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G4C11

AMATEUR RADIO PRACTICES · - Interference to consumer electronics; grounding and bonding

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What technique helps to minimize RF "hot spots" in an amateur station?

  1. ABuilding all equipment in a metal enclosure
  2. BUsing surge suppressor power outlets
  3. CBonding all equipment enclosures together
  4. DPlacing low-pass filters on all feed lines
Why RF "hot spots" are points where you can get an RF burn or stray RF current because two pieces of gear sit at different RF potentials. Short, wide bonding straps tying all chassis and enclosures together put everything at the same RF potential, so there is no voltage difference to burn you or to couple RF into audio and control lines. This bonding is separate from safety and lightning grounding, though the bonded bus should also connect to the station ground panel with a short conductor.
Watch out Metal enclosures alone do not help if the cabinets float at different RF potentials from each other; the shielding only works once the boxes are bonded. Low-pass filters address harmonic output, and surge suppressors handle AC line transients, neither of which is an RF potential problem.
Hot spots come from voltage differences. Bond everything together and there is no difference left.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of G4C

  1. G4C01 Which of the following might be useful in reducing RF interference to audio frequency circuits?
  2. G4C02 Which of the following could be a cause of interference covering a wide range of frequencies?
  3. G4C03 What sound is heard from an audio device experiencing RF interference from a single sideband phone transmitte…
  4. G4C04 What sound is heard from an audio device experiencing RF interference from a CW transmitter?
  5. G4C05 What is a possible cause of high voltages that produce RF burns?
  6. G4C06 What is a possible effect of a resonant ground connection?
  7. G4C07 Why should soldered joints not be used in lightning protection ground connections?
  8. G4C08 Which of the following would reduce RF interference caused by common-mode current on an audio cable?
  9. G4C09 How can the effects of ground loops be minimized?
  10. G4C10 What could be a symptom caused by a ground loop in your station's audio connections?
  11. G4C11 What technique helps to minimize RF "hot spots" in an amateur station?
  12. G4C12 Why must all metal enclosures of station equipment be grounded?
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