules, Wiring accessories- switches, fuses, MCB, ELCB, MCCB, PART 3 RCCB, relays Earthing- megger, earth tester, DC generator- Principle, parts and functions, types, EMF equation. Voltage buildup.Three phase induction motor Principle, parts and functions. Slip, speed, rotor Frequency, torque, copper loss, applications. 1. Wiring Electrical wiring involves the installation of electrical cables and accessories for distributing electricity within a building or structure. There are several types of wiring methods: Cleat Wiring: Open wiring supported on insulated cleats. It’s simple and used temporarily. Conduit Wiring: Wires are enclosed in a conduit (plastic or metal pipe) for protection. Batten Wiring: Conductors are laid on wooden battens, secured by clips. Casing and Capping: Wires run through wooden or plastic channels with protective capping. 2. IE Rules (Indian Electricity Rules) Indian Electricity (IE) Rules govern the safe installation and operation of electrical equipment to prevent electrical hazards. Key aspects include: Rule 29: Ensures protection against electrical shock. Rule 46: Requires inspection and testing of electrical installations. Rule 61: Defines proper earthing for safety. These rules emphasize safety in wiring, installation, and maintenance. 3. Wiring Accessories a. Switches: Single-pole switch: Controls one circuit, commonly used for lights. Double-pole switch: Controls two circuits simultaneously. b. Fuses: A fuse protects circuits by breaking the connection if the current exceeds a safe level, preventing overheating and fire hazards. c. MCB (Miniature Circuit Breaker): Protects against overcurrent and short circuits. It automatically disconnects the circuit when the current exceeds the limit. d. ELCB (Earth Leakage Circuit Breaker): Protects against earth faults. It trips when leakage current to the earth is detected, preventing electric shocks. e. MCCB (Molded Case Circuit Breaker): Protects circuits from overloads and short circuits with adjustable trip settings, used in high-power industrial applications. f. RCCB (Residual Current Circuit Breaker): Similar to ELCB, but more advanced. It trips if there is a mismatch between live and neutral currents, protecting against earth leakage faults. g. Relays: Relays are electrically operated switches used for controlling a high-power circuit using a low-power signal. 4. Earthing Earthing ensures that in the event of a fault, the excess electricity flows directly to the ground, protecting equipment and individuals from electric shock. a. Megger: A megger is an instrument used to measure the insulation resistance of electrical systems to ensure safety and detect faults. b. Earth Tester: An earth tester measures the resistance of the earthing system, ensuring proper grounding. 5. DC Generator A DC generator converts mechanical energy into direct current (DC) electrical energy. Let’s cover its principle, parts, and equations. a. Principle: It operates on Faraday’s Law of Electromagnetic Induction: When a conductor moves through a magnetic field, an EMF (electromotive force) is induced in the conductor. b. Parts and Functions: Yoke: Provides mechanical support and acts as a protective cover. Field Windings: Produce the magnetic field. Armature: Rotating part where the EMF is induced. Commutator: Converts the AC generated in the armature into DC. Brushes: Provide contact between the rotating commutator and the external circuit. c. Types of DC Generators: Series Generator: Field windings are in series with the armature.  Shunt Generator: Field windings are in parallel with the armature. Compound Generator: Combination of series and shunt windings. d. EMF Equation: The EMF generated in a DC generator is given by: e. Voltage Build-up: Voltage build-up in a DC generator occurs due to the residual magnetism in the field windings. As the generator starts, a small voltage is induced, and this causes current to flow through the field windings, strengthening the magnetic field and building up the voltage. 6. Three-Phase Induction Motor A three-phase induction motor is a self-starting motor commonly used in industries. It operates based on the principle of electromagnetic induction. a. Principle: The rotating magnetic field created by the three-phase AC supply induces a current in the rotor, generating torque that causes the rotor to rotate. b. Parts and Functions: Stator: The stationary part, containing the windings to which the three-phase supply is given. Rotor: The rotating part, either squirrel cage or wound rotor, which interacts with the magnetic field generated by the stator. Slip Rings (for wound rotor motors): Facilitate current to flow into the rotor windings. f. Torque: The torque produced by an induction motor is proportional to the rotor current and the strength of the magnetic field. For maximum torque, the slip should be optimum. g. Copper Loss: Copper loss occurs due to the resistance of the windings. In an induction motor, copper losses occur in both stator and rotor windings. h. Applications: Induction motors are widely used in pumps, compressors, conveyors, fans, and other industrial machinery due to their robustness and efficiency. Summary of Concepts: 1. Wiring: Safe and efficient methods of electrical wiring are crucial for residential and industrial installations. 2. Wiring Accessories: Protection devices like MCBs, ELCBs, and RCCBs ensure electrical safety. 3. Earthing: Proper grounding and use of testers like the megger and earth tester prevent electric shocks. 4. DC Generator: Converts mechanical energy into DC electricity using parts like the yoke, field windings, armature, commutator, and brushes. The EMF equation explains the voltage generated. 5. Three-Phase Induction Motor: Operates on electromagnetic induction, with slip, torque, and speed being key performance parameters. It’s used in a variety of industrial applications.