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Extra Class Exam Question Pool

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

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2016-E7E: Modulation and demodulation: reactance, phase and balanced modulators; detectors; mixer stages

2016-E7E01: Which of the following can be used to generate FM phone emissions?

A reactance modulator on the oscillator

A balanced modulator on the audio amplifier

A reactance modulator on the final amplifier

A balanced modulator on the oscillator



2016-E7E02: What is the function of a reactance modulator?

To produce PM signals by using an electrically variable inductance or capacitance

To produce PM signals by using an electrically variable resistance

To produce AM signals by using an electrically variable inductance or capacitance

To produce AM signals by using an electrically variable resistance



2016-E7E03: How does an analog phase modulator function?

By varying the tuning of an amplifier tank circuit to produce PM signals

By varying the tuning of a microphone preamplifier to produce PM signals

By varying the tuning of an amplifier tank circuit to produce AM signals

By varying the tuning of a microphone preamplifier to produce AM signals



2016-E7E04: What is one way a single-sideband phone signal can be generated?

By using a balanced modulator followed by a filter

By using a reactance modulator followed by a mixer

By using a loop modulator followed by a mixer

By driving a product detector with a DSB signal



2016-E7E05: What circuit is added to an FM transmitter to boost the higher audio frequencies?

A pre-emphasis network

A de-emphasis network

A heterodyne suppressor

An audio prescaler



2016-E7E06: Why is de-emphasis commonly used in FM communications receivers?

For compatibility with transmitters using phase modulation

To reduce impulse noise reception

For higher efficiency

To remove third-order distortion products



2016-E7E07: What is meant by the term baseband in radio communications?

The frequency components present in the modulating signal

The lowest frequency band that the transmitter or receiver covers

The unmodulated bandwidth of the transmitted signal

The basic oscillator frequency in an FM transmitter that is multiplied to increase the deviation and carrier frequency



2016-E7E08: What are the principal frequencies that appear at the output of a mixer circuit?

The two input frequencies along with their sum and difference frequencies

Two and four times the original frequency

The sum, difference and square root of the input frequencies

1.414 and 0.707 times the input frequency



2016-E7E09: What occurs when an excessive amount of signal energy reaches a mixer circuit?

Spurious mixer products are generated

Mixer blanking occurs

Automatic limiting occurs

A beat frequency is generated



2016-E7E10: How does a diode detector function?

By rectification and filtering of RF signals

By breakdown of the Zener voltage

By mixing signals with noise in the transition region of the diode

By sensing the change of reactance in the diode with respect to frequency



2016-E7E11: Which type of detector is used for demodulating SSB signals?

Product detector

Discriminator

Phase detector

Phase comparator



2016-E7E12: What is a frequency discriminator stage in a FM receiver?

A circuit for detecting FM signals

An FM generator circuit

A circuit for filtering two closely adjacent signals

An automatic band-switching circuit





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2016-E7F: DSP filtering and other operations; Software Defined Radio Fundamentals; DSP modulation and demodulation
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