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Extra Class Exam Question Pool

effective 7/01/2016 thru 6/29/2020

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2016-E7H: Oscillators and signal sources: types of oscillators; synthesizers and phase-locked loops; direct digital synthesizers; stabilizing thermal drift; microphonics; high accuracy oscillators

2016-E7H01: What are three oscillator circuits used in Amateur Radio equipment?

Colpitts, Hartley and Pierce

Taft, Pierce and negative feedback

Pierce, Fenner and Beane

Taft, Hartley and Pierce



2016-E7H02: Which describes a microphonic?

Changes in oscillator frequency due to mechanical vibration

An IC used for amplifying microphone signals

Distortion caused by RF pickup on the microphone cable

Excess loading of the microphone by an oscillator



2016-E7H03: How is positive feedback supplied in a Hartley oscillator?

Through a tapped coil

Through a capacitive divider

Through link coupling

Through a neutralizing capacitor



2016-E7H04: How is positive feedback supplied in a Colpitts oscillator?

Through a capacitive divider

Through a tapped coil

Through link coupling

Through a neutralizing capacitor



2016-E7H05: How is positive feedback supplied in a Pierce oscillator?

Through a quartz crystal

Through a tapped coil

Through link coupling

Through a neutralizing capacitor



2016-E7H06: Which of the following oscillator circuits are commonly used in VFOs?

Colpitts and Hartley

Pierce and Zener

Armstrong and deForest

Negative feedback and balanced feedback



2016-E7H07: How can an oscillator's microphonic responses be reduced?

Mechanically isolating the oscillator circuitry from its enclosure

Use of NP0 capacitors

Eliminating noise on the oscillator’s power supply

Using the oscillator only for CW and digital signals



2016-E7H08: Which of the following components can be used to reduce thermal drift in crystal oscillators?

NP0 capacitors

Toroidal inductors

Wirewound resistors

Non-inductive resistors



2016-E7H09: What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital to analog converter, and a low-pass anti-alias filter?

A direct digital synthesizer

A hybrid synthesizer

A phase locked loop synthesizer

A diode-switching matrix synthesizer



2016-E7H10: What information is contained in the lookup table of a direct digital frequency synthesizer?

The amplitude values that represent a sine-wave output

The phase relationship between a reference oscillator and the output waveform

The phase relationship between a voltage-controlled oscillator and the output waveform

The synthesizer frequency limits and frequency values stored in the radio memories



2016-E7H11: What are the major spectral impurity components of direct digital synthesizers?

Spurious signals at discrete frequencies

Broadband noise

Digital conversion noise

Nyquist limit noise



2016-E7H12: Which of the following must be done to insure that a crystal oscillator provides the frequency specified by the crystal manufacturer?

Provide the crystal with a specified parallel capacitance

Provide the crystal with a specified parallel inductance

Bias the crystal at a specified voltage

Bias the crystal at a specified current



2016-E7H13: Which of the following is a technique for providing highly accurate and stable oscillators needed for microwave transmission and reception?

All of these choices are correct

Use a GPS signal reference

Use a rubidium stabilized reference oscillator

Use a temperature-controlled high Q dielectric resonator



2016-E7H14: What is a phase-locked loop circuit?

An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator

An electronic servo loop consisting of a ratio detector, reactance modulator, and voltage-controlled oscillator

An electronic circuit also known as a monostable multivibrator

An electronic circuit consisting of a precision push-pull amplifier with a differential input



2016-E7H15: Which of these functions can be performed by a phase-locked loop?

Frequency synthesis, FM demodulation

Wide-band AF and RF power amplification

Comparison of two digital input signals, digital pulse counter

Photovoltaic conversion, optical coupling





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2016-E7G: Active filters and op-amp circuits: active audio filters; characteristics; basic circuit design; operational amplifiers
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2016-E8A: AC waveforms: sine, square, sawtooth and irregular waveforms; AC measurements; average and PEP of RF signals; Fourier analysis; Analog to digital conversion: Digital to Analog conversion
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