Question
What is the meaning of the term “picket fencing”?
Answer Options
- A) Alternating transmissions during a net operation
- B) Rapid flutter on mobile signals due to multipath propagation
- C) A type of ground system used with vertical antennas
- D) Local vs long-distance communications
Correct Answer: B
Explanation
The term picket fencing describes a characteristic, rapid on/off flutter in the received audio, most often heard on mobile FM signals that are moving. It gets its name because the sound resembles running a pencil quickly over a picket fence, with the signal quickly cutting in and out.
It is caused by the moving vehicle constantly passing through areas where the signal is reinforced or canceled (fading and peaking) due to multipath propagation (T3A01). As the car moves, the signal path geometry rapidly changes, causing the signal to quickly drop out and return, creating the distinct, fluttering audio effect.
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