E7E Modulators: reactance, phase,
balanced; detectors; mixer stages;
frequency synthesizers
E7E01
(B)
How is
an F3E FM-phone emission produced?
A. With a balanced modulator on the audio
amplifier
B. With a reactance
modulator on the oscillator
C. With a reactance modulator on the final
amplifier
D. With a balanced modulator on the oscillator
E7E02
(C)
How
does a reactance modulator work?
A. It acts as a variable resistance or
capacitance to produce FM signals
B. It acts as a variable resistance or
capacitance to produce AM signals
C. It acts as a variable
inductance or capacitance to produce FM signals
D. It acts as a variable inductance or
capacitance to produce AM signals
E7E03
(C)
How
does a phase modulator work?
A. It varies the tuning of a microphone
preamplifier to produce FM signals
B. It varies the tuning of an amplifier tank
circuit to produce AM signals
C. It varies the tuning of
an amplifier tank circuit to produce FM signals
D. It varies the tuning of a microphone preamplifier
to produce AM signals
E7E04
(A)
How can
a single-sideband phone signal be generated?
A. By using a balanced
modulator followed by a filter
B. By using a reactance modulator followed by a
mixer
C. By using a loop modulator followed by a
mixer
D. By driving a product detector with a DSB
signal
E7E05
(D)
What
audio shaping network is added at a transmitter to proportionally attenuate the
lower audio frequencies, giving an even spread to the energy in the audio band?
A. A de-emphasis network
B. A heterodyne suppressor
C. An audio prescaler
D. A pre-emphasis network
E7E06
(A)
What
audio shaping network is added at a receiver to restore proportionally
attenuated lower audio frequencies?
A. A de-emphasis network
B. A heterodyne suppressor
C. An audio prescaler
D. A pre-emphasis network
E7E07
(D)
What is
the mixing process?
A. The elimination of noise in a wideband
receiver by phase comparison
B. The elimination of noise in a wideband
receiver by phase differentiation
C. The recovery of the intelligence from a
modulated RF signal
D. The combination of two
signals to produce sum and difference frequencies
E7E08
(C)
What
are the principal frequencies that appear at the output of a mixer circuit?
A. Two and four times the original frequency
B. The sum, difference and square root of the
input frequencies
C. The original frequencies
and the sum and difference frequencies
D. 1.414 and 0.707 times the input frequency
E7E09
(A)
What
occurs in a receiver when an excessive amount of signal energy reaches the
mixer circuit?
A. Spurious mixer products
are generated
B. Mixer blanking occurs
C. Automatic limiting occurs
D. A beat frequency is generated
E7E10
(C)
What
type of frequency synthesizer circuit uses a stable voltage- controlled oscillator,
programmable divider, phase detector, loop filter and a reference frequency
source?
A. A direct digital synthesizer
B. A hybrid synthesizer
C. A phase-locked loop
synthesizer
D. A diode-switching matrix synthesizer
E7E11
(A)
What
type of frequency synthesizer circuit uses a phase accumulator, lookup table,
digital to analog converter and a low-pass antialias filter?
A. A direct digital
synthesizer
B. A hybrid synthesizer
C. A phase-locked loop synthesizer
D. A diode-switching matrix synthesizer
E7E12
(D)
What
are the main blocks of a direct digital frequency synthesizer?
A. A variable-frequency crystal oscillator,
phase accumulator, digital to analog converter and a loop filter
B. A stable voltage-controlled oscillator,
programmable divider, phase detector, loop filter and a digital to analog
converter
C. A variable-frequency oscillator,
programmable divider, phase detector and a low-pass antialias filter
D. A phase accumulator,
lookup table, digital to analog converter and a low-pass antialias filter
E7E13
(B)
What
information is contained in the lookup table of a direct digital frequency
synthesizer?
A. The phase relationship between a reference
oscillator and the output waveform
B. The amplitude values that
represent a sine-wave output
C. The phase relationship between a
voltage-controlled oscillator and the output waveform
D. The synthesizer frequency limits and
frequency values stored in the radio memories
E7E14
(C)
What
are the major spectral impurity components of direct digital synthesizers?
A. Broadband noise
B. Digital conversion noise
C. Spurs at discrete
frequencies
D. Nyquist limit noise
E7E15
(A)
What
are the major spectral impurity components of phase-locked loop synthesizers?
A. Broadband noise
B. Digital conversion noise
C. Spurs at discrete frequencies
D. Nyquist limit noise