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Ham Extra 2016-2020 > E7 Practical Circuits > Flashcards

E7 Practical Circuits Flashcards

1
Q

E7A01 (C) Which is a bi-stable circuit?

A

C. A flip-flop

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2
Q

E7A02 (A) What is the function of a decade counter digital IC?

A

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

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3
Q

E7A03 (B) Which of the following can divide the frequency of a pulse train by 2?

A

B. A flip-flop

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4
Q

E7A04 (B) How many flip-flops are required to divide a signal frequency by 4?

A

B. 2

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5
Q

E7A05 (D) Which of the following is a circuit that continuously alternates between two states without an external clock?

A

D. Astable multivibrator

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6
Q

E7A06 (A) What is a characteristic of a monostable multivibrator?

A

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

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7
Q

E7A07 (D) What logical operation does a NAND gate perform?

A

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

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8
Q

E7A08 (A) What logical operation does an OR gate perform?

A

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

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9
Q

E7A09 (C) What logical operation is performed by an exclusive NOR gate?

A

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

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10
Q

E7A10 (C) What is a truth table?

A

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

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11
Q

E7A11 (D) What type of logic defines “1” as a high voltage?

A

D. Positive Logic

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12
Q

E7A12 (C) What type of logic defines “0” as a high voltage?

A

C. Negative logic

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13
Q

E7B01 (A) For what portion of a signal cycle does a Class AB amplifier operate?

A

A. More than 180 degrees but less than 360 degrees

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14
Q

E7B02 (A) What is a Class D amplifier?

A

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

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15
Q

E7B03 (A) Which of the following components form the output of a class D amplifier circuit?

A

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

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16
Q

E7B04 (A) Where on the load line of a Class A common emitter amplifier would bias normally be set?

A

A. Approximately half-way between saturation and cutoff

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17
Q

E7B05 (C) What can be done to prevent unwanted oscillations in an RF power amplifier?

A

C. Install parasitic suppressors and/or neutralize the stage

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18
Q

E7B06 (B) Which of the following amplifier types reduces or eliminates even order harmonics?

A

B. Push-pull

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19
Q

E7B07 (D) Which of the following is a likely result when a Class C amplifier is used to amplify a single-sideband phone signal?

A

D. Signal distortion and excessive bandwidth

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20
Q

E7B08 (C) How can an RF power amplifier be neutralized?

A

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

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21
Q

E7B09 (D) 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

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

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22
Q

E7B10 (B) In Figure E7-1, what is the purpose of R1 and R2?

A

B. Fixed bias

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23
Q

E7B11 (D) In Figure E7-1, what is the purpose of R3?

A

D. Self bias

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24
Q

E7B12 (C) What type of amplifier circuit is shown in Figure E7-1?

A

C. Common emitter

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25
Q

E7B13 (A) In Figure E7-2, what is the purpose of R?

A

A. Emitter load

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26
Q

E7B14 (B) Why are switching amplifiers more efficient than linear amplifiers?

A

B. The power transistor is at saturation or cut off most of the time, resulting in low power dissipation

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27
Q

E7B15 (C) What is one way to prevent thermal runaway in a bipolar transistor amplifier?

A

C. Use a resistor in series with the emitter

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28
Q

E7B16 (A) What is the effect of intermodulation products in a linear power amplifier?

A

A. Transmission of spurious signals

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29
Q

E7B17 (A) Why are odd-order rather than even-order intermodulation distortion products of concern in linear power amplifiers?

A

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

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30
Q

E7B18 (C) What is a characteristic of a grounded-grid amplifier?

A

C. Low input impedance

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31
Q

E7C01 (D) How are the capacitors and inductors of a low-pass filter Pi-network arranged between the network’s 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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32
Q

E7C02 (C) Which of the following is a property of a T-network with series capacitors and a parallel shunt inductor?

A

C. It is a high-pass filter

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33
Q

E7C03 (A) What advantage does a Pi-L-network have over a regular Pi-network for impedance matching between the final amplifier of a vacuum-tube transmitter and an antenna?

A

A. Greater harmonic suppression

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34
Q

E7C04 (C) How does an impedance-matching circuit transform a complex impedance to a resistive impedance?

A

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

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35
Q

E7C05 (D) Which filter type is described as having ripple in the passband and a sharp cutoff?

A

D. A Chebyshev filter

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36
Q

E7C06 (C) What are the distinguishing features of an elliptical filter?

A

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

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37
Q

E7C07 (B) What kind of filter would you use to attenuate an interfering carrier signal while receiving an SSB transmission?

A

B. A notch filter

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38
Q

E7C08 (A) Which of the following factors has the greatest effect in helping determine the bandwidth and response shape of a crystal ladder filter?

A

A. The relative frequencies of the individual crystals

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39
Q

E7C09 (B) What is a Jones filter as used as part of an HF receiver IF stage?

A

B. A variable bandwidth crystal lattice filter

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40
Q

E7C10 (B) Which of the following filters would be the best choice for use in a 2 meter repeater duplexer?

A

B. A cavity filter

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41
Q

E7C11 (D) 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 two inductors in series and the capacitors in shunt at the input and output?

A

D. Pi

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42
Q

E7C12 (B) Which describes a Pi-L-network used for matching a vacuum tube final amplifier to a 50 ohm unbalanced output?

A

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

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43
Q

E7C13 (A) What is one advantage of a Pi-matching network over an L-matching network consisting of a single inductor and a single capacitor?

A

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

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44
Q

E7C14 (C) Which mode is most affected by non-linear phase response in a receiver IF filter?

A

C. Digital

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45
Q

E7C15 (D) What is a crystal lattice filter?

A

D. A filter with narrow bandwidth and steep skirts made using quartz crystals

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46
Q

E7D01 (D) What is one characteristic of a linear electronic voltage regulator?

A

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

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47
Q

E7D02 (C) What is one characteristic of a switching electronic voltage regulator?

A

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

48
Q

E7D03 (A) What device is typically used as a stable reference voltage in a linear voltage regulator?

A

A. A Zener diode

49
Q

E7D04 (B) Which of the following types of linear voltage regulator usually make the most efficient use of the primary power source?

A

B. A series regulator

50
Q

E7D05 (D) Which of the following types of linear voltage regulator places a constant load on the unregulated voltage source?

A

D. A shunt regulator

51
Q

E7D06 (C) What is the purpose of Q1 in the circuit shown in Figure E7-3?

A

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

52
Q

E7D07 (A) What is the purpose of C2 in the circuit shown in Figure E7-3?

A

A. It bypasses hum around D1

53
Q

E7D08 (C) What type of circuit is shown in Figure E7-3?

A

C. Linear voltage regulator

54
Q

E7D09 (C) What is the main reason to use a charge controller with a solar power system?

A

C. Prevention of battery damage due to overcharge

55
Q

E7D10 (C) What is the primary reason that a high-frequency switching type high voltage power supply can be both less expensive and lighter in weight than a conventional power supply?

A

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

56
Q

E7D11 (D) What circuit element is controlled by a series analog voltage regulator to maintain a constant output voltage?

A

D. Pass transistor

57
Q

E7D12 (C) What is the drop-out voltage of an analog voltage regulator?

A

C. Minimum input-to-output voltage required to maintain regulation

58
Q

E7D13 (C) What is the equation for calculating power dissipation by a series connected linear voltage regulator?

A

C. Voltage difference from input to output multiplied by output current

59
Q

E7D14 (C) What is one purpose of a “bleeder” resistor in a conventional unregulated power supply?

A

C. To improve output voltage regulation

60
Q

E7D15 (D) What is the purpose of a “step-start” circuit in a high voltage power supply?

A

D. To allow the filter capacitors to charge gradually

61
Q

E7D16 (D) 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

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

62
Q

E7E01 (B) Which of the following can be used to generate FM phone emissions?

A

B. A reactance modulator on the oscillator

63
Q

E7E02 (D) What is the function of a reactance modulator?

A

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

64
Q

E7E03 (C) How does an analog phase modulator function?

A

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

65
Q

E7E04 (A) What is one way a single-sideband phone signal can be generated?

A

A. By using a balanced modulator followed by a filter

66
Q

E7E05 (D) What circuit is added to an FM transmitter to boost the higher audio frequencies?

A

D. A pre-emphasis network

67
Q

E7E06 (A) Why is de-emphasis commonly used in FM communications receivers?

A

A. For compatibility with transmitters using phase modulation

68
Q

E7E07 (B) What is meant by the term baseband in radio communications?

A

B. The frequency components present in the modulating signal

69
Q

E7E08 (C) What are the principal frequencies that appear at the output of a mixer circuit?

A

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

70
Q

E7E09 (A) What occurs when an excessive amount of signal energy reaches a mixer circuit?

A

A. Spurious mixer products are generated

71
Q

E7E10 (A) How does a diode detector function?

A

A. By rectification and filtering of RF signals

72
Q

E7E11 (C) Which type of detector is used for demodulating SSB signals?

A

C. Product detector

73
Q

E7E12 (D) What is a frequency discriminator stage in a FM receiver?

A

D. A circuit for detecting FM signals

74
Q

E7F01 (C) What is meant by direct digital conversion as applied to software defined radios?

A

C. Incoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal

75
Q

E7F02 (A) What kind of digital signal processing audio filter is used to remove unwanted noise from a received SSB signal?

A

A. An adaptive filter

76
Q

E7F03 (C) What type of digital signal processing filter is used to generate an SSB signal?

A

C. A Hilbert-transform filter

77
Q

E7F04 (D) What is a common method of generating an SSB signal using digital signal processing?

A

D. Combine signals with a quadrature phase relationship

78
Q

E7F05 (B) How frequently must an analog signal be sampled by an analog-to-digital converter so that the signal can be accurately reproduced?

A

B. At twice the rate of the highest frequency component of the signal

79
Q

E7F06 (D) What is the minimum number of bits required for an analog-to-digital converter to sample a signal with a range of 1 volt at a resolution of 1 millivolt?

A

D. 10 bits

80
Q

E7F07 (C) What function can a Fast Fourier Transform perform?

A

C. Converting digital signals from the time domain to the frequency domain

81
Q

E7F08 (B) What is the function of decimation with regard to digital filters?

A

B. Reducing the effective sample rate by removing samples

82
Q

E7F09 (A) Why is an anti-aliasing digital filter required in a digital decimator?

A

A. It removes high-frequency signal components which would otherwise be reproduced as lower frequency components

83
Q

E7F10 (A) What aspect of receiver analog-to-digital conversion determines the maximum receive bandwidth of a Direct Digital Conversion SDR?

A

A. Sample rate

84
Q

E7F11 (B) What sets the minimum detectable signal level for an SDR in the absence of atmospheric or thermal noise?

A

B. Reference voltage level and sample width in bits

85
Q

E7F12 (A) What digital process is applied to I and Q signals in order to recover the baseband modulation information?

A

A. Fast Fourier Transform

86
Q

E7F13 (D) What is the function of taps in a digital signal processing filter?

A

D. Provide incremental signal delays for filter algorithms

87
Q

E7F14 (B) Which of the following would allow a digital signal processing filter to create a sharper filter response?

A

B. More taps

88
Q

E7F15 (A) Which of the following is an advantage of a Finite Impulse Response (FIR) filter vs an Infinite Impulse Response (IIR) digital filter?

A

A. FIR filters delay all frequency components of the signal by the same amount

89
Q

E7F16 (D) How might the sampling rate of an existing digital signal be adjusted by a factor of 3/4?

A

D. Interpolate by a factor of three, then decimate by a factor of four

90
Q

E7F17 (D) What do the letters I and Q in I/Q Modulation represent?

A

D. In-phase and Quadrature

91
Q

E7G01 (A) What is the typical output impedance of an integrated circuit op-amp?

A

A. Very low

92
Q

E7G02 (D) What is the effect of ringing in a filter?

A

D. Undesired oscillations added to the desired signal

93
Q

E7G03 (D) What is the typical input impedance of an integrated circuit op-amp?

A

D. Very high

94
Q

E7G04 (C) What is meant by the term op-amp input offset voltage?`

A

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

95
Q

E7G05 (A) How can unwanted ringing and audio instability be prevented in a multi-section op-amp RC audio filter circuit?

A

A. Restrict both gain and Q

96
Q

E7G06 (D) Which of the following is the most appropriate use of an op-amp active filter?

A

D. As an audio filter in a receiver

97
Q

E7G07 (C) 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?

98
Q

E7G08 (D) How does the gain of an ideal operational amplifier vary with frequency?

A

D. It does not vary with frequency

99
Q

E7G09 (D) 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

D. -2.3 volts

100
Q

E7G10 (C) What absolute voltage gain can be expected from the circuit in Figure E7-4 when R1 is 1800 ohms and RF is 68 kilohms?

101
Q

E7G11 (B) What absolute voltage gain can be expected from the circuit in Figure E7-4 when R1 is 3300 ohms and RF is 47 kilohms?

102
Q

E7G12 (A) What is an integrated circuit operational amplifier?

A

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

103
Q

E7H01 (D) What are three oscillator circuits used in Amateur Radio equipment?

A

D. Colpitts, Hartley and Pierce

104
Q

E7H02 (C) Which describes a microphonic?

A

C. Changes in oscillator frequency due to mechanical vibration

105
Q

E7H03 (A) How is positive feedback supplied in a Hartley oscillator?

A

A. Through a tapped coil

106
Q

E7H04 (C) How is positive feedback supplied in a Colpitts oscillator?

A

C. Through a capacitive divider

107
Q

E7H05 (D) How is positive feedback supplied in a Pierce oscillator?

A

D. Through a quartz crystal

108
Q

E7H06 (B) Which of the following oscillator circuits are commonly used in VFOs?

A

B. Colpitts and Hartley

109
Q

E7H07 (D) How can an oscillator’s microphonic responses be reduced?

A

D. Mechanically isolating the oscillator circuitry from its enclosure

110
Q

E7H08 (A) Which of the following components can be used to reduce thermal drift in crystal oscillators?

A

A. NP0 capacitors

111
Q

E7H09 (A) 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. A direct digital synthesizer

112
Q

E7H10 (B) What information is contained in the lookup table of a direct digital frequency synthesizer?

A

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

113
Q

E7H11 (C) What are the major spectral impurity components of direct digital synthesizers?

A

C. Spurious signals at discrete frequencies

114
Q

E7H12 (B) Which of the following must be done to insure that a crystal oscillator provides the frequency specified by the crystal manufacturer?

A

B. Provide the crystal with a specified parallel capacitance

115
Q

E7H13 (D) Which of the following is a technique for providing highly accurate and stable oscillators needed for microwave transmission and reception?

A

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

116
Q

E7H14 (C) What is a phase-locked loop circuit?

A

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

117
Q

E7H15 (D) Which of these functions can be performed by a phase-locked loop?

A

D. Frequency synthesis, FM demodulation

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