How HF signals bounce off the ionosphere to travel far, and how ground waves stay near the surface.
What you will be able to do
Describe sky wave (skip) propagation and the ionosphere's role
Give the HF, VHF and UHF frequency ranges
Compare the range of sky waves with ground waves
Describe ground-wave propagation
How does a radio signal get from one place to another?
Radio waves can reach a distant station by more than one route. This lesson covers the two ways HF
signals travel.
Sky waves
Sky wave (also called skip) propagation is when radio signals are refracted (bent) back to
Earth by the ionosphere, so they reach a distant point.
The Ionosphere is the portion of the atmosphere that reflects HF radio signals.
An HF signal goes up, is bent back by the ionosphere and lands far away; the ground wave only reaches a short distance
Sky-wave signals travel much farther than ground waves. In fact, skywave signals on 10 m from
3,000 miles away can overpower local signals a few miles away.
HF, VHF and UHF
Range
Frequencies
HF
3 to 30 MHz
VHF
30 to 300 MHz
UHF
300 to 3000 MHz
Ground waves
Ground wave propagation is when radio signals travel along the surface of the Earth, up to
about 100 miles from the antenna. The range of a ground wave is much smaller than that of a
sky wave.