Editing Propagation Basics (section)

== Two ways a signal travels ==
* '''Groundwave''': the signal follows the ground outward from the antenna. It dominates short range (out to a few tens of kilometers on all bands, farther on lower frequencies) and favours '''vertically polarized''' antennas and good ground (sea water is best). Groundwave range shrinks quickly as frequency rises; on the higher HF bands it is essentially local.
* '''Skywave''': the signal refracts off the ionosphere and returns to Earth hundreds to thousands of kilometers away. This is how HF covers distance. Multiple hops extend the range further at the cost of extra loss.

Between the end of groundwave and the first skywave return there can be a '''skip zone''' where the station is inaudible even though it is heard both closer and farther away.