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Amateur Radio Question PoolsNew! View the differences between the 2008 Extra question pool and the previous pool. Amateur Extra (Eff. July 2008) Question PoolPrev 1 2 3 4 5 6 7 8 9 0 NextE8A01 What type of wave is made up of a sine wave plus all of its odd harmonics? A square wave A sine wave A cosine wave A tangent wave E8A02 What type of wave has a rise time significantly faster than its fall time (or vice versa)? A cosine wave A square wave A sawtooth wave A sine wave E8A03 What type of wave is made up of sine waves of a given fundamental frequency plus all its harmonics? A sawtooth wave A square wave A sine wave A cosine wave E8A04 What is the equivalent to the root-mean-square value of an AC voltage? The AC voltage found by taking the square of the average value of the peak AC voltage The DC voltage causing the same amount of heating in a given resistor as the corresponding peak AC voltage The DC voltage causing the same amount of heating in a resistor as the corresponding RMS AC voltage The AC voltage found by taking the square root of the average AC value E8A05 What would be the most accurate way of measuring the RMS voltage of a complex waveform? By using a grid dip meter By measuring the voltage with a D'Arsonval meter By using an absorption wavemeter By measuring the heating effect in a known resistor E8A06 What is the approximate ratio of PEP-to-average power in a typical voice-modulated single-sideband phone signal? 2.5 to 1 25 to 1 1 to 1 100 to 1 E8A07 What determines the PEP-to-average power ratio of a single-sideband phone signal? The frequency of the modulating signal The characteristics of the modulating signal The degree of carrier suppression The amplifier gain E8A08 What is the period of a wave? The time required to complete one cycle The number of degrees in one cycle The number of zero crossings in one cycle The amplitude of the wave E8A09 What type of waveform is produced by human speech? Sinusoidal Logarithmic Irregular Trapezoidal E8A10 Which of the following is a distinguishing characteristic of a pulse waveform? Regular sinusoidal oscillations Narrow bursts of energy separated by periods of no signal A series of tones that vary between two frequencies A signal that contains three or more discrete tones E8A11 What is one use for a pulse modulated signal? Linear amplification PSK31 data transmission Multiphase power transmission Digital data transmission E8A12 What type of information can be conveyed using digital waveforms? Human speech Video signals Data All of these answers are correct E8A13 What is an advantage of using digital signals instead of analog signals to convey the same information? Less complex circuitry is required for digital signal generation and detection Digital signals always occupy a narrower bandwidth Digital signals can be regenerated multiple times without error All of these answers are correct E8A14 Which of these methods is commonly used to convert analog signals to digital signals? Sequential sampling Harmonic regeneration Level shifting Phase reversal E8A15 What would the waveform of a digital data stream signal look like on a conventional oscilloscope? A series of sine waves with evenly spaced gaps A series of pulses with varying patterns A running display of alpha-numeric characters None of the above; this type of signal cannot be seen on a conventional oscilloscope 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? FM compressibility Quieting index Percentage of modulation Modulation index E8B02 How does the modulation index of a phase-modulated emission vary with RF carrier frequency (the modulated frequency)? It increases as the RF carrier frequency increases It decreases as the RF carrier frequency increases It varies with the square root of the RF carrier frequency It does not depend on the RF carrier 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? 3 0.3 3000 1000 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? 6000 3 2000 1/3 E8B05 What is the deviation ratio of an FM-phone signal having a maximum frequency swing of plus-or-minus 5 kHz and accepting a maximum modulation rate of 3 kHz? 60 0.167 0.6 1.67 E8B06 What is the deviation ratio of an FM-phone signal having a maximum frequency swing of plus or minus 7.5 kHz and accepting a maximum modulation frequency of 3.5 kHz? 2.14 0.214 0.47 47 E8B07 When using a pulse-width modulation system, why is the transmitter's peak power greater than its average power? The signal duty cycle is less than 100% The signal reaches peak amplitude only when voice modulated The signal reaches peak amplitude only when voltage spikes are generated within the modulator The signal reaches peak amplitude only when the pulses are also amplitude modulated E8B08 What parameter does the modulating signal vary in a pulse-position modulation system? The number of pulses per second The amplitude of the pulses The duration of the pulses The time at which each pulse occurs E8B09 How are the pulses of a pulse-modulated signal usually transmitted? A pulse of relatively short duration is sent; a relatively long period of time separates each pulse A pulse of relatively long duration is sent; a relatively short period of time separates each pulse A group of short pulses are sent in a relatively short period of time; a relatively long period of time separates each group A group of short pulses are sent in a relatively long period of time; a relatively short period of time separates each group E8B10 What is meant by deviation ratio? The ratio of the audio modulating frequency to the center carrier frequency The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency The ratio of the carrier center frequency to the audio modulating frequency The ratio of the highest audio modulating frequency to the average audio modulating frequency E8B11 Which of these methods can be used to combine several separate analog information streams into a single analog radio frequency signal? Frequency shift keying A diversity combiner Frequency division multiplexing Pulse compression E8B12 Which of the following describes frequency division multiplexing? The transmitted signal jumps from band to band at a predetermined rate Two or more information streams are merged into a "baseband", which then modulates the transmitter The transmitted signal is divided into packets of information Two or more information streams are merged into a digital combiner, which then pulse position modulates the transmitter E8B13 What is time division multiplexing? Two or more data streams are assigned to discrete sub-carriers on an FM transmitter Two or more signals are arranged to share discrete time slots of a digital data transmission Two or more data streams share the same channel by transmitting time of transmission as the sub-carrier Two or more signals are quadrature modulated to increase bandwidth efficiency E8C01 Which one of the following digital codes consists of elements having unequal length? ASCII AX.25 Baudot Morse code E8C02 What are some of the differences between the Baudot digital code and ASCII? Baudot uses four data bits per character, ASCII uses seven; Baudot uses one character as a shift code, ASCII has no shift code Baudot uses five data bits per character, ASCII uses seven; Baudot uses two characters as shift codes, ASCII has no shift code Baudot uses six data bits per character, ASCII uses seven; Baudot has no shift code, ASCII uses two characters as shift codes Baudot uses seven data bits per character, ASCII uses eight; Baudot has no shift code, ASCII uses two characters as shift codes E8C03 What is one advantage of using the ASCII code for data communications? It includes built-in error-correction features It contains fewer information bits per character than any other code It is possible to transmit both upper and lower case text It uses one character as a shift code to send numeric and special characters E8C04 What is one of the differences between MT63 and PSK31? ((new)) MT63 is an FM signal; PSK31 is an AM signal MT63 uses the Baudot code; PSK31 uses Varicode MT63 requires less bandwidth for an equivalent bit rate than PSK31 MT63 incorporates error correction; PSK31 does not E8C05 What technique is used to minimize the bandwidth requirements of a PSK-31 signal? Zero-sum character encoding Reed-Solomon character encoding Use of sinusoidal data pulses Use of trapezoidal data pulses E8C06 What is the necessary bandwidth of a 13-WPM international Morse code transmission? Approximately 13 Hz Approximately 26 Hz Approximately 52 Hz Approximately 104 Hz E8C07 What is the necessary bandwidth of a 170-hertz shift, 300-baud ASCII transmission? 0.1 Hz 0.3 kHz 0.5 kHz 1.0 kHz E8C08 What is the necessary bandwidth of a 4800-Hz frequency shift, 9600-baud ASCII FM transmission? 15.36 kHz 9.6 kHz 4.8 kHz 5.76 kHz E8C09 What term describes a wide-bandwidth communications system in which the transmitted carrier frequency varies according to some predetermined sequence? Amplitude compandored single sideband AMTOR Time-domain frequency modulation Spread-spectrum communication E8C10 Which of these techniques causes a digital signal to appear as wide-band noise to a conventional receiver? Spread-spectrum Independent sideband Regenerative detection Exponential addition E8C11 What spread-spectrum communications technique alters the center frequency of a conventional carrier many times per second in accordance with a pseudo-random list of channels? Frequency hopping Direct sequence Time-domain frequency modulation Frequency compandored spread-spectrum E8C12 What spread-spectrum communications technique uses a high speed binary bit stream to shift the phase of an RF carrier? Frequency hopping Direct sequence Binary phase-shift keying Phase compandored spread-spectrum E8C13 What makes spread-spectrum communications resistant to interference? Interfering signals are removed by a frequency-agile crystal filter Spread-spectrum transmitters use much higher power than conventional carrier-frequency transmitters Spread-spectrum transmitters can hunt for the best carrier frequency to use within a given RF spectrum Only signals using the correct spreading sequence are received E8C14 What is the advantage of including a parity bit with an ASCII character stream? Faster transmission rate The signal can overpower interfering signals Foreign language characters can be sent Some types of errors can be detected E8C15 What is one advantage of using JT-65 coding? Uses only a 65 Hz bandwidth Virtually perfect decoding of signals well below the noise Easily copied by ear if necessary Permits fast-scan TV transmissions over narrow bandwidth E8D01 What is the easiest voltage amplitude parameter to measure when viewing a pure sine wave signal on an oscilloscope? (was E8D02) Peak-to-peak voltage RMS voltage Average voltage DC voltage E8D02 What is the relationship between the peak-to-peak voltage and the peak voltage amplitude in a symmetrical waveform? (was E8D03;) 0.707:1 2:1 1.414:1 4:1 E8D03 What input-amplitude parameter is valuable in evaluating the signal-handling capability of a Class A amplifier? Peak voltage RMS voltage Average power Resting voltage E8D04 What is the PEP output of a transmitter that has a maximum peak of 30 volts to a 50-ohm load as observed on an oscilloscope? 4.5 watts 9 watts 16 watts 18 watts E8D05 If an RMS-reading AC voltmeter reads 65 volts on a sinusoidal waveform, what is the peak-to-peak voltage? 46 volts 92 volts 130 volts 184 volts E8D06 What is the advantage of using a peak-reading wattmeter to monitor the output of a SSB phone transmitter? (replaces E) It is easier to determine the correct tuning of the output circuit It gives a more accurate display of the PEP output when modulation is present It makes it easier to detect high SWR on the feed-line It can determine if any "flat-topping" is present during modulation peaks E8D07 What is an electromagnetic wave? Alternating currents in the core of an electromagnet A wave consisting of two electric fields at right angles to each other A wave consisting of an electric field and a magnetic field oscillating at right angles to each other A wave consisting of two magnetic fields at right angles to each other E8D08 Which of the following best describes electromagnetic waves traveling in free space? Electric and magnetic fields become aligned as they travel The energy propagates through a medium with a high refractive index The waves are reflected by the ionosphere and return to their source Changing electric and magnetic fields propagate the energy E8D09 What is meant by circularly polarized electromagnetic waves? Waves with an electric field bent into a circular shape Waves with a rotating electric field Waves that circle the Earth Waves produced by a loop antenna E8D10 What is the polarization of an electromagnetic wave if its magnetic field is parallel to the surface of the Earth? Circular Horizontal Elliptical Vertical E8D11 What is the polarization of an electromagnetic wave if its magnetic field is perpendicular to the surface of the Earth? Horizontal Circular Elliptical Vertical E8D12 At approximately what speed do electromagnetic waves travel in free space? 300 million meters per second 186,300 meters per second 186,300 feet per second 300 million miles per second E8D13 What type of meter should be used to monitor the output signal of a voice-modulated single-sideband transmitter to ensure you do not exceed the maximum allowable power? An SWR meter reading in the forward direction A modulation meter An average reading wattmeter A peak-reading wattmeter E8D14 What is the average power dissipated by a 50-ohm resistive load during one complete RF cycle having a peak voltage of 35 volts? 12.2 watts 9.9 watts 24.5 watts 16 watts E8D15 If an RMS reading voltmeter reads 34 volts on a sinusoidal waveform, what is the peak voltage? 123 volts 96 volts 55 volts 48 volts E8D16 Which of the following is a typical value for the peak voltage at a common household electrical outlet? 240 volts 170 volts 120 volts 340 volts E8D17 Which of the following is a typical value for the peak-to-peak voltage at a common household electrical outlet? 240 volts 120 volts 340 volts 170 volts E8D18 Which of the following is a typical value for the RMS voltage at a common household electrical power outlet? 120-V AC 340-V AC 85-V AC 170-V AC E8D19 What is the RMS value of a 340-volt peak-to-peak pure sine wave? 120-V AC 170-V AC 240-V AC 300-V AC |
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