Question T3A05
From subelement T3 - T3A
When using a directional antenna, how might your station be able to communicate with a distant repeater if buildings or obstructions are blocking the direct line of sight path?
Why is this correct?
The correct answer is B because radio signals can bounce off buildings, mountains, and other surfaces to reach their destination, similar to bouncing a ball off a wall. When direct line-of-sight is blocked, using a directional antenna to find a reflection path allows communication with the repeater. Changing polarization (A) won't overcome physical obstructions. The long path (D) refers to HF propagation, not VHF/UHF repeater work. Increasing SWR (D) actually degrades performance and wastes power.
Memory tip
Think 'billiards shot' - when you can't make a direct shot, angle for a bank shot off the cushion. Directional antennas let you precisely aim at reflective surfaces like large buildings or hillsides to bounce your signal around obstacles to the repeater.
Learn more
This technique exploits specular reflection, where VHF/UHF signals behave somewhat like light rays bouncing off smooth surfaces. In urban environments, large flat building surfaces, water towers, or metal structures can serve as effective reflectors. The key is finding the geometry where your transmitted signal angle equals the reflected angle toward the repeater - basic physics applied to radio frequency propagation. Some hams systematically map reflection points in their area for reliable emergency communication paths.
Think about it
Why do you think this reflection technique works better with directional antennas than omnidirectional ones when trying to reach repeaters around obstacles?