The Basic lessons · Radio wave propagation · B-007-007

VHF and UHF Propagation: Bending, Ducts, and Auroras

Learn how the atmosphere bends radio waves to extend your range beyond the horizon. Discover the specific conditions that allow 2-metre and 6-metre signals to travel hundreds of kilometres.

This lesson is part of SignalPrep Pro. The subsection's 11 exam questions are free to practise: practise B-007-007.

What this subsection asks

• Which ionospheric region most affects sky-wave propagation on the 6-metre band?
• What effect does tropospheric bending have on 2-metre radio waves?
• What causes tropospheric ducting of radio waves?
• What term describes that portion of a transmitted wave kept close to the Earth's surface due to bending in the atmosphere?
• What is a sporadic-E condition?
• On which amateur radio band is the extended-distance propagation effect of sporadic-E most often observed?
• In the northern hemisphere, in which direction should a directional antenna be pointed to take maximum advantage of auroral propagation?
• Where in the ionosphere does auroral activity occur?
• Which analog emission mode is the most reliable in auroral propagation?
• Excluding enhanced propagation modes, what is the approximate range of normal VHF tropospheric propagation?
• What effect is responsible for propagating a VHF signal over 800 km?