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Extra Class Exam Question Pool

effective 7/01/2016 thru 6/29/2020

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Topic 2016-E7: Practical Circuits


2016-E7A: Digital circuits: digital circuit principles and logic circuits: classes of logic elements; positive and negative logic; frequency dividers; truth tables

2016-E7A01: Which is a bi-stable circuit?

A flip-flop

An "AND" gate

An "OR" gate

A clock



2016-E7A02: What is the function of a decade counter digital IC?

It produces one output pulse for every ten input pulses

It decodes a decimal number for display on a seven segment LED display

It produces ten output pulses for every input pulse

It adds two decimal numbers together



2016-E7A03: Which of the following can divide the frequency of a pulse train by 2?

A flip-flop

An XOR gate

An OR gate

A multiplexer



2016-E7A04: How many flip-flops are required to divide a signal frequency by 4?

2

1

4

8



2016-E7A05: Which of the following is a circuit that continuously alternates between two states without an external clock?

Astable multivibrator

Monostable multivibrator

J-K flip-flop

T flip-flop



2016-E7A06: What is a characteristic of a monostable multivibrator?

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

It produces a continuous square wave oscillating between 1 and 0

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

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



2016-E7A07: What logical operation does a NAND gate perform?

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

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

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

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



2016-E7A08: What logical operation does an OR gate perform?

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

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

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

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



2016-E7A09: What logical operation is performed by an exclusive NOR gate?

It produces logic "0" at its output if any single input is logic "1"

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

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

It produces logic "1" at its output if any single input is logic "1"



2016-E7A10: What is a truth table?

A list of inputs and corresponding outputs for a digital device

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

A diagram showing logic states when the digital device output is true

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



2016-E7A11: What type of logic defines "1" as a high voltage?

Positive Logic

Reverse Logic

Assertive Logic

Negative logic



2016-E7A12: What type of logic defines "0" as a high voltage?

Negative logic

Reverse Logic

Assertive Logic

Positive Logic






2016-E7B: Amplifiers: Class of operation; vacuum tube and solid-state circuits; distortion and intermodulation; spurious and parasitic suppression; microwave amplifiers; switching-type amplifiers

2016-E7B01: For what portion of a signal cycle does a Class AB amplifier operate?

More than 180 degrees but less than 360 degrees

Exactly 180 degrees

The entire cycle

Less than 180 degrees



2016-E7B02: What is a Class D amplifier?

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

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

An amplifier that uses drift-mode FETs for high efficiency

A frequency doubling amplifier



2016-E7B03: Which of the following components form the output of a class D amplifier circuit?

A low-pass filter to remove switching signal components

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

A matched load resistor to prevent damage by switching transients

A temperature compensating load resistor to improve linearity



2016-E7B04: Where on the load line of a Class A common emitter amplifier would bias normally be set?

Approximately half-way between saturation and cutoff

Where the load line intersects the voltage axis

At a point where the bias resistor equals the load resistor

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



2016-E7B05: What can be done to prevent unwanted oscillations in an RF power amplifier?

Install parasitic suppressors and/or neutralize the stage

Tune the stage for maximum SWR

Tune both the input and output for maximum power

Use a phase inverter in the output filter



2016-E7B06: Which of the following amplifier types reduces or eliminates even order harmonics?

Push-pull

Push-push

Class C

Class AB



2016-E7B07: Which of the following is a likely result when a Class C amplifier is used to amplify a single-sideband phone signal?

Signal distortion and excessive bandwidth

Reduced intermodulation products

Increased overall intelligibility

Signal inversion



2016-E7B08: How can an RF power amplifier be neutralized?

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

By increasing the driving power

By reducing the driving power

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



2016-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?

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

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

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

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



2016-E7B10: In Figure E7-1, what is the purpose of R1 and R2?

Fixed bias

Load resistors

Self bias

Feedback



2016-E7B11: In Figure E7-1, what is the purpose of R3?

Self bias

Fixed bias

Emitter bypass

Output load resistor



2016-E7B12: What type of amplifier circuit is shown in Figure E7-1?

Common emitter

Common base

Common collector

Emitter follower



2016-E7B13: In Figure E7-2, what is the purpose of R?

Emitter load

Fixed bias

Collector load

Voltage regulation



2016-E7B14: Why are switching amplifiers more efficient than linear amplifiers?

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

Switching amplifiers operate at higher voltages

Linear amplifiers have high gain resulting in higher harmonic content

Switching amplifiers use push-pull circuits



2016-E7B15: What is one way to prevent thermal runaway in a bipolar transistor amplifier?

Use a resistor in series with the emitter

Neutralization

Select transistors with high beta

All of these choices are correct



2016-E7B16: What is the effect of intermodulation products in a linear power amplifier?

Transmission of spurious signals

Creation of parasitic oscillations

Low efficiency

All of these choices are correct



2016-E7B17: Why are odd-order rather than even-order intermodulation distortion products of concern in linear power amplifiers?

Because they are relatively close in frequency to the desired signal

Because they are relatively far in frequency from the desired signal

Because they invert the sidebands causing distortion

Because they maintain the sidebands, thus causing multiple duplicate signals



2016-E7B18: What is a characteristic of a grounded-grid amplifier?

Low input impedance

High power gain

High filament voltage

Low bandwidth






2016-E7C: Filters and matching networks: types of networks; types of filters; filter applications; filter characteristics; impedance matching; DSP filtering

2016-E7C01: How are the capacitors and inductors of a low-pass filter Pi-network arranged between the network's input and output?

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

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

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

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



2016-E7C02: Which of the following is a property of a T-network with series capacitors and a parallel shunt inductor?

It is a high-pass filter

It is a low-pass filter

It is a band-pass filter

It is a notch filter



2016-E7C03: 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?

Greater harmonic suppression

Higher efficiency

Lower losses

Greater transformation range



2016-E7C04: How does an impedance-matching circuit transform a complex impedance to a resistive impedance?

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

It introduces negative resistance to cancel the resistive part of impedance

It introduces transconductance to cancel the reactive part of impedance

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



2016-E7C05: Which filter type is described as having ripple in the passband and a sharp cutoff?

A Chebyshev filter

A Butterworth filter

An active LC filter

A passive op-amp filter



2016-E7C06: What are the distinguishing features of an elliptical filter?

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

Gradual passband rolloff with minimal stop band ripple

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

Gradual passband rolloff with extreme stop band ripple



2016-E7C07: What kind of filter would you use to attenuate an interfering carrier signal while receiving an SSB transmission?

A notch filter

A band-pass filter

A Pi-network filter

An all-pass filter



2016-E7C08: Which of the following factors has the greatest effect in helping determine the bandwidth and response shape of a crystal ladder filter?

The relative frequencies of the individual crystals

The DC voltage applied to the quartz crystal

The gain of the RF stage preceding the filter

The amplitude of the signals passing through the filter



2016-E7C09: What is a Jones filter as used as part of an HF receiver IF stage?

A variable bandwidth crystal lattice filter

An automatic notch filter

A special filter that emphasizes image responses

A filter that removes impulse noise



2016-E7C10: Which of the following filters would be the best choice for use in a 2 meter repeater duplexer?

A cavity filter

A crystal filter

A DSP filter

An L-C filter



2016-E7C11: 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?

Pi

Pi-L

Cascode

Omega



2016-E7C12: Which describes a Pi-L-network used for matching a vacuum tube final amplifier to a 50 ohm unbalanced output?

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

A Phase Inverter Load network

A network with only three discrete parts

A matching network in which all components are isolated from ground



2016-E7C13: What is one advantage of a Pi-matching network over an L-matching network consisting of a single inductor and a single capacitor?

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

L-networks cannot perform impedance transformation

Pi-networks have fewer components

Pi-networks are designed for balanced input and output



2016-E7C14: Which mode is most affected by non-linear phase response in a receiver IF filter?

Digital

Meteor scatter

Single-Sideband voice

Video



2016-E7C15: What is a crystal lattice filter?

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

A power supply filter made with interlaced quartz crystals

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

A filter with wide bandwidth and shallow skirts made using quartz crystals






2016-E7D: Power supplies and voltage regulators; Solar array charge controllers

2016-E7D01: What is one characteristic of a linear electronic voltage regulator?

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

It has a ramp voltage as its output

It eliminates the need for a pass transistor

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



2016-E7D02: What is one characteristic of a switching electronic voltage regulator?

The controlled device's duty cycle is changed to produce a constant average output voltage

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

It is generally less efficient than a linear regulator

It gives a ramp voltage at its output



2016-E7D03: What device is typically used as a stable reference voltage in a linear voltage regulator?

A Zener diode

A tunnel diode

An SCR

A varactor diode



2016-E7D04: Which of the following types of linear voltage regulator usually make the most efficient use of the primary power source?

A series regulator

A series current source

A shunt regulator

A shunt current source



2016-E7D05: Which of the following types of linear voltage regulator places a constant load on the unregulated voltage source?

A shunt regulator

A constant current source

A series regulator

A shunt current source



2016-E7D06: What is the purpose of Q1 in the circuit shown in Figure E7-3?

It increases the current-handling capability of the regulator

It provides negative feedback to improve regulation

It provides a constant load for the voltage source

It provides D1 with current



2016-E7D07: What is the purpose of C2 in the circuit shown in Figure E7-3?

It bypasses hum around D1

It is a brute force filter for the output

To self-resonate at the hum frequency

To provide fixed DC bias for Q1



2016-E7D08: What type of circuit is shown in Figure E7-3?

Linear voltage regulator

Switching voltage regulator

Grounded emitter amplifier

Emitter follower



2016-E7D09: What is the main reason to use a charge controller with a solar power system?

Prevention of battery damage due to overcharge

Prevention of battery undercharge

Control of electrolyte levels during battery discharge

Matching of day and night charge rates



2016-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?

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

The inverter design does not require any output filtering

It uses a diode bridge rectifier for increased output

It uses a large power factor compensation capacitor to create free power from the unused portion of the AC cycle



2016-E7D11: What circuit element is controlled by a series analog voltage regulator to maintain a constant output voltage?

Pass transistor

Reference voltage

Switching inductance

Error amplifier



2016-E7D12: What is the drop-out voltage of an analog voltage regulator?

Minimum input-to-output voltage required to maintain regulation

Minimum input voltage for rated power dissipation

Maximum amount that the output voltage drops when the input voltage is varied over its specified range

Maximum amount that the output voltage may decrease at rated load



2016-E7D13: What is the equation for calculating power dissipation by a series connected linear voltage regulator?

Voltage difference from input to output multiplied by output current

Input voltage multiplied by input current

Input voltage divided by output current

Output voltage multiplied by output current



2016-E7D14: What is one purpose of a "bleeder" resistor in a conventional unregulated power supply?

To improve output voltage regulation

To cut down on waste heat generated by the power supply

To balance the low-voltage filament windings

To boost the amount of output current



2016-E7D15: What is the purpose of a "step-start" circuit in a high voltage power supply?

To allow the filter capacitors to charge gradually

To provide a dual-voltage output for reduced power applications

To compensate for variations of the incoming line voltage

To allow for remote control of the power supply



2016-E7D16: 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?

All of these choices are correct

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

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

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






2016-E7E: Modulation and demodulation: reactance, phase and balanced modulators; detectors; mixer stages

2016-E7E01: Which of the following can be used to generate FM phone emissions?

A reactance modulator on the oscillator

A balanced modulator on the audio amplifier

A reactance modulator on the final amplifier

A balanced modulator on the oscillator



2016-E7E02: What is the function of a reactance modulator?

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

To produce PM signals by using an electrically variable resistance

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

To produce AM signals by using an electrically variable resistance



2016-E7E03: How does an analog phase modulator function?

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

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

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

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



2016-E7E04: What is one way a single-sideband phone signal can be generated?

By using a balanced modulator followed by a filter

By using a reactance modulator followed by a mixer

By using a loop modulator followed by a mixer

By driving a product detector with a DSB signal



2016-E7E05: What circuit is added to an FM transmitter to boost the higher audio frequencies?

A pre-emphasis network

A de-emphasis network

A heterodyne suppressor

An audio prescaler



2016-E7E06: Why is de-emphasis commonly used in FM communications receivers?

For compatibility with transmitters using phase modulation

To reduce impulse noise reception

For higher efficiency

To remove third-order distortion products



2016-E7E07: What is meant by the term baseband in radio communications?

The frequency components present in the modulating signal

The lowest frequency band that the transmitter or receiver covers

The unmodulated bandwidth of the transmitted signal

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



2016-E7E08: What are the principal frequencies that appear at the output of a mixer circuit?

The two input frequencies along with their sum and difference frequencies

Two and four times the original frequency

The sum, difference and square root of the input frequencies

1.414 and 0.707 times the input frequency



2016-E7E09: What occurs when an excessive amount of signal energy reaches a mixer circuit?

Spurious mixer products are generated

Mixer blanking occurs

Automatic limiting occurs

A beat frequency is generated



2016-E7E10: How does a diode detector function?

By rectification and filtering of RF signals

By breakdown of the Zener voltage

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

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



2016-E7E11: Which type of detector is used for demodulating SSB signals?

Product detector

Discriminator

Phase detector

Phase comparator



2016-E7E12: What is a frequency discriminator stage in a FM receiver?

A circuit for detecting FM signals

An FM generator circuit

A circuit for filtering two closely adjacent signals

An automatic band-switching circuit






2016-E7F: DSP filtering and other operations; Software Defined Radio Fundamentals; DSP modulation and demodulation

2016-E7F01: What is meant by direct digital conversion as applied to software defined radios?

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

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

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

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



2016-E7F02: What kind of digital signal processing audio filter is used to remove unwanted noise from a received SSB signal?

An adaptive filter

A crystal-lattice filter

A Hilbert-transform filter

A phase-inverting filter



2016-E7F03: What type of digital signal processing filter is used to generate an SSB signal?

A Hilbert-transform filter

An adaptive filter

A notch filter

An elliptical filter



2016-E7F04: What is a common method of generating an SSB signal using digital signal processing?

Combine signals with a quadrature phase relationship

Mixing products are converted to voltages and subtracted by adder circuits

A frequency synthesizer removes the unwanted sidebands

Emulation of quartz crystal filter characteristics



2016-E7F05: How frequently must an analog signal be sampled by an analog-to-digital converter so that the signal can be accurately reproduced?

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

At half the rate of the highest frequency component of the signal

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

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



2016-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?

10 bits

4 bits

6 bits

8 bits



2016-E7F07: What function can a Fast Fourier Transform perform?

Converting digital signals from the time domain to the frequency domain

Converting analog signals to digital form

Converting digital signals to analog form

Converting 8-bit data to 16 bit data



2016-E7F08: What is the function of decimation with regard to digital filters?

Reducing the effective sample rate by removing samples

Converting data to binary code decimal form

Attenuating the signal

Removing unnecessary significant digits



2016-E7F09: Why is an anti-aliasing digital filter required in a digital decimator?

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

It peaks the response of the decimator, improving bandwidth

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

It notches out the sampling frequency to avoid sampling errors



2016-E7F10: What aspect of receiver analog-to-digital conversion determines the maximum receive bandwidth of a Direct Digital Conversion SDR?

Sample rate

Sample width in bits

Sample clock phase noise

Processor latency



2016-E7F11: What sets the minimum detectable signal level for an SDR in the absence of atmospheric or thermal noise?

Reference voltage level and sample width in bits

Sample clock phase noise

Data storage transfer rate

Missing codes and jitter



2016-E7F12: What digital process is applied to I and Q signals in order to recover the baseband modulation information?

Fast Fourier Transform

Decimation

Signal conditioning

Quadrature mixing



2016-E7F13: What is the function of taps in a digital signal processing filter?

Provide incremental signal delays for filter algorithms

To reduce excess signal pressure levels

Provide access for debugging software

Select the point at which baseband signals are generated



2016-E7F14: Which of the following would allow a digital signal processing filter to create a sharper filter response?

More taps

Higher data rate

Complex phasor representations

Double-precision math routines



2016-E7F15: Which of the following is an advantage of a Finite Impulse Response (FIR) filter vs an Infinite Impulse Response (IIR) digital filter?

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

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

FIR filters can respond faster to impulses

All of these choices are correct



2016-E7F16: How might the sampling rate of an existing digital signal be adjusted by a factor of 3/4?

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

Change the gain by a factor of 3/4

Multiply each sample value by a factor of 3/4

Add 3 to each input value and subtract 4 from each output value



2016-E7F17: What do the letters I and Q in I/Q Modulation represent?

In-phase and Quadrature

Inactive and Quiescent

Instantaneous and Quasi-stable

Instantaneous and Quenched






2016-E7G: Active filters and op-amp circuits: active audio filters; characteristics; basic circuit design; operational amplifiers

2016-E7G01: What is the typical output impedance of an integrated circuit op-amp?

Very low

Very high

100 ohms

1000 ohms



2016-E7G02: What is the effect of ringing in a filter?

Undesired oscillations added to the desired signal

An echo caused by a long time delay

A reduction in high frequency response

Partial cancellation of the signal over a range of frequencies



2016-E7G03: What is the typical input impedance of an integrated circuit op-amp?

Very high

100 ohms

1000 ohms

Very low



2016-E7G04: What is meant by the term op-amp input offset voltage?

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

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

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

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



2016-E7G05: How can unwanted ringing and audio instability be prevented in a multi-section op-amp RC audio filter circuit?

Restrict both gain and Q

Restrict gain but increase Q

Restrict Q but increase gain

Increase both gain and Q



2016-E7G06: Which of the following is the most appropriate use of an op-amp active filter?

As an audio filter in a receiver

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

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

For smoothing power supply output



2016-E7G07: 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?

47

0.21

94

24



2016-E7G08: How does the gain of an ideal operational amplifier vary with frequency?

It does not vary with frequency

It increases linearly with increasing frequency

It decreases linearly with increasing frequency

It decreases logarithmically with increasing frequency



2016-E7G09: 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?

-2.3 volts

0.23 volts

2.3 volts

-0.23 volts



2016-E7G10: What absolute voltage gain can be expected from the circuit in Figure E7-4 when R1 is 1800 ohms and RF is 68 kilohms?

38

1

0.03

76



2016-E7G11: What absolute voltage gain can be expected from the circuit in Figure E7-4 when R1 is 3300 ohms and RF is 47 kilohms?

14

28

7

0.07



2016-E7G12: What is an integrated circuit operational amplifier?

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

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

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

A RF amplifier used in the UHF and microwave regions






2016-E7H: Oscillators and signal sources: types of oscillators; synthesizers and phase-locked loops; direct digital synthesizers; stabilizing thermal drift; microphonics; high accuracy oscillators

2016-E7H01: What are three oscillator circuits used in Amateur Radio equipment?

Colpitts, Hartley and Pierce

Taft, Pierce and negative feedback

Pierce, Fenner and Beane

Taft, Hartley and Pierce



2016-E7H02: Which describes a microphonic?

Changes in oscillator frequency due to mechanical vibration

An IC used for amplifying microphone signals

Distortion caused by RF pickup on the microphone cable

Excess loading of the microphone by an oscillator



2016-E7H03: How is positive feedback supplied in a Hartley oscillator?

Through a tapped coil

Through a capacitive divider

Through link coupling

Through a neutralizing capacitor



2016-E7H04: How is positive feedback supplied in a Colpitts oscillator?

Through a capacitive divider

Through a tapped coil

Through link coupling

Through a neutralizing capacitor



2016-E7H05: How is positive feedback supplied in a Pierce oscillator?

Through a quartz crystal

Through a tapped coil

Through link coupling

Through a neutralizing capacitor



2016-E7H06: Which of the following oscillator circuits are commonly used in VFOs?

Colpitts and Hartley

Pierce and Zener

Armstrong and deForest

Negative feedback and balanced feedback



2016-E7H07: How can an oscillator's microphonic responses be reduced?

Mechanically isolating the oscillator circuitry from its enclosure

Use of NP0 capacitors

Eliminating noise on the oscillator’s power supply

Using the oscillator only for CW and digital signals



2016-E7H08: Which of the following components can be used to reduce thermal drift in crystal oscillators?

NP0 capacitors

Toroidal inductors

Wirewound resistors

Non-inductive resistors



2016-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 direct digital synthesizer

A hybrid synthesizer

A phase locked loop synthesizer

A diode-switching matrix synthesizer



2016-E7H10: What information is contained in the lookup table of a direct digital frequency synthesizer?

The amplitude values that represent a sine-wave output

The phase relationship between a reference oscillator and the output waveform

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

The synthesizer frequency limits and frequency values stored in the radio memories



2016-E7H11: What are the major spectral impurity components of direct digital synthesizers?

Spurious signals at discrete frequencies

Broadband noise

Digital conversion noise

Nyquist limit noise



2016-E7H12: Which of the following must be done to insure that a crystal oscillator provides the frequency specified by the crystal manufacturer?

Provide the crystal with a specified parallel capacitance

Provide the crystal with a specified parallel inductance

Bias the crystal at a specified voltage

Bias the crystal at a specified current



2016-E7H13: Which of the following is a technique for providing highly accurate and stable oscillators needed for microwave transmission and reception?

All of these choices are correct

Use a GPS signal reference

Use a rubidium stabilized reference oscillator

Use a temperature-controlled high Q dielectric resonator



2016-E7H14: What is a phase-locked loop circuit?

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

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

An electronic circuit also known as a monostable multivibrator

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



2016-E7H15: Which of these functions can be performed by a phase-locked loop?

Frequency synthesis, FM demodulation

Wide-band AF and RF power amplification

Comparison of two digital input signals, digital pulse counter

Photovoltaic conversion, optical coupling





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