top of page ## Amateur Extra Class Exam Question Pool- Subelement E-7

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

E7A - Digital circuits: digital circuit principles and logic circuits; classes of logic elements; positive and negative logic; frequency dividers; truth tables

E7A01

Which circuit is bistable?

A. An AND gate

B. An OR gate

C. A flip-flop

D. A bipolar amplifier

~~

E7A02

What is the function of a decade counter?

A. It produces one output pulse for every 10 input pulses

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

C. It produces 10 output pulses for every input pulse

D. It decodes a binary number for display on a seven-segment LED display

~~

E7A03

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

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E7A04

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

A. 1

B. 2

C. 4

D. 8

~~

E7A05

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

~~

E7A06

What is a characteristic of a monostable multivibrator?

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

B. It 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

~~

E7A07

What logical operation does a NAND gate perform?

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

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

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

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

~~

E7A08

What logical operation does an OR gate perform?

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

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

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

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

~~

E7A09

What logical operation is performed by an exclusive NOR gate?

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

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

C. It produces logic 0 at its output if only one input is logic 1

D. It produces logic 1 at its output if only one input is logic 1

~~

E7A10

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 output is true

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

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

~~

E7A11

What type of logic defines "1" as a high voltage?

A. Reverse Logic

B. Assertive Logic

C. Negative logic

D. Positive Logic

~~

E7B - Amplifiers: Class of operation; vacuum tube and solid-state circuits; distortion and intermodulation; spurious and parasitic suppression; microwave amplifiers; switching-type amplifiers

E7B01

For what portion of the signal cycle does each active element in a push-pull Class AB amplifier conduct?

A. More than 180 degrees but less than 360 degrees

B. Exactly 180 degrees

C. The entire cycle

D. Less than 180 degrees

~~

E7B02

What is a Class D amplifier?

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

B. A low power amplifier that uses a differential amplifier for improved linearity

C. An amplifier that uses drift-mode FETs for high efficiency

D. A frequency doubling amplifier

~~

E7B03

Which of the following components form 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 compensating load resistor to improve linearity

~~

E7B04

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

A. Approximately halfway 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

~~

E7B05

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

~~

E7B06

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

A. Push-push

B. Push-pull

C. Class C

D. Class AB

~~

E7B07

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

~~

E7B08

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

~~

E7B09

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

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E7B10

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

B. Voltage divider bias

C. Self bias

D. Feedback

~~

E7B11

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

A. Fixed bias

B. Emitter bypass

D. Self bias

~~

E7B12

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

A. Common base

B. Common collector

C. Common emitter

D. Emitter follower

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E7B13

Which of the following describes an emitter follower (or common collector) amplifier?

A. A two-transistor amplifier with the emitters sharing a common bias resistor

B. A differential amplifier with both inputs fed to the emitter of the input transistor

C. An OR circuit with only one emitter used for output

D. An amplifier with a low impedance output that follows the base input voltage

~~

E7B14

Why are switching amplifiers more efficient than linear amplifiers?

A. Switching amplifiers operate at higher voltages

B. The power transistor is at saturation or cutoff most of the time

C. Linear amplifiers have high gain resulting in higher harmonic content

D. Switching amplifiers use push-pull circuits

~~

E7B15

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 these choices are correct

~~

E7B16

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 these choices are correct

~~

E7B17

Why are odd-order rather than even-order intermodulation distortion products of 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

~~

E7B18

What is a characteristic of a grounded-grid amplifier?

A. High power gain

B. High filament voltage

C. Low input impedance

D. Low bandwidth

~~

E7C - Filters and matching networks: types of networks; types of filters; filter applications; filter characteristics; impedance matching; DSP filtering

E7C01

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

~~

E7C02

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

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

~~

E7C03

What advantage does a series-L Pi-L-network have over a series-L 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. Does not require a capacitor

D. Greater transformation range

~~

E7C04

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. Reactive currents are dissipated in matched resistances

~~

E7C05

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

~~

E7C06

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

~~

E7C07

Which 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

~~

E7C08

Which of the following factors has the greatest effect on the bandwidth and response shape of a crystal ladder filter?

A. The relative frequencies of the individual crystals

B. The DC voltage applied to the quartz crystal

C. The gain of the RF stage preceding the filter

D. The amplitude of the signals passing through the filter

~~

E7C09

What is a crystal lattice filter?

A. A power supply filter made with interlaced quartz crystals

B. An audio filter made with four quartz crystals that resonate at 1 kHz intervals

C. A filter using lattice-shaped quartz crystals for high-Q performance

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

~~

E7C10

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

A. A crystal filter

B. A cavity filter

C. A DSP filter

D. An L-C filter

~~

E7C11

Which of the following describes a receiving filter’s ability to reject signals occupying an adjacent channel?

A. Passband ripple

B. Phase response

C. Shape factor

D. Noise factor

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E7C12

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 controlled

B. L-networks cannot perform impedance transformation

C. Pi-networks are more stable

D. Pi-networks provide balanced input and output

~~

E7D - Power supplies and voltage regulators; Solar array charge controllers

E7D01

How does a linear electronic voltage regulator work?

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

~~

E7D02

What is a 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 controlled device’s duty cycle is changed to produce a constant average output voltage

D. It gives a ramp voltage at its output

~~

E7D03

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

A. A Zener diode

B. A tunnel diode

C. An SCR

D. A varactor diode

~~

E7D04

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

~~

E7D05

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

~~

E7D06

What is the purpose of Q1 in the circuit shown in Figure E7-2?

A. It provides negative feedback to improve regulation

B. It provides a constant load for the voltage source

C. It controls the current supplied to the load

D. It provides D1 with current

~~

E7D07

What is the purpose of C2 in the circuit shown in Figure E7-2?

A. It bypasses rectifier output ripple 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

~~

E7D08

What type of circuit is shown in Figure E7-2?

A. Switching voltage regulator

B. Grounded emitter amplifier

C. Linear voltage regulator

D. Monostable multivibrator

~~

E7D09

What is the main reason to use a charge controller with a solar power system?

A. Prevention of battery undercharge

B. Control of electrolyte levels during battery discharge

C. Prevention of battery damage due to overcharge

D. Matching of day and night charge rates

~~

E7D10

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. 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 recover power from the unused portion of the AC cycle

~~

E7D11

What is the function of the pass transistor in a linear voltage regulator circuit?

A. Permits a wide range of output voltage settings

B. Provides a stable input impedance over a wide range of source voltage

C. Maintains nearly constant output impedance over a wide range of load current

D. Maintains nearly constant output voltage over a wide range of load current

~~

E7D12

What is the dropout voltage of an analog voltage regulator?

A. Minimum input voltage for rated power dissipation

B. Maximum output voltage drops when the input voltage is varied over its specified range

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

D. Maximum that the output voltage may decrease at rated load

~~

E7D13

What is the equation for calculating power dissipated by a series linear voltage regulator?

A. Input voltage multiplied by input current

B. Input voltage divided by output current

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

D. Output voltage multiplied by output current

~~

E7D14

What is the purpose of connecting equal-value resistors across power supply filter capacitors connected in series?

A. Equalize the voltage across each capacitor

B. Discharge the capacitors when voltage is removed

C. Provide a minimum load on the supply

D. All these choices are correct

~~

E7D15

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

~~

E7E - Modulation and demodulation: reactance, phase and balanced modulators; detectors; mixer stages

E7E01

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

~~

E7E02

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 or FM signals by using an electrically variable inductance or capacitance

~~

E7E03

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

~~

E7E04

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

~~

E7E05

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

A. A de-emphasis network

B. A heterodyne suppressor

C. A heterodyne enhancer

D. A pre-emphasis network

~~

E7E06

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

~~

E7E07

What is meant by the term “baseband” in radio communications?

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

B. The frequency range occupied by a message signal prior to modulation

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

~~

E7E08

What are the principal frequencies that appear at the output of a mixer circuit?

A. Two and four times the original frequency

B. The square root of the product of input frequencies

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

D. 1.414 and 0.707 times the input frequency

~~

E7E09

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

~~

E7E10

How does a diode envelope 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

~~

E7E11

Which type of detector circuit is used for demodulating SSB signals?

A. Discriminator

B. Phase detector

C. Product detector

D. Phase comparator

~~

E7F -  DSP filtering and other operations; software defined radio fundamentals; DSP modulation and demodulation

E7F01

What is meant by direct digital conversion as applied to software defined radios?

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

B. Incoming RF is converted to a control voltage for a voltage controlled oscillator

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

D. A switching mixer is used to generate I and Q signals directly from the RF input

~~

E7F02

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

B. A crystal-lattice filter

C. A Hilbert-transform filter

D. A phase-inverting filter

~~

E7F03

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

B. A notch filter

C. A Hilbert-transform filter

D. An elliptical filter

~~

E7F04

What is a common method of generating an SSB signal 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. Varying quartz crystal characteristics emulated in digital form

D. Signals are combined in quadrature phase relationship

~~

E7F05

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

A. At least half the rate of the highest frequency component of the signal

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

C. At the same rate as the highest frequency component of the signal

D. At four times the rate of the highest frequency component of the signal

~~

E7F06

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. 4 bits

B. 6 bits

C. 8 bits

D. 10 bits

~~

E7F07

What function is performed by a Fast Fourier Transform?

A. Converting analog signals to digital form

B. Converting digital signals to analog form

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

D. Converting 8-bit data to 16-bit data

~~

E7F08

What is the function of decimation?

A. Converting data to binary code decimal form

B. Reducing the effective sample rate by removing samples

C. Attenuating the signal

D. Removing unnecessary significant digits

~~

E7F09

Why is an anti-aliasing digital filter required in a digital decimator?

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

B. It peaks the response of the decimator, improving bandwidth

C. It removes low-frequency signal components to eliminate the need for DC restoration

D. It notches out the sampling frequency to avoid sampling errors

~~

E7F10

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

A. Sample rate

B. Sample width in bits

C. Sample clock phase noise

D. Processor latency

~~

E7F11

What sets the minimum detectable signal level for a direct-sampling SDR receiver in the absence of atmospheric or thermal noise?

A. Sample clock phase noise

B. Reference voltage level and sample width in bits

C. Data storage transfer rate

D. Missing codes and jitter

~~

E7F12

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

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

B. FIR filters are easier to implement for a given set of passband rolloff requirements

C. FIR filters can respond faster to impulses

D. All these choices are correct

~~

E7F13

What is the function of taps in a digital signal processing filter?

A. To reduce excess signal pressure levels

B. Provide access for debugging software

C. Select the point at which baseband signals are generated

D. Provide incremental signal delays for filter algorithms

~~

E7F14

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

A. Higher data rate

B. More taps

C. Complex phasor representations

D. Double-precision math routines

~~

E7G - Active filters and op-amp circuits: active audio filters; characteristics; basic circuit design; operational amplifiers

E7G01

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

A. Very low

B. Very high

C. 100 ohms

D. 1000 ohms

~~

E7G02

What is 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

~~

E7G03

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

A. 100 ohms

B. 1000 ohms

C. Very low

D. Very high

~~

E7G04

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 difference between the output voltage of the op-amp and the input voltage required in the immediately following stage

C. The differential 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

~~

E7G05

How can unwanted ringing and audio instability be prevented in an 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

~~

E7G06

What is the gain-bandwidth of an operational amplifier?

A. The maximum frequency for a filter circuit using that type of amplifier

B. The frequency at which the open-loop gain of the amplifier equals one

C. The gain of the amplifier at a filter’s cutoff frequency

D. The frequency at which the amplifier’s offset voltage is zero

~~

E7G07

What magnitude of voltage gain can be expected from the circuit in Figure E7‑3 when R1 is 10 ohms and RF is 470 ohms?

A. 0.21

B. 94

C. 47

D. 24

~~

E7G08

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

~~

E7G09

What will be the output voltage of the circuit shown in Figure E7-3 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

~~

E7G10

What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 1800 ohms and RF is 68 kilohms?

A. 1

B. 0.03

C. 38

D. 76

~~

E7G11

What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 3300 ohms and RF is 47 kilohms?

A. 28

B. 14

C. 7

D. 0.07

~~

E7G12

What is an operational amplifier?

A. A high-gain, direct-coupled differential amplifier with very high input impedance 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. A RF amplifier used in the UHF and microwave regions

~~

E7H - Oscillators and signal sources: types of oscillators; synthesizers and phase-locked loops; direct digital synthesizers; stabilizing thermal drift; microphonics; high-accuracy oscillators

E7H01

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

~~

E7H02

What is a microphonic?

A. An IC used for amplifying microphone signals

B. Distortion caused by RF pickup on the microphone cable

C. Changes in oscillator frequency due to mechanical vibration

~~

E7H03

How is positive feedback supplied in a Hartley oscillator?

A. Through a tapped coil

B. Through a capacitive divider

D. Through a neutralizing capacitor

~~

E7H04

How is positive feedback supplied in a Colpitts oscillator?

A. Through a tapped coil

C. Through a capacitive divider

D. Through a neutralizing capacitor

~~

E7H05

How is positive feedback supplied in a Pierce oscillator?

A. Through a tapped coil

C. Through a neutralizing capacitor

D. Through a quartz crystal

~~

E7H06

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

~~

E7H07

How can an oscillator’s microphonic responses be reduced?

A. Use NP0 capacitors

B. Reduce noise on the oscillator’s power supply

C. Increase the bias voltage

D. Mechanically isolate the oscillator circuitry from its enclosure

~~

E7H08

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

A. NP0 capacitors

B. Toroidal inductors

C. Wirewound resistors

D. Non-inductive resistors

~~

E7H09

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

~~

E7H10

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

A. The phase relationship between a reference oscillator and the output waveform

B. Amplitude values that represent the desired waveform

C. The phase relationship between a voltage-controlled oscillator and the output waveform

D. Frequently used receiver and transmitter frequencies

~~

E7H11

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

B. Digital conversion noise

C. Spurious signals at discrete frequencies

D. Nyquist limit noise

~~

E7H12

Which of the following must be done to ensure that a crystal oscillator provides the frequency specified by the crystal manufacturer?

A. Provide the crystal with a specified parallel inductance

B. Provide the crystal with a specified parallel capacitance

C. Bias the crystal at a specified voltage

D. Bias the crystal at a specified current

~~

E7H13

Which of the following is a technique for providing highly accurate and stable 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 these choices are correct

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E7H14

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

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E7H15

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

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