Amateur Extra E4C Chapter 7

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