Which of the following factors do engineers need to consider when determining the installation height of the antenna in a long-distance point-to-point scenario? (Multiple choice)

Question

Options

• ASignal transmission frequency
• BDistance between transmit and receive antennas
• CAntenna beamwidth
• DEarth curvature

• A
  76% (34)
• C
  24% (11)

Explanation

In long-distance point-to-point links, antenna height must be sufficient to maintain line-of-sight and clear the Fresnel zone - an elliptical region around the signal path that must be kept largely obstacle-free. Frequency (A) directly determines the Fresnel zone radius: lower frequencies produce larger Fresnel zones requiring more height clearance. Distance (B) matters because the Fresnel zone is largest at the midpoint of the path, and that midpoint bulge grows with path length. Earth curvature (D) introduces an effective "earth bulge" between the two antennas - over long distances this can amount to tens of meters, forcing engineers to raise antennas to compensate.

Antenna beamwidth (C) is incorrect because beamwidth describes how wide or narrow the radiated beam is (a property of the antenna's radiation pattern), not how high the antenna needs to be mounted. Beamwidth affects aiming precision and interference, but plays no role in calculating the clearance height needed over terrain or the Earth's surface.

Memory tip: Use the mnemonic "FDE - Fresnel, Distance, Earth" - the three factors that physically push the signal path up and demand greater installation height. Beamwidth is about the shape of the beam, not its elevation.

No community discussion yet for this question.