In the outdoor backhaul scenario, which of the following descriptions of the site selection principle is wrong?

Question

Options

• AIf there is other Wi-Fi interference near the site, you can set it to a different channel or coordinate
• BThe site should be selected away from strong electric and magnetic fields
• CThe site should be located in an open area with no obstacles nearby.
• DIf there are obstacles near the site, the height of the pole only needs to be higher than the

• A
  10% (4)
• B
  5% (2)
• C
  3% (1)
• D
  83% (33)

Explanation

Option D is the wrong site selection principle because it presents an incomplete and misleading rule: simply mounting a pole higher than nearby obstacles is insufficient. In outdoor backhaul, you must also ensure Fresnel zone clearance - the elliptical radio propagation path between antennas must be clear of obstructions by a recommended margin (typically 60% of the first Fresnel zone), not just line-of-sight.

Why the distractors (A, B, C) are correct principles:

• A is correct - switching channels or coordinating with neighboring Wi-Fi networks is a valid interference mitigation strategy.
• B is correct - strong electromagnetic fields can degrade signal quality and damage equipment, so avoidance is standard practice.
• C is correct - open, unobstructed sites are ideal for backhaul because they maximize signal strength and minimize multipath interference.

Memory tip: Think of the phrase "Higher than ≠ clear enough." Wireless signals don't travel in straight lines - they spread in a football-shaped zone (Fresnel zone). A pole that merely clears an obstacle can still suffer significant signal loss if that zone is partially blocked. Whenever you see an answer that oversimplifies pole height as the only consideration, it's likely the wrong principle.

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