Download G7 - PRACTICAL CIRCUITS [2 exam question - 2 groups]

G7 - PRACTICAL CIRCUITS
[2 exam question - 2 groups]
G7A Power supplies; transmitters and receivers; filters;
schematic symbols
G7B Digital circuits (gates, flip-flops, shift registers);
amplifiers and oscillators
1
Practical Circuits
G7A Power supplies
•
•
•
•
A power-supply bleeder resistor discharges the filter
capacitors providing a safety feature
Capacitors and inductors are used in a power-supply
filter network
The minimum peak-inverse-voltage rating of the
rectifier in a full-wave power supply should be double
the normal peak output voltage of the power supply
The approximate minimum peak-inverse-voltage
rating of the rectifier in a half-wave power supply
should be two times the normal peak output voltage of the
power supply
2
Practical Circuits
G7A Power supplies cont’d
•
•
•
•
•
A desirable characteristic for capacitors used to
filter the DC output of a switching power supply is
low equivalent series resistance
An advantage of a switched-mode power supply as
compared to a linear power supply is high frequency
operation allows the use of smaller components
A 180 degree portion of the AC cycle is converted to
DC by a half-wave rectifier
A 360 degree portion of the AC cycle is converted to
DC by a full-wave rectifier
The output waveform of an unfiltered full-wave
rectifier connected to a resistive load is a series of DC
pulses at twice the frequency of the AC input
3
Practical Circuits
7A Transmitters
•
A Balanced modulator circuit is used to combine
signals from the carrier oscillator and speech amplifier and
send the result to the filter in a typical single-sideband
phone transmitter
•
An advantage of a crystal controlled transmitter is
stable output frequency
4
Practical Circuits
G7A Receivers
•
•
•
A Mixer circuit is used to process signals from the RF
amplifier and local oscillator and send the results to the IF
filter in a super heterodyne receiver
A Product detector circuit is used to process signals
from the IF amplifier and BFO and send the result to the
AF amplifier in a single-sideband phone superheterodyne
receiver
The simplest combination of stages that can be
combined to implement a superhedterodyne
receiver is an HF oscillator, mixer, and detector
5
Practical Circuits
G7A Receivers cont’d
•
A direct conversion receiver is suitable for CW and SSB
reception but does not require a mixer stage or an IF
amplifier
•
A Discriminator circuit is used in many FM receivers to
convert signals coming from the IF amplifier to audio
6
Practical Circuits
G7A Filters
•
The impedance of a low-pass filter as compared to
the impedance of the transmission line into which it
is to be inserted should be about the same
•
A Filter might be used to process signals from the
balanced modulator and send them to the mixer in a
single-sideband phone transmitter
7
Practical Circuits
G7A Schematic drawing symbols
3. Fixed resistor
4. NPN Transistor
5. Variable
capacitor
6. Transformer
11. Single pole
switch
13. Single cell
battery
8
Practical Circuits
G7A01 What safety feature does a powersupply bleeder resistor provide?
A.
B.
C.
D.
It
It
It
It
acts as a fuse for excess voltage
discharges the filter capacitors
removes shock hazards from the induction coils
eliminates ground-loop current
9
Practical Circuits
G7A01 What safety feature does a powersupply bleeder resistor provide?
A. It acts as a fuse for excess voltage
B.
It discharges the filter capacitors
C. It removes shock hazards from the induction coils
D. It eliminates ground-loop current
10
Practical Circuits
G7A02 What components are used in a
power-supply filter network?
A.
B.
C.
D.
Diodes
Transformers and transistors
Quartz crystals
Capacitors and inductors
11
Practical Circuits
G7A02 What components are used in a
power-supply filter network?
A. Diodes
B. Transformers and transistors
C. Quartz crystals
D.
Capacitors and inductors
12
Practical Circuits
G7A03 What should be the minimum peakinverse-voltage rating of the rectifier in a
full-wave power supply?
A. One-quarter the normal output voltage of the power supply
B. Half the normal output voltage of the power supply
C. Double the normal peak output voltage of the power
supply
D. Equal to the normal output voltage of the power supply
13
Practical Circuits
G7A03 What should be the minimum peakinverse-voltage rating of the rectifier in a
full-wave power supply?
A. One-quarter the normal output voltage of the power supply
B. Half the normal output voltage of the power supply
C.
Double the normal peak output voltage of the
power supply
D. Equal to the normal output voltage of the power supply
14
Practical Circuits
G7A04 What should be the approximate
minimum peak-inverse-voltage rating of the
rectifier in a half-wave power supply?
A. One-half the normal peak output voltage of the power
supply
B. Half the normal output voltage of the power supply
C. Equal to the normal output voltage of the power supply
D. Two times the normal peak output voltage of the power
supply
15
Practical Circuits
G7A04 What should be the approximate
minimum peak-inverse-voltage rating of the
rectifier in a half-wave power supply?
A. One-half the normal peak output voltage of the power
supply
B. Half the normal output voltage of the power supply
C. Equal to the normal output voltage of the power supply
D.
Two times the normal peak output voltage of
the power supply
16
Practical Circuits
G7A05 What should be the impedance of a
low-pass filter as compared to the
impedance of the transmission line into
which it is inserted?
A.
B.
C.
D.
Substantially higher
About the same
Substantially lower
Twice the transmission line impedance
17
Practical Circuits
G7A05 What should be the impedance of a
low-pass filter as compared to the
impedance of the transmission line into
which it is inserted?
A. Substantially higher
B.
About the same
C. Substantially lower
D. Twice the transmission line impedance
18
Practical Circuits
G7A06 Which of the following might be used
to process signals from the balanced
modulator and send them to the mixer in a
single-sideband phone transmitter?
A.
B.
C.
D.
Carrier oscillator
Filter
IF amplifier
RF amplifier
19
Practical Circuits
G7A06 Which of the following might be used
to process signals from the balanced
modulator and send them to the mixer in a
single-sideband phone transmitter?
Antenna
Mic
Speech
Amp
Balanced
Modulator
IF
Filter
Carrier
Oscillator
LSB
IF Amp
IF
Mixer
Second
Oscillator
IF Amp
VFO
Mixer
Power
Amp
VFO
USB
20
Practical Circuits
G7A06 Which of the following might be used
to process signals from the balanced
modulator and send them to the mixer in a
single-sideband phone transmitter?
A. Carrier oscillator
B.
Filter
C. IF amplifier
D. RF amplifier
Mic
Speech
Amp
Balanced
Modulator
Antenna
IF
Filter
Carrier
Oscillator
LSB
IF
Amp
IF
Mixer
Second
Oscillator
IF
Amp
VFO
Mixer
Power
Amp
VFO
USB
21
Practical Circuits
G7A07 Which circuit is used to combine
signals from the carrier oscillator and speech
amplifier and send the result to the filter in a
typical single-sideband phone transmitter?
A.
B.
C.
D.
Mixer
Detector
IF amplifier
Balanced modulator
22
Practical Circuits
G7A07 Which circuit is used to combine
signals from the carrier oscillator and speech
amplifier and send the result to the filter in a
typical single-sideband phone transmitter?
A. Mixer
B. Detector
C. IF amplifier
D.
Antenna
Balanced modulator
Mic
Speech
Amp
Balanced
Modulator
IF
Filter
Carrier
Oscillator
LSB
IF
Amp
IF
Mixer
Second
Oscillator
IF
Amp
VFO
Mixer
Power
Amp
VFO
USB
23
Practical Circuits
G7A08 What circuit is used to process
signals from the RF amplifier and local
oscillator and send the result to the IF filter
in a superheterodyne receiver?
A.
B.
C.
D.
Balanced modulator
IF amplifier
Mixer
Detector
24
Practical Circuits
G7A08 What circuit is used to process
signals from the RF amplifier and local
oscillator and send the result to the IF filter
in a superheterodyne receiver?
A. Balanced modulator
B. IF amplifier
C.
Mixer
D. Detector
25
Practical Circuits
G7A09 What circuit is used to process
signals from the IF amplifier and BFO and
send the result to the AF amplifier in a
single-sideband phone superheterodyne
receiver?
A.
B.
C.
D.
RF oscillator
IF filter
Balanced modulator
Product detector
26
Practical Circuits
G7A09 What circuit is used to process
signals from the IF amplifier and BFO and
send the result to the AF amplifier in a
single-sideband phone superheterodyne
receiver?
A. RF oscillator
B. IF filter
C. Balanced modulator
D.
Product detector
27
Practical Circuits
G7A10 What is an advantage of a crystal
controlled transmitter?
A.
B.
C.
D.
Stable output frequency
Excellent modulation clarity
Ease of switching between bands
Ease of changing frequency
28
Practical Circuits
G7A10 What is an advantage of a crystal
controlled transmitter?
A.
Stable output frequency
B. Excellent modulation clarity
C. Ease of switching between bands
D. Ease of changing frequency
29
Practical Circuits
G7A11 What is the simplest combination of
stages that can be combined to implement a
superheterodyne receiver?
A.
B.
C.
D.
RF amplifier, detector, audio amplifier
RF amplifier, mixer, if amplifier
HF oscillator, mixer, detector
HF oscillator, product detector, audio amplifier
30
Practical Circuits
G7A11 What is the simplest combination of
stages that can be combined to implement a
superheterodyne receiver?
A. RF amplifier, detector, audio amplifier
B. RF amplifier, mixer, if amplifier
C.
HF oscillator, mixer, detector
D. HF oscillator, product detector, audio amplifier
31
Practical Circuits
G7A12 What type of receiver is suitable for
CW and SSB reception but does not require a
mixer stage or an IF amplifier?
A.
B.
C.
D.
A
A
A
A
super-regenerative receiver
TRF receiver
super-heterodyne receiver
direct conversion receiver
32
Practical Circuits
G7A12 What type of receiver is suitable for
CW and SSB reception but does not require a
mixer stage or an IF amplifier?
A. A super-regenerative receiver
B. A TRF receiver
C. A super-heterodyne receiver
D.
A direct conversion receiver
33
Practical Circuits
G7A13 What type of circuit is used in many
FM receivers to convert signals coming from
the IF amplifier to audio?
A.
B.
C.
D.
Product detector
Phase inverter
Mixer
Discriminator
34
Practical Circuits
G7A13 What type of circuit is used in many
FM receivers to convert signals coming from
the IF amplifier to audio?
A. Product detector
B. Phase inverter
C. Mixer
D.
Discriminator
35
Practical Circuits
G7A14 Which of the following is a desirable
characteristic for capacitors used to filter the
DC output of a switching power supply?
A.
B.
C.
D.
Low equivalent series resistance
High equivalent series resistance
Low Temperature coefficient
High Temperature coefficient
36
Practical Circuits
G7A14 Which of the following is a desirable
characteristic for capacitors used to filter the
DC output of a switching power supply?
A.
Low equivalent series resistance
B. High equivalent series resistance
C. Low Temperature coefficient
D. High Temperature coefficient
37
Practical Circuits
G7A15 Which of the following is an
advantage of a switched-mode power supply
as compared to a linear power supply?
A. Faster switching time makes higher output voltage possible
B. Fewer circuit components are required
C. High frequency operation allows the use of smaller
components
D. All of these choices are correct
38
Practical Circuits
G7A15 Which of the following is an
advantage of a switched-mode power supply
as compared to a linear power supply?
A. Faster switching time makes higher output voltage possible
B. Fewer circuit components are required
C.
High frequency operation allows the use of
smaller components
D. All of these choices are correct
39
Practical Circuits
Half Wave Rectifier
40
Practical Circuits
G7A16 What portion of the AC cycle is
converted to DC by a half-wave rectifier?
A.
B.
C.
D.
90 degrees
180 degrees
270 degrees
360 degrees
41
Practical Circuits
G7A16 What portion of the AC cycle is
converted to DC by a half-wave rectifier?
A. 90 degrees
B.
180 degrees
C. 270 degrees
D. 360 degrees
42
Practical Circuits
G7A17 What portion of the AC cycle is
converted to DC by a full-wave rectifier?
A.
B.
C.
D.
90 degrees
180 degrees
270 degrees
360 degrees
43
Practical Circuits
G7A17 What portion of the AC cycle is
converted to DC by a full-wave rectifier?
A. 90 degrees
B. 180 degrees
C. 270 degrees
D.
360 degrees
44
Practical Circuits
G7A18 What is the output waveform of an
unfiltered full-wave rectifier connected to a
resistive load?
A. A series of DC pulses at twice the frequency of the AC
input
B. A series of DC pulses at the same frequency as the AC
input
C. A sine wave at half the frequency of the AC input
D. A steady DC voltage
45
Practical Circuits
G7A18 What is the output waveform of an
unfiltered full-wave rectifier connected to a
resistive load?
A.
A series of DC pulses at twice the frequency of
the AC input
B. A series of DC pulses at the same frequency as the AC
input
C. A sine wave at half the frequency of the AC input
D. A steady DC voltage
46
Practical Circuits
G7A19 Which symbol in figure G7-1
represents a fixed resistor?
A.
B.
C.
D.
Symbol
Symbol
Symbol
Symbol
2
6
3
12
47
Practical Circuits
G7A19 Which symbol in figure G7-1
represents a fixed resistor?
A. Symbol 2
B. Symbol 6
C.
Symbol 3
D. Symbol 12
48
Practical Circuits
G7A20 Which symbol in figure G7-1
represents a single cell battery?
A.
B.
C.
D.
Symbol
Symbol
Symbol
Symbol
5
12
8
13
49
Practical Circuits
G7A20 Which symbol in figure G7-1
represents a single cell battery?
A. Symbol 5
B. Symbol 12
C. Symbol 8
D.
Symbol 13
50
Practical Circuits
G7A21 Which symbol in figure G7-1
represents a NPN transistor?
A.
B.
C.
D.
Symbol
Symbol
Symbol
Symbol
2
4
10
12
51
Practical Circuits
G7A21 Which symbol in figure G7-1
represents a NPN transistor?
A. Symbol 2
B.
Symbol 4
C. Symbol 10
D. Symbol 12
52
Practical Circuits
G7A22 Which symbol in figure G7-1
represents a variable capacitor?
A.
B.
C.
D.
Symbol
Symbol
Symbol
Symbol
2
11
5
12
53
Practical Circuits
G7A22 Which symbol in figure G7-1
represents a variable capacitor?
A. Symbol 2
B. Symbol 11
C.
Symbol 5
D. Symbol 12
54
Practical Circuits
G7A23 Which symbol in figure G7-1
represents a transformer?
A.
B.
C.
D.
Symbol 6
Symbol 4
Symbol 10
symbol 2
55
Practical Circuits
G7A23 Which symbol in figure G7-1
represents a transformer?
A.
Symbol 6
B. Symbol 4
C. Symbol 10
D. symbol 2
56
Practical Circuits
G7A24 Which symbol in figure G7-1
represents a single pole switch?
A.
B.
C.
D.
Symbol
Symbol
Symbol
Symbol
2
3
11
12
57
Practical Circuits
G7A24 Which symbol in figure G7-1
represents a single pole switch?
A. Symbol 2
B. Symbol 3
C.
Symbol 11
D. Symbol 12
58
Practical Circuits
G7B Digital circuits (gates, flip-flops, shift
registers
•
•
•
A “flip-flop” circuit is a digital circuit with two stable
states
Digital circuits use the binary number system because
binary “ones” and “zeros” are easy to represent with an
“on” and “off” state
The output of a two-input NAND gate, given both
inputs are “one” is Zero
59
Practical Circuits
G7B Digital circuits cont’d
•
•
•
The output of a NOR gate given that both inputs
are “zero” is one
There are 8 states in a 3-bit binary counter
A shift register is a clocked array of circuits that
passes data in steps along the array
60
Practical Circuits
G7B Amplifiers
•
Low distortion is a characteristic of a Class A amplifier
•
A Class “C” power stage is appropriate for amplifying a
modulated signal for the CW mode
•
High efficiency is an advantage of a Class C amplifier
•
The efficiency of an RF power amplifier is determined
by dividing the RF output power by the DC input power
•
A linear amplifier is an amplifier whose output preserves
the input waveform
61
Practical Circuits
G7B Oscillators
•
The basic components of virtually all oscillators are
a filter and and amplifier operating in a feedback loop
•
The phase shift of the RC feedback circuit determines
the frequency of an RC oscillator
* The inductance and capacitance in the tank circuit
determines the frequency of an LC oscillator
62
Practical Circuits
G7B01 Which of the following describes a
"flip-flop" circuit?
A.
B.
C.
D.
A transmit-receive circuit
A digital circuit with two stable states
An RF limiter
A voice-operated switch
63
Practical Circuits
G7B01 Which of the following describes a
"flip-flop" circuit?
A. A transmit-receive circuit
B.
A digital circuit with two stable states
C. An RF limiter
D. A voice-operated switch
64
Practical Circuits
G7B02 Why do digital circuits use the binary
number system?
A. Binary "ones" and "zeros" are easy to represent with an
"on" or "off" state
B. The binary number system is most accurate
C. Binary numbers are more compatible with analog circuitry
D. All of these answers are correct
65
Practical Circuits
G7B02 Why do digital circuits use the binary
number system?
A.
Binary "ones" and "zeros" are easy to represent
with an "on" or "off" state
B. The binary number system is most accurate
C. Binary numbers are more compatible with analog circuitry
D. All of these answers are correct
66
Practical Circuits
G7B03 What is the output of a two-input
NAND gate, given both inputs are "one"?
A.
B.
C.
D.
Two
One
Zero
Minus One
67
Practical Circuits
G7B03 What is the output of a two-input
NAND gate, given both inputs are "one"?
A. Two
B. One
C.
Zero
D. Minus One
68
Practical Circuits
G7B04 What is the output of a NOR gate
given that both inputs are "zero"?
A.
B.
C.
D.
Zero
One
Minus one
The opposite from the previous state
69
Practical Circuits
G7B04 What is the output of a NOR gate
given that both inputs are "zero"?
A. Zero
B.
One
C. Minus one
D. The opposite from the previous state
70
Practical Circuits
G7B05 How many states are there in a 3-bit
binary counter?
A.
B.
C.
D.
3
6
8
16
71
Practical Circuits
G7B05 How many states are there in a 3-bit
binary counter?
A. 3
B. 6
C.
8
D. 16
72
Practical Circuits
G7B06 What is a shift register?
A. A clocked array of circuits that passes data in steps along
the array
B. An array of operational amplifiers used for tri-state
arithmetic operations
C. A digital mixer
D. An analog mixer
73
Practical Circuits
G7B06 What is a shift register?
A.
A clocked array of circuits that passes data in
steps along the array
B. An array of operational amplifiers used for tri-state
arithmetic operations
C. A digital mixer
D. An analog mixer
74
Practical Circuits
G7B07 What are the basic components of
virtually all oscillators?
A.
B.
C.
D.
An amplifier and a divider
A frequency multiplier and a mixer
A circulator and a filter operating in a feed-forward loop
A filter and an amplifier operating in a feedback loop
75
Practical Circuits
G7B07 What are the basic components of
virtually all oscillators?
A. An amplifier and a divider
B. A frequency multiplier and a mixer
C. A circulator and a filter operating in a feed-forward loop
D.
A filter and an amplifier operating in a feedback
loop
76
Practical Circuits
G7B08 What determines the frequency of an
RC oscillator?
A.
B.
C.
D.
The
The
The
The
ratio of the capacitors in the feedback loop
value of the inductor in the tank circuit
phase shift of the RC feedback circuit
gain of the amplifier
77
Practical Circuits
G7B08 What determines the frequency of an
RC oscillator?
A. The ratio of the capacitors in the feedback loop
B. The value of the inductor in the tank circuit
C.
The phase shift of the RC feedback circuit
D. The gain of the amplifier
78
Practical Circuits
G7B09 What determines the frequency of an
LC oscillator?
A.
B.
C.
D.
The
The
The
The
number of stages in the counter
number of stages in the divider
inductance and capacitance in the tank circuit
time delay of the lag circuit
79
Practical Circuits
G7B09 What determines the frequency of an
LC oscillator?
A. The number of stages in the counter
B. The number of stages in the divider
C.
The inductance and capacitance in the tank
circuit
D. The time delay of the lag circuit
80
Practical Circuits
G7B10 Which of the following is a
characteristic of a Class A amplifier?
A.
B.
C.
D.
Low standby power
High Efficiency
No need for bias
Low distortion
81
Practical Circuits
G7B10 Which of the following is a
characteristic of a Class A amplifier?
A. Low standby power
B. High Efficiency
C. No need for bias
D.
Low distortion
82
Practical Circuits
G7B11 For which of the following modes is a
Class C power stage appropriate for
amplifying a modulated signal?
A.
B.
C.
D.
SSB
CW
AM
All of these answers are correct
83
Practical Circuits
G7B11 For which of the following modes is a
Class C power stage appropriate for
amplifying a modulated signal?
A. SSB
B.
CW
C. AM
D. All of these answers are correct
84
Practical Circuits
G7B12 Which of the following is an
advantage of a Class C amplifier?
A.
B.
C.
D.
High efficiency
Linear operation
No need for tuned circuits
All of these answers are correct
85
Practical Circuits
G7B12 Which of the following is an
advantage of a Class C amplifier?
A.
High efficiency
B. Linear operation
C. No need for tuned circuits
D. All of these answers are correct
86
Practical Circuits
G7B13 How is the efficiency of an RF power
amplifier determined?
A. Divide the DC input power by the DC output power
B. Divide the RF output power by the DC input power
C. Multiply the RF input power by the reciprocal of the RF
output power
D. Add the RF input power to the DC output power
87
Practical Circuits
G7B13 How is the efficiency of an RF power
amplifier determined?
A. Divide the DC input power by the DC output power
B.
Divide the RF output power by the DC input
power
C. Multiply the RF input power by the reciprocal of the RF
output power
D. Add the RF input power to the DC output power
88
Practical Circuits
G7B14 Which of the following describes a
linear amplifier?
A. Any RF power amplifier used in conjunction with an
amateur transceiver
B. An amplifier whose output preserves the input waveform
C. A Class C high efficiency amplifier
D. An amplifier used as a frequency multiplier
89
Practical Circuits
G7B14 Which of the following describes a
linear amplifier?
A. Any RF power amplifier used in conjunction with an
amateur transceiver
B.
An amplifier whose output preserves the input
waveform
C. A Class C high efficiency amplifier
D. An amplifier used as a frequency multiplier
90
Practical Circuits
G7 - PRACTICAL CIRCUITS
[2 exam question - 2 groups]
91
Practical Circuits