E4C01:

What is an effect of excessive phase noise in a receiver's local oscillator?

1. It limits the receiver's ability to receive strong signals
2. It can affect the receiver's frequency calibration
3. It decreases receiver third-order intercept point
4. It can combine with strong signals on nearby frequencies to generate interference

E4C02:

Which of the following receiver circuits can be effective in eliminating interference from strong out-of-band signals?

1. A front-end filter or pre-selector
2. A narrow IF filter
3. A notch filter
4. A properly adjusted product detector

E4C03:

What is the term for the suppression in an FM receiver of one signal by another stronger signal on the same frequency?

1. Desensitization
2. Cross-modulation interference
3. Capture effect
4. Frequency discrimination

E4C04:

What is the noise figure of a receiver?

1. The ratio of atmospheric noise to phase noise
2. The ratio of the noise bandwidth in hertz to the theoretical bandwidth of a resistive network
3. The ratio of thermal noise to atmospheric noise
4. 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?

1. The minimum detectable signal as a function of receive frequency
2. The theoretical noise in a 1 Hz bandwidth at the input of a perfect receiver at room temperature
3. The noise figure of a 1 Hz bandwidth receiver
4. 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?

1. -174 dBm
2. -164 dBm
3. -155 dBm
4. -148 dBm

E4C07:

What does the MDS of a receiver represent?

1. The meter display sensitivity
2. The minimum discernible signal
3. The multiplex distortion stability
4. The maximum detectable spectrum

E4C08:

An SDR receiver is overloaded when input signals exceed what level?

1. One-half the maximum sample rate
2. One-half the maximum sampling buffer size
3. The maximum count value of the analog-to-digital converter
4. 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 communications receiver?

1. Fewer components in the receiver
2. Reduced drift
3. Easier for front-end circuitry to eliminate image responses
4. Improved receiver noise figure

E4C10:

What is an advantage of having a variety of receiver IF bandwidths from which to select?

1. The noise figure of the RF amplifier can be adjusted to match the modulation type, thus increasing receiver sensitivity
2. Receiver power consumption can be reduced when wider bandwidth is not required
3. Receive bandwidth can be set to match the modulation bandwidth, maximizing signal-to-noise ratio and minimizing interference
4. 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?

1. The attenuator has a low-pass filter to increase the strength of lower frequency signals
2. The attenuator has a noise filter to suppress interference
3. Signals are attenuated separately from the noise
4. 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?

1. CPU register width in bits
2. Anti-aliasing input filter bandwidth
3. RAM speed used for data storage
4. Analog-to-digital converter sample width in bits

E4C13:

How does a narrow-band roofing filter affect receiver performance?

1. It improves sensitivity by reducing front end noise
2. It improves intelligibility by using low Q circuitry to reduce ringing
3. It improves dynamic range by attenuating strong signals near the receive frequency
4. All these choices are correct

E4C14:

What transmit frequency might generate an image response signal in a receiver tuned to 14.300 MHz and that uses a 455 kHz IF frequency?

1. 13.845 MHz
2. 14.755 MHz
3. 14.445 MHz
4. 15.210 MHz

E4C15:

What is reciprocal mixing?

1. Two out-of-band signals mixing to generate an in-band spurious signal
2. In-phase signals cancelling in a mixer resulting in loss of receiver sensitivity
3. Two digital signals combining from alternate time slots
4. Local oscillator phase noise mixing with adjacent strong signals to create interference to desired signals