E4E: Noise suppression: system noise; electrical appliance noise; line noise; locating noise sources; DSP noise reduction; noise blankers
E4E01:
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:
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:
Which of the following signals might a receiver noise blanker be able to remove from desired signals?
Signals which appear correlated 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:
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 connecting the radio to the battery by the longest possible path and installing 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:
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 ferrite bead on the AC line used to power the motor
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:
What is a major cause of atmospheric static?
Thunderstorms
Solar radio frequency emissions
Geomagnetic storms
Meteor showers
E4E07:
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:
What type of signal is picked up by electrical wiring near a radio transmitter?
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:
What undesirable effect can occur when using an IF type 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:
What is a common characteristic of interference caused by a "touch controlled" electrical device?
All of these answers are correct
The interfering signal sounds like AC hum on an AM receiver or a carrier modulated by 60 Hz FM 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:
What is the most likely cause if you are hearing combinations of local AM broadcast signals inside one or more of the MF or HF ham bands?
Nearby corroded metal joints are mixing and re-radiating the BC 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:
What is one disadvantage of using some 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 always 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:
What might be the cause of a loud "roaring" or "buzzing" AC line type of interference that comes and goes at intervals?
All of these answers 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:
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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