E7 Questions
91 questions in this subelement. Click any question ID for more details.
Answer: A
What is the function of a decade counter?
AIt produces one output pulse for every 10 input pulses
BIt decodes a decimal number for display on a seven-segment LED display
CIt produces 10 output pulses for every input pulse
DIt decodes a binary number for display on a seven-segment LED display
Answer: B
Which of the following can divide the frequency of a pulse train by 2?
AAn XOR gate
BA flip-flop
CAn OR gate
DA multiplexer
Answer: D
Which of the following circuits continuously alternates between two states without an external clock signal?
AMonostable multivibrator
BJ-K flip-flop
CT flip-flop
DAstable multivibrator
Answer: A
What is a characteristic of a monostable multivibrator?
AIt switches temporarily to an alternate state for a set time
BIt produces a continuous square wave
CIt stores one bit of data
DIt maintains a constant output voltage, regardless of variations in the input voltage
Answer: D
What logical operation does a NAND gate perform?
AIt produces a 0 at its output only if all inputs are 0
BIt produces a 1 at its output only if all inputs are 1
CIt produces a 0 at its output if some but not all inputs are 1
DIt produces a 0 at its output only if all inputs are 1
Answer: A
What logical operation does an OR gate perform?
AIt produces a 1 at its output if any input is 1
BIt produces a 0 at its output if all inputs are 1
CIt produces a 0 at its output if some but not all inputs are 1
DIt produces a 1 at its output if all inputs are 0
Answer: C
What logical operation is performed by a two-input exclusive NOR gate?
AIt produces a 0 at its output only if all inputs are 0
BIt produces a 1 at its output only if all inputs are 1
CIt produces a 0 at its output if one and only one of its inputs is 1
DIt produces a 1 at its output if one and only one input is 1
Answer: B
What is a truth table?
AA list of inputs and corresponding outputs for an op-amp
BA list of inputs and corresponding outputs for a digital device
CA diagram showing logic states when the digital gate output is true
DA table of logic symbols that indicate the logic states of an op-amp
Answer: B
What does “positive logic” mean in reference to logic devices?
AThe logic devices have high noise immunity
BHigh voltage represents a 1, low voltage a 0
CThe logic circuit is in the “true” condition
D1s and 0s are defined as different positive voltage levels
Answer: A
What is a Class D amplifier?
AAn amplifier that uses switching technology to achieve high efficiency
BA low power amplifier that uses a differential amplifier for improved linearity
CAn amplifier that uses drift-mode FETs for high efficiency
DAn amplifier biased to be relatively free from distortion
Answer: A
What circuit is required at the output of an RF switching amplifier?
AA filter to remove harmonic content
BA high-pass filter to compensate for low gain at low frequencies
CA matched load resistor to prevent damage by switching transients
DA temperature compensating load resistor to improve linearity
Answer: A
What is the operating point of a Class A common emitter amplifier?
AApproximately halfway between saturation and cutoff
BApproximately halfway between the emitter voltage and the base voltage
CAt a point where the bias resistor equals the load resistor
DAt a point where the load line intersects the zero bias current curve
Answer: C
What can be done to prevent unwanted oscillations in an RF power amplifier?
ATune the stage for minimum loading
BTune both the input and output for maximum power
CInstall parasitic suppressors and/or neutralize the stage
DUse a phase inverter in the output filter
Answer: B
What is a characteristic of a grounded-grid amplifier?
AHigh power gain
BLow input impedance
CHigh electrostatic damage protection
DLow bandwidth
Answer: D
Which of the following is the likely result of using a Class C amplifier to amplify a single-sideband phone signal?
AReduced intermodulation products
BIncreased overall intelligibility
CReduced third-order intermodulation
DSignal distortion and excessive bandwidth
Answer: B
Why are switching amplifiers more efficient than linear amplifiers?
ASwitching amplifiers operate at higher voltages
BThe switching device is at saturation or cutoff most of the time
CLinear amplifiers have high gain resulting in higher harmonic content
DSwitching amplifiers use push-pull circuits
Answer: D
What is characteristic of an emitter follower (or common collector) amplifier?
ALow input impedance and phase inversion from input to output
BDifferential inputs and single output
CActs as an OR circuit if one input is grounded
DInput and output signals in-phase
Answer: B
In Figure E7-1, what is the purpose of R1 and R2?
ALoad resistors
BVoltage divider bias
CSelf bias
DFeedback
Answer: D
In Figure E7-1, what is the purpose of R3?
AFixed bias
BEmitter bypass
COutput load resistor
DSelf bias
Answer: C
What type of amplifier circuit is shown in Figure E7-1?
ACommon base
BCommon collector
CCommon emitter
DEmitter follower
Answer: B
What is the frequency response of a T-network with series capacitors and a shunt inductor?
ALow-pass
BHigh-pass
CBand-pass
DNotch
Answer: A
What is the purpose of adding an inductor to a Pi-network to create a Pi-L-network?
AGreater harmonic suppression
BHigher efficiency
CTo eliminate one capacitor
DGreater transformation range
Answer: C
How does an impedance-matching circuit transform a complex impedance to a resistive impedance?
AIt introduces negative resistance to cancel the resistive part of impedance
BIt introduces transconductance to cancel the reactive part of impedance
CIt cancels the reactive part of the impedance and changes the resistive part to the desired value
DReactive currents are dissipated in matched resistances
Answer: D
Which filter type has ripple in the passband and a sharp cutoff?
AA Butterworth filter
BAn active LC filter
CA passive op-amp filter
DA Chebyshev filter
Answer: C
What are the characteristics of an elliptical filter?
AGradual passband rolloff with minimal stop-band ripple
BExtremely flat response over its pass band with gradually rounded stop-band corners
CExtremely sharp cutoff with one or more notches in the stop band
DGradual passband rolloff with extreme stop-band ripple
Answer: B
Which describes a Pi-L network?
AA Phase Inverter Load network
BA Pi-network with an additional output series inductor
CA network with only three discrete parts
DA matching network in which all components are isolated from ground
Answer: B
Which of the following is most frequently used as a band-pass or notch filter in VHF and UHF transceivers?
AA Sallen-Key filter
BA helical filter
CA swinging choke filter
DA finite impulse response filter
Answer: D
What is a crystal lattice filter?
AA power supply filter made with interlaced quartz crystals
BAn audio filter made with four quartz crystals that resonate at 1 kHz intervals
CA filter using lattice-shaped quartz crystals for high-Q performance
DA filter for low-level signals made using quartz crystals
Answer: B
Which of the following filters is used in a 2-meter band repeater duplexer?
AA crystal filter
BA cavity filter
CA DSP filter
DAn L-C filter
Answer: C
Which of the following measures a filter’s ability to reject signals in adjacent channels?
APassband ripple
BPhase response
CShape factor
DNoise factor
Answer: B
How does a switchmode voltage regulator work?
ABy alternating the output between positive and negative voltages
BBy varying the duty cycle of pulses input to a filter
CBy varying the conductivity of a pass element
DBy switching between two Zener diode reference voltages
Answer: A
What device is used as a stable voltage reference?
AA Zener diode
BA digital-to-analog converter
CAn SCR
DAn analog-to-digital converter
Answer: B
Which of the following describes a three-terminal voltage regulator?
AA series current source
BA series regulator
CA shunt regulator
DA shunt current source
Answer: D
Which of the following types of linear voltage regulator operates by loading the unregulated voltage source?
AA constant current source
BA series regulator
CA shunt current source
DA shunt regulator
Answer: C
What is the purpose of Q1 in the circuit shown in Figure E7-2?
AIt provides negative feedback to improve regulation
BIt provides a constant load for the voltage source
CIt controls the current to keep the output voltage constant
DIt provides regulation by switching or “chopping” the input DC voltage
Answer: A
What is the purpose of C2 in the circuit shown in Figure E7-2?
AIt bypasses rectifier output ripple around D1
BIt is a brute force filter for the output
CTo prevent self-oscillation
DTo provide fixed DC bias for Q1
Answer: C
What type of circuit is shown in Figure E7-2?
ASwitching voltage regulator
BCommon emitter amplifier
CLinear voltage regulator
DCommon base amplifier
Answer: C
How is battery operating time calculated?
AAverage current divided by capacity in amp-hours
BAverage current divided by internal resistance
CCapacity in amp-hours divided by average current
DInternal resistance divided by average current
Answer: C
Why is a switching type power supply less expensive and lighter than an equivalent linear power supply?
AThe inverter design does not require an output filter circuit
BThe control circuitry uses less current, therefore smaller heat sinks are required
CThe high frequency inverter design uses much smaller transformers and filter components for an equivalent power output
DIt recovers power from the unused portion of the AC cycle, thus using fewer components
Answer: D
What is the purpose of an inverter connected to a solar panel output?
AReduce AC ripple on the output
BMaintain voltage with varying illumination levels
CPrevent discharge when panel is not illuminated
DConvert the panel’s output from DC to AC
Answer: C
What is the dropout voltage of a linear voltage regulator?
AMinimum input voltage for rated power dissipation
BMaximum output voltage drop when the input voltage is varied over its specified range
CMinimum input-to-output voltage required to maintain regulation
DMaximum that the output voltage may decrease at rated load
Answer: C
Which of the following calculates power dissipated by a series linear voltage regulator?
AInput voltage multiplied by input current
BInput voltage divided by output current
CVoltage difference from input to output multiplied by output current
DOutput voltage multiplied by output current
Answer: D
What is the purpose of connecting equal-value resistors across power supply filter capacitors connected in series?
AEqualize the voltage across each capacitor
BDischarge the capacitors when voltage is removed
CProvide a minimum load on the supply
DAll these choices are correct
Answer: D
What is the purpose of a step-start circuit in a high-voltage power supply?
ATo provide a dual-voltage output for reduced power applications
BTo compensate for variations of the incoming line voltage
CTo prevent arcing across the input power switch or relay contacts
DTo allow the filter capacitors to charge gradually
Answer: D
What is the function of a reactance modulator?
AProduce PM or FM signals by varying a resistance
BProduce AM signals by varying an inductance
CProduce AM signals by varying a resistance
DProduce PM or FM signals by varying a capacitance
Answer: D
What is a frequency discriminator?
AAn FM generator circuit
BA circuit for filtering closely adjacent signals
CAn automatic band-switching circuit
DA circuit for detecting FM signals
Answer: A
What is one way to produce a single-sideband phone signal?
AUse a balanced modulator followed by a filter
BUse a reactance modulator followed by a mixer
CUse a loop modulator followed by a mixer
DUse a product detector with a DSB signal
Answer: D
What is added to an FM speech channel to boost the higher audio frequencies?
AA de-emphasis network
BA harmonic enhancer
CA heterodyne enhancer
DA pre-emphasis network
Answer: A
Why is de-emphasis used in FM communications receivers?
AFor compatibility with transmitters using phase modulation
BTo reduce impulse noise reception
CFor higher efficiency
DTo remove third-order distortion products
Answer: B
What is meant by the term “baseband” in radio communications?
AThe lowest frequency band that the transmitter or receiver covers
BThe frequency range occupied by a message signal prior to modulation
CThe unmodulated bandwidth of the transmitted signal
DThe basic oscillator frequency in an FM transmitter that is multiplied to increase the deviation and carrier frequency
Answer: C
What are the principal frequencies that appear at the output of a mixer?
ATwo and four times the input frequency
BThe square root of the product of input frequencies
CThe two input frequencies along with their sum and difference frequencies
D1.414 and 0.707 times the input frequency
Answer: A
What occurs when the input signal levels to a mixer are too high?
ASpurious mixer products are generated
BMixer blanking occurs
CAutomatic limiting occurs
DExcessive AGC voltage levels are generated
Answer: A
How does a diode envelope detector function?
ABy rectification and filtering of RF signals
BBy breakdown of the Zener voltage
CBy mixing signals with noise in the transition region of the diode
DBy sensing the change of reactance in the diode with respect to frequency
Answer: C
Which type of detector is used for demodulating SSB signals?
ADiscriminator
BPhase detector
CProduct detector
DPhase comparator
Answer: A
What kind of digital signal processing audio filter is used to remove unwanted noise from a received SSB signal?
AAn adaptive filter
BA crystal-lattice filter
CA Hilbert-transform filter
DA phase-inverting filter
Answer: C
What type of digital signal processing filter is used to generate an SSB signal?
AAn adaptive filter
BA notch filter
CA Hilbert-transform filter
DAn elliptical filter
Answer: D
Which method generates an SSB signal using digital signal processing?
AMixing products are converted to voltages and subtracted by adder circuits
BA frequency synthesizer removes unwanted sidebands
CVarying quartz crystal characteristics are emulated in digital form
DSignals are combined in quadrature phase relationship
Answer: B
How frequently must an analog signal be sampled to be accurately reproduced?
AAt least half the rate of the highest frequency component of the signal
BAt least twice the rate of the highest frequency component of the signal
CAt the same rate as the highest frequency component of the signal
DAt four times the rate of the highest frequency component of the signal
Answer: D
What is the minimum number of bits required to sample a signal with a range of 1 volt at a resolution of 1 millivolt?
A4 bits
B6 bits
C8 bits
D10 bits
Answer: C
What function is performed by a Fast Fourier Transform?
AConverting analog signals to digital form
BConverting digital signals to analog form
CConverting signals from the time domain to the frequency domain
DConverting signals from the frequency domain to the time domain
Answer: B
What is the function of decimation?
AConverting data to binary-coded decimal form
BReducing the effective sample rate by removing samples
CAttenuating the signal
DRemoving unnecessary significant digits
Answer: A
Why is an anti-aliasing filter required in a decimator?
AIt removes high-frequency signal components that would otherwise be reproduced as lower frequency components
BIt peaks the response of the decimator, improving bandwidth
CIt removes low-frequency signal components to eliminate the need for DC restoration
DIt notches out the sampling frequency to avoid sampling errors
Answer: A
What aspect of receiver analog-to-digital conversion determines the maximum receive bandwidth of a direct-sampling software defined radio (SDR)?
ASample rate
BSample width in bits
CIntegral non-linearity
DDifferential non-linearity
Answer: B
What sets the minimum detectable signal level for a direct-sampling software defined receiver in the absence of atmospheric or thermal noise?
ASample clock phase noise
BReference voltage level and sample width in bits
CData storage transfer rate
DMissing codes and jitter
Answer: A
Which of the following is generally true of Finite Impulse Response (FIR) filters?
AFIR filters can delay all frequency components of the signal by the same amount
BFIR filters are easier to implement for a given set of passband rolloff requirements
CFIR filters can respond faster to impulses
DAll these choices are correct
Answer: D
What is the function of taps in a digital signal processing filter?
ATo reduce excess signal pressure levels
BProvide access for debugging software
CSelect the point at which baseband signals are generated
DProvide incremental signal delays for filter algorithms
Answer: B
Which of the following would allow a digital signal processing filter to create a sharper filter response?
AHigher data rate
BMore taps
CLower Q
DDouble-precision math routines
Answer: B
What is the frequency response of the circuit in E7-3 if a capacitor is added across the feedback resistor?
AHigh-pass filter
BLow-pass filter
CBand-pass filter
DNotch filter
Answer: D
What is the typical input impedance of an op-amp?
A100 ohms
B10,000 ohms
CVery low
DVery high
Answer: C
What is meant by the term “op-amp input offset voltage”?
AThe output voltage of the op-amp minus its input voltage
BThe difference between the output voltage of the op-amp and the input voltage required in the immediately following stage
CThe differential input voltage needed to bring the open loop output voltage to zero
DThe potential between the amplifier input terminals of the op-amp in an open loop condition
Answer: A
How can unwanted ringing and audio instability be prevented in an op-amp audio filter?
ARestrict both gain and Q
BRestrict gain but increase Q
CRestrict Q but increase gain
DIncrease both gain and Q
Answer: B
What is the gain-bandwidth of an operational amplifier?
AThe maximum frequency for a filter circuit using that type of amplifier
BThe frequency at which the open-loop gain of the amplifier equals one
CThe gain of the amplifier at a filter’s cutoff frequency
DThe frequency at which the amplifier’s offset voltage is zero
Answer: C
What voltage gain can be expected from the circuit in Figure E7-3 when R1 is 10 ohms and RF is 470 ohms?
A0.21
B4700
C47
D24
Answer: D
How does the gain of an ideal operational amplifier vary with frequency?
AIt increases linearly with increasing frequency
BIt decreases linearly with increasing frequency
CIt decreases logarithmically with increasing frequency
DIt does not vary with frequency
Answer: D
What will be the output voltage of the circuit shown in Figure E7-3 if R1 is 1,000 ohms, RF is 10,000 ohms, and 0.23 volts DC is applied to the input?
A0.23 volts
B2.3 volts
C-0.23 volts
D-2.3 volts
Answer: C
What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 1,800 ohms and RF is 68 kilohms?
A1
B0.03
C38
D76
Answer: B
What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 3,300 ohms and RF is 47 kilohms?
A28
B14
C7
D0.07
Answer: A
What is an operational amplifier?
AA high-gain, direct-coupled differential amplifier with very high input impedance and very low output impedance
BA digital audio amplifier whose characteristics are determined by components external to the amplifier
CAn amplifier used to increase the average output of frequency modulated amateur signals to the legal limit
DA RF amplifier used in the UHF and microwave regions
Answer: C
What is a microphonic?
AAn IC used for amplifying microphone signals
BDistortion caused by RF pickup on the microphone cable
CChanges in oscillator frequency caused by mechanical vibration
DExcess loading of the microphone by an oscillator
Answer: C
What is a phase-locked loop?
AAn electronic servo loop consisting of a ratio detector, reactance modulator, and voltage-controlled oscillator
BAn electronic circuit also known as a monostable multivibrator
CAn electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator
DAn electronic circuit consisting of a precision push-pull amplifier with a differential phase input
Answer: C
How is positive feedback supplied in a Colpitts oscillator?
AThrough a tapped coil
BThrough link coupling
CThrough a capacitive divider
DThrough a neutralizing capacitor
Answer: D
How is positive feedback supplied in a Pierce oscillator?
AThrough a tapped coil
BThrough link coupling
CThrough a neutralizing capacitor
DThrough a quartz crystal
Answer: B
Which of these functions can be performed by a phase-locked loop?
AWide-band AF and RF power amplification
BFrequency synthesis and FM demodulation
CPhotovoltaic conversion and optical coupling
DComparison of two digital input signals and digital pulse counting
Answer: D
How can an oscillator’s microphonic responses be reduced?
AUse NP0 capacitors
BReduce noise on the oscillator’s power supply
CIncrease the gain
DMechanically isolate the oscillator circuitry from its enclosure
Answer: A
Which of the following components can be used to reduce thermal drift in crystal oscillators?
ANP0 capacitors
BToroidal inductors
CWirewound resistors
DNon-inductive resistors
Answer: A
What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital-to-analog converter, and a low-pass anti-alias filter?
AA direct digital synthesizer
BA hybrid synthesizer
CA phase-locked loop synthesizer
DA direct conversion synthesizer
Answer: B
What information is contained in the lookup table of a direct digital synthesizer (DDS)?
AThe phase relationship between a reference oscillator and the output waveform
BAmplitude values that represent the desired waveform
CThe phase relationship between a voltage-controlled oscillator and the output waveform
DFrequently used receiver and transmitter frequencies
Answer: C
What are the major spectral impurity components of direct digital synthesizers?
ABroadband noise
BDigital conversion noise
CSpurious signals at discrete frequencies
DHarmonics of the local oscillator
Answer: B
Which of the following ensures that a crystal oscillator operates on the frequency specified by the crystal manufacturer?
AProvide the crystal with a specified parallel inductance
BProvide the crystal with a specified parallel capacitance
CBias the crystal at a specified voltage
DBias the crystal at a specified current
Answer: D
Which of the following is a technique for providing highly accurate and stable oscillators needed for microwave transmission and reception?
AUse a GPS signal reference
BUse a rubidium stabilized reference oscillator
CUse a temperature-controlled high Q dielectric resonator
DAll these choices are correct