Extra-Study/pages/E7H.md

E7H Oscillators and signal sources: types of oscillators; synthesizers and phase-locked loops; direct digital synthesizers; stabilizing thermal drift; microphonics; high-accuracy oscillators

• E7H01 (D) What are three common oscillator circuits? #card
  • A. Taft, Pierce, and negative feedback
  • B. Pierce, Fenner, and Beane
  • C. Taft, Hartley, and Pierce
  • D. Colpitts, Hartley, and Pierce
• E7H02 (C) What is a microphonic? #card
  • A. An IC used for amplifying microphone signals
  • B. Distortion caused by RF pickup on the microphone cable
  • C. Changes in oscillator frequency caused by mechanical vibration
  • D. Excess loading of the microphone by an oscillator
• E7H03 (C) What is a phase-locked loop? #card
  • A. An electronic servo loop consisting of a ratio detector, reactance modulator, and voltage-controlled oscillator
  • B. An electronic circuit also known as a monostable multivibrator
  • C. An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator
  • D. An electronic circuit consisting of a precision push-pull amplifier with a differential phase input
• E7H04 (C) How is positive feedback supplied in a Colpitts oscillator? #card
  • A. Through a tapped coil
  • B. Through link coupling
  • C. Through a capacitive divider
  • D. Through a neutralizing capacitor
• E7H05 (D) How is positive feedback supplied in a Pierce oscillator? #card
  • A. Through a tapped coil
  • B. Through link coupling
  • C. Through a neutralizing capacitor
  • D. Through a quartz crystal
• E7H06 (B) Which of these functions can be performed by a phase-locked loop? #card
  • A. Wide-band AF and RF power amplification
  • B. Frequency synthesis and FM demodulation
  • C. Photovoltaic conversion and optical coupling
  • D. Comparison of two digital input signals and digital pulse counting
• E7H07 (D) How can an oscillator’s microphonic responses be reduced? #card
  • A. Use NP0 capacitors
  • B. Reduce noise on the oscillator’s power supply
  • C. Increase the gain
  • D. Mechanically isolate the oscillator circuitry from its enclosure
• E7H08 (A) Which of the following components can be used to reduce thermal drift in crystal oscillators? #card
  • A. NP0 capacitors
  • B. Toroidal inductors
  • C. Wirewound resistors
  • D. Non-inductive resistors
• E7H09 (A) What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital-to-analog converter, and a low-pass anti-alias filter? #card
  • A. A direct digital synthesizer
  • B. A hybrid synthesizer
  • C. A phase-locked loop synthesizer
  • D. A direct conversion synthesizer
• E7H10 (B) What information is contained in the lookup table of a direct digital synthesizer (DDS)? #card
  • A. The phase relationship between a reference oscillator and the output waveform
  • B. Amplitude values that represent the desired waveform
  • C. The phase relationship between a voltage-controlled oscillator and the output waveform
  • D. Frequently used receiver and transmitter frequencies
• E7H11 (C) What are the major spectral impurity components of direct digital synthesizers? #card
  • A. Broadband noise
  • B. Digital conversion noise
  • C. Spurious signals at discrete frequencies
  • D. Harmonics of the local oscillator
• E7H12 (B) Which of the following ensures that a crystal oscillator operates on the frequency specified by the crystal manufacturer? #card
  • A. Provide the crystal with a specified parallel inductance
  • B. Provide the crystal with a specified parallel capacitance
  • C. Bias the crystal at a specified voltage
  • D. Bias the crystal at a specified current
• E7H13 (D) Which of the following is a technique for providing highly accurate and stable oscillators needed for microwave transmission and reception? #card
  • A. Use a GPS signal reference
  • B. Use a rubidium stabilized reference oscillator
  • C. Use a temperature-controlled high Q dielectric resonator
  • D. All these choices are correct