Which of the following limits the highest frequency signal that can be accurately displayed on a digital oscilloscope?
ASampling rate of the analog-to-digital converter
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Subelement E4 question review
All 63 official questions with the exact winning phrase marked.
Which of the following parameters does a spectrum analyzer display on the vertical and horizontal axes?
BSignal amplitude and frequency
Which of the following test instruments is used to display spurious signals and/or intermodulation distortion products generated by an SSB transmitter?
BSpectrum analyzer
How is compensation of an oscilloscope probe performed?
AA square wave is displayed, and the probe is adjusted until the horizontal portions of the displayed wave are as nearly flat as possible
What is the purpose of using a prescaler with a frequency counter?
DReduce the signal frequency to within the counter's operating range
What is the effect of aliasing on a digital oscilloscope when displaying a waveform?
AA false, jittery low-frequency version of the waveform is displayed
Which of the following is an advantage of using an antenna analyzer compared to an SWR bridge?
BAntenna analyzers compute SWR and impedance automatically
Which of the following is used to measure SWR?
DAll these choices are correct
Which of the following is good practice when using an oscilloscope probe?
AMinimize the length of the probe's ground connection
Which trigger mode is most effective when using an oscilloscope to measure a linear power supply’s output ripple?
DLine
Which of the following can be measured with an antenna analyzer?
DAll these choices are correct
Which of the following factors most affects the accuracy of a frequency counter?
BTime base accuracy
What is the significance of voltmeter sensitivity expressed in ohms per volt?
AThe full scale reading of the voltmeter multiplied by its ohms per volt rating is the input impedance of the voltmeter
Which S parameter is equivalent to forward gain?
CS21
Which S parameter represents input port return loss or reflection coefficient (equivalent to VSWR)?
AS11
What three test loads are used to calibrate an RF vector network analyzer?
BShort circuit, open circuit, and 50 ohms
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?
D75 watts
What do the subscripts of S parameters represent?
AThe port or ports at which measurements are made
Which of the following can be used to determine the Q of a series-tuned circuit?
CThe bandwidth of the circuit's frequency response
Which of the following can be measured by a two-port vector network analyzer?
BFilter frequency response
Which of the following methods measures intermodulation distortion in an SSB transmitter?
BModulate the transmitter using two AF signals having non-harmonically related frequencies and observe the RF output with a spectrum analyzer
Which of the following can be measured with a vector network analyzer?
DAll these choices are correct
What is an effect of excessive phase noise in an SDR receiver’s master clock oscillator?
DIt can combine with strong signals on nearby frequencies to generate interference
Which of the following receiver circuits can be effective in eliminating interference from strong out-of-band signals?
AA front-end filter or preselector
What is the term for the suppression in an FM receiver of one signal by another stronger signal on the same frequency?
CCapture effect
What is the noise figure of a receiver?
DThe ratio in dB of the noise generated by the receiver to the theoretical minimum noise
What does a receiver noise floor of -174 dBm represent?
BThe theoretical noise in a 1 Hz bandwidth at the input of a perfect receiver at room temperature
How much does increasing a receiver’s bandwidth from 50 Hz to 1,000 Hz increase the receiver’s noise floor?
D13 dB
What does the MDS of a receiver represent?
BThe minimum discernible signal
An SDR receiver is overloaded when input signals exceed what level?
DThe reference voltage of the analog-to-digital converter
Which of the following choices is a good reason for selecting a high IF for a superheterodyne HF or VHF communications receiver?
CEasier for front-end circuitry to eliminate image responses
What is an advantage of having a variety of receiver bandwidths from which to select?
CReceive bandwidth can be set to match the modulation bandwidth, maximizing signal-to-noise ratio and minimizing interference
Why does input attenuation reduce receiver overload on the lower frequency HF bands with little or no impact on signal-to-noise ratio?
DAtmospheric noise is generally greater than internally generated noise even after attenuation
How does a narrow-band roofing filter affect receiver performance?
CIt improves blocking dynamic range by attenuating strong signals near the receive frequency
What is reciprocal mixing?
DLocal oscillator phase noise mixing with adjacent strong signals to create interference to desired signals
What is the purpose of the receiver IF Shift control?
CTo reduce interference from stations transmitting on adjacent frequencies
What is meant by the blocking dynamic range of a receiver?
AThe difference in dB between the noise floor and the level of an incoming signal that will cause 1 dB of gain compression
Which of the following describes problems caused by poor dynamic range in a receiver?
ASpurious signals caused by cross modulation and desensitization from strong adjacent signals
What creates intermodulation interference between two repeaters in close proximity?
BThe output signals mix in the final amplifier of one or both transmitters
Which of the following is used to reduce or eliminate intermodulation interference in a repeater caused by a nearby transmitter?
BA properly terminated circulator at the output of the repeater’s transmitter
What is the term for the reduction in receiver sensitivity caused by a strong signal near the received frequency?
CDesensitization
Which of the following reduces the likelihood of receiver desensitization?
AInsert attenuation before the first RF stage
What causes intermodulation in an electronic circuit?
CNonlinear circuits or devices
What is the purpose of the preselector in a communications receiver?
CTo increase the rejection of signals outside the band being received
What does a third-order intercept level of 40 dBm mean with respect to receiver performance?
CA pair of 40 dBm input signals will theoretically generate a third-order intermodulation product that has the same output amplitude as either of the input signals
Why are odd-order intermodulation products, created within a receiver, of particular interest compared to other products?
AOdd-order products of two signals in the band being received are also likely to be within the band
What is the link margin in a system with a transmit power level of 10 W (+40 dBm), a system antenna gain of 10 dBi, a cable loss of 3 dB, a path loss of 136 dB, a receiver minimum discernable signal of -103 dBm, and a required signal-to-noise ratio of 6 dB?
C+8dB
What is the received signal level with a transmit power of 10 W (+40 dBm), a transmit antenna gain of 6 dBi, a receive antenna gain of 3 dBi, and a path loss of 100 dB?
A-51 dBm
What power level does a receiver minimum discernible signal of -100 dBm represent?
D0.1 picowatts
What problem can occur when using an automatic notch filter (ANF) to remove interfering carriers while receiving CW signals?
ARemoval of the CW signal as well as the interfering carrier
Which of the following types of noise can often be reduced by a digital noise reduction?
DAll these choices are correct
Which of the following types of noise are removed by a noise blanker?
BImpulse noise
How can conducted noise from an automobile battery charging system be suppressed?
DBy installing ferrite chokes on the charging system leads
What is used to suppress radio frequency interference from a line-driven AC motor?
BA brute-force AC-line filter in series with the motor’s power leads
What type of electrical interference can be caused by computer network equipment?
CThe appearance of unstable modulated or unmodulated signals at specific frequencies
Which of the following can cause shielded cables to radiate or receive interference?
BCommon-mode currents on the shield and conductors
What current flows equally on all conductors of an unshielded multiconductor cable?
BCommon-mode current
What undesirable effect can occur when using a noise blanker?
CStrong signals may be distorted and appear to cause spurious emissions
Which of the following can create intermittent loud roaring or buzzing AC line interference?
DAll these choices are correct
What could be the cause of local AM broadcast band signals combining to generate spurious signals on the MF or HF bands?
BNearby corroded metal connections are mixing and reradiating the broadcast signals
What causes interference received as a series of carriers at regular intervals across a wide frequency range?
ASwitch-mode power supplies
Where should a station AC surge protector be installed?
COn the single point ground panel
What is the purpose of a single point ground panel?
DEnsure all lightning protectors activate at the same time