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Amateur Radio - Extra > E7 - PRACTICAL CIRCUITS [8 Exam Questions - 8 Groups] > Flashcards

E7 - PRACTICAL CIRCUITS [8 Exam Questions - 8 Groups] Flashcards

1
Q

Which of the following is a bistable circuit?

A. An “AND” gate

B. An “OR” gate

C. A flip-flop

D. A clock

A

C. A flip-flop

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2
Q

How many output level changes are obtained for every two trigger pulses applied to the input of a T flip-flop circuit?

A. None

B. One

C. Two

D. Four

A

C. Two

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3
Q

Which of the following can divide the frequency of a pulse train by 2?

A. An XOR gate

B. A flip-flop

C. An OR gate

D. A multiplexer

A

B. A flip-flop

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4
Q

How many flip-flops are required to divide a signal frequency by 4?

A. 1

B. 2

C. 4

D. 8

A

B. 2

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5
Q

Which of the following is a circuit that continuously alternates between two states without an external clock?

A. Monostable multivibrator

B. J-K flip-flop

C. T flip-flop

D. Astable multivibrator

A

D. Astable multivibrator

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6
Q

What is a characteristic of a monostable multivibrator?

A. It switches momentarily to the opposite binary state and then returns, after a set time, to its original state

B. It is a clock that produces a continuous square wave oscillating between 1 and 0

C. It stores one bit of data in either a 0 or 1 state

D. It maintains a constant output voltage, regardless of variations in the input voltage

A

A. It switches momentarily to the opposite binary state and then returns, after a set time, to its original state

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7
Q

What logical operation does a NAND gate perform?

A. It produces a logic “0” at its output only when all inputs are logic “0”

B. It produces a logic “1” at its output only when all inputs are logic “1”

C. It produces a logic “0” at its output if some but not all of its inputs are logic “1”

D. It produces a logic “0” at its output only when all inputs are logic “1”

A

D. It produces a logic “0” at its output only when all inputs are logic “1”

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8
Q

What logical operation does an OR gate perform?

A. It produces a logic “1” at its output if any or all inputs are logic “1”

B. It produces a logic “0” at its output if all inputs are logic “1”

C. It only produces a logic “0” at its output when all inputs are logic “1”

D. It produces a logic “1” at its output if all inputs are logic “0”

A

A. It produces a logic “1” at its output if any or all inputs are logic “1”

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9
Q

What logical operation is performed by a two-input exclusive NOR gate?

A. It produces a logic “0” at its output only if all inputs are logic “0”

B. It produces a logic “1” at its output only if all inputs are logic “1”

C. It produces a logic “0” at its output if any single input is a logic “1”?

D. It produces a logic “1” at its output if any single input is a logic “1”?

A

C. It produces a logic “0” at its output if any single input is a logic “1”?

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10
Q

What is a truth table?

A. A table of logic symbols that indicate the high logic states of an op-amp

B. A diagram showing logic states when the digital device’s output is true

C. A list of inputs and corresponding outputs for a digital device

D. A table of logic symbols that indicates the low logic states of an op-amp

A

C. A list of inputs and corresponding outputs for a digital device

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11
Q

What is the name for logic which represents a logic “1” as a high voltage?

A. Reverse Logic

B. Assertive Logic

C. Negative logic

D. Positive Logic

A

D. Positive Logic

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12
Q

What is the name for logic which represents a logic “0” as a high voltage?

A. Reverse Logic

B. Assertive Logic

C. Negative logic

D. Positive Logic

A

C. Negative logic

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13
Q

What is an SR or RS flip-flop?

A. A speed-reduced logic device with high power capability

B. A set/reset flip-flop whose output is low when R is high and S is low, high when S is high and R is low, and unchanged when both inputs are low

C. A speed-reduced logic device with very low voltage operation capability

D. A set/reset flip-flop that toggles whenever the T input is pulsed, unless both inputs are high

A

B. A set/reset flip-flop whose output is low when R is high and S is low, high when S is high and R is low, and unchanged when both inputs are low

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14
Q

What is a JK flip-flop?

A. A flip-flop similar to an RS except that it toggles when both J and K are high

B. A flip-flop utilizing low power, low temperature Joule-Kelvin devices

C. A flip-flop similar to a D flip-flop except that it triggers on the negative clock edge

D. A flip-flop originally developed in Japan and Korea which has very low power consumption

A

A. A flip-flop similar to an RS except that it toggles when both J and K are high

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15
Q

What is a D flip-flop?

A. A flip-flop whose output takes on the state of the D input when the clock signal transitions from low to high

B. A differential class D amplifier used as a flip-flop circuit

C. A dynamic memory storage element

D. A flip-flop whose output is capable of both positive and negative voltage excursions

A

A. A flip-flop whose output takes on the state of the D input when the clock signal transitions from low to high

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16
Q

For what portion of a signal cycle does a Class AB amplifier operate?

A. More than 180 degrees but less than 360 degrees

B. Exactly 180 degrees

C. The entire cycle

D. Less than 180 degrees

A

A. More than 180 degrees but less than 360 degrees

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17
Q

What is a Class D amplifier?

A. A type of amplifier that uses switching technology to achieve high efficiency

B. A low power amplifier using a differential amplifier for improved linearity

C. An amplifier using drift-mode FETs for high efficiency

D. A frequency doubling amplifier

A

A. A type of amplifier that uses switching technology to achieve high efficiency

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18
Q

Which of the following forms the output of a class D amplifier circuit?

A. A low-pass filter to remove switching signal components

B. A high-pass filter to compensate for low gain at low frequencies

C. A matched load resistor to prevent damage by switching transients

D. A temperature-compensated load resistor to improve linearity

A

A. A low-pass filter to remove switching signal components

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19
Q

Where on the load line of a Class A common emitter amplifier would bias normally be set?

A. Approximately half-way between saturation and cutoff

B. Where the load line intersects the voltage axis

C. At a point where the bias resistor equals the load resistor

D. At a point where the load line intersects the zero bias current curve

A

A. Approximately half-way between saturation and cutoff

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20
Q

What can be done to prevent unwanted oscillations in an RF power amplifier?

A. Tune the stage for maximum SWR

B. Tune both the input and output for maximum power

C. Install parasitic suppressors and/or neutralize the stage

D. Use a phase inverter in the output filter

A

C. Install parasitic suppressors and/or neutralize the stage

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21
Q

Which of the following amplifier types reduces or eliminates even-order harmonics?

A. Push-push

B. Push-pull

C. Class C

D. Class AB

A

B. Push-pull

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22
Q

Which of the following is a likely result when a Class C amplifier is used to amplify a single-sideband phone signal?

A. Reduced intermodulation products

B. Increased overall intelligibility

C. Signal inversion

D. Signal distortion and excessive bandwidth

A

D. Signal distortion and excessive bandwidth

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23
Q

How can an RF power amplifier be neutralized?

A. By increasing the driving power

B. By reducing the driving power

C. By feeding a 180-degree out-of-phase portion of the output back to the input

D. By feeding an in-phase component of the output back to the input

A

C. By feeding a 180-degree out-of-phase portion of the output back to the input

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24
Q

Which of the following describes how the loading and tuning capacitors are to be adjusted when tuning a vacuum tube RF power amplifier that employs a pi-network output circuit?

A. The loading capacitor is set to maximum capacitance and the tuning capacitor is adjusted for minimum allowable plate current

B. The tuning capacitor is set to maximum capacitance and the loading capacitor is adjusted for minimum plate permissible current

C. The loading capacitor is adjusted to minimum plate current while alternately adjusting the tuning capacitor for maximum allowable plate current

D. The tuning capacitor is adjusted for minimum plate current, while the loading capacitor is adjusted for maximum permissible plate current

A

D. The tuning capacitor is adjusted for minimum plate current, while the loading capacitor is adjusted for maximum permissible plate current

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25
Q

In Figure E7-1, what is the purpose of R1 and R2?

A. Load resistors

B. Fixed bias

C. Self bias

D. Feedback

A

B. Fixed bias

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26
Q

In Figure E7-1, what is the purpose of R3?

A. Fixed bias

B. Emitter bypass

C. Output load resistor

D. Self bias

A

D. Self bias

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27
Q

What type of circuit is shown in Figure E7-1?

A. Switching voltage regulator

B. Linear voltage regulator

C. Common emitter amplifier

D. Emitter follower amplifier

A

C. Common emitter amplifier

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28
Q

In Figure E7-2, what is the purpose of R?

A. Emitter load

B. Fixed bias

C. Collector load

D. Voltage regulation

A

A. Emitter load

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29
Q

In Figure E7-2, what is the purpose of C2?

A. Output coupling

B. Emitter bypass

C. Input coupling

D. Hum filtering

A

A. Output coupling

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30
Q

What is one way to prevent thermal runaway in a bipolar transistor amplifier?

A. Neutralization

B. Select transistors with high beta

C. Use a resistor in series with the emitter

D. All of these choices are correct

A

C. Use a resistor in series with the emitter

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31
Q

What is the effect of intermodulation products in a linear power amplifier?

A. Transmission of spurious signals

B. Creation of parasitic oscillations

C. Low efficiency

D. All of these choices are correct

A

A. Transmission of spurious signals

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32
Q

Why are third-order intermodulation distortion products of particular concern in linear power amplifiers?

A. Because they are relatively close in frequency to the desired signal

B. Because they are relatively far in frequency from the desired signal

C. Because they invert the sidebands causing distortion

D. Because they maintain the sidebands, thus causing multiple duplicate signals

A

A. Because they are relatively close in frequency to the desired signal

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33
Q

Which of the following is a characteristic of a grounded-grid amplifier?

A. High power gain

B. High filament voltage

C. Low input impedance

D. Low bandwidth

A

C. Low input impedance

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34
Q

What is a klystron?

A. A high speed multivibrator

B. An electron-coupled oscillator utilizing a pentode vacuum tube

C. An oscillator utilizing ceramic elements to achieve stability

D. A VHF, UHF, or microwave vacuum tube that uses velocity modulation

A

D. A VHF, UHF, or microwave vacuum tube that uses velocity modulation

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35
Q

What is a parametric amplifier?

A. A type of bipolar operational amplifier with excellent linearity derived from use of very high voltage on the collector

B. A low-noise VHF or UHF amplifier relying on varying reactance for amplification

C. A high power amplifier for HF application utilizing the Miller effect to increase gain

D. An audio push-pull amplifier using silicon carbide transistors for extremely low noise

A

B. A low-noise VHF or UHF amplifier relying on varying reactance for amplification

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36
Q

Which of the following devices is generally best suited for UHF or microwave power amplifier applications?

A. Field effect transistor

B. Nuvistor

C. Silicon controlled rectifier

D. Triac

A

A. Field effect transistor

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37
Q

How are the capacitors and inductors of a low-pass filter Pi-network arranged between the network’s input and output?

A. Two inductors are in series between the input and output, and a capacitor is connected between the two inductors and ground

B. Two capacitors are in series between the input and output and an inductor is connected between the two capacitors and ground

C. An inductor is connected between the input and ground, another inductor is connected between the output and ground, and a capacitor is connected between the input and output

D. A capacitor is connected between the input and ground, another capacitor is connected between the output and ground, and an inductor is connected between input and output

A

D. A capacitor is connected between the input and ground, another capacitor is connected between the output and ground, and an inductor is connected between input and output

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38
Q

A T-network with series capacitors and a parallel shunt inductor has which of the following properties?

A. It is a low-pass filter

B. It is a band-pass filter

C. It is a high-pass filter

D. It is a notch filter

A

C. It is a high-pass filter

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39
Q

What advantage does a Pi-L-network have over a Pi-network for impedance matching between the final amplifier of a vacuum-tube transmitter and an antenna?

A. Greater harmonic suppression

B. Higher efficiency

C. Lower losses

D. Greater transformation range

A

A. Greater harmonic suppression

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40
Q

How does an impedance-matching circuit transform a complex impedance to a resistive impedance?

A. It introduces negative resistance to cancel the resistive part of impedance

B. It introduces transconductance to cancel the reactive part of impedance

C. It cancels the reactive part of the impedance and changes the resistive part to a desired value

D. Network resistances are substituted for load resistances and reactances are matched to the resistances

A

C. It cancels the reactive part of the impedance and changes the resistive part to a desired value

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41
Q

Which filter type is described as having ripple in the passband and a sharp cutoff?

A. A Butterworth filter

B. An active LC filter

C. A passive op-amp filter

D. A Chebyshev filter

A

D. A Chebyshev filter

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42
Q

What are the distinguishing features of an elliptical filter?

A. Gradual passband rolloff with minimal stop band ripple

B. Extremely flat response over its pass band with gradually rounded stop band corners

C. Extremely sharp cutoff with one or more notches in the stop band

D. Gradual passband rolloff with extreme stop band ripple

A

C. Extremely sharp cutoff with one or more notches in the stop band

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43
Q

What kind of filter would you use to attenuate an interfering carrier signal while receiving an SSB transmission?

A. A band-pass filter

B. A notch filter

C. A Pi-network filter

D. An all-pass filter

A

B. A notch filter

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44
Q

What kind of digital signal processing audio filter might be used to remove unwanted noise from a received SSB signal?

A. An adaptive filter

B. A crystal-lattice filter

C. A Hilbert-transform filter

D. A phase-inverting filter

A

A. An adaptive filter

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45
Q

What type of digital signal processing filter might be used to generate an SSB signal?

A. An adaptive filter

B. A notch filter

C. A Hilbert-transform filter

D. An elliptical filter

A

C. A Hilbert-transform filter

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46
Q

Which of the following filters would be the best choice for use in a 2 meter repeater duplexer?

A. A crystal filter

B. A cavity filter

C. A DSP filter

D. An L-C filter

A

B. A cavity filter

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47
Q

Which of the following is the common name for a filter network which is equivalent to two L networks connected back-to-back with the inductors in series and the capacitors in shunt at the input and output?

A. Pi-L

B. Cascode

C. Omega

D. Pi

A

D. Pi

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48
Q

Which of the following describes a Pi-L network used for matching a vacuum-tube final amplifier to a 50-ohm unbalanced output?

A. A Phase Inverter Load network

B. A Pi network with an additional series inductor on the output

C. A network with only three discrete parts

D. A matching network in which all components are isolated from ground

A

B. A Pi network with an additional series inductor on the output

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49
Q

What is one advantage of a Pi matching network over an L matching network consisting of a single inductor and a single capacitor?

A. The Q of Pi networks can be varied depending on the component values chosen

B. L networks cannot perform impedance transformation

C. Pi networks have fewer components

D. Pi networks are designed for balanced input and output

A

A. The Q of Pi networks can be varied depending on the component values chosen

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50
Q

Which of these modes is most affected by non-linear phase response in a receiver IF filter?

A. Meteor Scatter

B. Single-Sideband voice

C. Digital

D. Video

A

C. Digital

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51
Q

What is one characteristic of a linear electronic voltage regulator?

A. It has a ramp voltage as its output

B. It eliminates the need for a pass transistor

C. The control element duty cycle is proportional to the line or load conditions

D. The conduction of a control element is varied to maintain a constant output voltage

A

D. The conduction of a control element is varied to maintain a constant output voltage

52
Q

What is one characteristic of a switching electronic voltage regulator?

A. The resistance of a control element is varied in direct proportion to the line voltage or load current

B. It is generally less efficient than a linear regulator

C. The control device’s duty cycle is controlled to produce a constant average output voltage

D. It gives a ramp voltage at its output

A

C. The control device’s duty cycle is controlled to produce a constant average output voltage

53
Q

What device is typically used as a stable reference voltage in a linear voltage regulator?

A. A Zener diode

B. A tunnel diode

C. An SCR

D. A varactor diode

A

A. A Zener diode

54
Q

Which of the following types of linear voltage regulator usually make the most efficient use of the primary power source?

A. A series current source

B. A series regulator

C. A shunt regulator

D. A shunt current source

A

B. A series regulator

55
Q

Which of the following types of linear voltage regulator places a constant load on the unregulated voltage source?

A. A constant current source

B. A series regulator

C. A shunt current source

D. A shunt regulator

A

D. A shunt regulator

56
Q

What is the purpose of Q1 in the circuit shown in Figure E7-3?

A. It provides negative feedback to improve regulation

B. It provides a constant load for the voltage source

C. It increases the current-handling capability of the regulator

D. It provides D1 with current

A

C. It increases the current-handling capability of the regulator

57
Q

What is the purpose of C2 in the circuit shown in Figure E7-3?

A. It bypasses hum around D1

B. It is a brute force filter for the output

C. To self-resonate at the hum frequency

D. To provide fixed DC bias for Q1

A

A. It bypasses hum around D1

58
Q

What type of circuit is shown in Figure E7-3?

A. Switching voltage regulator

B. Grounded emitter amplifier

C. Linear voltage regulator

D. Emitter follower

A

C. Linear voltage regulator

59
Q

What is the purpose of C1 in the circuit shown in Figure E7-3?

A. It resonates at the ripple frequency

B. It provides fixed bias for Q1

C. It decouples the output

D. It filters the supply voltage

A

D. It filters the supply voltage

60
Q

What is the purpose of C3 in the circuit shown in Figure E7-3?

A. It prevents self-oscillation

B. It provides brute force filtering of the output

C. It provides fixed bias for Q1

D. It clips the peaks of the ripple

A

A. It prevents self-oscillation

61
Q

What is the purpose of R1 in the circuit shown in Figure E7-3?

A. It provides a constant load to the voltage source

B. It couples hum to D1

C. It supplies current to D1

D. It bypasses hum around D1

A

C. It supplies current to D1

62
Q

What is the purpose of R2 in the circuit shown in Figure E7-3?

A. It provides fixed bias for Q1

B. It provides fixed bias for D1

C. It decouples hum from D1

D. It provides a constant minimum load for Q1

A

D. It provides a constant minimum load for Q1

63
Q

What is the purpose of D1 in the circuit shown in Figure E7-3?

A. To provide line voltage stabilization

B. To provide a voltage reference

C. Peak clipping

D. Hum filtering

A

B. To provide a voltage reference

64
Q

What is one purpose of a “bleeder” resistor in a conventional (unregulated) power supply?

A. To cut down on waste heat generated by the power supply

B. To balance the low-voltage filament windings

C. To improve output voltage regulation

D. To boost the amount of output current

A

C. To improve output voltage regulation

65
Q

What is the purpose of a “step-start” circuit in a high-voltage power supply?

A. To provide a dual-voltage output for reduced power applications

B. To compensate for variations of the incoming line voltage

C. To allow for remote control of the power supply

D. To allow the filter capacitors to charge gradually

A

D. To allow the filter capacitors to charge gradually

66
Q

When several electrolytic filter capacitors are connected in series to increase the operating voltage of a power supply filter circuit, why should resistors be connected across each capacitor?

A. To equalize, as much as possible, the voltage drop across each capacitor

B. To provide a safety bleeder to discharge the capacitors when the supply is off

C. To provide a minimum load current to reduce voltage excursions at light loads

D. All of these choices are correct

A

D. All of these choices are correct

67
Q

What is the primary reason that a high-frequency inverter type high-voltage power supply can be both less expensive and lighter in weight than a conventional power supply?

A. The inverter design does not require any output filtering

B. It uses a diode bridge rectifier for increased output

C. The high frequency inverter design uses much smaller transformers and filter components for an equivalent power output

D. It uses a large power-factor compensation capacitor to create “free power” from the unused portion of the AC cycle

A

C. The high frequency inverter design uses much smaller transformers and filter components for an equivalent power output

68
Q

Which of the following can be used to generate FM phone emissions?

A. A balanced modulator on the audio amplifier

B. A reactance modulator on the oscillator

C. A reactance modulator on the final amplifier

D. A balanced modulator on the oscillator

A

B. A reactance modulator on the oscillator

69
Q

What is the function of a reactance modulator?

A. To produce PM signals by using an electrically variable resistance

B. To produce AM signals by using an electrically variable inductance or capacitance

C. To produce AM signals by using an electrically variable resistance

D. To produce PM signals by using an electrically variable inductance or capacitance

A

D. To produce PM signals by using an electrically variable inductance or capacitance

70
Q

How does an analog phase modulator function?

A. By varying the tuning of a microphone preamplifier to produce PM signals

B. By varying the tuning of an amplifier tank circuit to produce AM signals

C. By varying the tuning of an amplifier tank circuit to produce PM signals

D. By varying the tuning of a microphone preamplifier to produce AM signals

A

C. By varying the tuning of an amplifier tank circuit to produce PM signals

71
Q

What is one way a single-sideband phone signal can 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

A

A. By using a balanced modulator followed by a filter

72
Q

What circuit is added to an FM transmitter to boost the higher audio frequencies?

A. A de-emphasis network

B. A heterodyne suppressor

C. An audio prescaler

D. A pre-emphasis network

A

D. A pre-emphasis network

73
Q

Why is de-emphasis commonly used in FM communications receivers?

A. For compatibility with transmitters using phase modulation

B. To reduce impulse noise reception

C. For higher efficiency

D. To remove third-order distortion products

A

A. For compatibility with transmitters using phase modulation

74
Q

What is meant by the term baseband in radio communications?

A. The lowest frequency band that the transmitter or receiver covers

B. The frequency components present in the modulating signal

C. The unmodulated bandwidth of the transmitted signal

D. The basic oscillator frequency in an FM transmitter that is multiplied to increase the deviation and carrier frequency

A

B. The frequency components present in the modulating signal

75
Q

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 two input frequencies along with their sum and difference frequencies

D. 1.414 and 0.707 times the input frequency

A

C. The two input frequencies along with their sum and difference frequencies

76
Q

What occurs when an excessive amount of signal energy reaches a mixer circuit?

A. Spurious mixer products are generated

B. Mixer blanking occurs

C. Automatic limiting occurs

D. A beat frequency is generated

A

A. Spurious mixer products are generated

77
Q

How does a diode detector function?

A. By rectification and filtering of RF signals

B. By breakdown of the Zener voltage

C. By mixing signals with noise in the transition region of the diode

D. By sensing the change of reactance in the diode with respect to frequency

A

A. By rectification and filtering of RF signals

78
Q

Which of the following types of detector is well suited for demodulating SSB signals?

A. Discriminator

B. Phase detector

C. Product detector

D. Phase comparator

A

C. Product detector

79
Q

What is a frequency discriminator stage in a FM receiver?

A. An FM generator circuit

B. A circuit for filtering two closely adjacent signals

C. An automatic band-switching circuit

D. A circuit for detecting FM signals

A

D. A circuit for detecting FM signals

80
Q

Which of the following describes a common means of generating an SSB signal when using digital signal processing?

A. Mixing products are converted to voltages and subtracted by adder circuits

B. A frequency synthesizer removes the unwanted sidebands

C. Emulation of quartz crystal filter characteristics

D. The quadrature method

A

D. The quadrature method

81
Q

What is meant by direct conversion when referring to a software defined receiver?

A. Software is converted from source code to object code during operation of the receiver

B. Incoming RF is converted to the IF frequency by rectification to generate the control voltage for a voltage controlled oscillator

C. Incoming RF is mixed to “baseband” for analog-to-digital conversion and subsequent processing

D. Software is generated in machine language, avoiding the need for compilers

A

C. Incoming RF is mixed to “baseband” for analog-to-digital conversion and subsequent processing

82
Q

What is the purpose of a prescaler circuit?

A. It converts the output of a JK flip flop to that of an RS flip-flop

B. It multiplies a higher frequency signal so a low-frequency counter can display the operating frequency

C. It prevents oscillation in a low-frequency counter circuit

D. It divides a higher frequency signal so a low-frequency counter can display the input frequency

A

D. It divides a higher frequency signal so a low-frequency counter can display the input frequency

83
Q

Which of the following would be used to reduce a signal’s frequency by a factor of ten?

A. A preamp

B. A prescaler

C. A marker generator

D. A flip-flop

A

B. A prescaler

84
Q

What is the function of a decade counter digital IC?

A. It produces one output pulse for every ten input pulses

B. It decodes a decimal number for display on a seven-segment LED display

C. It produces ten output pulses for every input pulse

D. It adds two decimal numbers together

A

A. It produces one output pulse for every ten input pulses

85
Q

What additional circuitry must be added to a 100-kHz crystal-controlled marker generator so as to provide markers at 50 and 25 kHz?

A. An emitter-follower

B. Two frequency multipliers

C. Two flip-flops

D. A voltage divider

A

C. Two flip-flops

86
Q

Which of the following is a technique for providing high stability oscillators needed for microwave transmission and reception?

A. Use a GPS signal reference

B. Use a rubidium stabilized reference oscillator

C. Use a temperature-controlled high Q dielectric resonator

D. All of these choices are correct

A

D. All of these choices are correct

87
Q

What is one purpose of a marker generator?

A. To add audio markers to an oscilloscope

B. To provide a frequency reference for a phase locked loop

C. To provide a means of calibrating a receiver’s frequency settings

D. To add time signals to a transmitted signal

A

C. To provide a means of calibrating a receiver’s frequency settings

88
Q

What determines the accuracy of a frequency counter?

A. The accuracy of the time base

B. The speed of the logic devices used

C. Accuracy of the AC input frequency to the power supply

D. Proper balancing of the mixer diodes

A

A. The accuracy of the time base

89
Q

Which of the following is performed by a frequency counter?

A. Determining the frequency deviation with an FM discriminator

B. Mixing the incoming signal with a WWV reference

C. Counting the number of input pulses occurring within a specific period of time

D. Converting the phase of the measured signal to a voltage which is proportional to the frequency

A

C. Counting the number of input pulses occurring within a specific period of time

90
Q

What is the purpose of a frequency counter?

A. To provide a digital representation of the frequency of a signal

B. To generate a series of reference signals at known frequency intervals

C. To display all frequency components of a transmitted signal

D. To provide a signal source at a very accurate frequency

A

A. To provide a digital representation of the frequency of a signal

91
Q

What alternate method of determining frequency, other than by directly counting input pulses, is used by some counters?

A. GPS averaging

B. Period measurement plus mathematical computation

C. Prescaling

D. D/A conversion

A

B. Period measurement plus mathematical computation

92
Q

What is an advantage of a period-measuring frequency counter over a direct-count type?

A. It can run on battery power for remote measurements

B. It does not require an expensive high-precision time base

C. It provides improved resolution of low-frequency signals within a comparable time period

D. It can directly measure the modulation index of an FM transmitter

A

C. It provides improved resolution of low-frequency signals within a comparable time period

93
Q

What primarily determines the gain and frequency characteristics of an op-amp RC active filter?

A. The values of capacitors and resistors built into the op-amp

B. The values of capacitors and resistors external to the op-amp

C. The input voltage and frequency of the op-amp’s DC power supply

D. The output voltage and smoothness of the op-amp’s DC power supply

A

B. The values of capacitors and resistors external to the op-amp

94
Q

What is the effect of ringing in a filter?

A. An echo caused by a long time delay

B. A reduction in high frequency response

C. Partial cancellation of the signal over a range of frequencies

D. Undesired oscillations added to the desired signal

A

D. Undesired oscillations added to the desired signal

95
Q

Which of the following is an advantage of using an op-amp instead of LC elements in an audio filter?

A. Op-amps are more rugged

B. Op-amps are fixed at one frequency

C. Op-amps are available in more varieties than are LC elements

D. Op-amps exhibit gain rather than insertion loss

A

D. Op-amps exhibit gain rather than insertion loss

96
Q

Which of the following is a type of capacitor best suited for use in high-stability op-amp RC active filter circuits?

A. Electrolytic

B. Disc ceramic

C. Polystyrene

D. Paper

A

C. Polystyrene

97
Q

How can unwanted ringing and audio instability be prevented in a multi-section op-amp RC audio filter circuit?

A. Restrict both gain and Q

B. Restrict gain, but increase Q

C. Restrict Q, but increase gain

D. Increase both gain and Q

A

A. Restrict both gain and Q

98
Q

Which of the following is the most appropriate use of an op-amp active filter?

A. As a high-pass filter used to block RFI at the input to receivers

B. As a low-pass filter used between a transmitter and a transmission line

C. For smoothing power-supply output

D. As an audio filter in a receiver

A

D. As an audio filter in a receiver

99
Q

What magnitude of voltage gain can be expected from the circuit in Figure E7-4 when R1 is 10 ohms and RF is 470 ohms?

A. 0.21

B. 94

C. 47

D. 24

A

C. 47

100
Q

How does the gain of an ideal operational amplifier vary with frequency?

A. It increases linearly with increasing frequency

B. It decreases linearly with increasing frequency

C. It decreases logarithmically with increasing frequency

D. It does not vary with frequency

A

D. It does not vary with frequency

101
Q

What will be the output voltage of the circuit shown in Figure E7-4 if R1 is 1000 ohms, RF is 10,000 ohms, and 0.23 volts dc is applied to the input?

A. 0.23 volts

B. 2.3 volts

C. -0.23 volts

D. -2.3 volts

A

D. -2.3 volts

102
Q

What absolute voltage gain can be expected from the circuit in Figure E7-4 when R1 is 1800 ohms and RF is 68 kilohms?

A. 1

B. 0.03

C. 38

D. 76

A

C. 38

103
Q

What absolute voltage gain can be expected from the circuit in Figure E7-4 when R1 is 3300 ohms and RF is 47 kilohms?

A. 28

B. 14

C. 7

D. 0.07

A

B. 14

104
Q

What is an integrated circuit operational amplifier?

A. A high-gain, direct-coupled differential amplifier with very high input and very low output impedance

B. A digital audio amplifier whose characteristics are determined by components external to the amplifier

C. An amplifier used to increase the average output of frequency modulated amateur signals to the legal limit

D. An RF amplifier used in the UHF and microwave regions

A

A. A high-gain, direct-coupled differential amplifier with very high input and very low output impedance

105
Q

What is meant by the term op-amp input-offset voltage?

A. The output voltage of the op-amp minus its input voltage

B. The differential input voltage needed to bring the open-loop output voltage to zero

C. The input voltage needed to bring the open-loop output voltage to zero

D. The potential between the amplifier input terminals of the op-amp in an open-loop condition

A

C. The input voltage needed to bring the open-loop output voltage to zero

106
Q

What is the typical input impedance of an integrated circuit op-amp?

A. 100 ohms

B. 1000 ohms

C. Very low

D. Very high

A

D. Very high

107
Q

What is the typical output impedance of an integrated circuit op-amp?

A. Very low

B. Very high

C. 100 ohms

D. 1000 ohms

A

A. Very low

108
Q

What are three oscillator circuits used in Amateur Radio equipment?

A. Taft, Pierce and negative feedback

B. Pierce, Fenner and Beane

C. Taft, Hartley and Pierce

D. Colpitts, Hartley and Pierce

A

D. Colpitts, Hartley and Pierce

109
Q

What condition must exist for a circuit to oscillate?

A. It must have at least two stages

B. It must be neutralized

C. It must have positive feedback with a gain greater than 1

D. It must have negative feedback sufficient to cancel the input signal

A

C. It must have positive feedback with a gain greater than 1

110
Q

How is positive feedback supplied in a Hartley oscillator?

A. Through a tapped coil

B. Through a capacitive divider

C. Through link coupling

D. Through a neutralizing capacitor

A

A. Through a tapped coil

111
Q

How is positive feedback supplied in a Colpitts oscillator?

A. Through a tapped coil

B. Through link coupling

C. Through a capacitive divider

D. Through a neutralizing capacitor

A

C. Through a capacitive divider

112
Q

How is positive feedback supplied in a Pierce oscillator?

A. Through a tapped coil

B. Through link coupling

C. Through a neutralizing capacitor

D. Through a quartz crystal

A

D. Through a quartz crystal

113
Q

Which of the following oscillator circuits are commonly used in VFOs?

A. Pierce and Zener

B. Colpitts and Hartley

C. Armstrong and deForest

D. Negative feedback and balanced feedback

A

B. Colpitts and Hartley

114
Q

What is a magnetron oscillator?

A. An oscillator in which the output is fed back to the input by the magnetic field of a transformer

B. A crystal oscillator in which variable frequency is obtained by placing the crystal in a strong magnetic field

C. A UHF or microwave oscillator consisting of a diode vacuum tube with a specially shaped anode, surrounded by an external magnet

D. A reference standard oscillator in which the oscillations are synchronized by magnetic coupling to a rubidium gas tube

A

C. A UHF or microwave oscillator consisting of a diode vacuum tube with a specially shaped anode, surrounded by an external magnet

115
Q

What is a Gunn diode oscillator?

A. An oscillator based on the negative resistance properties of properly-doped semiconductors

B. An oscillator based on the argon gas diode

C. A highly stable reference oscillator based on the tee-notch principle

D. A highly stable reference oscillator based on the hot-carrier effect

A

A. An oscillator based on the negative resistance properties of properly-doped semiconductors

116
Q

What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital to analog converter and a low-pass anti-alias filter?

A. A direct digital synthesizer

B. A hybrid synthesizer

C. A phase locked loop synthesizer

D. A diode-switching matrix synthesizer

A

A. A direct digital synthesizer

117
Q

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

A

B. The amplitude values that represent a sine-wave output

118
Q

What are the major spectral impurity components of direct digital synthesizers?

A. Broadband noise

B. Digital conversion noise

C. Spurious signals at discrete frequencies

D. Nyquist limit noise

A

C. Spurious signals at discrete frequencies

119
Q

Which of the following is a principal component of a direct digital synthesizer (DDS)?

A. Phase splitter

B. Hex inverter

C. Chroma demodulator

D. Phase accumulator

A

D. Phase accumulator

120
Q

What is the capture range of a phase-locked loop circuit?

A. The frequency range over which the circuit can lock

B. The voltage range over which the circuit can lock

C. The input impedance range over which the circuit can lock

D. The range of time it takes the circuit to lock

A

A. The frequency range over which the circuit can lock

121
Q

What is a phase-locked loop circuit?

A. An electronic servo loop consisting of a ratio detector, reactance modulator, and voltage-controlled oscillator

B. An electronic circuit also known as a monostable multivibrator

C. An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator

D. An electronic circuit consisting of a precision push-pull amplifier with a differential input

A

C. An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator

122
Q

Which of these functions can be performed by a phase-locked loop?

A. Wide-band AF and RF power amplification

B. Comparison of two digital input signals, digital pulse counter

C. Photovoltaic conversion, optical coupling

D. Frequency synthesis, FM demodulation

A

D. Frequency synthesis, FM demodulation

123
Q

Why is the short-term stability of the reference oscillator important in the design of a phase locked loop (PLL) frequency synthesizer?

A. Any amplitude variations in the reference oscillator signal will prevent the loop from locking to the desired signal

B. Any phase variations in the reference oscillator signal will produce phase noise in the synthesizer output

C. Any phase variations in the reference oscillator signal will produce harmonic distortion in the modulating signal

D. Any amplitude variations in the reference oscillator signal will prevent the loop from changing frequency

A

B. Any phase variations in the reference oscillator signal will produce phase noise in the synthesizer output

124
Q

Why is a phase-locked loop often used as part of a variable frequency synthesizer for receivers and transmitters?

A. It generates FM sidebands

B. It eliminates the need for a voltage controlled oscillator

C. It makes it possible for a VFO to have the same degree of frequency stability as a crystal oscillator

D. It can be used to generate or demodulate SSB signals by quadrature phase synchronization

A

C. It makes it possible for a VFO to have the same degree of frequency stability as a crystal oscillator

125
Q

What are the major spectral impurity components of phase-locked loop synthesizers?

A. Phase noise

B. Digital conversion noise

C. Spurious signals at discrete frequencies

D. Nyquist limit noise

A

A. Phase noise

Amateur Radio - Extra (10 decks)

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