E8 Questions
44 questions in this subelement. Click any question ID for more details.
Answer: A
Which of the following is a type of analog-to-digital conversion?
ASuccessive approximation
BHarmonic regeneration
CLevel shifting
DPhase reversal
Answer: B
Which of the following describes a signal in the time domain?
APower at intervals of phase
BAmplitude at different times
CFrequency at different times
DDiscrete impulses in time order
Answer: B
What is “dither” with respect to analog-to-digital converters?
AAn abnormal condition where the converter cannot settle on a value to represent the signal
BA small amount of noise added to the input signal to reduce quantization noise
CAn error caused by irregular quantization step size
DA method of decimation by randomly skipping samples
Answer: D
What is the benefit of making voltage measurements with a true-RMS calculating meter?
AAn inverse Fourier transform can be used
BThe signal’s RMS noise factor is also calculated
CThe calculated RMS value can be converted directly into phasor form
DRMS is measured for both sinusoidal and non-sinusoidal signals
Answer: A
What is the approximate ratio of PEP-to-average power in an unprocessed single-sideband phone signal?
A2.5 to 1
B25 to 1
C1 to 1
D13 to 1
Answer: B
What determines the PEP-to-average power ratio of an unprocessed single-sideband phone signal?
AThe frequency of the modulating signal
BSpeech characteristics
CThe degree of carrier suppression
DAmplifier gain
Answer: C
Why are direct or flash conversion analog-to-digital converters used for a software defined radio?
AVery low power consumption decreases frequency drift
BImmunity to out-of-sequence coding reduces spurious responses
CVery high speed allows digitizing high frequencies
DAll these choices are correct
Answer: D
How many different input levels can be encoded by an analog-to-digital converter with 8-bit resolution?
A8
B8 multiplied by the gain of the input amplifier
C256 divided by the gain of the input amplifier
D256
Answer: C
What is the purpose of a low-pass filter used at the output of a digital-to-analog converter?
ALower the input bandwidth to increase the effective resolution
BImprove accuracy by removing out-of-sequence codes from the input
CRemove spurious sampling artifacts from the output signal
DAll these choices are correct
Answer: A
Which of the following is a measure of the quality of an analog-to-digital converter?
ATotal harmonic distortion
BPeak envelope power
CReciprocal mixing
DPower factor
Answer: D
How does the modulation index of a phase-modulated emission vary with RF carrier frequency?
AIt increases as the RF carrier frequency increases
BIt decreases as the RF carrier frequency increases
CIt varies with the square root of the RF carrier frequency
DIt does not depend on the RF carrier frequency
Answer: A
What is the modulation index of an FM phone signal having a maximum frequency deviation of 3000 Hz either side of the carrier frequency if the highest modulating frequency is 1000 Hz?
A3
B0.3
C6
D0.6
Answer: B
What is the modulation index of an FM phone signal having a maximum carrier deviation of plus or minus 6 kHz if the highest modulating frequency is 2 kHz?
A0.3
B3
C0.6
D6
Answer: D
What is the deviation ratio of an FM phone signal having a maximum frequency swing of plus or minus 5 kHz if the highest modulation frequency is 3 kHz?
A6
B0.167
C0.6
D1.67
Answer: A
What is the deviation ratio of an FM phone signal having a maximum frequency swing of plus or minus 7.5 kHz if the highest modulation frequency is 3.5 kHz?
A2.14
B0.214
C0.47
D47
Answer: A
Orthogonal frequency-division multiplexing (OFDM) is a technique used for which types of amateur communication?
ADigital modes
BExtremely low-power contacts
CEME
DOFDM signals are not allowed on amateur bands
Answer: D
What describes orthogonal frequency-division multiplexing (OFDM)?
AA frequency modulation technique that uses non-harmonically related frequencies
BA bandwidth compression technique using Fourier transforms
CA digital mode for narrow-band, slow-speed transmissions
DA digital modulation technique using subcarriers at frequencies chosen to avoid intersymbol interference
Answer: B
What is deviation ratio?
AThe ratio of the audio modulating frequency to the center carrier frequency
BThe ratio of the maximum carrier frequency deviation to the highest audio modulating frequency
CThe ratio of the carrier center frequency to the audio modulating frequency
DThe ratio of the highest audio modulating frequency to the average audio modulating frequency
Answer: B
What is frequency division multiplexing (FDM)?
AThe transmitted signal jumps from band to band at a predetermined rate
BDividing the transmitted signal into separate frequency bands that each carry a different data stream
CThe transmitted signal is divided into packets of information
DTwo or more information streams are merged into a digital combiner, which then pulse position modulates the transmitter
Answer: B
What is digital time division multiplexing?
ATwo or more data streams are assigned to discrete sub-carriers on an FM transmitter
BTwo or more signals are arranged to share discrete time slots of a data transmission
CTwo or more data streams share the same channel by transmitting time of transmission as the sub- carrier
DTwo or more signals are quadrature modulated to increase bandwidth efficiency
Answer: C
What is the definition of symbol rate in a digital transmission?
AThe number of control characters in a message packet
BThe maximum rate at which the forward error correction code can make corrections
CThe rate at which the waveform changes to convey information
DThe number of characters carried per second by the station-to-station link
Answer: A
Why should the phase of a PSK signal be changed at the zero crossing of the RF signal?
ATo minimize bandwidth
BTo simplify modulation
CTo improve carrier suppression
DAll these choices are correct
Answer: C
What technique minimizes the bandwidth of a PSK31 signal?
AZero-sum character encoding
BReed-Solomon character encoding
CUse of sinusoidal data pulses
DUse of linear data pulses
Answer: C
What is the approximate bandwidth of a 13-WPM International Morse Code transmission?
A13 Hz
B26 Hz
C52 Hz
D104 Hz
Answer: A
What is the bandwidth of a 4,800-Hz frequency shift, 9,600-baud ASCII FM transmission?
A15.36 kHz
B9.6 kHz
C4.8 kHz
D5.76 kHz
Answer: D
How does ARQ accomplish error correction?
ASpecial binary codes provide automatic correction
BSpecial polynomial codes provide automatic correction
CIf errors are detected, redundant data is substituted
DIf errors are detected, a retransmission is requested
Answer: D
Which digital code allows only one bit to change between sequential code values?
ABinary Coded Decimal Code
BExtended Binary Coded Decimal Interchange Code
CExtended ASCII
DGray code
Answer: C
How can data rate be increased without increasing bandwidth?
AIt is impossible
BIncreasing analog-to-digital conversion resolution
CUsing a more efficient digital code
DUsing forward error correction
Answer: A
What is the relationship between symbol rate and baud?
AThey are the same
BBaud is twice the symbol rate
CBaud rate is half the symbol rate
DThe relationship depends on the specific code used
Answer: C
What factors affect the bandwidth of a transmitted CW signal?
AIF bandwidth and Q
BModulation index and output power
CKeying speed and shape factor (rise and fall time)
DAll these choices are correct
Answer: B
What is described by the constellation diagram of a QAM or QPSK signal?
AHow many carriers may be present at the same time
BThe possible phase and amplitude states for each symbol
CFrequency response of the signal stream
DThe number of bits used for error correction in the protocol
Answer: C
What type of addresses do nodes have in a mesh network?
AEmail
BTrust server
CInternet Protocol (IP)
DTalk group
Answer: C
What technique do individual nodes use to form a mesh network?
AForward error correction and Viterbi codes
BActing as store-and-forward digipeaters
CDiscovery and link establishment protocols
DCustom code plugs for the local trunking systems
Answer: B
What spread spectrum communications technique uses a high-speed binary bit stream to shift the phase of an RF carrier?
AFrequency hopping
BDirect sequence
CBinary phase-shift keying
DPhase compandored spread spectrum
Answer: D
Which describes spread spectrum frequency hopping?
AIf interference is detected by the receiver, it will signal the transmitter to change frequencies
BRF signals are clipped to generate a wide band of harmonics which provides redundancy to correct errors
CA binary bit stream is used to shift the phase of an RF carrier very rapidly in a pseudorandom sequence
DRapidly varying the frequency of a transmitted signal according to a pseudorandom sequence
Answer: C
What is the primary effect of extremely short rise or fall time on a CW signal?
AMore difficult to copy
BThe generation of RF harmonics
CThe generation of key clicks
DMore difficult to tune
Answer: A
What is the most common method of reducing key clicks?
AIncrease keying waveform rise and fall times
BInsert low-pass filters at the transmitter output
CReduce keying waveform rise and fall times
DInsert high-pass filters at the transmitter output
Answer: D
What is the advantage of including parity bits in ASCII characters?
AFaster transmission rate
BSignal-to-noise ratio is improved
CA larger character set is available
DSome types of errors can be detected
Answer: D
What is a common cause of overmodulation of AFSK signals?
AExcessive numbers of retries
BExcessive frequency deviation
CBit errors in the modem
DExcessive transmit audio levels
Answer: D
What parameter evaluates distortion of an AFSK signal caused by excessive input audio levels?
ASignal-to-noise ratio
BBaud error rate
CRepeat Request Rate (RRR)
DIntermodulation Distortion (IMD)
Answer: D
What is considered an acceptable maximum IMD level for an idling PSK signal?
A+5 dB
B+10 dB
C+15 dB
D-30 dB
Answer: B
What are some of the differences between the Baudot digital code and ASCII?
ABaudot uses 4 data bits per character, ASCII uses 7 or 8; Baudot uses 1 character as a letters/figures shift code, ASCII has no letters/figures code
BBaudot uses 5 data bits per character, ASCII uses 7 or 8; Baudot uses 2 characters as letters/figures shift codes, ASCII has no letters/figures shift code
CBaudot uses 6 data bits per character, ASCII uses 7 or 8; Baudot has no letters/figures shift code, ASCII uses 2 letters/figures shift codes
DBaudot uses 7 data bits per character, ASCII uses 8; Baudot has no letters/figures shift code, ASCII uses 2 letters/figures shift codes
Answer: C
What is one advantage of using ASCII code for data communications?
AIt includes built-in error correction features
BIt contains fewer information bits per character than any other code
CIt is possible to transmit both uppercase and lowercase text
DIt uses one character as a shift code to send numeric and special characters