Chapter 3 Problems
ECET 214
Prof. Park
NJIT
Problem 1
Which of the following is not an advantage of a
synchronous detection?
a. Low distortion
b. Eliminate diagonal clipping
c. Greater ability to follow fast-modulated signals
d. Ability to produce gain
Problem 2
The mixer is often referred to as:
a. RF amplifier
b. oscillator generator
c. second detector
d. first detector
Problem 3
Varactor diodes are used for tuning by:
a. capacitance adjustment through a reverse bias
diode.
b. capacitance adjustment through forward bias.
c. temperature compensation of diodes.
d. all of the above.
Problem 4
In a varactor diode, as voltage increases,
capacitance:
a. increases
b. stays the same
c. decreases
d. none of the above
Problem 5
The only roadblock to having complete
receivers on a chip aside from station
selection and volume controls is:
a. limiting factors of tuned circuits.
b. local oscillator.
c. mixer circuits.
d. IF amplifier.
Problem 6
The radio receiver that simply consists of an
RF amplifier, detector, and audio amplifier is
known as:
a. a superheterodyne receiver
b. a TRF receiver
c. a selective receiver
d. a sensitive receiver
Problem 7
A receiver’s sensitivity is:
a. the extent to which a receiver is capable of
differentiating between the desired signal and other
signals.
b. its ability to drive the output speaker to an acceptable
level.
c. the ability of the receiver to demodulate a modulated
signal.
d. the ability of a receiver to attenuate noise signals.
Problem 8
A receiver’s selectivity is:
a. the extent to which a receiver is capable of
differentiating between the desired signal and other
signals.
b. its ability to drive the output speaker to an acceptable
level.
c. the ability of the receiver to demodulate a modulated
signal.
d. the ability of a receiver to attenuate noise signals.
Problem 9
If a receiver is overly selective:
a. too much noise is picked up and amplified by the
receiver.
b. only part of the bandwidth of the AM signal is
amplified, causing some of the sideband information to
be lost and distortion results.
c. the tank circuits within the tuned amplifiers have
insufficient Q.
d. when the volume control is turned up to maximum,
the desired station is very weak.
Problem 10
If a receiver is underselective:
a. only part of the bandwidth of the AM signal is
amplified, causing some of the sideband information to
be lost and distortion results.
b. the tank circuits within the tuned amplifiers have too
high a Q.
c. when the volume control is turned up to maximum, the
desired station is very weak.
d. more than one radio station on different frequencies
may be picked up by the receiver at the same time.
Problem 11
A TRF receiver is to be designed with a single
tuned circuit using an 8.2 uH inductor. If the
frequency is to be tuned from 550 kHz to 1600
kHz, find the BW that results at 550 kHz if there
is exactly 10 kHz BW at a frequency of 1050 kHz.
a. 105 kHz
b. 15.24 kHz
c. 5.24 kHz
d. 10 kHz
Problem 12
The diode detector:
a. is one of the simplest and most effective AM
detectors.
b. consists of a nonlinear diode and low-pass filter.
c. is sometimes referred to as an envelope
detector.
d. all of the above.
Problem 13
Which is not an advantage of diode detectors?
a. Power absorbed from the tuned circuit by the
diode detector reduces the Q of the tuned
circuit.
b. They develop a readily usable dc voltage for
automatic gain control circuits.
c. They are highly efficient.
d. Distortion decreases as the amplitude of the AM
signal increases.
Problem 14
Diagonal clipping:
a. occurs if the time constant of the low-pass filter is too
large compared to the period of the RF waveform.
b. is a type of distortion that occurs with diode detectors.
c. is characterized by having the capacitor voltage not
follow the full changes of the envelope of the AM
waveform.
d. all of the above.
Problem 15
Synchronous detectors:
a. are often called product detectors.
b. offer low distortion compared to diode
detectors.
c. have the ability to provide gain.
d. all of the above.
Problem 16
The superheterodyne receiver design is superior
to the TRF design:
a. since it allows for a constant selectivity over the
entire tuning range of the receiver.
b. since it always uses synchronous detectors
instead of diode detectors.
c. since it uses many RF amplifier stages before the
RF signal is mixed with the local oscillator signal.
d. all of the above.
Problem 17
An AM signal having a carrier frequency of 560
kHz is to be mixed with a local oscillator signal at
a frequency of 1035 kHz. What does the output
of the IF amplifier consist of?
a. a 455 kHz carrier
b. a 475 kHz sinewave
c. a 475 kHz AM signal
d. the original intelligence signal
Problem 18
In Figure 3-1, the output
signal of stage (e) is:
a. an AM signal with a carrier
frequency of 490 kHz.
b. an AM signal with a carrier
frequency of 1850 kHz.
c. a 490 kHz sinewave.
d. an 1850 kHz sinewave.
Problem 19
In Figure 3-1, the output
signal of stage (d) is:
a. an AM signal with a carrier
frequency of 490 kHz.
b. an AM signal with a carrier
frequency of 1360 kHz.
c. a 490 kHz sinewave.
d. a 1 kHz sinewave.
Problem 20
In Figure 3-1, the output of
stage (a) is:
a. an AM signal with a carrier
frequency of 1360 kHz.
b. an AM signal with a carrier
frequency of 1850 kHz.
c. a 490 kHz sinewave.
d. an 1850 kHz sinewave.
Problem 21
In Figure 3-1, the output
signal of stage (c) is:
a. an AM signal with a carrier
signal of 490 kHz.
b. an AM signal with a carrier
frequency of 1360 kHz.
c. a 490 kHz sinewave.
d. a 1 kHz sinewave.
Problem 22
In Figure 3-1, the receiver
design is known as:
a. regenerative
b. superheterodyne
c. TRF
d. synchronous
Problem 23
In Figure 3-1, the stage
sometimes referred to as
the first detector is:
a. stage a
b. stage b
c. stage c
d. stage d
Problem 24
In Figure 3-1, the stages
that contain tuned
circuits are:
a. stages a, b and d.
b. stages a, b and c.
c. stages a, d and e.
d. stages a, c and d.
Problem 25
In Figure 3-1, the stages
that must contain
nonlinear devices are:
a. stages a, b and c.
b. stages a and e.
c. stages b and d.
d. stages b and c.
Problem 26
In Figure 3-1, the image
frequency would be:
a. 980 kHz
b. 2340 kHz
c. 1850 kHz
d. 870 kHz
Problem 27
A padder capacitor:
a. is placed in series with the tank inductor to provide tracking at
the low end of a large frequency band.
b. is placed in parallel with each section of the ganged capacitors
of the tank to provide tracking at the high end of a large
frequency band.
c. is placed in an RF amplifier to provide for proper
neutralization.
d. is placed in a tank circuit to provide for electronic tuning.
Problem 28
A trimmer capacitor:
a. is placed in series with the tank inductor to provide tracking at
the low end of a large frequency band.
b. is placed in parallel with each section of the ganged capacitor
of the tank to provide tracking at the high end of a large
frequency band.
c. is placed in an RF amplifier to provide for proper
neutralization.
d. is placed in a tank circuit to provide for electronic tuning.
Problem 29
A varicap:
a. is placed in series with the tank inductor to provide
tracking at the low end of a large frequency band.
b. is placed in parallel with each section of the ganged
capacitors of the tank to provide tracking at the high end
of a large frequency band.
c. is placed in an RF amplifier to provide for proper
neutralization.
d. is placed in a tank circuit to provide for electronic tuning.
Problem 31
Image frequency rejection on a standard AM broadcast
band receiver is not a major problem since:
a. the image frequency is not close to the IF frequency.
b. the image frequency is not close to the LO frequency.
c. the image frequency is not produced by mixing action.
d. the image frequency is so far away from the RF
amplifier stage’s tuned frequency.
Problem 32
Which of the following is not a major benefit of
using RF amplifier stages in superheterodyne
receiver design?
a. improved image frequency rejection
b. larger frequency tuning range
c. more gain resulting in improved sensitivity
d. improved noise characteristics
Problem 33
Which of the following is not an advantage of FETs
over BJTs in RF amplifier usage?
a. Their input impedance does not load down the Q
of the circuit preceding the FET stage.
b. The availability of dual gate FETs provides an
isolated injection point for the AGC.
c. Their input/output square-law relationship allows
for lower distortion levels.
d. They have improved image frequency rejection.
Problem 34
An autodyne mixer is:
a. a stage that provides the mixing and generates the
LO at the same time.
b. a mixer that uses a dual-gate FET.
c. a mixer that automatically provides for AGC action.
d. a stage that mixes the LO with the AM signal without
the use of a transistor.
Problem 35
In a superheterodyne receiver the bulk of the
receiver’s sensitivity and selectivity is due to the:
a. RF amplifier stages.
b. converter stages.
c. IF amplifier stages.
d. local oscillator.
Problem 36
Double conversion is:
a. a receiver design that uses two superheterodyne
receivers to receive a weak signal.
b. a technique used to reduce image frequency
problems in a superheterodyne receiver.
c. a technique used to solve the TRF tuning problems.
d. a method that ensures that a superheterodyne
receiver does not break into oscillations due to stray
positive feedback.
Problem 37
The circuit of Figure 3-2 is an
example of:
a. an RF mixer, local
oscillator, and IF filter
b. an autodyne mixer
c. a receive converter
d. all of the above
Problem 38
In Figure 3-2, the tank circuit
made up of L1 and C1 is
tuned at:
a. the IF frequency.
b. the LO frequency.
c. the RF carrier frequency.
d. the image frequency.
Problem 39
In Figure 3-2, the tank circuit
made up of L4 and C4 is
tuned at:
a. the IF frequency.
b. the LO frequency.
c. the RF carrier frequency.
d. the image frequency.
Problem 40
In Figure 3-2, the tank circuit
made up of L5 and C5 is
tuned at:
a. the IF frequency.
b. the LO frequency.
c. the RF carrier frequency.
d. the image frequency.
Problem 41
In Figure 3-2, the purpose of C3
is:
a. to determine the frequency
of oscillation of the LO.
b. to couple the local oscillator
frequency from the tank
circuit to be amplified by Q1.
c. to act as a bypass capacitor
for R3.
d. to neutralize the RF amplifier
stage.
Problem 42
The AGC control voltage:
a. is actually the dc voltage component produced by
the mixing action in the AM demodulator stage.
b. varies as the signal strength of the received signal
varies.
c. is a negative feedback voltage.
d. is produced by an RC circuit having a much larger
time constant than that of the detector.
e. all of the above.
Problem 43
In Figure 3-3, the tank circuit made up of L1, A, and B is tuned
to:
a. the LO frequency.
b. the RF carrier frequency.
c. the IF frequency.
d. the image frequency.
Problem 44
In Figure 3-3, the tank circuit made up of L4, C, and D is tuned
to:
a. the LO frequency.
b. the RF carrier frequency.
c. the IF frequency.
d. the image frequency.
Problem 45
In Figure 3-3, the tank circuit inside of T1 is tuned to:
a. the LO frequency.
b. the RF carrier frequency.
c. the IF frequency.
d. the image frequency.
Problem 46
In Figure 3-3, the transistor Q1 is used as:
a. the nonlinear device in an RF mixer stage.
b. the active part of an RF amplifier.
c. the active part of an LO stage.
d. all of the above.
Problem 47
In Figure 3-3, the transistor Q2 is used as:
a. an RF mixer stage transistor.
b. an IF amplifier stage transistor.
c. a detector transistor.
d. an audio amplifier stage transistor.
Problem 48
In Figure 3-3, the transistor Q3 is used as:
a. an RF mixer stage transistor.
b. an IF amplifier stage transistor.
c. a detector transistor.
d. an audio amplifier stage transistor.
Problem 49
In Figure 3-3, the transistor Q4 is used as:
a. an RF mixer stage transistor.
b. an IF amplifier stage transistor.
c. a detector transistor.
d. an audio amplifier stage transistor.
Problem 50
In Figure 3-3, the AM demodulation is accomplished by:
a. transistor - Q3.
b. diode - E1.
c. diode - E2.
d. transistor - Q4.
Problem 51
In Figure 3-3, the filter that produces the AGC voltage consists
of:
a. R11 and C11.
b. R5 and C4.
c. R11 and C12.
d. R10 and C10.
Problem 52
In Figure 3-3, the inductors L1 and L2 function as:
a. an IF transformer.
b. a loopstick antenna.
c. part of the local oscillator.
d. a nonlinear mixer.
Problem 53
In Figure 3-3, the transformer, T3, is tuned to:
a. the intelligence frequencies.
b. the RF carrier frequency of the received station.
c. the IF frequency.
d. the local oscillator frequency.
Problem 54
In Figure 3-3, the selectivity is accomplished by:
a. T1, T2, and T3.
b. L1 and L2.
c. L3 and L4.
d. R11 and C11.
Problem 55
In Figure 3-3, E1 functions as:
a. an auxillary AGC diode.
b. a mixer diode.
c. an AM detector diode.
d. an IF amplifier diode.
Problem 56
In Figure 3-3, the volume is controlled by adjusting:
a. T3
b. R12
c. capacitors B and D
d. R17
Problem 57
The reference level for the unit, dBm, is:
a. the milliwatt.
b. the milliampere.
c. the watt.
d. the millivolt.
Problem 58
In Figure 3-4, the power
driven into the audio
amplifier stage is:
a. 2.51W.
b. 2.51 mW.
c. 0.398 mW.
d. 398 mW.
Problem 59
The conversion gain of
the mixer in Figure 3-4 is:
a. -81 dB
b. 3 dB
c. -3 dB
d. -78 dB
Problem 60
The total gain of the entire
receiver in Figure 3-4 from
the antenna input to the
audio amplifier output is:
a. 89 dB.
b. 59 dB.
c. 119 dB.
d. 30 dBm.
Problem 61
The power gain of the
audio amplifier in Figure
3-4 expressed as a ratio
quantity is approximately:
a. 1000.
b. 2512.
c. 34 dB.
d. 30 dBm.
Problem 62
A receiver has a dynamic range of 65 dB. It has a
sensitivity of 0.88 nW. The maximum allowable
input signal is approximately:
a. 1.56 uW.
b. 278 mW.
c. 2.78 mW.
d. 156 uW.
Problem 63
A receiver has a maximum input signal of 75
mW before distortion occurs. Its sensitivity is
measured to be 1.5 nW. Its dynamic range is
approximately:
a. 47 dB.
b. 77 dB.
c. 154 dB.
d. 87 dB.
Problem 64
Good troubleshooting practice says:
a. perform a visual check and check the power
supply voltages.
b. prepare a trouble report
c. log the serial and model number
d. check the power supply voltages
e. none of the above
Problem 65
Electronics Workbench Multisim provides a feature
that allows for the addition of a component fault in
a circuit. This is accomplished by:
a. replacing the part with an F-prefix part
b. replacing the part with a non model part
c. double-clicking on the component, select fault
and specify the type of failure
d. all of the above
e. none of the above