E4E Noise and interference: external RF interference; electrical and computer noise; line noise; DSP filtering and noise reduction; common-mode current; surge protectors; single point ground panel
- E4E01 (A)
What problem can occur when using an automatic notch filter (ANF) to remove interfering carriers while receiving CW signals? #card
- A. Removal of the CW signal as well as the interfering carrier
- B. Any nearby signal passing through the DSP system will overwhelm the desired signal
- C. Excessive ringing
- D. All these choices are correct
- E4E02 (D)
Which of the following types of noise can often be reduced by a digital noise reduction? #card
- A. Broadband white noise
- B. Ignition noise
- C. Power line noise
- D. All these choices are correct
- E4E03 (B)
Which of the following types of noise are removed by a noise blanker? #card
- A. Broadband white noise
- B. Impulse noise
- C. Hum and buzz
- D. All these choices are correct
- E4E04 (D)
How can conducted noise from an automobile battery charging system be suppressed? #card
- A. By installing filter capacitors in series with the alternator leads
- B. By installing a noise suppression resistor and a blocking capacitor at the battery
- C. By installing a high-pass filter in series with the radio’s power lead and a low-pass filter in parallel with the antenna feed line
- D. By installing ferrite chokes on the charging system leads
- E4E05 (B)
What is used to suppress radio frequency interference from a line-driven AC motor? #card
- A. A high-pass filter in series with the motor’s power leads
- B. A brute-force AC-line filter in series with the motor’s power leads
- C. A bypass capacitor in series with the motor’s field winding
- D. A bypass choke in parallel with the motor’s field winding
- E4E06 (C)
What type of electrical interference can be caused by computer network equipment? #card
- A. A loud AC hum in the audio output of your station’s receiver
- B. A clicking noise at intervals of a few seconds
- C. The appearance of unstable modulated or unmodulated signals at specific frequencies
- D. A whining-type noise that continually pulses off and on
- E4E07 (B)
Which of the following can cause shielded cables to radiate or receive interference? #card
- A. Low inductance ground connections at both ends of the shield
- B. Common-mode currents on the shield and conductors
- C. Use of braided shielding material
- D. Tying all ground connections to a common point resulting in differential-mode currents in the shield
- E4E08 (B)
What current flows equally on all conductors of an unshielded multiconductor cable? #card
- A. Differential-mode current
- B. Common-mode current
- C. Reactive current only
- D. Magnetically-coupled current only
- E4E09 (C)
What undesirable effect can occur when using a noise blanker? #card
- A. Received audio in the speech range might have an echo effect
- B. The audio frequency bandwidth of the received signal might be compressed
- C. Strong signals may be distorted and appear to cause spurious emissions
- D. FM signals can no longer be demodulated
- E4E10 (D)
Which of the following can create intermittent loud roaring or buzzing AC line interference? #card
- A. Arcing contacts in a thermostatically controlled device
- B. A defective doorbell or doorbell transformer inside a nearby residence
- C. A malfunctioning illuminated advertising display
- D. All these choices are correct
- E4E11 (B)
What could be the cause of local AM broadcast band signals combining to generate spurious signals on the MF or HF bands? #card
- A. One or more of the broadcast stations is transmitting an over-modulated signal
- B. Nearby corroded metal connections are mixing and reradiating the broadcast signals
- C. You are receiving skywave signals from a distant station
- D. Your station receiver IF amplifier stage is overloaded
- E4E12 (A)
What causes interference received as a series of carriers at regular intervals across a wide frequency range? #card
- A. Switch-mode power supplies
- B. Radar transmitters
- C. Wireless security camera transmitters
- D. Electric fences
- E4E13 (C)
Where should a station AC surge protector be installed? #card
- A. At the AC service panel
- B. At an AC outlet
- C. On the single point ground panel
- D. On a ground rod outside the station
- E4E14 (D)
What is the purpose of a single point ground panel? #card
- A. Remove AC power in case of a short-circuit
- B. Prevent common-mode transients in multi-wire systems
- C. Eliminate air gaps between protected and non-protected circuits
- D. Ensure all lightning protectors activate at the same time
