Question
What is a possible cause of high voltages that produce RF burns?
Answer Options
- A) Flat braid rather than round wire has been used for the ground wire
- B) Insulated wire has been used for the ground wire
- C) The ground rod is resonant
- D) The ground wire has high impedance on that frequency
Correct Answer: D
Explanation
High radio frequency (RF) voltages on equipment enclosures, which are capable of causing painful RF burns when touched, are typically caused by a failure of the station’s grounding system to effectively shunt the stray RF current to true ground. An ineffective ground is one that presents a high impedance at the operating frequency.
High impedance occurs when the ground wire is too long or coiled, causing it to act as an unintended antenna or a quarter-wave stub. This causes the stray RF current to meet resistance and build up a high RF voltage potential on the chassis of the equipment, rather than smoothly flowing to the Earth ground, making the ground wire has high impedance on that frequency the direct cause of the high voltage.
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