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Technician Licensing Class

Technician Licensing Class. Multi-Mode Radio Excitement Section 6. Multi-Mode Radio Excitement. T7A9 A multi-mode VHF transceiver is most useful for VHF weak-signal communication. Multi-mode VHF/UHF transceiver. Multi-Mode Radio Excitement.

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Technician Licensing Class

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  1. Technician Licensing Class Multi-Mode Radio Excitement Section 6

  2. Multi-Mode Radio Excitement T7A9 A multi-mode VHF transceiver is most useful for VHF weak-signal communication. Multi-mode VHF/UHF transceiver

  3. Multi-Mode Radio Excitement T8A5CW is the type of emission that has the narrowest bandwidth. T8A11150 Hz is the approximate maximum bandwidth required to transmit a CW signal. T8A10The typical bandwidth of analog fast-scan TV transmissions on the 70 cm band about 6 MHz. CW Signal 150 Hz wide SSB Signal 2 - 3 kHz wide FM Signal 5 - 15 kHz wide UHF Fast-Scan TV ~ 6 MHz

  4. Multi-Mode Radio Excitement T7A5The function of block 1, if figure T4 is a simple CW transmitter is an oscillator. Antenna 1 Driver Power Amplifier oscillator Telegraph Key Figure T4

  5. Multi-Mode Radio Excitement T4B10500 Hz is an appropriate receive filter to select in order to minimize noise and interference for CW reception. Bandwidth filters vary for the mode being received. T7A2The type of receiver shown in Figure T6 is a single-conversion superheterodyne. Single-conversion superhet has only one IF amplifier. Block 1 is a detector • Super • heterodyne

  6. Multi-Mode Radio Excitement T7A1The function of a product detector is to detect CW and SSB signals. Block 1 as a product detector will detect CW and SSB A Product detector is necessary in simple Morse code (CW) and single-sideband (SSB) receivers.

  7. Multi-Mode Radio Excitement

  8. Multi-Mode Radio Excitement T8A1Single sideband is a form of amplitude modulation. T8A83 kHz is the approximate bandwidth of a single sideband voice signal. Carrier only CW Tones produce both side bands or AM Remove one sideband and suppress carrier becomes SSB

  9. Multi-Mode Radio Excitement T7A8A circuit that combines a speech signal and an RF carrier is a modulator. T7A3 The function of a mixer in a superheterodyne receiver is to shift the incoming signal to an intermediate frequency. Station Signal MIXER (In AM Broadcast Receiver) Signal C at 455 kHz Signal A at 800 kHz (or at 1200 kHz) Intermediate Frequency Local Oscillator Signal B at 1255 kHz (or at 1655 kHz) Block Diagram of an AM Broadcast Receiver Mixer

  10. Multi-Mode Radio Excitement T4B8The advantage of having multiple receive bandwidth choices on a multimode transceiver will permit noise or interference reduction by selecting a bandwidth matching the mode. T4B92400 Hz is an appropriate receive filter to select in order to minimize noise and interference for SSB reception.

  11. Multi-Mode Radio Excitement T4B6The receiver RIT or clarifier controls could be used if the voice pitch of a single-sideband signal seems too high or low. T4B7The term "RIT" means Receiver Incremental Tuning. Set knob to neutral, press RIT button to turn on function, and then adjust slightly for proper SSB voice reception RIT adjusts voice pitch, not the frequency of received station. • T7A13 An RF preamplifier is installed between the antenna and receiver.

  12. Multi-Mode Radio Excitement T7B2In reference to a receiver, interference by very strong signals causes fundamental overload. T7A12Selectivity is the term that describes the ability of a receiver to discriminate between multiple signals. T2B5The amplitude of the modulating signal determines the amount of deviation of an FM signal. Good TV Reception. Fundamental Overload

  13. Multi-Mode Radio Excitement T2B6When the deviation of an FM transmitter is increased its signal occupies more bandwidth. T7A4The circuit pictured in Figure T7, if block 1 is a frequency discriminator, is an FM receiver. T7A11A discriminator (Block 1) demodulates FM signals Radio Frequency Amplifier Mixer Wide Filter Intermediate Frequency Amplifier Figure T7 Oscillator Audio Amplifier Limiter Block 1

  14. Take Aways • A multi-mode VHF transceiver is most useful for VHF weak‑signal communication. • In comparison to SSB and FM, CW emission has the narrowest bandwidth. • The approximate maximum bandwidth required to transmit a CW signal is 150 Hz. • If figure T4 is a simple CW transmitter, the function of block 1 is an Oscillator.

  15. Take Aways • An appropriate receive filter to select in order to minimize noise and interference for CW reception is 500 Hz. • A Modulator combines a speech signal and an RF carrier. • A Single-conversion Superheterodyne receiver is shown in Figure T6.

  16. Take Aways • The function of a mixer in a superheterodyne receiver is to shift the incoming signal to an intermediate frequency. • Single sideband (SSB) is a form of amplitude modulation (AM). • The approximate bandwidth of a single sideband voice signal is 3 kHz. • The function of a product detector is to detect CW and SSB signals. • Selectivity is the ability of a receiver to discriminate between multiple signals. • The advantage of having multiple receive bandwidth choices on a multimode transceiver is that it permits noise or interference reduction by selecting a bandwidth matching the mode.

  17. Take Aways If block 1 is afrequency discriminator, a FM receiver is pictured in Figure T7.

  18. Take Aways • An appropriate receive filter to select in order to minimize noise and interference for SSB reception is 2400 Hz. • The receiver RIT or clarifier controls could be used if the voice pitch of a single-sideband signal seems too high or low. • The acronym for Receiver Incremental Tuning is “RIT”. • A fundamental overload in reference to a receiver is interference caused by very strong signals. • An RF preamplifier installed between the antenna and receiver. • The amplitude of the modulating signal determines the amount of deviation of an FM signal.

  19. Take Aways • When the deviation of an FM transmitter is increased it’s signal occupies more bandwidth. • A Discriminator demodulates FM signals. • The typical bandwidth of analog fast-scan TV transmissions on the 70 cm band is about 6 MHz.

  20. Element 2 Technician Class Question Pool Element 2 Technician Class Question Pool Multi-Mode Radio Excitement Valid July 1, 2010 Through June 30, 2014

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

  22. T8A05 Which of the following types of emission has the narrowest bandwidth? • FM voice • SSB voice • CW • Slow-scan TV

  23. T8A11 What is the approximate maximum bandwidth required to transmit a CW signal? • 2.4 kHz • 150 Hz • 1000 Hz • 15 kHz

  24. T7A05 What is the function of block 1 if figure T4 is a simple CW transmitter? • Reactance modulator • Product detector • Low-pass filter • Oscillator Antenna 1 Driver Power Amplifier Telegraph Key Figure T4

  25. T4B10 Which of the following is an appropriate receive filter to select in order to minimize noise and interference for CW reception? • 500 Hz • 1000 Hz • 2400 Hz • 5000 Hz

  26. T7A02 What type of receiver is shown in Figure T6? • Direct conversion • Super-regenerative • Single-conversion superheterodyne • Dual-conversion superheterodyne

  27. T7A01 What is the function of a product detector? • Detect phase modulated signals • Demodulate FM signals • Detect CW and SSB signals • Combine speech and RF signals

  28. T8A01 Which of the following is a form of amplitude modulation? • Spread-spectrum • Packet radio • Single sideband • Phase shift keying

  29. T8A08 What is the approximate bandwidth of a single sideband voice signal? • 1 kHz • 3 kHz • 6 kHz • 15 kHz

  30. T7A08 Which of the following circuits combines a speech signal and an RF carrier? • Beat frequency oscillator • Discriminator • Modulator • Noise blanker

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

  32. T4B08 What is the advantage of having multiple receive bandwidth choices on a multimode transceiver? • Permits monitoring several modes at once • Permits noise or interference reduction by selecting a bandwidth matching the mode • Increases the number of frequencies that can be stored in memory • Increases the amount of offset between receive and transmit frequencies

  33. T4B09 Which of the following is an appropriate receive filter to select in order to minimize noise and interference for SSB reception? • 500 Hz • 1000 Hz • 2400 Hz • 5000 Hz

  34. T4B06 Which of the following controls could be used if the voice pitch of a single-sideband signal seems too high or low? • The AGC or limiter • The bandwidth selection • The tone squelch • The receiver RIT or clarifier

  35. T4B07 What does the term "RIT" mean? • Receiver Input Tone • Receiver Incremental Tuning • Rectifier Inverter Test • Remote Input Transmitter

  36. T7A12 Which term describes the ability of a receiver to discriminate between multiple signals? • Tuning rate • Sensitivity • Selectivity • Noise floor

  37. T7B02 What is meant by fundamental overload in reference to a receiver? • Too much voltage from the power supply • Too much current from the power supply • Interference caused by very strong signals • Interference caused by turning the volume up too high

  38. T7A13 Where is an RF preamplifier installed? • Between the antenna and receiver • At the output of the transmitter’s power amplifier • Between a transmitter and antenna tuner • At the receiver’s audio output

  39. T2B05 What determines the amount of deviation of an FM signal? • Both the frequency and amplitude of the modulating signal • The frequency of the modulating signal • The amplitude of the modulating signal • The relative phase of the modulating signal and the carrier

  40. T2B06 What happens when the deviation of an FM transmitter is increased? • Its signal occupies more bandwidth • Its output power increases • Its output power and bandwidth increases • Asymmetric modulation occurs

  41. T7A04 What circuit is pictured in Figure T7, if block 1 is a frequency discriminator? • A double-conversion receiver • A regenerative receiver • A superheterodyne receiver • An FM receiver Radio Frequency Amplifier Mixer Wide Filter Intermediate Frequency Amplifier Figure T7 Oscillator Audio Amplifier Limiter Block 1

  42. T7A11 Which of the following circuits demodulates FM signals? • Limiter • Discriminator • Product detector • Phase inverter

  43. T8A10 What is the typical bandwidth of analog fast-scan TV transmissions on the 70 cm band? • More than 10 MHz • About 6 MHz • About 3 MHz • About 1 MHz

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