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General Licensing Class “G7”

General Licensing Class “G7”. Presented by the Acadiana Amateur Radio Assoc. Lafayette, Louisiana. General Class Element 3 Course Presentation. ELEMENT 3 SUB-ELEMENTS G1 – Commission’s Rules G2 – Operating Procedures G3 – Radio Wave Propagation G4 – Amateur Radio Practices

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General Licensing Class “G7”

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  1. General Licensing Class“G7” Presented by the Acadiana Amateur Radio Assoc. Lafayette, Louisiana

  2. General Class Element 3 Course Presentation ELEMENT 3 SUB-ELEMENTS G1 – Commission’s Rules G2 – Operating Procedures G3 – Radio Wave Propagation G4 – Amateur Radio Practices G5 – Electrical Principles G6 – Circuit Components G7 – Practical Circuits G8 – Signals and Emissions G9 – Antennas G0 – Electrical and RF Safety 2

  3. G7 … Practical Circuits G7A • Power Supplies • A power-supply bleeder resistor discharges the filter capacitors providing a safety feature. • Capacitors and inductors are used in a power-supply filter network.

  4. G7 … Practical Circuits G7A • Power Supplies (cont) • An advantage of a switched-mode power supply as compared to a linear power supply is high frequency operation allows the use of smaller components. Interior view of a switched-mode power supply: A - bridge rectifierB - Input filter capacitorsC - TransformerD - output filter coilE - output filter capacitors

  5. G7 … Practical Circuits G7A • Power Supplies (cont) • A 180 degree portion of the AC cycle is converted to DC by a half-wave rectifier.

  6. G7 … Practical Circuits G7A • Power Supplies (cont) (Repeat) • A 180 degree portion of the AC cycle is converted to DC by a half-wave rectifier.

  7. G7 … Practical Circuits G7A • Power Supplies (cont) • A 360 degree portion of the AC cycle is converted to DC by a full-wave rectifier. • The output waveform of an unfiltered full-wave rectifier connected to a resistive load is a series of DC pulses at twice the frequency of the AC input.

  8. G7 … Practical Circuits G7A • Power Supplies (cont) (Repeat) • A 360 degree portion of the AC cycle is converted to DC by a full-wave rectifier. • The output waveform of an unfiltered full-wave rectifier connected to a resistive load is a series of DC pulses at twice the frequency of the AC input.

  9. G7 … Practical Circuits G7A • Power Supplies (cont) • The minimum peak-inverse-voltage rating of the rectifier in a full-wave power supply should be double the normal peak output voltage of the power supply. • The approximate minimum peak-inverse-voltage rating of the rectifier in a half-wave power supply should be two times the normal peak output voltage of the power supply. • A desirable characteristic for capacitors used to filter the DC output of a switching power supply is low equivalent series resistance.

  10. G7 … Practical Circuits G7A • Transmitters • A Balanced modulator circuit is used to combine signals from the carrier oscillator and speech amplifier and send the result to the filter in a typical single‑sideband phone transmitter. • An advantage of a crystal controlled transmitter is a Stable output frequency.

  11. G7 … Practical Circuits G7A • Receivers • A Mixer circuit is used to process signals from the RF amplifier and local oscillator and send the result to the IF filter in a super heterodyne receiver.

  12. G7 … Practical Circuits • Receivers (cont) • Frequency conversion process.

  13. G7 … Practical Circuits G7A • Receivers (cont) • A Product detector circuit is used to process signals from the IF amplifier and BFO and send the result to the AF amplifier in a single-sideband phone superheterodyne receiver.

  14. G7 … Practical Circuits G7A • Receivers (cont) • A direct conversion receiver is suitable for CW and SSB reception but does not require a mixer stage or an IF amplifier.

  15. G7 … Practical Circuits • Receivers (cont) • Compared to previous slide, this receiver has 2 IF’s, 2 mixers, and 2 oscillators, hence the term: Dual-Conversion Receiver.

  16. G7 … Practical Circuits G7A • Receivers (cont) • The simplest combination of stages that can be combined to implement a superheterodyne receiver is a HF oscillator, mixer, and detector.

  17. G7 … Practical Circuits G7A • Receivers (cont) • A Discriminator circuit is used in many FM receivers to convert signals coming from the IF amplifier to audio. Discriminator

  18. G7 … Practical Circuits G7A • Filters • The impedance of a low-pass filter as compared to the impedance of the transmission line into which it is inserted should be about the same. • A Filter might be used to process signals from the balanced modulator and send them to the mixer in a single-sideband phone transmitter. Filter

  19. G7 … Schematic drawing symbols • Symbol 3 represents a fixed resistor. • Symbol 13 represents a single cell battery. • Symbol 4 represents a NPN transistor. • Symbol 5 represents a variable capacitor. • Symbol 6 represents a transformer. • Symbol 11 represents a single pole switch.

  20. G7 … Practical Circuits G7B • Digital circuits • A “flip-flop” circuit is a digital circuit with two stable states. • Digital circuits use the binary number system because binary "ones" and "zeros" are easy to represent with an "on" or "off" state.

  21. G7 … Practical Circuits G7B • Digital circuits (cont) • The output of a two-input NAND gate, given both inputs are “one” is Zero.

  22. G7 … Practical Circuits G7B • Digital circuits (cont) • The output of a NOR gate given that both inputs are “zero” is One.

  23. G7 … Practical Circuits G7B • Digital circuits(cont) • There are 8 states in a 3-bit binary counter. • 000 001 010 011 • 100 101 110 111 • A shift register is a clocked array of circuits that passes data in steps along the array.

  24. G7 … Practical Circuits G7B • Amplifiers • Low distortion is a characteristic of a Class A amplifier. • A Class “C” power stage is appropriate for amplifying a modulated signal for the CW mode. • High efficiency is an advantage of a Class C amplifier

  25. G7 … Practical Circuits G7B • Amplifiers (cont) • The efficiency of an RF power amplifier is determined by dividing the RF output power by the DC input power. • A linear amplifier is an amplifier whose output preserves the input waveform. RF Output Power _____________________ Efficiency = DC Input Power

  26. G7 … Practical Circuits G7B • Oscillators • The basic components of virtually all oscillators are a filter and an amplifier operating in a feedback loop.

  27. G7 … Practical Circuits G7B • Oscillators(cont) • The phase shift of the RC feedback circuit determines the frequency of an RC oscillator. • (Placed in the positive feedback loop.) • The inductance and capacitance in the tank circuit determines the frequency of an LC oscillator.

  28. Element 3 General Class Question Pool Valid July 1, 2007 Through June 30, 2011

  29. G7A01 What safety feature does a power-supply bleeder resistor provide? • It acts as a fuse for excess voltage • It discharges the filter capacitors • It removes shock hazards from the induction coils • It eliminates ground-loop current

  30. G7A02 What components are used in a power-supply filter network? • Diodes • Transformers and transistors • Quartz crystals • Capacitors and inductors

  31. G7A03 What should be the minimum peak-inverse-voltage rating of the rectifier in a full-wave power supply? • One-quarter the normal output voltage of the power supply • Half the normal output voltage of the power supply • Double the normal peak output voltage of the power supply • Equal to the normal output voltage of the power supply

  32. G7A04 What should be the approximate minimum peak-inverse-voltage rating of the rectifier in a half-wave power supply? • One-half the normal peak output voltage of the power supply • Half the normal output voltage of the power supply • Equal to the normal output voltage of the power supply • Two times the normal peak output voltage of the power supply

  33. G7A05 What should be the impedance of a low-pass filter as compared to the impedance of the transmission line into which it is inserted? • Substantially higher • About the same • Substantially lower • Twice the transmission line impedance

  34. G7A06 Which of the following might be used to process signals from the balanced modulator and send them to the mixer in a single-sideband phone transmitter? • Carrier oscillator • Filter • IF amplifier • RF amplifier

  35. G7A07 Which circuit is used to combine signals from the carrier oscillator and speech amplifier and send the result to the filter in a typical single-sideband phone transmitter? • Mixer • Detector • IF amplifier • Balanced modulator

  36. G7A08 What circuit is used to process signals from the RF amplifier and local oscillator and send the result to the IF filter in a superheterodyne receiver? • Balanced modulator • IF amplifier • Mixer • Detector

  37. G7A09 What circuit is used to process signals from the IF amplifier and BFO and send the result to the AF amplifier in a single-sideband phone superheterodyne receiver? • RF oscillator • IF filter • Balanced modulator • Product detector

  38. G7A10 What is an advantage of a crystal controlled transmitter? • Stable output frequency • Excellent modulation clarity • Ease of switching between bands • Ease of changing frequency

  39. G7A11 What is the simplest combination of stages that can be combined to implement a superheterodyne receiver? • RF amplifier, detector, audio amplifier • RF amplifier, mixer, if amplifier • HF oscillator, mixer, detector • HF oscillator, product detector, audio amplifier

  40. G7A12 What type of receiver is suitable for CW and SSB reception but does not require a mixer stage or an IF amplifier? • A super-regenerative receiver • A TRF receiver • A super-heterodyne receiver • A direct conversion receiver

  41. G7A13 What type of circuit is used in many FM receivers to convert signals coming from the IF amplifier to audio? • Product detector • Phase inverter • Mixer • Discriminator

  42. G7A14 Which of the following is a desirable characteristic for capacitors used to filter the DC output of a switching power supply? • Low equivalent series resistance • High equivalent series resistance • Low Temperature coefficient • High Temperature coefficient

  43. G7A15 Which of the following is an advantage of a switched-mode power supply as compared to a linear power supply? • Faster switching time makes higher output voltage possible • Fewer circuit components are required • High frequency operation allows the use of smaller components • All of these choices are correct

  44. G7A16 What portion of the AC cycle is converted to DC by a half-wave rectifier? • 90 degrees • 180 degrees • 270 degrees • 360 degrees

  45. G7A17 What portion of the AC cycle is converted to DC by a full-wave rectifier? • 90 degrees • 180 degrees • 270 degrees • 360 degrees

  46. G7A18 What is the output waveform of an unfiltered full-wave rectifier connected to a resistive load? • A series of DC pulses at twice the frequency of the AC input • A series of DC pulses at the same frequency as the AC input • A sine wave at half the frequency of the AC input • A steady DC voltage

  47. G7A19 Which symbol in figure G7-1 represents a fixed resistor? • Symbol 2 • Symbol 6 • Symbol 3 • Symbol 12

  48. G7A20 Which symbol in figure G7-1 represents a single cell battery? • Symbol 5 • Symbol 12 • Symbol 8 • Symbol 13

  49. G7A21 Which symbol in figure G7-1 represents a NPN transistor? • Symbol 2 • Symbol 4 • Symbol 10 • Symbol 12

  50. G7A22 Which symbol in figure G7-1 represents a variable capacitor? • Symbol 2 • Symbol 11 • Symbol 5 • Symbol 12

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