Question T3C04
From subelement T3 - T3C
Which of the following types of propagation is most commonly associated with occasional strong signals on the 10, 6, and 2 meter bands from beyond the radio horizon?
Why is this correct?
Sporadic E is correct because it creates occasional strong signals on VHF bands (10, 6, and 2 meters) from beyond the radio horizon. The ionosphere's E layer sometimes forms patches of enhanced ionization that reflect VHF signals back to Earth, enabling unexpected long-distance contacts. Backscatter occurs but produces weaker, distorted signals. D region absorption actually weakens signals rather than creating strong ones. Gray-line propagation primarily affects HF bands, not VHF.
Memory tip
Look for the word 'occasional' in propagation questions - it's a key indicator for sporadic phenomena. Sporadic E gets its name from being unpredictable and intermittent, unlike regular propagation modes. When you see VHF bands combined with 'occasional strong signals,' think sporadic E propagation.
Learn more
Sporadic E propagation demonstrates how the ionosphere can create temporary frequency privileges beyond normal VHF line-of-sight limitations. During sporadic E events, operators on 10, 6, and 2 meters may suddenly hear distant stations that would normally be impossible to receive. This propagation mode is particularly valuable for VHF weak-signal communication and can create pile-ups when rare DX stations become workable through these ionospheric enhancements.
Think about it
Why do you think sporadic E propagation is more significant for VHF operators than HF operators who routinely work long distances?