# Extra Class License Exam Questions

### Subelement E8

Signals and Emissions

Question Display Options:
Group E8A AC waveforms: sine, square, sawtooth and irregular waveforms; AC measurements; average and PEP of RF signals; Fourier analysis; Analog to digital conversion: Digital to Analog conversion
E8A01 What is the name of the process that shows that a square wave is made up of a sine wave plus all of its odd harmonics?
E8A02 What type of wave has a rise time significantly faster than its fall time (or vice versa)?
E8A03 What type of wave does a Fourier analysis show to be made up of sine waves of a given fundamental frequency plus all of its harmonics?
E8A04 What is "dither" with respect to analog to digital converters?
E8A05 What would be the most accurate way of measuring the RMS voltage of a complex waveform?
E8A06 What is the approximate ratio of PEP-to-average power in a typical single-sideband phone signal?
E8A07 What determines the PEP-to-average power ratio of a single-sideband phone signal?
E8A08 Why would a direct or flash conversion analog-to-digital converter be useful for a software defined radio?
E8A09 How many levels can an analog-to-digital converter with 8 bit resolution encode?
E8A10 What is the purpose of a low pass filter used in conjunction with a digital-to-analog converter?
E8A11 What type of information can be conveyed using digital waveforms?
E8A12 What is an advantage of using digital signals instead of analog signals to convey the same information?
E8A13 Which of these methods is commonly used to convert analog signals to digital signals?
Group E8B Modulation and demodulation: modulation methods; modulation index and deviation ratio; frequency and time division multiplexing; Orthogonal Frequency Division Multiplexing
E8B01 What is the term for the ratio between the frequency deviation of an RF carrier wave and the modulating frequency of its corresponding FM-phone signal?
E8B02 How does the modulation index of a phase-modulated emission vary with RF carrier frequency (the modulated frequency)?
E8B03 What is the modulation index of an FM-phone signal having a maximum frequency deviation of 3000 Hz either side of the carrier frequency when the modulating frequency is 1000 Hz?
E8B04 What is the modulation index of an FM-phone signal having a maximum carrier deviation of plus or minus 6 kHz when modulated with a 2 kHz modulating frequency?
E8B05 What is the deviation ratio of an FM-phone signal having a maximum frequency swing of plus-or-minus 5 kHz when the maximum modulation frequency is 3 kHz?
E8B06 What is the deviation ratio of an FM-phone signal having a maximum frequency swing of plus or minus 7.5 kHz when the maximum modulation frequency is 3.5 kHz?
E8B07 Orthogonal Frequency Division Multiplexing is a technique used for which type of amateur communication?
E8B08 What describes Orthogonal Frequency Division Multiplexing?
E8B09 What is meant by deviation ratio?
E8B10 What describes frequency division multiplexing?
E8B11 What is digital time division multiplexing?
Group E8C Digital signals: digital communication modes; information rate vs bandwidth; error correction
E8C01 How is Forward Error Correction implemented?
E8C02 What is the definition of symbol rate in a digital transmission?
E8C03 When performing phase shift keying, why is it advantageous to shift phase precisely at the zero crossing of the RF carrier?
E8C04 What technique is used to minimize the bandwidth requirements of a PSK31 signal?
E8C05 What is the necessary bandwidth of a 13-WPM international Morse code transmission?
E8C06 What is the necessary bandwidth of a 170-hertz shift, 300-baud ASCII transmission?
E8C07 What is the necessary bandwidth of a 4800-Hz frequency shift, 9600-baud ASCII FM transmission?
E8C08 How does ARQ accomplish error correction?
E8C09 Which is the name of a digital code where each preceding or following character changes by only one bit?
E8C10 What is an advantage of Gray code in digital communications where symbols are transmitted as multiple bits
E8C11 What is the relationship between symbol rate and baud?
Group E8D Keying defects and overmodulation of digital signals; digital codes; spread spectrum