Noise suppression: system noise; electrical appliance noise; line noise; locating noise sources; DSP noise reduction; noise blankers
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E4E-2012: Noise suppression: system noise; electrical appliance noise; line noise; locating noise sources; DSP noise reduction; noise blankers

E4E01-2012: Which of the following types of receiver noise can often be reduced by use of a receiver noise blanker?

Ignition noise

Broadband white noise

Heterodyne interference

All of these choices are correct



E4E02-2012: Which of the following types of receiver noise can often be reduced with a DSP noise filter?

All of these choices are correct

Broadband white noise

Ignition noise

Power line noise



E4E03-2012: Which of the following signals might a receiver noise blanker be able to remove from desired signals?

Signals which appear across a wide bandwidth

Signals which are constant at all IF levels

Signals which appear at one IF but not another

Signals which have a sharply peaked frequency distribution



E4E04-2012: How can conducted and radiated noise caused by an automobile alternator be suppressed?

By connecting the radio's power leads directly to the battery and by installing coaxial capacitors in line with the alternator leads

By installing filter capacitors in series with the DC power lead and by installing a blocking capacitor in the field lead

By installing a noise suppression resistor and a blocking capacitor in both leads

By installing a high-pass filter in series with the radio's power lead and a low-pass filter in parallel with the field lead



E4E05-2012: How can noise from an electric motor be suppressed?

By installing a brute-force AC-line filter in series with the motor leads

By installing a high pass filter in series with the motor's power leads

By installing a bypass capacitor in series with the motor leads

By using a ground-fault current interrupter in the circuit used to power the motor



E4E06-2012: What is a major cause of atmospheric static?

Thunderstorms

Solar radio frequency emissions

Geomagnetic storms

Meteor showers



E4E07-2012: How can you determine if line noise interference is being generated within your home?

By turning off the AC power line main circuit breaker and listening on a battery operated radio

By checking the power line voltage with a time domain reflectometer

By observing the AC power line waveform with an oscilloscope

By observing the AC power line voltage with a spectrum analyzer



E4E08-2012: What type of signal is picked up by electrical wiring near a radio antenna?

A common-mode signal at the frequency of the radio transmitter

An electrical-sparking signal

A differential-mode signal at the AC power line frequency

Harmonics of the AC power line frequency



E4E09-2012: What undesirable effect can occur when using an IF noise blanker?

Nearby signals may appear to be excessively wide even if they meet emission standards

Received audio in the speech range might have an echo effect

The audio frequency bandwidth of the received signal might be compressed

FM signals can no longer be demodulated



E4E10-2012: What is a common characteristic of interference caused by a touch controlled electrical device?

All of these choices are correct

The interfering signal sounds like AC hum on an AM receiver or a carrier modulated by 60 Hz hum on a SSB or CW receiver

The interfering signal may drift slowly across the HF spectrum

The interfering signal can be several kHz in width and usually repeats at regular intervals across a HF band



E4E11-2012: Which of the following is the most likely cause if you are hearing combinations of local AM broadcast signals within one or more of the MF or HF ham bands?

Nearby corroded metal joints are mixing and re-radiating the broadcast signals

The broadcast station is transmitting an over-modulated signal

You are receiving sky wave signals from a distant station

Your station receiver IF amplifier stage is defective



E4E12-2012: What is one disadvantage of using some types of automatic DSP notch-filters when attempting to copy CW signals?

The DSP filter can remove the desired signal at the same time as it removes interfering signals

Any nearby signal passing through the DSP system will overwhelm the desired signal

Received CW signals will appear to be modulated at the DSP clock frequency

Ringing in the DSP filter will completely remove the spaces between the CW characters



E4E13-2012: What might be the cause of a loud roaring or buzzing AC line interference that comes and goes at intervals?

All of these choices are correct

Arcing contacts in a thermostatically controlled device

A defective doorbell or doorbell transformer inside a nearby residence

A malfunctioning illuminated advertising display



E4E14-2012: What is one type of electrical interference that might be caused by the operation of a nearby personal computer?

The appearance of unstable modulated or unmodulated signals at specific frequencies

A loud AC hum in the audio output of your station receiver

A clicking noise at intervals of a few seconds

A whining type noise that continually pulses off and on





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E4D-2012: Receiver performance characteristics, blocking dynamic range, intermodulation and cross-modulation interference; 3rd order intercept; desensitization; preselection
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