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E4E09

AMATEUR PRACTICES · 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

E4E09E4E →

What undesirable effect can occur when using a noise blanker?

  1. AReceived audio in the speech range might have an echo effect
  2. BThe audio frequency bandwidth of the received signal might be compressed
  3. CStrong signals may be distorted and appear to cause spurious emissions
  4. DFM signals can no longer be demodulated
Why A noise blanker works by sensing impulse noise in a wideband channel and briefly muting (gating) the receive path during each pulse. That gating is a fast switching action applied to everything in the passband, so a strong nearby signal can trigger or be chopped by the blanker, producing intermodulation and splatter-like artifacts. The result is that a clean strong station can sound distorted and appear to be transmitting spurious emissions that are actually generated inside your own receiver.
Watch out Echo and bandwidth compression describe audio processing effects like DSP delay or speech compression, not the pulse-gating action of a blanker, and a noise blanker does not prevent FM demodulation.
Blanker chops the whole passband: strong signals get chopped too, so the splatter you hear may be your own rig.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of E4E

  1. E4E01 What problem can occur when using an automatic notch filter (ANF) to remove interfering carriers while receiv…
  2. E4E02 Which of the following types of noise can often be reduced by a digital noise reduction?
  3. E4E03 Which of the following types of noise are removed by a noise blanker?
  4. E4E04 How can conducted noise from an automobile battery charging system be suppressed?
  5. E4E05 What is used to suppress radio frequency interference from a line-driven AC motor?
  6. E4E06 What type of electrical interference can be caused by computer network equipment?
  7. E4E07 Which of the following can cause shielded cables to radiate or receive interference?
  8. E4E08 What current flows equally on all conductors of an unshielded multiconductor cable?
  9. E4E09 What undesirable effect can occur when using a noise blanker?
  10. E4E10 Which of the following can create intermittent loud roaring or buzzing AC line interference?
  11. E4E11 What could be the cause of local AM broadcast band signals combining to generate spurious signals on the MF o…
  12. E4E12 What causes interference received as a series of carriers at regular intervals across a wide frequency range?
  13. E4E13 Where should a station AC surge protector be installed?
  14. E4E14 What is the purpose of a single point ground panel?
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