Question
What effect does multi-path propagation have on data transmissions?
Answer Options
- A) Transmission rates must be increased by a factor equal to the number of separate paths observed
- B) Transmission rates must be decreased by a factor equal to the number of separate paths observed
- C) No significant changes will occur if the signals are transmitted using FM
- D) Error rates are likely to increase
Correct Answer: D
Explanation
In multi-path propagation, the signal arrives via multiple routes at different times (T3A01). These delayed, duplicated signals cause echoes, where the trailing edge of one symbol of data overlaps with the leading edge of the next symbol. This overlap is known as inter-symbol interference.
This interference makes it difficult for the receiving modem to correctly distinguish between the different data symbols, meaning the data error rates are likely to increase. To compensate, advanced digital modes often employ slow transmission rates or special error correction techniques.
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