Question
What could be a symptom caused by a ground loop in your station’s audio connections?
Answer Options
- A) You receive reports of “hum” on your station’s transmitted signal
- B) The SWR reading for one or more antennas is suddenly very high
- C) An item of station equipment starts to draw excessive amounts of current
- D) You receive reports of harmonic interference from your station
Correct Answer: A
Explanation
A ground loop is a circular current path formed when interconnected equipment is grounded at multiple points with slightly different potential. When this occurs in the audio wiring between a microphone or sound card and the transceiver, the unwanted circulating current can induce 60 \text{Hz} (or 50 \text{Hz}) mains frequency noise into the audio signal path.
When this noisy audio is amplified and transmitted by the radio, the symptom is that you receive reports of ‘hum’ on your station’s transmitted signal. This hum is a low-frequency AC noise superimposed on your voice or data modulation, which is a classic indicator of an audio ground loop.
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