93 lines
4.2 KiB
Markdown
93 lines
4.2 KiB
Markdown
E7H Oscillators and signal sources: types of oscillators; synthesizers and phase-locked loops; direct digital synthesizers; stabilizing thermal drift; microphonics; high-accuracy oscillators
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- [[E7H01]] (D)
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What are three common oscillator circuits? #card
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- [[A.]] Taft, Pierce, and negative feedback
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- [[B.]] Pierce, Fenner, and Beane
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- [[C.]] Taft, Hartley, and Pierce
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- [[D.]] Colpitts, Hartley, and Pierce
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- [[E7H02]] (C)
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What is a microphonic? #card
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- [[A.]] An IC used for amplifying microphone signals
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- [[B.]] Distortion caused by RF pickup on the microphone cable
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- [[C.]] Changes in oscillator frequency caused by mechanical vibration
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- [[D.]] Excess loading of the microphone by an oscillator
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- [[E7H03]] (C)
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What is a phase-locked loop? #card
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- [[A.]] An electronic servo loop consisting of a ratio detector, reactance modulator, and voltage-controlled oscillator
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- [[B.]] An electronic circuit also known as a monostable multivibrator
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- [[C.]] An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator
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- [[D.]] An electronic circuit consisting of a precision push-pull amplifier with a differential phase input
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- [[E7H04]] (C)
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How is positive feedback supplied in a Colpitts oscillator? #card
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- [[A.]] Through a tapped coil
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- [[B.]] Through link coupling
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- [[C.]] Through a capacitive divider
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- [[D.]] Through a neutralizing capacitor
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- [[E7H05]] (D)
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How is positive feedback supplied in a Pierce oscillator? #card
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- [[A.]] Through a tapped coil
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- [[B.]] Through link coupling
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- [[C.]] Through a neutralizing capacitor
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- [[D.]] Through a quartz crystal
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- [[E7H06]] (B)
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Which of these functions can be performed by a phase-locked loop? #card
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- [[A.]] Wide-band AF and RF power amplification
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- [[B.]] Frequency synthesis and FM demodulation
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- [[C.]] Photovoltaic conversion and optical coupling
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- [[D.]] Comparison of two digital input signals and digital pulse counting
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- [[E7H07]] (D)
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How can an oscillator’s microphonic responses be reduced? #card
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- [[A.]] Use NP0 capacitors
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- [[B.]] Reduce noise on the oscillator’s power supply
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- [[C.]] Increase the gain
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- [[D.]] Mechanically isolate the oscillator circuitry from its enclosure
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- [[E7H08]] (A)
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Which of the following components can be used to reduce thermal drift in crystal oscillators? #card
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- [[A.]] NP0 capacitors
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- [[B.]] Toroidal inductors
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- [[C.]] Wirewound resistors
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- [[D.]] Non-inductive resistors
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- [[E7H09]] (A)
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What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital-to-analog converter, and a low-pass anti-alias filter? #card
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- [[A.]] A direct digital synthesizer
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- [[B.]] A hybrid synthesizer
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- [[C.]] A phase-locked loop synthesizer
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- [[D.]] A direct conversion synthesizer
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- [[E7H10]] (B)
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What information is contained in the lookup table of a direct digital synthesizer (DDS)? #card
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- [[A.]] The phase relationship between a reference oscillator and the output waveform
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- [[B.]] Amplitude values that represent the desired waveform
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- [[C.]] The phase relationship between a voltage-controlled oscillator and the output waveform
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- [[D.]] Frequently used receiver and transmitter frequencies
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- [[E7H11]] (C)
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What are the major spectral impurity components of direct digital synthesizers? #card
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- [[A.]] Broadband noise
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- [[B.]] Digital conversion noise
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- [[C.]] Spurious signals at discrete frequencies
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- [[D.]] Harmonics of the local oscillator
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- [[E7H12]] (B)
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Which of the following ensures that a crystal oscillator operates on the frequency specified by the crystal manufacturer? #card
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- [[A.]] Provide the crystal with a specified parallel inductance
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- [[B.]] Provide the crystal with a specified parallel capacitance
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- [[C.]] Bias the crystal at a specified voltage
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- [[D.]] Bias the crystal at a specified current
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- [[E7H13]] (D)
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Which of the following is a technique for providing highly accurate and stable oscillators needed for microwave transmission and reception? #card
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- [[A.]] Use a GPS signal reference
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- [[B.]] Use a rubidium stabilized reference oscillator
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- [[C.]] Use a temperature-controlled high Q dielectric resonator
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- [[D.]] All these choices are correct
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