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WorksheetsAmateur Extra E4C Chapter 7
Total questions: 15
Worksheet time: 14mins
E4C01: What is an effect of excessive phase noise in a receiver's local oscillator?
It limits the receiver's ability to receive strong signals
It can affect the receiver's frequency calibration
It decreases receiver third-order intercept point
It can combine with strong signals on nearby frequencies to generate interference
E402. Which of the following receiver circuits can be effective in eliminating interference from strong out-of-band signals?
A front-end filter or pre-selector
A narrow IF filter
A notch filter
A properly adjusted product detector
E4C03. Which is the term for the suppression in an FM receiver of one signal by another stronger signal on the same frequency?
Desensitization
Cross-modulation interference
Capture effect
Frequency discrimination
E4C04. What is the noise figure of a receiver?
The ratio of atmospheric noise to phase noise
The ratio of atmospheric noise to phase noise
The ration of thermal noise to atmospheric noise
The ratio in dB of the noise generated by the receiver to the theoretical minimum noise
E4C05. What does a receiver noise floor of ~174 dBm represent?
The minimum detectable signal as a function of receive frequency
The theoretical noise in a 1 Hz bandwidth 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. A CW receiver with the AGC off has an equivalent input noise power density of ~174 dBm/Hz. What would be the level of an unmodulated carrier input to this receiver that would yield an audio output SNR of 0 dB in a 400 Hz noise bandwidth?
~174 dBm
~165 dBm
~155 dBm
~148 dBm
E4C07. What does the MDS of receiver represent?
The meter display sensitivity
The minimum discernible signal
The multiplex distortion stability
The maximum detectable spectrum
E4C08. An SDR receiver is overloaded when input signals exceed what level?
One-half the maximum sample rate
One-half the maximum sampling buffer size
The maximum count value of the analog-to-digital converter
The reference voltage of the analog-to-digital converter
E4C09. Which of the following choices is a good reason for selecting a high frequency for the design of the IF in a superheterodyne HF or VHF communication receiver?
Fewer components in the receiver
Reduced drift
Easier for front-end circuitry to eliminate image responses
Improved receiver noise figure
E4C10. What is an advantage of having a variety of receiver IF bandwidths from which to select?
The noise figure of the RF amplifier can be adjusted to match the modulation type, thus increasing receiver sensitivity
Receiver power consumption can be reduced when wider bandwidth is not required
Receive bandwidth can be set to match the modulation bandwidth, maximizing signal-to-noise ratio and minimizing interference
Multiple frequencies can be received simultaneously if desired
E4C11. Why can an attenuator be used to reduce receiver overload on the lower frequency HF bands with little or no impact on signal-to-noise ratio?
The attenuator has a low-pass filter to increase the strength of lower frequency signals
The attenuator has a noise filter to suppress interference
Signals are attenuated separately from the noise
Atmospheric noise is generally greater than internally generated noise even after attenuation
E4C12. Which of the following has the largest effect on an SDR receiver's dynamic range?
CPU register width in bits
Anti-aliasing input filter bandwidth
RAM speed used for data storage
Analog-to-digital converter sample width in bits
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 attenuating strong signals near the receive frequency
All these choices are correct.
E4C14. What transmit frequency might generate an image response signal in a receiver tuned to 14.3000 MHz and that uses a 455 kHz IF frequency?
13.845 MHz
14.755 MHz
14.445 MHz
15.210 MHz
E4C15. What is reciprocal mixing?
Two out-of-band signals mixing to generate an in-band spurious signal
In-phase signals cancelling in a mixer resulting in loss of receiver sensitivity
Two digital signals combining from alternate time slots
Local oscillator phase noise mixing with adjacent strong signals to create interference to designed signals
