E7E: Modulation and demodulation: reactance, phase and balanced modulators; detectors; mixer stages; DSP modulation and demodulation; software defined radio systems
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
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
E7E03:
What is the fundamental principle of a phase modulator?
It varies the tuning of an amplifier tank circuit to produce PM signals
It varies the tuning of a microphone preamplifier to produce PM signals
It varies the tuning of an amplifier tank circuit to produce AM signals
It varies the tuning of a microphone preamplifier to produce AM signals
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
E7E05:
What circuit is added to an FM transmitter to proportionally attenuate the lower audio frequencies?
A pre-emphasis network
A de-emphasis network
A heterodyne suppressor
An audio prescaler
E7E06:
What circuit is added to an FM receiver to restore attenuated lower audio frequencies?
A de-emphasis network
A heterodyne suppressor
An audio prescaler
A pre-emphasis network
E7E07:
What is one result of the process of mixing two signals?
The creation of new signals at the sum and difference frequencies
The elimination of noise in a wideband receiver by phase comparison
The elimination of noise in a wideband receiver by phase differentiation
The recovery of the intelligence from a modulated RF signal
E7E08:
What are the principal frequencies that appear at the output of a mixer circuit?
The original frequencies, and the 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
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
E7E10:
What is the process of detection?
The recovery of information from a modulated RF signal
The extraction of weak signals from noise
The modulation of a carrier
The mixing of noise with a received signal
E7E11:
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
E7E12:
Which of the following types of detector is well suited for demodulating SSB signals?
Product detector
Discriminator
Phase detector
Phase comparator
E7E13:
What is a frequency discriminator?
A circuit for detecting FM signals
An FM generator circuit
A circuit for filtering two closely adjacent signals
An automatic band-switching circuit
E7E14:
Which of the following describes a common means of generating a SSB signal when using digital signal processing?
The phasing or quadrature method
Mixing products are converted to voltages and subtracted by adder circuits
A frequency synthesizer removes the unwanted sidebands
Emulation of quartz crystal filter characteristics
E7E15:
What is meant by “direct conversion” when referring to a software defined receiver?
Incoming RF is mixed to “baseband” for analog-to-digital conversion and subsequent processing
Software is converted from source code to object code during operation of the receiver
Incoming RF is converted to the IF frequency by rectification to generate the control voltage for a voltage controlled oscillator
Software is generated in machine language, avoiding the need for compilers
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