Radar horizon refers to...

• A. The ability to go beyond the geometric horizon because RF energy dissipates over distance.
• B. The physical horizon at sea level.
• C. The maximum physical diameter of the radar dish.
• D. The angle of the antenna during scanning.

Answer: (A)

Radar horizon is about how far you can detect with a radar, taking into account how radio waves actually travel through the atmosphere. Radio waves don’t travel in a perfect straight line along the geometric line of sight; the atmosphere bends them downward (refraction) and they can diffract around the Earth’s curvature. That bending effectively extends the usable range beyond the geometric horizon, so targets below the geometric line of sight can still be detected if they’re within this extended “radio horizon.” The fact that signal strength fades with distance doesn’t negate this extension—the horizon distance is about where detection becomes possible, not where the wave ceases to exist. The physical horizon at sea level is just the straight-line limit, the size of the radar dish doesn’t set the horizon, and the antenna scan angle affects where you’re looking at any moment, not the fundamental horizon distance.