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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 NextE4A01 How does a spectrum analyzer differ from a conventional oscilloscope? A spectrum analyzer measures ionospheric reflection; an oscilloscope displays electrical signals A spectrum analyzer displays the peak amplitude of signals; an oscilloscope displays the average amplitude of signals A spectrum analyzer displays signals in the frequency domain; an oscilloscope displays signals in the time domain A spectrum analyzer displays radio frequencies; an oscilloscope displays audio frequencies E4A02 Which of the following parameters would a typical spectrum analyzer display on the horizontal axis? SWR Q Time Frequency E4A03 Which of the following parameters would a typical spectrum analyzer display on the vertical axis? Amplitude Duration SWR Q E4A04 Which of the following test instruments is used to display spurious signals from a radio transmitter? A spectrum analyzer A wattmeter A logic analyzer A time-domain reflectometer E4A05 Which of the following test instruments is used to display intermodulation distortion products in an SSB transmission? A wattmeter A spectrum analyzer A logic analyzer A time-domain reflectometer E4A06 Which of the following could be determined with a spectrum analyzer? The degree of isolation between the input and output ports of a 2 meter duplexer Whether a crystal is operating on its fundamental or overtone frequency The spectral output of a transmitter All of these choices are correct E4A07 Which of the following is an advantage of using an antenna analyzer vs. a SWR bridge to measure antenna SWR? Antenna analyzers automatically tune your antenna for resonance Antenna analyzers typically do not need an external RF source Antenna analyzers typically display a time-varying representation of the modulation envelope All of the above E4A08 Which of the following instruments would be best for measuring the SWR of a beam antenna? A spectrum analyzer A Q meter An ohmmeter An antenna analyzer E4A09 Which of the following is most important when adjusting PSK31 transmitting levels? Power output PA current ALC level SWR E4A10 Which of the following is a useful test for a functioning NPN transistor in an active circuit where the transistor should be biased "on" ? Measure base-to-emitter resistance with an ohmmeter; it should be approximately 6 to 7 ohms Measure base-to-emitter resistance with an ohmmeter; it should be approximately 0.6 to 0.7 ohms Measure base-to-emitter voltage with a voltmeter; it should be approximately 6 to 7 volts Measure base-to-emitter voltage with a voltmeter; it should be approximately 0.6 to 0.7 volts E4A11 Which of the following test instruments can be used to indicate pulse conditions in a digital logic circuit? A logic probe An ohmmeter An electroscope A Wheatstone bridge E4A12 Which of the following procedures is an important precaution to follow when connecting a spectrum analyzer to a transmitter output? Use high quality double shielded coaxial cables to reduce signal losses Attenuate the transmitter output going to the spectrum analyzer Match the antenna to the load All of these choices are correct E4B01 Which of the following is a characteristic of a good harmonic frequency marker? Wide tuning range Frequency stability Linear output amplifier All of the above E4B02 Which of the following factors most affects the accuracy of a frequency counter? Input attenuator accuracy Time base accuracy Decade divider accuracy Temperature coefficient of the logic E4B03 What is an advantage of using a bridge circuit to measure impedance? It provides an excellent match under all conditions It is relatively immune to drift in the signal generator source The measurement is based on obtaining a null in voltage, which can be done very precisely It can display results directly in Smith chart format E4B04 If a frequency counter with a specified accuracy of +/- 1.0 ppm reads 146,520,000 Hz, what is the most the actual frequency being measured could differ from the reading? 165.2 Hz 14.652 kHz 146.52 Hz 1.4652 MHz E4B05 If a frequency counter with a specified accuracy of +/- 0.1 ppm reads 146,520,000 Hz, what is the most the actual frequency being measured could differ from the reading? 14.652 Hz 0.1 MHz 1.4652 Hz 1.4652 kHz E4B06 If a frequency counter with a specified accuracy of +/- 10 ppm reads 146,520,000 Hz, what is the most the actual frequency being measured could differ from the reading? 146.52 Hz 10 Hz 146.52 kHz 1465.20 Hz E4B07 How much power is being absorbed by the load when a directional power meter connected between a transmitter and a terminating load reads 100 watts forward power and 25 watts reflected power? 100 watts 125 watts 25 watts 75 watts E4B08 Which of the following is good practice when using an oscilloscope probe? Keep the ground connection of the probe as short as possible Never use a high impedance probe to measure a low impedance circuit Never use a DC-coupled probe to measure an AC circuit All of these choices are correct E4B09 Which of the following is a characteristic of a good DC voltmeter? High reluctance input Low reluctance input High impedance input Low impedance input E4B10 What is indicated if the current reading on an RF ammeter placed in series with the antenna feedline of a transmitter increases as the transmitter is tuned to resonance? There is possibly a short to ground in the feedline The transmitter is not properly neutralized There is an impedance mismatch between the antenna and feedline There is more power going into the antenna E4B11 Which of the following describes a method to measure intermodulation distortion in an SSB transmitter? Modulate the transmitter with two non-harmonically related radio frequencies and observe the RF output with a spectrum analyzer Modulate the transmitter with two non-harmonically related audio frequencies and observe the RF output with a spectrum analyzer Modulate the transmitter with two harmonically related audio frequencies and observe the RF output with a peak reading wattmeter Modulate the transmitter with two harmonically related audio frequencies and observe the RF output with a logic analyzer E4B12 How should a portable SWR analyzer be connected when measuring antenna resonance and feedpoint impedance? Loosely couple the analyzer near the antenna base Connect the analyzer via a high-impedance transformer to the antenna Connect the antenna and a dummy load to the analyzer Connect the antenna feed line directly to the analyzer's connector E4B13 What is the significance of voltmeter sensitivity expressed in ohms per volt? The full scale reading of the voltmeter multiplied by its ohms per volt rating will provide the input impedance of the voltmeter When used as a galvanometer, the reading in volts multiplied by the ohms/volt will determine the power drawn by the device under test When used as an ohmmeter, the reading in ohms divided by the ohms/volt will determine the voltage applied to the circuit When used as an ammeter, the full scale reading in amps divided by ohms/volt will determine the size of shunt needed E4B14 How is the compensation of an oscilloscope probe typically adjusted? A square wave is observed and the probe is adjusted until the horizontal portions of the displayed wave is as nearly flat as possible A high frequency sine wave is observed, and the probe is adjusted for maximum amplitude A frequency standard is observed, and the probe is adjusted until the deflection time is accurate A DC voltage standard is observed, and the probe is adjusted until the displayed voltage is accurate E4B15 What happens if a dip-meter is too tightly coupled to a tuned circuit being checked? Harmonics are generated A less accurate reading results Cross modulation occurs Intermodulation distortion occurs E4B16 Which of these factors limits the accuracy of a D'Arsonval-type meter? Its magnetic flux density Coil impedance Deflection rate Electromagnet current E4B17 Which of the following can be used as a relative measurement of the Q for a series-tuned circuit? The inductance to capacitance ratio The frequency shift The bandwidth of the circuit's frequency response The resonant frequency of the circuit E4C01 What is the effect of excessive phase noise in the local oscillator section of a receiver? It limits the receiver ability to receive strong signals It reduces the receiver sensitivity It decreases the receiver third-order intermodulation distortion dynamic range It can cause strong signals on nearby frequencies to interfere with reception of weak signals E4C02 Which of the following is the result of the capture effect in an FM receiver? All signals on a frequency are demodulated None of the signals could be heard The strongest signal received is the only demodulated signal The weakest signal received is the only demodulated signal E4C03 What is the term for the blocking of one FM phone signal by another, stronger FM phone signal? Desensitization Cross-modulation interference Capture effect Frequency discrimination E4C04 What is meant by the noise floor of a receiver? The minimum level of noise at the audio output when the RF gain is turned all the way down The equivalent phase noise power generated by the local oscillator The minimum level of noise that will overload the RF amplifier stage The equivalent input noise power when the antenna is replaced with a matched dummy load E4C05 What does a value of -174 dBm/Hz represent with regard to the noise floor of a receiver? The minimum detectable signal as a function of receive frequency The theoretical noise at the input of a perfect receiver at room temperature The noise figure of a 1 Hz bandwidth receiver The galactic noise contribution to minimum detectable signal E4C06 The thermal noise value of a receiver is -174 dBm/Hz. What is the theoretically best minimum detectable signal for a 400 Hz bandwidth receiver? 174 dBm -164 dBm -155 dBm -148 dBm E4C07 What does the MDS of a receiver represent? The meter display sensitivity The minimum discernible signal The multiplex distortion stability The maximum detectable spectrum E4C08 How might lowering the noise figure affect receiver performance? It would reduce the signal to noise ratio It would increase signal to noise ratio It would reduce bandwidth It would increase bandwidth E4C09 Which of the following is most likely to be the limiting condition for sensitivity in a modern communications receiver operating at 14 MHz? The noise figure of the RF amplifier Mixer noise Conversion noise Atmospheric noise E4C10 Which of the following is a desirable amount of selectivity for an amateur RTTY HF receiver? 100 Hz 300 Hz 6000 Hz 2400 Hz E4C11 Which of the following is a desirable amount of selectivity for an amateur single-sideband phone receiver? 1 kHz 2.4 kHz 4.2 kHz 4.8 kHz E4C12 What is an undesirable effect of using too wide a filter bandwidth in the IF section of a receiver? Output-offset overshoot Filter ringing Thermal-noise distortion Undesired signals may be heard E4C13 How does a narrow band roofing filter affect receiver performance? It improves sensitivity by reducing front end noise It improves intelligibility by using low Q circuitry to reduce ringing It improves dynamic range by keeping strong signals near the receive frequency out of the IF stages All of these choice are correct E4C14 Which of these choices is a desirable amount of selectivity for an amateur VHF FM receiver? 1 kHz 2.4 kHz 4.2 kHz 15 kHz E4C15 What is the primary source of noise that can be heard from an HF-band receiver with an antenna connected? Detector noise Induction motor noise Receiver front-end noise Atmospheric noise E4D01 What is meant by the blocking dynamic range of a receiver? The difference in dB between the level of an incoming signal which will cause 1 dB of gain compression, and the level of the noise floor The minimum difference in dB between the levels of two FM signals which will cause one signal to block the other The difference in dB between the noise floor and the third order intercept point The minimum difference in dB between two signals which produce third order intermodulation products greater than the noise floor E4D02 Which of the following describes two types of problems caused by poor dynamic range in a communications receiver? Cross modulation of the desired signal and desensitization from strong adjacent signals Oscillator instability requiring frequent retuning, and loss of ability to recover the opposite sideband, should it be transmitted Cross modulation of the desired signal and insufficient audio power to operate the speaker Oscillator instability and severe audio distortion of all but the strongest received signals E4D03 How can intermodulation interference between two repeaters occur? When the repeaters are in close proximity and the signals cause feedback in one or both transmitter final amplifiers When the repeaters are in close proximity and the signals mix in one or both transmitter final amplifiers When the signals from the transmitters are reflected out of phase from airplanes passing overhead When the signals from the transmitters are reflected in phase from airplanes passing overhead E4D04 What is an effective way to reduce or eliminate intermodulation interference between two repeater transmitters operating in close proximity to one another? By installing a band-pass filter in the feed line between the transmitter and receiver By installing a properly terminated circulator at the output of the transmitter By using a Class C final amplifier By using a Class D final amplifier E4D05 If a receiver tuned to 146.70 MHz receives an intermodulation-product signal whenever a nearby transmitter transmits on 146.52 MHz, what are the two most likely frequencies for the other interfering signal? 146.34 MHz and 146.61 MHz 146.88 MHz and 146.34 MHz 146.10 MHz and 147.30 MHz 73.35 MHz and 239.40 MHz E4D06 If the signals of two transmitters mix together in one or both of their final amplifiers, and unwanted signals at the sum and difference frequencies of the original signals are generated, what is this called? Amplifier desensitization Neutralization Adjacent channel interference Intermodulation interference E4D07 Which of the following describes the most significant effect of an off-frequency signal when it is causing cross-modulation interference to a desired signal? A large increase in background noise A reduction in apparent signal strength The desired signal can no longer be heard The off-frequency unwanted signal is heard in addition to the desired signal E4D08 What causes intermodulation in an electronic circuit? Too little gain Lack of neutralization Nonlinear circuits or devices Positive feedback E4D09 What is the purpose of the preselector in a communications receiver? To store often-used frequencies To provide a range of AGC time constants To improve rejection of unwanted signals To allow selection of the optimum RF amplifier device E4D10 What does a third-order intercept level of 40 dBm mean with respect to receiver performance? Signals less than 40 dBm will not generate audible third-order intermodulation products The receiver can tolerate signals up to 40 dB above the noise floor without producing third-order intermodulation products A pair of 40 dBm signals will theoretically generate the same output on the third order intermodulation frequency as on the input frequency A pair of 1 mW input signals will produce a third-order intermodulation product which is 40 dB stronger than the input signal E4D11 Why are third-order intermodulation products within a receiver of particular interest compared to other products? The third-order product of two signals which are in the band is itself likely to be within the band The third-order intercept is much higher than other orders Third-order products are an indication of poor image rejection Third-order intermodulation produces three products for every input signal E4D12 What is the term for the reduction in receiver sensitivity caused by a strong signal near the received frequency? Desensitization Quieting Cross-modulation interference Squelch gain rollback E4D13 Which of the following can cause receiver desensitization? Audio gain adjusted too low Strong adjacent-channel signals Audio bias adjusted too high Squelch gain adjusted too low E4D14 Which of the following is a way to reduce the likelihood of receiver desensitization? Decrease the RF bandwidth of the receiver Raise the receiver IF frequency Increase the receiver front end gain Switch from fast AGC to slow AGC E4E01 Which of the following types of receiver noise can often be reduced by use of a receiver noise blanker? Ignition Noise Broadband “white†noise Heterodyne interference All of these choices are correct E4E02 Which of the following types of receiver noise can often be reduced with a DSP noise filter? Broadband “white†noise Ignition noise Power line noise All of these choices are correct E4E03 Which of the following signals might a receiver noise blanker be able to remove from desired signals? Signals which are constant at all IF levels Signals which appear correlated across a wide bandwidth Signals which appear at one IF but not another Signals which have a sharply peaked frequency distribution E4E04 How can conducted and radiated noise caused by an automobile alternator be suppressed? By installing filter capacitors in series with the DC power lead and by installing a blocking capacitor in the field lead By connecting the radio to the battery by the longest possible path and installing a blocking capacitor in both leads By installing a high-pass filter in series with the radio's power lead and a low-pass filter in parallel with the field lead By connecting the radio's power leads directly to the battery and by installing coaxial capacitors in line with the alternator leads E4E05 How can noise from an electric motor be suppressed? By installing a ferrite bead on the AC line used to power the motor By installing a brute-force AC-line filter in series with the motor leads By installing a bypass capacitor in series with the motor leads By using a ground-fault current interrupter in the circuit used to power the motor E4E06 What is a major cause of atmospheric static? Solar radio frequency emissions Thunderstorms Geomagnetic storms Meteor showers E4E07 How can you determine if line-noise interference is being generated within your home? By checking the power-line voltage with a time-domain reflectometer By observing the AC power line waveform with an oscilloscope By turning off the AC power line main circuit breaker and listening on a battery-operated radio By observing the AC power line voltage with a spectrum analyzer E4E08 What type of signal is picked up by electrical wiring near a radio transmitter? A common-mode signal at the frequency of the radio transmitter An electrical-sparking signal A differential-mode signal at the AC power line frequency Harmonics of the AC power line frequency E4E09 What undesirable effect can occur when using an IF type noise blanker? Received audio in the speech range might have an echo effect The audio frequency bandwidth of the received signal might be compressed Nearby signals may appear to be excessively wide even if they meet emission standards FM signals can no longer be demodulated E4E10 What is a common characteristic of interference caused by a "touch controlled" electrical device? The interfering signal sounds like AC hum on an AM receiver or a carrier modulated by 60 Hz FM on a SSB or CW receiver The interfering signal may drift slowly across the HF spectrum The interfering signal can be several kHz in width and usually repeats at regular intervals across a HF band All of these answers are correct E4E11 What is the most likely cause if you are hearing combinations of local AM broadcast signals inside one or more of the MF or HF ham bands? The broadcast station is transmitting an over-modulated signal Nearby corroded metal joints are mixing and re-radiating the BC signals You are receiving sky-wave signals from a distant station Your station receiver IF amplifier stage is defective E4E12 What is one disadvantage of using some automatic DSP notch-filters when attempting to copy CW signals? The DSP filter can remove the desired signal at the same time as it removes interfering signals Any nearby signal passing through the DSP system will always overwhelm the desired signal Received CW signals will appear to be modulated at the DSP clock frequency Ringing in the DSP filter will completely remove the spaces between the CW characters E4E13 What might be the cause of a loud "roaring" or "buzzing" AC line type of interference that comes and goes at intervals? Arcing contacts in a thermostatically controlled device A defective doorbell or doorbell transformer inside a nearby residence A malfunctioning illuminated advertising display All of these answers are correct E4E14 What is one type of electrical interference that might be caused by the operation of a nearby personal computer? A loud AC hum in the audio output of your station receiver A clicking noise at intervals of a few seconds The appearance of unstable modulated or unmodulated signals at specific frequencies A whining type noise that continually pulses off and on |
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