Which antenna type is commonly used for mobile or mast-mounted operations due to its ground-plane or top-loaded design?

• A. Quarter-wave whip.
• B. Dipole.
• C. Ground-plane or top-loaded monopole.
• D. Loop antenna.

Answer: (C)

The idea here is the efficiency and practicality of a vertical radiator on a mobile or mounting surface. A monopole that uses a ground plane—like the vehicle body or a dedicated conductive surface—completes the radiator as a half-wave vertical. When you add a top-loading feature (such as a loading coil or a higher current point near the top), you can resonate the antenna at the intended operating frequency while keeping the physical height compact. This setup yields an omnidirectional vertical pattern, good efficiency, and easy mounting on a vehicle or mast, which is exactly what mobile or mast-mounted operations require.

Quarter-wave whips rely on a ground plane for some efficiency, but they can be space-limited or less effective if the ground plane isn’t ideal. Dipoles need two elements and a balanced feed, which isn’t as convenient on a vehicle or mast. Loop antennas have different radiation patterns and form factors that aren’t as typical for straightforward mobile vertical installations. So the ground-plane or top-loaded monopole best matches the described scenario.