Technician License Course Chapter 3 Types of Radios and Radio Circuits

1. Technician License CourseChapter 3 Types of Radios and Radio Circuits Module 7

2. The Basic Radio Station

3. Basic Station Organization • Station Equipment • Receiver • Transmitter • T R Switch • Antenna • Power Supply • Accessory Station Equipment • Microphones, CW Keys, etc.

4. Well equipped station

5. Transmit/Receive (TR) Switch • If the station antenna is shared between the transmitter and receiver, the TR switch allows the antenna to be switched to the transmitter when sending and to the receiver when receiving. • In a transceiver, this TR switch is inside the unit and requires no attention by the operator.

6. What Happens During Radio Communication? • Transmitting (sending a signal): • Information (voice, data, video, commands, etc.) is converted to electronic form. • The information in electronic form is attached or embedded on a radio wave (a carrier). • The radio wave is sent out from the station antenna into space.

7. What Happens During Radio Communication? • Receiving end: • The radio wave (carrier) with the information is intercepted by the receiving station antenna. • The receiver extracts the information from the carrier wave. • The information is then presented to the user in a format that can be understood (sound, picture, words on a computer screen, response to a command).

8. What Happens During Radio Communication? • This sounds pretty simple, but it in reality is pretty complex. • This complexity is one thing that makes ham radio fun…learning all about how radios work. • Don’t be intimidated. You will be required to only know the basics, but you can learn as much about the “art and science” of radio as you want.

9. Simple CW Transmitter Block Diagram

10. Receiver Circuits • Oscillators produce signals at a desired frequency. • Mixers combine signals, and produce both the sum and difference of the input signals. • Filters remove unwanted frequencies or signals. • Pre –amplifiers and amplifiers increase signal levels.

11. Receiver Design • It is always a challenge for receiver designers to balance the competing traits of selectivity and sensitivity. Selectivity expresses how well a receiver rejects adjacent signals. Sensitivity expresses how faint a signal can be detected. • Product detectors are used in receivers for SSB and CW signals to extract the modulation. • Frequency discriminators are used in receivers for FM signals to extract the modulation.

12. Transmitter Circuits • A modulator combines audio and RF signals. • A power amplifier increases the level of the modulated signal. Power amplifiers can be added externally to increase the transmitted signal strength. • A transverter is a device that converts a carrier frequency to another frequency. ( Eg: 28 Mhz to 220Mhz )

13. Receiver Block Diagram

14. Receiver Block Diagram w/ Preamp Pre-amplifier A pre-amplifier can be inserted between the antenna and receiver input to increase receiver sensitivity to weak signals.

15. Superheterodyne Receiver • One of the most widely used AM, SSB, and CW receiver designs is the superheterodyne receiver. The incoming signal is mixed with a local oscillator to produce an intermediate frequency, which is sent to a product detector for mixing with a beat frequency oscillator. The resulting audio frequency is amplified, and comes out the speaker. • Single conversion superhet receivers use a single IF stage. Dual conversion superhet receivers use two IF stages.

16. The Superheterodyne ReceiverBlock Diagram

17. FM Receivers • FM receivers are designed to detect the frequency variations on the carrier that are produced by this type of modulation. • A frequency discriminator detects the variation from the carrier frequency. • FM signals are less affected by natural noise than AM signals.

18. The FM ReceiverBlock Diagram

19. What is the function of a product detector? (T7A01) • A. Detect phase modulated signals • B. Demodulate FM signals • C. Detect CW and SSB signals • D. Combine speech and RF signals

20. What is the function of a product detector? (T7A01) • A. Detect phase modulated signals • B. Demodulate FM signals • C. Detect CW and SSB signals • D. Combine speech and RF signals

21. What type of receiver is shown in Figure T6? (T7A02) • A. Direct conversion • B. Super-regenerative • C. Single-conversion superheterodyne • D. Dual-conversion superheterodyne

22. What type of receiver is shown in Figure T6? (T7A02) • A. Direct conversion • B. Super-regenerative • C. Single-conversion superheterodyne • D. Dual-conversion superheterodyne

23. What is the function of a mixer in a superheterodyne receiver? (T7A03) • A. To reject signals outside of the desired passband • B. To combine signals from several stations together • C. To shift the incoming signal to an intermediate frequency • D. To connect the receiver with an auxiliary device, such as a TNC

24. What is the function of a mixer in a superheterodyne receiver? (T7A03) • A. To reject signals outside of the desired passband • B. To combine signals from several stations together • C. To shift the incoming signal to an intermediate frequency • D. To connect the receiver with an auxiliary device, such as a TNC

25. What circuit is pictured in Figure T7, if block 1 is a frequency discriminator? (T7A04) • A. A double-conversion receiver • B. A regenerative receiver • C. A superheterodyne receiver • D. An FM receiver

26. What circuit is pictured in Figure T7, if block 1 is a frequency discriminator? (T7A04) • A. A double-conversion receiver • B. A regenerative receiver • C. A superheterodyne receiver • D. An FM receiver

27. What is the function of block 1 if figure T4 is a simple CW transmitter? (T7A05) • A. Reactance modulator • B. Product detector • C. Low-pass filter • D. Oscillator

28. What is the function of block 1 if figure T4 is a simple CW transmitter? (T7A05) • A. Reactance modulator • B. Product detector • C. Low-pass filter • D. Oscillator

29. What device takes the output of a low-powered 28 MHz SSB exciter and produces a 222 MHz output signal? (T7A06) • A. High-pass filter • B. Low-pass filter • C. Transverter • D. Phase converter

30. What device takes the output of a low-powered 28 MHz SSB exciter and produces a 222 MHz output signal? (T7A06) • A. High-pass filter • B. Low-pass filter • C. Transverter • D. Phase converter

31. If figure T5 represents a transceiver in which block 1 is the transmitter portion and block 3 is the receiver portion, what is the function of block 2? (T7A07) • A. A balanced modulator • B. A transmit-receive switch • C. A power amplifier • D. A high-pass filter

32. If figure T5 represents a transceiver in which block 1 is the transmitter portion and block 3 is the receiver portion, what is the function of block 2? (T7A07) • A. A balanced modulator • B. A transmit-receive switch • C. A power amplifier • D. A high-pass filter

33. Which of the following circuits combines a speech signal and an RF carrier? (T7A08) • A. Beat frequency oscillator • B. Discriminator • C. Modulator • D. Noise blanker

34. Which of the following circuits combines a speech signal and an RF carrier? (T7A08) • A. Beat frequency oscillator • B. Discriminator • C. Modulator • D. Noise blanker

35. Which of the following devices is most useful for VHF weak-signal communication? (T7A09) • A. A quarter-wave vertical antenna • B. A multi-mode VHF transceiver • C. An omni-directional antenna • D. A mobile VHF FM transceiver

36. Which of the following devices is most useful for VHF weak-signal communication? (T7A09) • A. A quarter-wave vertical antenna • B. A multi-mode VHF transceiver • C. An omni-directional antenna • D. A mobile VHF FM transceiver

37. What device increases the low-power output from a handheld transceiver? (T7A10) • A. A voltage divider • B. An RF power amplifier • C. An impedance network • D. A voltage regulator

38. What device increases the low-power output from a handheld transceiver? (T7A10) • A. A voltage divider • B. An RF power amplifier • C. An impedance network • D. A voltage regulator

39. Which of the following circuits demodulates FM signals? (T7A11) • A. Limiter • B. Discriminator • C. Product detector • D. Phase inverter

40. Which of the following circuits demodulates FM signals? (T7A11) • A. Limiter • B. Discriminator • C. Product detector • D. Phase inverter

41. Which term describes the ability of a receiver to discriminate between multiple signals? (T7A12) • A. Tuning rate • B. Sensitivity • C. Selectivity • D. Noise floor

42. Which term describes the ability of a receiver to discriminate between multiple signals? (T7A12) • A. Tuning rate • B. Sensitivity • C. Selectivity • D. Noise floor

43. Where is an RF preamplifier installed? (T7A13) • A. Between the antenna and receiver • B. At the output of the transmitter’s power amplifier • C. Between a transmitter and antenna tuner • D. At the receiver’s audio output

44. Where is an RF preamplifier installed? (T7A13) • A. Between the antenna and receiver • B. At the output of the transmitter’s power amplifier • C. Between a transmitter and antenna tuner • D. At the receiver’s audio output