This document contains 50 sample questions for a Radio Amateur Examination (RAE) revision. The questions cover topics such as electrical components, circuits, radio wave properties, instruments and their uses. Example question topics include power supplies, Ohm's law, antenna polarization, bandwidth, propagation and receiver concepts.
Guidelines for becoming amateur radio operator in malaysia part aCharlie Chong
The document provides definitions for various terms related to amateur radio, including types of modulation like AM and FM, radio frequencies, components of radio systems, operating modes, and organizations. It includes glossaries of terms with descriptions of common words and acronyms in amateur radio like QSO, QSL, DX, and bands along with diagrams and a YouTube video to explain concepts. The document serves as a guide for those looking to understand terminology used in amateur radio communications and guidelines.
A variable frequency drive (VFD) controls the speed and torque of an AC electric motor by varying the frequency and voltage of the power supplied to the motor. It does this by drawing AC power from the utility, converting it to DC, and then converting the DC back to a variable AC waveform. VFDs help conserve energy by only providing the power needed based on the motor's load, rather than running the motor at full speed all the time. The document outlines the basic components and operation of a VFD, as well as goals and timelines for designing and building a VFD circuit.
This document discusses variable frequency drives (VFDs) which vary the frequency and voltage supplied to electric motors to control their speed. It describes the key components of a VFD including the rectifier, DC bus, and inverter. The rectifier converts AC power to DC, the DC bus stores and filters it, and the inverter converts it back to AC of variable frequency to control motor speed. VFDs can operate in scalar or vector control modes, and their parameters like frequency and voltage settings must be configured for the specific motor. VFDs allow controlling motor speed without a mechanical transmission and provide braking methods like DC injection to slow motors.
A variable frequency drive (VFD) controls the speed and torque of AC motors by varying the motor input frequency and voltage. It provides benefits like energy savings, better process control, adjustable speed, power factor correction, and overload protection. A VFD converts AC power to DC, stores it in capacitors, and uses pulse width modulation to invert the DC back to a variable frequency AC output to the motor. VFDs feature line reactors to reduce harmonics and are used widely in applications like fans, pumps, textile machinery and water supply to provide significant energy savings over fixed speed drives.
- Variable frequency drives (VFDs) allow the speed of AC motors to be varied by changing the frequency of the power supplied to the motor. VFDs first convert AC power to DC, then use an inverter to convert the DC back to variable frequency AC to control motor speed.
- The main components of a VFD are a rectifier to convert AC to DC, a DC bus to store the DC power, and an inverter to convert the DC back to variable frequency AC for the motor. Pulse width modulation is used to generate an AC waveform from the DC for motor control.
- VFDs allow parameters like maximum frequency, acceleration/deceleration rates, and torque boost to be set.
The document provides an overview of variable frequency drive (VFD) basics, including:
- The main components of a VFD are the converter section, which converts AC to DC, the DC bus section, which stores the DC voltage, and the inverter section, which converts the DC back to variable frequency AC to control motor speed.
- Pulse width modulation (PWM) is used to vary the width of output voltage pulses to adjust motor speed and torque.
- A VFD allows controlling motor torque at all speeds to meet application needs, unlike direct AC connection which is limited to a fixed speed-torque curve.
- Proper sizing and installation of input and output components like contactors
variable frequency drive (VFD) installationSakshi Vashist
This document discusses variable frequency drives (VFDs) and their use in industrial settings. It describes the basic components and functioning of a VFD, including how they convert AC power to DC and then back to variable AC to control motor speed. VFDs allow motors to operate at optimal speeds, saving energy and reducing wear. The document outlines how to determine if a location would benefit from a VFD, such as if a pump valve is more than 30% closed. It provides examples of energy savings from installing VFDs on pumps. Key considerations for VFD installation include motor specifications, cable sizing, and programming start parameters. The major advantages of VFDs are energy savings, improved process control, lower maintenance needs
The document discusses speed control of a DC motor using a PWM circuit with an IC. It describes how changing the potentiometer VR1 controls the speed by varying the pulse width of the IC output and thus the voltage to the motor. LabView and MATLAB simulations model the motor and add PID control. DC motors can be permanently excited, separately excited, or self-excited in shunt, series or compound configurations. The speed depends on the applied voltage, field flux and armature resistance. Different motor types are suited to applications requiring varying torque or speed characteristics.
Guidelines for becoming amateur radio operator in malaysia part aCharlie Chong
The document provides definitions for various terms related to amateur radio, including types of modulation like AM and FM, radio frequencies, components of radio systems, operating modes, and organizations. It includes glossaries of terms with descriptions of common words and acronyms in amateur radio like QSO, QSL, DX, and bands along with diagrams and a YouTube video to explain concepts. The document serves as a guide for those looking to understand terminology used in amateur radio communications and guidelines.
A variable frequency drive (VFD) controls the speed and torque of an AC electric motor by varying the frequency and voltage of the power supplied to the motor. It does this by drawing AC power from the utility, converting it to DC, and then converting the DC back to a variable AC waveform. VFDs help conserve energy by only providing the power needed based on the motor's load, rather than running the motor at full speed all the time. The document outlines the basic components and operation of a VFD, as well as goals and timelines for designing and building a VFD circuit.
This document discusses variable frequency drives (VFDs) which vary the frequency and voltage supplied to electric motors to control their speed. It describes the key components of a VFD including the rectifier, DC bus, and inverter. The rectifier converts AC power to DC, the DC bus stores and filters it, and the inverter converts it back to AC of variable frequency to control motor speed. VFDs can operate in scalar or vector control modes, and their parameters like frequency and voltage settings must be configured for the specific motor. VFDs allow controlling motor speed without a mechanical transmission and provide braking methods like DC injection to slow motors.
A variable frequency drive (VFD) controls the speed and torque of AC motors by varying the motor input frequency and voltage. It provides benefits like energy savings, better process control, adjustable speed, power factor correction, and overload protection. A VFD converts AC power to DC, stores it in capacitors, and uses pulse width modulation to invert the DC back to a variable frequency AC output to the motor. VFDs feature line reactors to reduce harmonics and are used widely in applications like fans, pumps, textile machinery and water supply to provide significant energy savings over fixed speed drives.
- Variable frequency drives (VFDs) allow the speed of AC motors to be varied by changing the frequency of the power supplied to the motor. VFDs first convert AC power to DC, then use an inverter to convert the DC back to variable frequency AC to control motor speed.
- The main components of a VFD are a rectifier to convert AC to DC, a DC bus to store the DC power, and an inverter to convert the DC back to variable frequency AC for the motor. Pulse width modulation is used to generate an AC waveform from the DC for motor control.
- VFDs allow parameters like maximum frequency, acceleration/deceleration rates, and torque boost to be set.
The document provides an overview of variable frequency drive (VFD) basics, including:
- The main components of a VFD are the converter section, which converts AC to DC, the DC bus section, which stores the DC voltage, and the inverter section, which converts the DC back to variable frequency AC to control motor speed.
- Pulse width modulation (PWM) is used to vary the width of output voltage pulses to adjust motor speed and torque.
- A VFD allows controlling motor torque at all speeds to meet application needs, unlike direct AC connection which is limited to a fixed speed-torque curve.
- Proper sizing and installation of input and output components like contactors
variable frequency drive (VFD) installationSakshi Vashist
This document discusses variable frequency drives (VFDs) and their use in industrial settings. It describes the basic components and functioning of a VFD, including how they convert AC power to DC and then back to variable AC to control motor speed. VFDs allow motors to operate at optimal speeds, saving energy and reducing wear. The document outlines how to determine if a location would benefit from a VFD, such as if a pump valve is more than 30% closed. It provides examples of energy savings from installing VFDs on pumps. Key considerations for VFD installation include motor specifications, cable sizing, and programming start parameters. The major advantages of VFDs are energy savings, improved process control, lower maintenance needs
The document discusses speed control of a DC motor using a PWM circuit with an IC. It describes how changing the potentiometer VR1 controls the speed by varying the pulse width of the IC output and thus the voltage to the motor. LabView and MATLAB simulations model the motor and add PID control. DC motors can be permanently excited, separately excited, or self-excited in shunt, series or compound configurations. The speed depends on the applied voltage, field flux and armature resistance. Different motor types are suited to applications requiring varying torque or speed characteristics.
Variable frequency drives (VFDs) are used in automation and programmable logic control systems to run AC motors at variable speeds and provide smooth motor starts. A VFD adjusts the frequency and voltage supplied to the motor to control its speed. It converts the input AC voltage to DC, filters it with capacitors, and converts it back to AC at the desired output frequency using transistors to control the motor speed. VFDs allow motors to run at speeds between 50-100% of their rated speed by varying the frequency supplied.
The document summarizes a student project to design and implement a 3-phase inverter using an 8051 microcontroller and MOSFET switches. Key aspects include:
1) The project uses Space Vector PWM (SVPWM) technique to generate sine waves with high voltage and low harmonic distortion for driving AC motors.
2) SVPWM approximates the reference voltage using combinations of the eight switching vector patterns.
3) An 8051 microcontroller was programmed to implement the SVPWM algorithm and control the MOSFET switches to generate the three-phase output voltages.
4) The students gained experience with electrical simulation tools and building the circuit with components.
This document discusses DC motors. It begins with an introduction, explaining that DC motors convert electrical energy to mechanical energy using electricity and magnetic fields. It then covers the principle, construction, and working of DC motors. The document discusses the three main types of DC motors: shunt motors, series motors, and compound motors. It provides details on the characteristics and workings of each type. Finally, it lists some common applications of DC shunt motors, series motors, and compound motors.
Brushless DC motors (BLDCMs) have a rotor with permanent magnets and a stator with coils. They are constructed with magnets on the rotor and electromagnets on the stator in a cross pattern. A controller uses Hall sensors to sense the rotor position and commutate current through the stator coils accordingly. BLDCMs are suitable for applications requiring variable or constant speed control such as industrial equipment, consumer goods, vehicles, and medical devices due to their speed-torque characteristics and lack of brush maintenance.
The document discusses Foundation Fieldbus, an open standard for process automation communication. It was established by the International Society of Automation to create a single international fieldbus standard. Foundation Fieldbus uses digital, serial communication between intelligent field devices. It provides wiring and installation savings, enhanced data availability, improved user interfaces, and interoperability between devices.
Speed control of induction motor using vf dsAli Hassan
This document discusses variable frequency drives (VFDs) and how they are used to control the speed of induction motors. It describes the main components of a VFD - the rectifier, DC bus, and inverter - and how they work together to convert incoming AC power to DC and then invert it back to AC at a variable frequency that controls motor speed. The document notes that VFDs are used in boilers at a company to control induced draft fans, forced draft fans, and bagasse feeders. It explains that VFDs provide energy savings of 25-30% by consuming only the power needed, with a return on investment period of 6 months to 2 years. Advantages include efficient motor speed control while
This document provides an overview of electrical machines and DC motors. It discusses various topics including:
- Types of electrical machines such as rotating and stationary machines.
- Faraday's law of electromagnetic induction and how it relates to the voltage induced in a coil.
- The operation of DC generators including Faraday's experiments, Lorentz force law, and the production of DC from an AC waveform using a commutator.
- Components of DC motors such as the stator, field coils, and commutator.
- Characteristics of DC motors including no-load speed-voltage relationship and loaded operation.
- Different DC motor connections such as shunt, series and separately excited and their applications.
-
A variable frequency drive (VFD) controls the speed of AC motors by adjusting both the voltage and frequency supplied to the motor. This allows for continuous speed control as opposed to discrete speeds from gearboxes. VFDs improve efficiency by matching the motor speed to the required process demands. They provide benefits like energy savings, improved power factor, soft starting and stopping of motors, and elimination of mechanical drive components. The document then discusses different types of motor loads and applications that can benefit from VFDs before explaining how pulse width modulation VFDs work by converting AC power to DC, and then back to AC with a controlled frequency.
A VFD can be used to control both the speed and torque of a standard induction AC electric motor.
It varies both the frequency and voltage of the AC waveform being delivered to the motor saving money in electricity.
This document discusses a presentation on variable frequency drives (VFDs). It includes sections on load profiles, motor and load torques, control methods for drives, VFD components and working principles, advantages of VFDs, and a case study on potential energy savings from installing VFDs at a power plant. The case study estimates total annual energy savings of 2,350,000 kWh and payback period of 41 months for a VFD installation project with a total investment of 1,758.6 lakhs.
Variable frequency drives (VFDs) are used to control the speed of AC induction motors by varying the frequency of the power supplied to the motor. A VFD system consists of an AC motor, controller, and operator interface. VFDs allow motors to operate at multiple speeds by adjusting the frequency of the power supplied. They provide benefits like energy savings, protection from overloads, and safe acceleration and deceleration of motors. Common applications of VFDs include controlling pumps, fans, conveyors, and compressors.
This document provides an overview of SCR (silicon controlled rectifier) characteristics and operating principles. It discusses:
1. SCR structure and characteristics, including static and transient two-transistor models.
2. Methods for turning SCRs on, including gate triggering, dv/dt triggering, and light triggering. Turn-on characteristics like delay time and rise time are examined.
3. Methods for turning SCRs off, including natural/line commutation in AC circuits and forced commutation techniques for DC circuits like load side commutation methods.
The document aims to explain SCR functionality and behavior for applications in power electronics circuits. Key aspects like turn-on, turn-
Design of stator & rotor for Wound Induction MotorParth Patel
The document provides details on the design of stator and rotor slots for a 3-phase wound-rotor induction motor. It discusses the construction of the motor including the stator core and winding, wound rotor with slip rings, and end shields. For stator design, it describes slot types, selection of number of slots, conductor cross-section, slot area and size, length of mean turn and resistance calculation. For rotor design, it discusses air gap length, number of rotor slots selection to avoid crawling and cogging, end ring current, design of wound rotor including number of turns and rotor current calculation. It provides an example design problem for a 30kW squirrel cage induction motor and asks to design a suitable rotor
BLDC motors are used widely due to various advantages.
This slide includes construction, working, modes of operation and braking, and applications. We also compare it with Brushed DC motor and Induction Motor.
This document discusses brushless DC motors. It explains that brushless DC motors are synchronous motors that use electronic commutation instead of brushes to create the rotating magnetic field. Hall sensors detect the rotor position and the commutation circuit controls current to the stator windings accordingly. Brushless DC motors have advantages like higher efficiency, longer life, and no sparking compared to brushed DC motors. They find applications in devices like electric vehicles, industrial equipment, appliances and consumer electronics.
This document discusses different types of inverters used in power electronics. It describes that an inverter converts DC power to AC power at a desired output voltage and frequency. It then classifies inverters as line-commutated and force-commutated. Various inverter circuits are presented including half-bridge, full-bridge, and three-phase inverters. The 180 and 120 degree modes of operation for three-phase inverters are explained. Pulse width modulation techniques for inverters like sinusoidal PWM and modified sinusoidal PWM are introduced. Current source inverters are also briefly discussed.
Study of Vector Control Algorithm and Inverter design for BLDC Motor, V/f con...Amol Mahurkar
This document summarizes a study on vector control algorithms and inverter design for BLDC motors. It discusses the objectives of studying BLDC motor operation, different control algorithms including vector control, and inverter design. It also covers V/F control of induction motors. Key topics covered include Clarke/Park transformations, sensorless control, inverter topologies, and a comparison of vector and V/F control techniques. The document is authored by engineering students and provides an overview of various motor control concepts and algorithms.
The document provides an overview of variable frequency drive (VFD) basics, including:
- The main components of a VFD are the converter section, which converts AC to DC, the DC bus section, which stores the DC voltage, and the inverter section, which converts the DC back to variable frequency AC to control motor speed.
- Pulse width modulation (PWM) is used to vary the width of output voltage pulses to adjust motor voltage and frequency.
- A VFD allows controlling motor torque across the entire speed range.
- Topics like input current sizing, single phase operation, overload protection, and enclosure ratings are also discussed.
Este documento proporciona instrucciones para construir un vúmetro, o medidor de nivel de señal, que puede conectarse a un amplificador. Incluye diagramas de circuitos para versiones mono y estéreo, listas de materiales necesarios, y diagramas de circuitos impresos para la construcción física del dispositivo. El propósito del vúmetro es indicar el nivel de salida de un preamplificador o amplificador de manera estética y funcional.
Testing and Troubleshooting 4-20 mA Control Loops Presented by Fluke and Tra...Transcat
This webinar will explore:
-What a control loop is and how it works.
-The most common culprits that can negatively impact the performance of a loop – and how to avoid them.
-Different methodologies and tools to calibrate and troubleshoot 4 to 20 mA control loops.
This document contains a sample exam for a Malaysian radio amateur examination, with 53 multiple choice questions testing knowledge of radio communication fundamentals. The questions cover topics like radio station definitions, amateur radio license classes and privileges, electrical formulas, components of radio transmitters and receivers, and safety considerations. The exam is intended to evaluate if applicants have sufficient technical skills and knowledge of radio operation to be licensed as amateur radio operators.
The document contains multiple choice questions related to electrical engineering topics. Some key points:
- The force per unit charge is known as the electric field.
- Metals have a dielectric constant of 0, as they do not allow an electric field to penetrate.
- The RMS value of an AC current is equal to the amount of DC current that would produce the same heating effect over the same time through the same resistance.
- For a three phase system, the line voltage is related to the phase voltage by a factor of the square root of 3.
Variable frequency drives (VFDs) are used in automation and programmable logic control systems to run AC motors at variable speeds and provide smooth motor starts. A VFD adjusts the frequency and voltage supplied to the motor to control its speed. It converts the input AC voltage to DC, filters it with capacitors, and converts it back to AC at the desired output frequency using transistors to control the motor speed. VFDs allow motors to run at speeds between 50-100% of their rated speed by varying the frequency supplied.
The document summarizes a student project to design and implement a 3-phase inverter using an 8051 microcontroller and MOSFET switches. Key aspects include:
1) The project uses Space Vector PWM (SVPWM) technique to generate sine waves with high voltage and low harmonic distortion for driving AC motors.
2) SVPWM approximates the reference voltage using combinations of the eight switching vector patterns.
3) An 8051 microcontroller was programmed to implement the SVPWM algorithm and control the MOSFET switches to generate the three-phase output voltages.
4) The students gained experience with electrical simulation tools and building the circuit with components.
This document discusses DC motors. It begins with an introduction, explaining that DC motors convert electrical energy to mechanical energy using electricity and magnetic fields. It then covers the principle, construction, and working of DC motors. The document discusses the three main types of DC motors: shunt motors, series motors, and compound motors. It provides details on the characteristics and workings of each type. Finally, it lists some common applications of DC shunt motors, series motors, and compound motors.
Brushless DC motors (BLDCMs) have a rotor with permanent magnets and a stator with coils. They are constructed with magnets on the rotor and electromagnets on the stator in a cross pattern. A controller uses Hall sensors to sense the rotor position and commutate current through the stator coils accordingly. BLDCMs are suitable for applications requiring variable or constant speed control such as industrial equipment, consumer goods, vehicles, and medical devices due to their speed-torque characteristics and lack of brush maintenance.
The document discusses Foundation Fieldbus, an open standard for process automation communication. It was established by the International Society of Automation to create a single international fieldbus standard. Foundation Fieldbus uses digital, serial communication between intelligent field devices. It provides wiring and installation savings, enhanced data availability, improved user interfaces, and interoperability between devices.
Speed control of induction motor using vf dsAli Hassan
This document discusses variable frequency drives (VFDs) and how they are used to control the speed of induction motors. It describes the main components of a VFD - the rectifier, DC bus, and inverter - and how they work together to convert incoming AC power to DC and then invert it back to AC at a variable frequency that controls motor speed. The document notes that VFDs are used in boilers at a company to control induced draft fans, forced draft fans, and bagasse feeders. It explains that VFDs provide energy savings of 25-30% by consuming only the power needed, with a return on investment period of 6 months to 2 years. Advantages include efficient motor speed control while
This document provides an overview of electrical machines and DC motors. It discusses various topics including:
- Types of electrical machines such as rotating and stationary machines.
- Faraday's law of electromagnetic induction and how it relates to the voltage induced in a coil.
- The operation of DC generators including Faraday's experiments, Lorentz force law, and the production of DC from an AC waveform using a commutator.
- Components of DC motors such as the stator, field coils, and commutator.
- Characteristics of DC motors including no-load speed-voltage relationship and loaded operation.
- Different DC motor connections such as shunt, series and separately excited and their applications.
-
A variable frequency drive (VFD) controls the speed of AC motors by adjusting both the voltage and frequency supplied to the motor. This allows for continuous speed control as opposed to discrete speeds from gearboxes. VFDs improve efficiency by matching the motor speed to the required process demands. They provide benefits like energy savings, improved power factor, soft starting and stopping of motors, and elimination of mechanical drive components. The document then discusses different types of motor loads and applications that can benefit from VFDs before explaining how pulse width modulation VFDs work by converting AC power to DC, and then back to AC with a controlled frequency.
A VFD can be used to control both the speed and torque of a standard induction AC electric motor.
It varies both the frequency and voltage of the AC waveform being delivered to the motor saving money in electricity.
This document discusses a presentation on variable frequency drives (VFDs). It includes sections on load profiles, motor and load torques, control methods for drives, VFD components and working principles, advantages of VFDs, and a case study on potential energy savings from installing VFDs at a power plant. The case study estimates total annual energy savings of 2,350,000 kWh and payback period of 41 months for a VFD installation project with a total investment of 1,758.6 lakhs.
Variable frequency drives (VFDs) are used to control the speed of AC induction motors by varying the frequency of the power supplied to the motor. A VFD system consists of an AC motor, controller, and operator interface. VFDs allow motors to operate at multiple speeds by adjusting the frequency of the power supplied. They provide benefits like energy savings, protection from overloads, and safe acceleration and deceleration of motors. Common applications of VFDs include controlling pumps, fans, conveyors, and compressors.
This document provides an overview of SCR (silicon controlled rectifier) characteristics and operating principles. It discusses:
1. SCR structure and characteristics, including static and transient two-transistor models.
2. Methods for turning SCRs on, including gate triggering, dv/dt triggering, and light triggering. Turn-on characteristics like delay time and rise time are examined.
3. Methods for turning SCRs off, including natural/line commutation in AC circuits and forced commutation techniques for DC circuits like load side commutation methods.
The document aims to explain SCR functionality and behavior for applications in power electronics circuits. Key aspects like turn-on, turn-
Design of stator & rotor for Wound Induction MotorParth Patel
The document provides details on the design of stator and rotor slots for a 3-phase wound-rotor induction motor. It discusses the construction of the motor including the stator core and winding, wound rotor with slip rings, and end shields. For stator design, it describes slot types, selection of number of slots, conductor cross-section, slot area and size, length of mean turn and resistance calculation. For rotor design, it discusses air gap length, number of rotor slots selection to avoid crawling and cogging, end ring current, design of wound rotor including number of turns and rotor current calculation. It provides an example design problem for a 30kW squirrel cage induction motor and asks to design a suitable rotor
BLDC motors are used widely due to various advantages.
This slide includes construction, working, modes of operation and braking, and applications. We also compare it with Brushed DC motor and Induction Motor.
This document discusses brushless DC motors. It explains that brushless DC motors are synchronous motors that use electronic commutation instead of brushes to create the rotating magnetic field. Hall sensors detect the rotor position and the commutation circuit controls current to the stator windings accordingly. Brushless DC motors have advantages like higher efficiency, longer life, and no sparking compared to brushed DC motors. They find applications in devices like electric vehicles, industrial equipment, appliances and consumer electronics.
This document discusses different types of inverters used in power electronics. It describes that an inverter converts DC power to AC power at a desired output voltage and frequency. It then classifies inverters as line-commutated and force-commutated. Various inverter circuits are presented including half-bridge, full-bridge, and three-phase inverters. The 180 and 120 degree modes of operation for three-phase inverters are explained. Pulse width modulation techniques for inverters like sinusoidal PWM and modified sinusoidal PWM are introduced. Current source inverters are also briefly discussed.
Study of Vector Control Algorithm and Inverter design for BLDC Motor, V/f con...Amol Mahurkar
This document summarizes a study on vector control algorithms and inverter design for BLDC motors. It discusses the objectives of studying BLDC motor operation, different control algorithms including vector control, and inverter design. It also covers V/F control of induction motors. Key topics covered include Clarke/Park transformations, sensorless control, inverter topologies, and a comparison of vector and V/F control techniques. The document is authored by engineering students and provides an overview of various motor control concepts and algorithms.
The document provides an overview of variable frequency drive (VFD) basics, including:
- The main components of a VFD are the converter section, which converts AC to DC, the DC bus section, which stores the DC voltage, and the inverter section, which converts the DC back to variable frequency AC to control motor speed.
- Pulse width modulation (PWM) is used to vary the width of output voltage pulses to adjust motor voltage and frequency.
- A VFD allows controlling motor torque across the entire speed range.
- Topics like input current sizing, single phase operation, overload protection, and enclosure ratings are also discussed.
Este documento proporciona instrucciones para construir un vúmetro, o medidor de nivel de señal, que puede conectarse a un amplificador. Incluye diagramas de circuitos para versiones mono y estéreo, listas de materiales necesarios, y diagramas de circuitos impresos para la construcción física del dispositivo. El propósito del vúmetro es indicar el nivel de salida de un preamplificador o amplificador de manera estética y funcional.
Testing and Troubleshooting 4-20 mA Control Loops Presented by Fluke and Tra...Transcat
This webinar will explore:
-What a control loop is and how it works.
-The most common culprits that can negatively impact the performance of a loop – and how to avoid them.
-Different methodologies and tools to calibrate and troubleshoot 4 to 20 mA control loops.
This document contains a sample exam for a Malaysian radio amateur examination, with 53 multiple choice questions testing knowledge of radio communication fundamentals. The questions cover topics like radio station definitions, amateur radio license classes and privileges, electrical formulas, components of radio transmitters and receivers, and safety considerations. The exam is intended to evaluate if applicants have sufficient technical skills and knowledge of radio operation to be licensed as amateur radio operators.
The document contains multiple choice questions related to electrical engineering topics. Some key points:
- The force per unit charge is known as the electric field.
- Metals have a dielectric constant of 0, as they do not allow an electric field to penetrate.
- The RMS value of an AC current is equal to the amount of DC current that would produce the same heating effect over the same time through the same resistance.
- For a three phase system, the line voltage is related to the phase voltage by a factor of the square root of 3.
The document is a sample model question paper containing 24 questions for an Electronics (EC) exam. The questions cover a range of topics in electronics including RLC circuits, amplifiers, analog-to-digital converters, microprocessors, communication systems, electromagnetism, and basic circuit elements like inductors and capacitors. The questions test understanding of concepts like resonance, signal processing, coding gain, noise figure, oscillator circuits, and transformations of circuit parameters.
This document contains 74 multiple choice questions covering a wide range of topics including electronics, digital logic, programming, mathematics and physics. The questions test knowledge of concepts such as AM and FM modulation, digital logic gates, VHDL, C programming, calculus, physics laws and more. The questions are in multiple choice format with options A through D for each question.
The document contains 15 multiple choice questions about circuits and circuit components. The questions cover topics like series and parallel circuits, resistors, capacitors, diodes, and more. Sample questions include identifying circuits like clippers, clamps, and rectifiers; calculating current, voltage, resistance, and power in circuits; and describing the behaviors of series and parallel connections.
Questions for circuit debugging, These questions are custom designed by Bhushan and Adhithya to test your understanding. Only if you understood the concepts you will be able to answer these questions.
These questions were framed for Coloumb 2022 a symposium conducted by Rajalakshmi engineering college Thandalam, Chennai.
This document contains a technical assessment with 82 multiple choice questions covering topics in electronics and semiconductor devices. The questions assess knowledge of key concepts like resistivity of materials like silicon and germanium, properties of intrinsic and doped semiconductors, diode characteristics, transistor operation, digital circuits, color television systems, communication systems, and operational amplifiers.
The document provides information about various components and aspects of electrical substations:
1) Stones are used in substations to drain oil from transformers if leaks occur and to prevent weed growth. Devices like synchronous condensers and reactors are used to improve power factor.
2) Minimum phase to phase clearances for 400kV conductors and common components like CVTs, wave traps, and arrestors are identified. Reactors are used to limit short circuit current.
3) Ring main distribution systems are generally used for distribution. Earthing conductivity is affected by various soil factors and emulsifier protection relates to multiple protections like grounding and fire.
This document contains a sample MCAT exam with 220 multiple choice questions covering physics, chemistry and biology. Some example questions are provided on topics like logic diagrams, stress-strain graphs, gas laws, radioactivity, optics and chemical reactions. The exam is designed for students completing their F.Sc. or non-F.Sc. degrees, with a maximum time of 150 minutes and total marks of 1100.
Exam 086044RR - Modulation and Detection CircuitsWhen you.docxSANSKAR20
Exam: 086044RR - Modulation and Detection Circuits
When you have completed your exam and reviewed your answers, click Submit Exam. Answers will not be recorded until you
hit Submit Exam. If you need to exit before completing the exam, click Cancel Exam.
Questions 1 to 25: Select the best answer to each question. Note that a question and its answers may be split across a page
break, so be sure that you have seen the entire question and all the answers before choosing an answer.
R
MAA/V—
f =600 kHz
C -0.000352
L =200 £iH
R=101A
1. Look at the circuit shown in the figure above. The frequency of the power supply is 600 kHz, the
capacitance of C is 0.000352 jiF the inductance of L is 200 |aH, and the resistance of R is 10 Q. What
would be the calculated effective resistance (RJ of this circuit?
A. 56,818 fi
B. 52,119 Q
C. 10,461 n
D. 43,167 n
2. An unmodulated carrier has an amplitude of 5 V. When modulated, the maximum amplitude is 10 V.
What is the modulation percentage?
A. 50 percent
B. 120 percent
C. 30 percent
D. 100 percent
3. In a standard AM transmission with 100 percent modulation,
A. the sideband amplitude is 70.7 percent of the carrier amplitude.
B. the sideband amplitude is one-eighth of the carrier amplitude.
C. the sideband amplitude is one-fourth of the carrier amplitude.
D. the sideband amplitude is 50 percent of the carrier amplitude.
^A/Wsr-
f =600 kHz
C =0,000352 fiF
L=20QmH
R=ioy?
4. For the circuit shown in the figure above, what would be the calculated value of the inductive reactance
(Xj)? (Round your answer to the nearest whole number.)
A. 942 D.
B. 1,057 a
C. 754 a
D. 598 a
5. A 1.5 MHz carrier frequency is amplitude-modulated by a 200 kHz sinewave audio signal. The
bandwidth would be
A. 4,000 kHz.
B. 400 kHz.
C. 405 kHz.
D. 40 kHz.
6 . modulation is particularly adaptable to computer systems, data transmission, and space
communications.
A. Pulse-amplistude
B. Pulse-position
C. Phase
D. Pulse
7. Some methods of pulse modulation provide for transmission of a number of channels on a single carrier.
That is accomplished by dividing the transmission time among the several channels, which is called
A. damping.
B. multiplexing.
C. frequency-shift keying.
D. duplexing.
8. A 1,200 kHz RF carrier is amplitude-modulated by a 500 Hz sinewave audio signal. The upper sideband
frequency would be
A. 1,195 kHz.
B. 1,205 kHz.
C. 120.5 kHz.
D. 1,200.5 kHz.
9. In a Foster-Seeley phase shift discriminator, certain voltage conditions depend on whether the input
signal is at, above, or below resonance. Look at the vector diagram shown in the figure above. Which of
the following statements correctly describes the circuit represented by this vector diagram?
A. The input signal in this circuit is at resonance, and the discriminator's secondary voltages cancel each other.
B. The input signal is above resonance, and no output signal will be produced.
C. The output signal produced will be directly ...
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1. RADIO AMATEUR EXAMINATION (RAE) SAMPLE QUESTIONS FOR REVISION
1. Power supplies to RF power amplifiers should:
a) be open wires
b) be AF filtered
c) be RF filtered
d) be inductively coupled
2. The value of a resistor to drop 100 volt with a current of 0.8 miliampere is:
a) 125 ohm c) 1250 ohm
b) 125 kilohm d) 1.25 kilohm
3. If a current of 2 amperes flows through a 50-ohm resistor, what is the voltage across the resistor?
a) 25 volts c) 100 volts
b) 52 volts d) 200 volts
The effective resistance of three 24 Ohm resistors connected in parallel is:
a) 8 ohms b) 12 ohms
c) 36 ohms d) 72 ohms
4. An electric current passing through a wire will produce around the conductor:
a) An electric field c) a superconductor
b) A magnetic field d) a semiconductor
5. The unit of impedance is the:
a) ampere c) Henry
b) farad d) ohm
6. One kilohm is:
a) 10 ohm c) 0.001 ohm
b) 0.01 ohm d) 1000 ohm
7. The watt is the unit of :
a) power c) electromagnetic field
strength
b) magnetic flux d) breakdown voltage
8. The unit of resistance is the:
2. a) farad c) ohm
b) watt d) resistor
9. Radio wave polarization is defined by the orientation of the radiated:
a) magnetic field b) electric field
c) inductive field d) capacitive field
10. The voltage drop across a germanium diode when conducting is about:
a) 0.3V b) 0.6V
c) 0.7V d) 1.3V
11. A 50 hertz current in a wire means that:
a) A potential difference of 50 volts exists across the wire
b) The current flowing in the wire is 50 amperes
c) The power dissipated in the wire is 50 watts
d) A cycle is completed 50 times in each second
12. Starting at a positive peak, how many times does a sine wave cross the zero axis in one complete cycle:
a) 180 times c) 2 times
b) 4 times d) 360 times
13 What is a wave called that abruptly changes back
and forth between two voltage levels and remains an equal time at each level?
a) A sine wave c) a square wave
b) A cosine wave d) a sawtooth wave
14. What would be the most accurate way of determining the RMS voltage of a complex waveform?
a) By using a grid dip meter
b) By measuring the voltage with a D’Arsonval meter
c) By using an absorption wavemeter
d) By measuring the heating effect in a known resistor
15 What are three good electrical conductors
a) Copper, gold, mica
b) Gold, silver, wood
c) gold, silver, aluminium
d) copper, aluminium, paper
17. An isolating transformer is used to
a) Ensure that faulty equipment connected to it will blow a fuse in the distribution board
3. b) Ensure that no voltage is developed between either output lead and ground
c) Ensure that no voltage is developed between the output leads
d) Step down the mains voltage to a safe value
17. What device is used to store electrical energy in an electrostatic field:
a) A battery c) a capacitor
b) A transformer d) an inductor
18. What dies a variable resistor or potentiometer do:
a) Its resistance changes when AC is applied to it
b) It transforms a variable voltage into a constant voltage
c) Its resistance changes when its slide or contact is moved
d) To create an open circuit when there is too much current in a circuit
19. Which component can amplify a small signal using low voltages:
a) PNP transistor
b) an electrolytic capacitor
c) A variable resistor
d) a multiple-cell battery
1
2
3
4
5
7
8
6
FIGURE N6-1
20. In figure N6-1, which symbol represents a fixed resistor:
a) Symbol 2 c) Symbol 4
b) Symbol 3 d) Symbol 5
4. In figure N6-1, which symbol represents a fuse
a) Symbol 1 c) Symbol 5
b) Symbol 3 d) Symbol 7
In figure N6-1, which symbol represents a single-cell battery
a) Symbol 7 b) Symbol 5
a) Symbol 1 d) Symbol 4
21 In figure N6-1, which symbol represents an earth ground:
a) Symbol 2 b) Symbol 5
c) Symbol 6 d) Symbol 8
22 In figure N6-1, which symbol represents an antenna
a) Symbol 2 b) Symbol 3
c) Symbol 6 d) Symbol 7
23 In figure N6-2, which symbol represents a single-pole, single-throw switch
1
2
3
4
FIGURE N6-2
b) Symbol 1 c) Symbol 3
c) Symbol 2 d) Symbol 4
24 What does a capacitor do:
a) It stores energy electrochemically and opposes a change in current
5. b) It stores energy electrostatically and opposes a change in voltage
c) It stores energy electromagnetically and opposes a change in current
d) It stores energy electromechanically and opposes a change in voltage
25 The mains transformer in a transmitter is fitted with an internal screen. To minimize the
possibility of introducing mains-borne interference it should be connected to:
a) the chassis
b) the VFO output
c) the live side of the mains
d) left floating
26 The total capacitance of two or more capacitors in series is :
a) always less than that of the smallest capacitor
b) always greater than hat of the largest capacitor
c) found by adding each of the capacitances together
d) found by adding the capacitances together and dividing by their total number
27 An absorption wavemeter is useful for:
a) Checking exact transmission frequency
b) Checking frequency drift
c) Checking peak modulation index
d) Checking for harmonic radiation
28 How does a spectrum analyzer differ from a conventional time-domain oscilloscope
a) A spectrum analyzer measures ionospheric reflection; an oscilloscope displays electrical signals
b) A spectrum analyser displays signals in the time domain; an oscilloscope displays signals in the frequency domain
c) A spectrum analyzer displays signals in the frequency domain; an oscilloscope displays signals in the
time domain
d) A spectrum analyzer displays radio frequencies; an oscilloscope displays audio frequencies
29 How is an ammeter usually connected to a circuit under test
a) In series with the circuit
b) in quadrature with the circuit
c) In parallel with the circuit
d) a phase with the circuit
30 What might happen if you switch a multimeter to measure resistance while you have it connected to measure
voltage
a) The multimeter would read half the actual voltage
b) It would probably destroy the meter circuitry
c) The multimeter would read twice the actual voltage
d) Nothing unusual would happen; the multimeter would measure the circuit’s resistance
31 Which instrument would you use to measure electric current:
6. a) an ohmmeter b) a wavemeter
c) a voltmeter d) an ammeter
32 What instrument can be used to determine the horizontal radiation pattern of an antenna
a) a field-strength meter
b) a grid-dip meter
c) an oscilloscope
d) a signal tracer & an audio amplifier
33 An absorption wavemeter can be used to check for:
a) Over-modulation
b) Receiver overloading
c) Band edge signals
d) Correct selection of harmonic from a multiplier circuit
34 Which of the following is NOT something you would determine with a spectrum analyzer
a) The degree of isolation between the input and output ports of a 2-meter duplexer
b) Whether a crystal is operating on its fundamental or overtone
c) The speed at which a transceiver switches from transmit to receive when being used for packet radio
d) The spectral output of a transmitter
35 What can a logic probe indicate about a digital logic circuit
a) a short-circuit fault
b) an open-circuit fault
c) the resistance between logic modules
d) the high & low logic states
36 The wavelength of a signal in free space with a frequency of 100 MHz is:
a) 30mm b) 0.3m
c) 3m d) 30m
37 What does a frequency counter do
a) It makes frequency measurements
b) It produces a reference frequency
c) It measures FM transmitter deviation
d) It generates broadband white noise
7. 38 What does a dip-meter do
a) It accurately indicates signal strength
b) It measures frequency accurately
c) It measures transmitter output power accurately
d) It gives an indication of the resonant frequency of a circuit
39 The following unit in a DC power supply performs a smoothing operation
a) an electrolytic capacitor
b) a fuse
c) a crowbar
d) a full-wave diode bridge
40 A mains operated DC power supply
a) Converts DC from the mains into AC of the same voltage
b) Converts energy from the mains into DC for operating electronic equipment
c) Is a diode-capacitor device for measuring mains power
d) Is a diode-choked device for measuring inductance power
41 A low pass filter will:
a) suppress sub-harmonics
b) reduce harmonics
c) always eliminate interference
d) improve harmonic radiation
42 A power supply is to power a solid-state transceiver. A suitable over-voltage protection device is a
a) Crowbar across the regulator output
b) 100uF capacitor across the transformer output
c) fuse in parallel with the regulator output
d) zener diode in series with the regulator
43 AGC stands for:
a) Amplified gain control
b) auxiliary gain cut-off
c) automatic ganging control
d) automatic gain control
8. 44 Over driving a power amplifier will:
a) give a high SWR
b) give minimum distortion on receive
c) generate excessive harmonics
d) minimize power output
45 VHF and UHF bands are frequently used for satellite communication because
a) Waves at these frequencies travel to & from the satellite relatively unaffected by the ionosphere
b) The Doppler frequency change caused by satellite motion is much less than at HF
c) Satellites move too fast for HF waves to follow
d) The Doppler effect would cause HF waves to be shifted into the VHF and UHF bands
46 When using voice, which of the following modes of transmissions required the least bandwidth?
a) single sideband
b) amplitude modulation
c) frequency modulation
d) phase modulation
47 The sensitivity of a receiver can be degraded by:
a) strong RF signals on a nearby frequency
b) removing all crystals
c) good RF filtering
d) incorrect adjustment of the volume control
48 Radio wave polarisation is defined by the orientation of the radiated
a) magnetic field b) electric field
c) inductive field d) capacitive field
49 For long distance propagation, the radiation angle of energy from the antenna should be:
a) less than 30 degrees
b) more than 30 degrees but less than 45
c) more than 45 degrees but less than 90
d) 90 degrees
9. 50 The ability of a receiver to separate signals close in frequency is called its:
a) noise figure b) sensitivity
c) bandwidth d) selectivity
51 What is the primary source of noise that can be heard in a VHF/UHF-band receiver with an antenna
connected?
a) receiver front-end noise
b) man-made noise
c) atmospheric noise
d) detector noise
52 Which of the following antenna arrangements is least likely to radiate harmonics:
a) a dipole fed with coaxial cable
b) a dipole fed with balanced feeder
c) an inverted L-Marconi with vertical feeder
d) a trap dipole
53 A stage in a receiver with input and output circuits tuned to the received frequency is the :
a) RF amplifier
b) local oscillator
c) audio frequency amplifier
d) detector
54 A communication receiver may have several IF filters of different bandwidths. The operator
selects one to:
a) improve the S-meter readings
b) improve the receiver sensitivity
c) improve the reception of different types of signal
d) increase the noise received
55 To obtain high frequency stability in a transmitter, the VFO should be:
a) Run from a non-regulated AC supply
10. b) powered from a regulated DC supply
c) In a plastic box
d) able to change frequency with temperature
56 The side of quad antenna is:
a) a quarter wavelength
b) a half wavelength
c) three quarter of a wavelength
d) a full wavelength
57 The driver stage of a transmitter is located:
a) Before the power amplifier
b) with the frequency multiplier
c) Between oscillator and buffer
d) after the output low-pass filter circuit
58 The process of modulation allows
a) Information to be impresses on to a carrier
b) Information to be removed from a carrier
c) Voice and Morse code to be combined
d) None of these
59 The output power rating of a linear amplifier is a SSB transmitter is a specified by the
a) peak DC input power
b) mean AC input power
c) peak envelope power
d) unmodulated carrier power
1
2
3
DIPOLE
BEAM
DUMMY
11. LOAD
FIGURE N7-2
60 In figure N7-2, if block 1 is a transceiver and block 3 is an antenna switch, what is block 2
a) a terminal-node switch
b) an SWR meter
c) a dipole antenna
d) a high-pass filter
61 Harmonic frequencies are
a) Always lower in the frequency than the fundamental frequency
b) At multiples of the fundamental frequency
c) Any unwanted frequency above the fundamental frequency
d) Any frequency causing TVI
62 A parasitic oscillation
a) Is an unwanted signal developed in a transmitter
b) Is generated by parasitic elements of a Yagi beam
c) Does not cause any radio interference
d) Is produced in a transmitter oscillator stage
63 Parasitic oscillations can cause interference. They are
a) Always the same frequency as the mains supply
b) Always twice the operating frequency
c) Not related to the operating frequency
d) Three times the operating frequency
64 Unwanted signals from a radio transmitter which cause harmful interference to other users are
known as
12. a) Rectified signals
b) Re-radiation signals
c) Reflected signals
d) Harmonic signals and spurious signals
65 To reduce the harmonic output from a high frequency transmitter, the following filter is usually
installed at the transmitter
a) band pass b) low pass
c) high pass d) active filter
66 Test should be made on one’s equipment to check for harmonic radiation. These should be
a) from time to time
b) every 6 months
c) at the time of renewal of the license
d) weekly
67 A harmonic is
a) a whole number multiple of a frequency
b) a sub multiple of a frequency
e) any frequency greater than the fundamental frequency
f) any frequency causing interference
68 Which of the following sets of components are used to make RF filters?
a) Diodes and resistors
b) Zener diodes and inductors
c) LEDs and capacitors
d) Inductors capacitors
69 Earth return circuits should always be:
a) high impedance b) highly reactive
c) low impedance d) inductive
13. 70 What is a folded dipole antenna
a) a dipole one-quarter wavelength long
b) a type of ground-plane antenna
c) a dipole whose ends are connected by a one-half wavelength piece of wire
d) a hypothetical antenna used in theoretical discussions to replace the radiation resistance
71 What is meant by antenna gain
a) the numerical ratio relating the radiated signal strength of an antenna to that of another antenna
b) the numerical ratio of the signal in the forward direction to the signal in the back direction
c) the numerical ratio of the amount of power radiated by an antenna compared tot eh transmitter output power
d) the final amplifier gain minus the transmission-line losses (including any phasing lines present)
72 A neighbour using a TV set top antenna complains of interference when you are transmitting at
VHF. As a first step to eliminating this problem you could suggest:
a) better coaxial cable on their antenna
b) they use a preamplifier
c) they use a roof mounted antenna
d) their set is no good
73 Which of the following does not rely on a magnetic field:
a) a dynamic microphone
b) a loudspeaker
c) a carbon microphone
d) a transformer
74 The main purpose of a Varactor Diode is:
a) tuning b) rectification
c) voltage regulation d) display
75 An antenna which transmits well is one direction is a
a) dipole with a reflector only
b) quarterwave grounder vertical
14. c) a yagi
d) none of the above
76 The purpose of a balun in a transmitting antenna system is to
a) balance harmonic radiation
b) reduce unbalanced standing waves
c) protect the antenna system from lightning strikes
d) match unbalanced and balanced transmission lines
77 The main characteristic of a vertical antenna is that it
a) requires few insulators
b) is very sensitive to signals coming from horizontal aerials
c) receives signals from all points around it equally well
d) is easy to feed with TV ribbon feeder
78 A noise blanker on a receiver is most effective to reduce:
a) 50 Hz power supply hum
b) noise originating from the mixer stage of the receiver
c) ignition noise
d) noise originating from the RF stage of the receiver
79 What does an antenna tuner do
a) it matches a transceiver output impedance to the antenna system impedance
b) it helps a receiver automatically tune in stations that are far away
c) it switches an antenna system to a transceiver when sending and to a receiver when listening
d) it switches a transceiver between different kinds of antennas connected to one feed line
80 How is a Yagi antenna constructed
a) two or more straight, parallel elements are fixed in line with each other
b) two or more square or circular loops are fixed in line with each other
c) two or more square or circular loops are stacked inside each other
d) a straight element is fixed in the center of three or more elements that angle toward the ground
15. 81 When operating a mobile HF set at home from a battery supply and using the base antenna there
is no interference problem. When using the same arrangement but with an earthed battery
charger connected interference occurs on an electronic organ. The possible cause is:
a) the production of sub-harmonics at the transmitter
b) very strong received signal
c) poor RF earthing
d) that the RF earthing is too good
82 Yagi antenna is said to have a power gain over a dipole antenna for the same frequency band
because
a) it radiates more power than a dipole
b) more powerful transmitters can use it
c) it concentrates the radiation in one direction
d) it can be used for more than one band
83 The bandwidth of a beam antenna is dependent on:
a) radiation resistance of the dipole
b) spacing of directors and reflectors
c) feed cable impedance
d) propagation conditions
84 What is a loop antenna
a) a large circularly-polarised antenna
b) a small coil of wire tightly wound around a toraidal ferrite core
c) several turns of wire wound in the shape of a large open coil
d) any antenna coupled to a feed line through an inductive loop of wire
85 What phenomenon has the most effect on radio communication beyond ground-wave or line-of-
sight ranges
a) solar activity
b) lunar tidal effects
c) the F1 region of the ionosphere
d) the F2 region of the ionosphere
86 An antenna which transmits equally well in all compass directions is a
a) dipole with a reflector only
16. b) quarterwave grounded vertical
c) dipole with director only
d) half-wave horizontal dipole
87 What pattern is desirable for a direction-finding antenna
a) one which is non-cardioids
b) one with good front-to-back and front-to-side ratios
c) one with good top-to-bottom and side-to-side ratios
d) one with shallow nulls
88 To check for harmonics in a radiated signal, which of the following could be used?
a) an SWR meter
b) an absorption wave meter
c) a digital frequency meter
d) an AVO meter
89 Radio wave polarisation is defined by the orientation of the radiated:
a) magnetic field c) inductive field
b) electric field d) capacitive field
90 For long distance propagation, the radiation angle of energy from the antenna should be
a) less than 30 degrees
b) more than 30 degrees but less than 45
c) more than 45 degrees but less than 90
d) 90 degrees
91 A band pass filter following a VHF transmitter will:
a) stop all transmitting frequencies
b) allow all harmonics to be radiated
c) allow all sub-harmonics to be radiated
d) pass the desired frequency range with minimum loss
92 The ionosphere layer mainly responsible for long distance communication at HF is:
a) D b) E
c) F2 d) F1
17. 93 High frequency long-distance propagation is most dependent on
a) ionospheric reflection
c) tropospheric reflection
d) ground reflection
d) inverted reflection
94 A low pass filter will
a) suppress sub-harmonics
b) reduce harmonics
c) always eliminate interference
d) improve harmonic radiation
95 To prevent unwanted radiation in the shack, RF connections between units should be by
a) open wire feeder
b) good quality coaxidel cable
c) bell wire
d) mains type cable
96 The coaxial cable from an SWR meter to an antenna at HF develops a fault so that no power
reaches the antenna. The SWR meter will read:
a) zero b) 1:1
c) high d) very low
97 What is the proper procedure for suppressing electrical noise in a mobile transceiver
a) apply shielding and filtering where necessary
b) insulate all place sheet metal surfaces from each other
c) apply antistatic spray liberally to all non-metallic surfaces
d) install filter capacitors in series with all DC wiring
98 The resonant frequency of a tuned circuit can be checked by:
a) a DC Voltmeter
b) a DIP Oscillator
c) a Digital Frequency Meter
d) an Ohm-Meter
99 How can alternator whine be minimized
a) by connecting the radio’s power leads to the battery by the longest possible path
b) by connecting the radio’s power leads to the battery by the shortest possible path
18. c) by installing a high-pass filter in series with the radio’s DC power lead to the vehicle’s electrical system
d) by installing filter capacitors in series with the DC power lead
100 A corroded connector on a neighbour’s TV receiving antenna may cause:
a) unwanted mixing products due to it exhibiting diode properties
b) mains rectification
c) enhanced signal reception due to its fitering properties
d) increased amplification
101 A band pass filter will
a) pass frequencies each side of a band
b) attenuate low frequencies but not high
c) attenuate frequencies each side of a band
d) attenuate high frequencies but not low
102 If the VFO of a transmitter is subject to varying temperatures, this might cause:
a) chrip
b) drift
c) harmonic generation
d) no problems
103 A braid-breaking choke in a TV antenna down load will block:
a) all AC signals
b) out phase interfering signals
c) in phase interfering signals
d) mains hum
104 When operating at HF, interference is caused on a TV. The most likely route for the interfering
signal is:
a) via the earth
b) through the transmitter power supply
c) by the TV antenna coaxial cable screen and/or IF stages
d) by frequency multiplication in free space
105 To reduce strong signals from a 21 MHz transmitter reaching a TV via antenna down lead, one
could fit:
a) a high pass filter in the TV down lead
b) a low pass filter in the TV down lead
19. c) a UHF amplifier in the TV down lead
d) a band reject filter at the TV channel frequency
106 A good dummy load for RF is constructed from:
a) light bulbs
b) a column of water
c) wire wound resistors
d) non-reactive resistors
107 Which of the following components could be attached to a moving coil meter in an attempt to
measure power?
a) resistor b) thermistor
c) thermocouple d) thimble
108 When transmitting Morse code, key clicks can be prevented by a
a) resistor in series with the key, and a choke across the key contacts
b) choke in series with the key, and a capacitor across the key contacts
c) choke across the key contacts, and a capacitor in series with the key
d) capacitor and choke in series with the key contacts
109 It is not a good practice to:
a) use double insulated cable on EHT circuits
b) use a separate RF earth
c) use a gas pipe for the earth connection
d) have safety switches
110 How much electrical current flowing through the human body will probably be fatal
a) as little as 1/10 of an ampere
b) approximately 10 amperes
c) more than 20 amperes
d) current through the human body is never fatal
20. 111 What could happen to your transceiver if you replace its blown 5 amp AC line fuse with a 30 amp
fuse
a) a 30-amp fuse would better protect your transceiver from using too much current
b) the transceiver would run cooler
c) the transceiver could use more current than 5 amps and a fire could occur
d) the transceiver would not be able to produce as much RF output
112 How can amateur station equipment best be protected from lighting damage
a) use heavy insulation on the wiring
b) never turn off the equipment
c) disconnect the ground system from all radios
d) disconnect all equipment from the power lines and antenna cables
113 Which of the following is the best way to install your antenna in relation to overhead electric
power lines
a) always be sure your antenna wire is higher than the power line, and crosses it at a 90-degree angle
b) always be sure your antenna and feed line are well clear of any power lines
c) always be sure your antenna is lower than the power line, and crosses it at a small angle
d) only use vertical antennas within 100 feet of a power line
114 ‘VOX’ stands for
a) volume operated extension speaker
b) variable oscillator transmitter
b) voice operated transmit
d) voice operated expander
115 The figure in a receiver’s specifications which indicates its sensitivity is the
a) bandwidth of the IF in kilohertz
b) signal plus noise to noise ratio
c) audio output in watts
d) number of RF amplifiers
116 The abbreviation AGC means:
21. a) attenuating gain capacitor
b) anode-grid capacitor
c) automatic gain control
d) amplified grid conductance
117 The coaxial cable from an SWR meter to an antenna at HF develops a fault so that no power
reaches the antenna. The SWR meter will read:
a) zero b) 1:1
c) high d) very low
118 Define Peak Envelope Power
a) means power supplied to an antenna by a radio receiver in a condition of no modulation
b) means the average power supplied to the antenna transmission lines by a transmitter during one radio-frequency
cycle at the highest crest of the modulation envelope taken under conditions of normal operation
c) means the average power that is supplied to the antenna transmission lines in a condition of no modulation
d) means the average power that is supplied to the antenna in a condition where such power does not create a
danger to life
119 Identify the correct statements
i All equipment should be controlled by one master switch, the position of which should be known to others in the
house or club
ii All equipment should be properly connected to a good and permanent earth
iii PVC water main pipes are commonly used as permanent earth
iv Indicator lamps should be installed showing that the equipment is live
v Indicator lamps should be clearly visible at the operating and test position
vi Faulty indicator lamps should be replaced immediately
vii Filament lamps are more reliable than gas-filled (neon) lamps
viii Antennas should always be connected to mains or other hot source
a) i, ii & iv c) v, vi & vii
b) ii, iii & v d) iii, vii & viii
120 For your safety, before checking a fault in a mains operated power supply unit, first
a) short the leads of the filter capacitor
b) turn off the power and remove the power plug
c) check the action of the capacitor bleeder resistance
22. d) remove and check the fuse in the power supply
121 Wires carrying high voltages in a transmitter should be well insulated to avoid
a) short circuits c) over modulation
b) overheating d) SWR effects
122 The purpose of using three wires in the mains power cord and plug on amateur radio equipment is
to
a) make it inconvenient to use
b) prevent the chassis from becoming live in case of an internal short to the chassis
c) prevent the plug from being reversed in the wall outlet
d) prevent short circuits
123 When switching on the power to your transmitter, for safety reasons ensure that
a) the other callsign followed by your own callsign
b) you callsign followed by the other callsign
c) your own callsign, repeated twice
d) the other callsign, repeated twice
124 The following should always be included as a standard protection device in any power supply
a) a saturating transformer
b) a fuse in the mains lead
c) a zener diode bridge limiter
d) a fuse in the filter capacitor negative lead
125 For equipment safety, before switching on your amateur radio equipment, check that the
equipment is connected to
a) an unregulated power supply unit
b) an antenna or a dummy load
c) check that your license is valid
d) answer a & b above
126 Two 10K Ohm resistors are connected in parallel across a 5V DC supply. Total current taken is:
a) 5uA
b) 1mA
23. c) 0.5mA
d) 1A
127 A 50 Ohm dummy loads are made from eleven 560 Ohm carbon resistors each of 5W rating. Total
safe power that can be dissipated is:
a) 0.5W b) 5.0W
c) 27.5W d) 55W
128 When monitoring the frequency of an un-modulated carrier, the readout of a digital frequency
counter should show:
a) the carrier frequency plus the number of significant harmonics present
b) how many sidebands there are
c) nothing
d) the constant carrier frequency
129 At 3.5MHz, a wire 40 meters long corresponds to:
a) a quarter wavelength
b) half wavelength
c) one wavelength
d) two wavelength
130 You can operate this number of identical lamps, each drawing a current of 250 mA, from a 5A
supply:
a) 50 b) 30
c) 20 d) 5