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logseq/bak/pages/E4C/2025-05-01T20_36_29.890Z.Desktop.md
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E4C Receiver performance: phase noise, noise floor, image rejection, minimum detectable signal (MDS), increasing signal-to-noise ratio and dynamic range, noise figure, reciprocal mixing; selectivity; SDR non-linearity; use of attenuators at low frequencies
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- [[E4C01]] (D)
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What is an effect of excessive phase noise in an SDR receiver’s master clock oscillator?
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- [[A.]] It limits the receiver’s ability to receive strong signals
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- [[B.]] It can affect the receiver’s frequency calibration
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- [[C.]] It decreases the receiver’s third-order intercept point
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- [[D.]] It can combine with strong signals on nearby frequencies to generate interference
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--
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- [[E4C02]] (A)
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Which of the following receiver circuits can be effective in eliminating interference from strong out-of-band signals?
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- [[A.]] A front-end filter or preselector
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- [[B.]] A narrow IF filter
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- [[C.]] A notch filter
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- [[D.]] A properly adjusted product detector
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--
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- [[E4C03]] (C)
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What is the term for the suppression in an FM receiver of one signal by another stronger signal on the same frequency?
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- [[A.]] Desensitization
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- [[B.]] Cross-modulation interference
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- [[C.]] Capture effect
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- [[D.]] Frequency discrimination
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--
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- [[E4C04]] (D)
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What is the noise figure of a receiver?
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- [[A.]] The ratio of atmospheric noise to phase noise
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- [[B.]] The ratio of the noise bandwidth in hertz to the theoretical bandwidth of a resistive network
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- [[C.]] The ratio in dB of the noise generated in the receiver to atmospheric noise
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- [[D.]] The ratio in dB of the noise generated by the receiver to the theoretical minimum noise
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--
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- [[E4C05]] (B)
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What does a receiver noise floor of -174 dBm represent?
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- [[A.]] The receiver noise is 6 dB above the theoretical minimum
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- [[B.]] The theoretical noise in a 1 Hz bandwidth at the input of a perfect receiver at room temperature
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- [[C.]] The noise figure of a 1 Hz bandwidth receiver
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- [[D.]] The receiver noise is 3 dB above theoretical minimum
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--
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- [[E4C06]] (D)
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How much does increasing a receiver’s bandwidth from 50 Hz to 1,000 Hz increase the receiver’s noise floor?
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- [[A.]] 3 dB
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- [[B.]] 5 dB
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- [[C.]] 10 dB
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- [[D.]] 13 dB
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--
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- [[E4C07]] (B)
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What does the MDS of a receiver represent?
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- [[A.]] The meter display sensitivity
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- [[B.]] The minimum discernible signal
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- [[C.]] The modulation distortion specification
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- [[D.]] The maximum detectable spectrum
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--
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- [[E4C08]] (D)
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An SDR receiver is overloaded when input signals exceed what level?
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- [[A.]] One-half of the maximum sample rate
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- [[B.]] One-half of the maximum sampling buffer size
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- [[C.]] The maximum count value of the analog-to-digital converter
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- [[D.]] The reference voltage of the analog-to-digital converter
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--
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- [[E4C09]] (C)
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Which of the following choices is a good reason for selecting a high IF for a superheterodyne HF or VHF communications receiver?
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- [[A.]] Fewer components in the receiver
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- [[B.]] Reduced drift
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- [[C.]] Easier for front-end circuitry to eliminate image responses
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- [[D.]] Improved receiver noise figure
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--
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- [[E4C10]] (C)
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What is an advantage of having a variety of receiver bandwidths from which to select?
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- [[A.]] The noise figure of the RF amplifier can be adjusted to match the modulation type, thus increasing receiver sensitivity
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- [[B.]] Receiver power consumption can be reduced when wider bandwidth is not required
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- [[C.]] Receive bandwidth can be set to match the modulation bandwidth, maximizing signal-to-noise ratio and minimizing interference
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- [[D.]] Multiple frequencies can be received simultaneously if desired
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--
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- [[E4C11]] (D)
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Why does input attenuation reduce receiver overload on the lower frequency HF bands with little or no impact on signal-to-noise ratio?
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- [[A.]] The attenuator has a low-pass filter to increase the strength of lower frequency signals
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- [[B.]] The attenuator has a noise filter to suppress interference
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- [[C.]] Signals are attenuated separately from the noise
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- [[D.]] Atmospheric noise is generally greater than internally generated noise even after attenuation
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--
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- [[E4C12]] (C)
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How does a narrow-band roofing filter affect receiver performance?
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- [[A.]] It improves sensitivity by reducing front-end noise
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- [[B.]] It improves intelligibility by using low Q circuitry to reduce ringing
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- [[C.]] It improves blocking dynamic range by attenuating strong signals near the receive frequency
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- [[D.]] All these choices are correct
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--
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- [[E4C13]] (D)
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What is reciprocal mixing?
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- [[A.]] Two out-of-band signals mixing to generate an in-band spurious signal
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- [[B.]] In-phase signals cancelling in a mixer resulting in loss of receiver sensitivity
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- [[C.]] Two digital signals combining from alternate time slots
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- [[D.]] Local oscillator phase noise mixing with adjacent strong signals to create interference to desired signals
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--
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- [[E4C14]] (C)
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What is the purpose of the receiver IF Shift control?
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- [[A.]] To permit listening on a different frequency from the transmitting frequency
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- [[B.]] To change frequency rapidly
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- [[C.]] To reduce interference from stations transmitting on adjacent frequencies
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- [[D.]] To tune in stations slightly off frequency without changing the transmit frequency
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99
logseq/bak/pages/E4C/2025-05-01T20_36_51.622Z.Desktop.md
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99
logseq/bak/pages/E4C/2025-05-01T20_36_51.622Z.Desktop.md
Normal file
@ -0,0 +1,99 @@
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E4C Receiver performance: phase noise, noise floor, image rejection, minimum detectable signal (MDS), increasing signal-to-noise ratio and dynamic range, noise figure, reciprocal mixing; selectivity; SDR non-linearity; use of attenuators at low frequencies
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- [[E4C01]] (D)
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What is an effect of excessive phase noise in an SDR receiver’s master clock oscillator? #card
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- [[A.]] It limits the receiver’s ability to receive strong signals
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- [[B.]] It can affect the receiver’s frequency calibration
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- [[C.]] It decreases the receiver’s third-order intercept point
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- [[D.]] It can combine with strong signals on nearby frequencies to generate interference
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--
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- [[E4C02]] (A)
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Which of the following receiver circuits can be effective in eliminating interference from strong out-of-band signals? #card
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- [[A.]] A front-end filter or preselector
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- [[B.]] A narrow IF filter
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- [[C.]] A notch filter
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- [[D.]] A properly adjusted product detector
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--
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- [[E4C03]] (C)
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What is the term for the suppression in an FM receiver of one signal by another stronger signal on the same frequency? #card
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- [[A.]] Desensitization
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- [[B.]] Cross-modulation interference
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- [[C.]] Capture effect
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- [[D.]] Frequency discrimination
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--
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- [[E4C04]] (D)
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What is the noise figure of a receiver? #card
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- [[A.]] The ratio of atmospheric noise to phase noise
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- [[B.]] The ratio of the noise bandwidth in hertz to the theoretical bandwidth of a resistive network
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- [[C.]] The ratio in dB of the noise generated in the receiver to atmospheric noise
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- [[D.]] The ratio in dB of the noise generated by the receiver to the theoretical minimum noise
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--
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- [[E4C05]] (B)
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What does a receiver noise floor of -174 dBm represent? #card
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- [[A.]] The receiver noise is 6 dB above the theoretical minimum
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- [[B.]] The theoretical noise in a 1 Hz bandwidth at the input of a perfect receiver at room temperature
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- [[C.]] The noise figure of a 1 Hz bandwidth receiver
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- [[D.]] The receiver noise is 3 dB above theoretical minimum
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--
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- [[E4C06]] (D)
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How much does increasing a receiver’s bandwidth from 50 Hz to 1,000 Hz increase the receiver’s noise floor? #card
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- [[A.]] 3 dB
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- [[B.]] 5 dB
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- [[C.]] 10 dB
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- [[D.]] 13 dB
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--
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- [[E4C07]] (B)
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What does the MDS of a receiver represent? #card
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- [[A.]] The meter display sensitivity
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- [[B.]] The minimum discernible signal
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- [[C.]] The modulation distortion specification
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- [[D.]] The maximum detectable spectrum
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--
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- [[E4C08]] (D)
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An SDR receiver is overloaded when input signals exceed what level? #card
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- [[A.]] One-half of the maximum sample rate
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- [[B.]] One-half of the maximum sampling buffer size
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- [[C.]] The maximum count value of the analog-to-digital converter
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- [[D.]] The reference voltage of the analog-to-digital converter
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--
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- [[E4C09]] (C)
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Which of the following choices is a good reason for selecting a high IF for a superheterodyne HF or VHF communications receiver? #card
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- [[A.]] Fewer components in the receiver
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- [[B.]] Reduced drift
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- [[C.]] Easier for front-end circuitry to eliminate image responses
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- [[D.]] Improved receiver noise figure
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--
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- [[E4C10]] (C)
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What is an advantage of having a variety of receiver bandwidths from which to select? #card
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- [[A.]] The noise figure of the RF amplifier can be adjusted to match the modulation type, thus increasing receiver sensitivity
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- [[B.]] Receiver power consumption can be reduced when wider bandwidth is not required
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- [[C.]] Receive bandwidth can be set to match the modulation bandwidth, maximizing signal-to-noise ratio and minimizing interference
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- [[D.]] Multiple frequencies can be received simultaneously if desired
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--
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- [[E4C11]] (D)
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Why does input attenuation reduce receiver overload on the lower frequency HF bands with little or no impact on signal-to-noise ratio? #card
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- [[A.]] The attenuator has a low-pass filter to increase the strength of lower frequency signals
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- [[B.]] The attenuator has a noise filter to suppress interference
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- [[C.]] Signals are attenuated separately from the noise
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- [[D.]] Atmospheric noise is generally greater than internally generated noise even after attenuation
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--
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- [[E4C12]] (C)
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How does a narrow-band roofing filter affect receiver performance? #card
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- [[A.]] It improves sensitivity by reducing front-end noise
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- [[B.]] It improves intelligibility by using low Q circuitry to reduce ringing
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- [[C.]] It improves blocking dynamic range by attenuating strong signals near the receive frequency
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- [[D.]] All these choices are correct
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--
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- [[E4C13]] (D)
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What is reciprocal mixing? #card
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- [[A.]] Two out-of-band signals mixing to generate an in-band spurious signal
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- [[B.]] In-phase signals cancelling in a mixer resulting in loss of receiver sensitivity
|
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- [[C.]] Two digital signals combining from alternate time slots
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- [[D.]] Local oscillator phase noise mixing with adjacent strong signals to create interference to desired signals
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--
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- [[E4C14]] (C)
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What is the purpose of the receiver IF Shift control? #card
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- [[A.]] To permit listening on a different frequency from the transmitting frequency
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- [[B.]] To change frequency rapidly
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- [[C.]] To reduce interference from stations transmitting on adjacent frequencies
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- [[D.]] To tune in stations slightly off frequency without changing the transmit frequency
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