The horizon distance for a radio link is estimated using the square root of which heights?

• A. The square root of the vessel total antenna height and the square root of the receiver total height
• B. The square root of the sea distance and the square root of the transmitter height
• C. The square root of the wind speed and the square root of humidity
• D. The sum of transmitter power and receiver sensitivity

Answer: (A)

The concept being tested is how the radio horizon is determined by geometry over the Earth’s curvature. The distance to the horizon from an elevated point increases with the square root of that height, not linearly. For a two-end link, you consider the horizon from both ends and add them together. So the overall line-of-sight distance depends on the square root of the transmitter’s height and the square root of the receiver’s height, then you sum those two values. This is why taking the square root of each height is the correct approach.

Other factors like sea distance, wind speed, humidity, or transmitter power and receiver sensitivity don’t set the geometric horizon. They influence propagation in non-line-of-sight conditions or link budgets, but the basic horizon distance is governed by the heights at each end and the Earth’s curvature.