What technique shows that a square wave is made up of a sine wave and its odd harmonics?
AFourier analysis
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Subelement E8 question review
All 48 official questions with the exact winning phrase marked.
Which of the following is a type of analog-to-digital conversion?
ASuccessive approximation
Which of the following describes a signal in the time domain?
BAmplitude at different times
What is “dither” with respect to analog-to-digital converters?
BA small amount of noise added to the input signal to reduce quantization noise
What is the benefit of making voltage measurements with a true-RMS calculating meter?
DRMS is measured for both sinusoidal and non-sinusoidal signals
What is the approximate ratio of PEP-to-average power in an unprocessed single-sideband phone signal?
A2.5 to 1
What determines the PEP-to-average power ratio of an unprocessed single-sideband phone signal?
BSpeech characteristics
Why are direct or flash conversion analog-to-digital converters used for a software defined radio?
CVery high speed allows digitizing high frequencies
How many different input levels can be encoded by an analog-to-digital converter with 8-bit resolution?
D256
What is the purpose of a low-pass filter used at the output of a digital-to-analog converter?
CRemove spurious sampling artifacts from the output signal
Which of the following is a measure of the quality of an analog-to-digital converter?
ATotal harmonic distortion
What is the modulation index of an FM signal?
AThe ratio of frequency deviation to modulating signal frequency
How does the modulation index of a phase-modulated emission vary with RF carrier frequency?
DIt does not depend on the RF carrier frequency
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
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?
B3
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?
D1.67
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
Orthogonal frequency-division multiplexing (OFDM) is a technique used for which types of amateur communication?
ADigital modes
What describes orthogonal frequency-division multiplexing (OFDM)?
DA digital modulation technique using subcarriers at frequencies chosen to avoid intersymbol interference
What is deviation ratio?
BThe ratio of the maximum carrier frequency deviation to the highest audio modulating frequency
What is frequency division multiplexing (FDM)?
BDividing the transmitted signal into separate frequency bands that each carry a different data stream
What is digital time division multiplexing?
BTwo or more signals are arranged to share discrete time slots of a data transmission
What is Quadrature Amplitude Modulation or QAM?
BTransmission of data by modulating the amplitude of two carriers of the same frequency but 90 degrees out of phase
What is the definition of symbol rate in a digital transmission?
CThe rate at which the waveform changes to convey information
Why should the phase of a PSK signal be changed at the zero crossing of the RF signal?
ATo minimize bandwidth
What technique minimizes the bandwidth of a PSK31 signal?
CUse of sinusoidal data pulses
What is the approximate bandwidth of a 13-WPM International Morse Code transmission?
C52 Hz
What is the bandwidth of an FT8 signal?
B50 Hz
What is the bandwidth of a 4,800-Hz frequency shift, 9,600-baud ASCII FM transmission?
A15.36 kHz
How does ARQ accomplish error correction?
DIf errors are detected, a retransmission is requested
Which digital code allows only one bit to change between sequential code values?
DGray code
How can data rate be increased without increasing bandwidth?
CUsing a more efficient digital code
What is the relationship between symbol rate and baud?
AThey are the same
What factors affect the bandwidth of a transmitted CW signal?
CKeying speed and shape factor (rise and fall time)
What is described by the constellation diagram of a QAM or QPSK signal?
BThe possible phase and amplitude states for each symbol
What type of addresses do nodes have in a mesh network?
CInternet Protocol (IP)
What technique do individual nodes use to form a mesh network?
CDiscovery and link establishment protocols
Why are received spread spectrum signals resistant to interference?
ASignals not using the spread spectrum algorithm are suppressed in the receiver
What spread spectrum communications technique uses a high-speed binary bit stream to shift the phase of an RF carrier?
BDirect sequence
Which describes spread spectrum frequency hopping?
DRapidly varying the frequency of a transmitted signal according to a pseudorandom sequence
What is the primary effect of extremely short rise or fall time on a CW signal?
CThe generation of key clicks
What is the most common method of reducing key clicks?
AIncrease keying waveform rise and fall times
What is the advantage of including parity bits in ASCII characters?
DSome types of errors can be detected
What is a common cause of overmodulation of AFSK signals?
DExcessive transmit audio levels
What parameter evaluates distortion of an AFSK signal caused by excessive input audio levels?
DIntermodulation Distortion (IMD)
What is considered an acceptable maximum IMD level for an idling PSK signal?
D-30 dB
What are some of the differences between the Baudot digital code and ASCII?
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
What is one advantage of using ASCII code for data communications?
CIt is possible to transmit both uppercase and lowercase text