E4C Receiver performance
characteristics (i.e., phase noise,
desensitization, capture effect, intercept point, noise floor, dynamic
range
{blocking and IMD}, image rejection, MDS, signal-to-noise-
ratio); intermodulation and cross-modulation interference
E4C01
(D)
What is
the effect of excessive phase noise in a receiver local oscillator?
A. It limits the receiver ability to receive
strong signals
B. It reduces the receiver sensitivity
C. It decreases the receiver third-order
intermodulation distortion dynamic range
D. It allows strong signals
on nearby frequencies to interfere with reception of weak signals
E4C02
(A)
What is
the term for the reduction in receiver sensitivity caused by a strong signal
near the received frequency?
A. Desensitization
B. Quieting
C. Cross-modulation interference
D. Squelch gain rollback
E4C03
(B)
What
causes receiver desensitization?
A. Audio gain adjusted too low
B. Strong adjacent-channel
signals
C. Squelch gain adjusted too high
D. Squelch gain adjusted too low
E4C04
(A)
What is
one way receiver desensitization can be reduced?
A. Shield the receiver from
the transmitter causing the problem
B. Increase the transmitter audio gain
C. Decrease the receiver squelch gain
D. Increase the receiver bandwidth
E4C05
(C)
What is
the capture effect?
A. All signals on a frequency are demodulated
by an FM receiver
B. All signals on a frequency are demodulated
by an AM receiver
C. The strongest signal
received is the only demodulated signal
D. The weakest signal received is the only
demodulated signal
E4C06
(C)
What is
the term for the blocking of one FM-phone signal by another stronger FM-phone
signal?
A. Desensitization
B. Cross-modulation interference
C. Capture effect
D. Frequency discrimination
E4C07
(A)
With
which emission type is capture effect most pronounced?
A. FM
B. SSB
C. AM
D. CW
E4C08
(D)
What is
meant by the noise floor of a receiver?
A. The weakest signal that can be detected
under noisy atmospheric conditions
B. The amount of phase noise generated by the
receiver local oscillator
C. The minimum level of noise that will
overload the receiver RF amplifier stage
D. The weakest signal that
can be detected above the receiver internal noise
E4C09
(B)
What is
the blocking dynamic range of a receiver that has an 8-dB noise figure and an
IF bandwidth of 500 Hz if the blocking level (1-dB compression point) is -20
dBm?
A. -119 dBm
B. 119 dB
C. 146 dB
D. -146 dBm
E4C10
(C)
What is
meant by the dynamic range of a communications receiver?
A. The number of kHz between the lowest and the
highest frequency to which the receiver can be tuned
B. The maximum possible undistorted audio
output of the receiver, referenced to one milliwatt
C. The ratio between the
minimum discernible signal and the largest tolerable signal without causing
audible distortion products
D. The difference between the lowest-frequency
signal and the highest-frequency signal detectable without moving the tuning
knob
E4C11
(A)
What
type of problems are caused by poor dynamic range in a communications receiver?
A. Cross modulation of the
desired signal and desensitization from strong adjacent signals
B. Oscillator instability requiring frequent
retuning, and loss of ability to recover the opposite sideband, should it be
transmitted
C. Cross modulation of the desired signal and
insufficient audio power to operate the speaker
D. Oscillator instability and severe audio
distortion of all but the strongest received signals
E4C12
(B)
What
part of a superheterodyne receiver determines the image rejection ratio of the
receiver?
A. Product detector
B. RF amplifier
C. AGC loop
D. IF filter
E4C13
(B)
If you
measured the MDS of a receiver, what would you be measuring?
A. The meter display sensitivity (MDS), or the
responsiveness of the receiver S-meter to all signals
B. The minimum discernible
signal (MDS), or the weakest signal that the receiver can detect
C. The minimum distorting signal (MDS), or the
strongest signal the receiver can detect without overloading
D. The maximum detectable spectrum (MDS), or
the lowest to highest frequency range of the receiver
E4C14
(B)
How
does intermodulation interference between two repeater transmitters usually
occur?
A. When the signals from the transmitters are
reflected out of phase from airplanes passing overhead
B. When they are in close
proximity and the signals mix in one or both of their final amplifiers
C. When they are in close proximity and the
signals cause feedback in one or both of their final amplifiers
D. When the signals from the transmitters are
reflected in phase from airplanes passing overhead
E4C15
(B)
How can
intermodulation interference between two repeater transmitters in close
proximity often be reduced or eliminated?
A. By using a Class C final amplifier with high
driving power
B. By installing a
terminated circulator or ferrite isolator in the feed line to the transmitter
and duplexer
C. By installing a band-pass filter in the
antenna feed line
D. By installing a low-pass filter in the
antenna feed line
E4C16
(A)
If a
receiver tuned to 146.70 MHz receives an intermodulation-product signal
whenever a nearby transmitter transmits on 146.52 MHz, what are the two most
likely frequencies for the other interfering signal?
A. 146.34 MHz and 146.61 MHz
B. 146.88 MHz and 146.34 MHz
C. 146.10 MHz and 147.30 MHz
D. 73.35 MHz and 239.40 MHz