Editing Propagation Basics (section)

== VHF, UHF and satellites ==
Above about 30 MHz the ionosphere rarely returns signals, so range depends on the line of sight.
* Hills and mountains block or diffract the signal. SimTX uses a 150 m terrain map, so a station behind a ridge hears less than one on top of it.
* Antenna height and a clear horizon matter more than power.
* Satellites are heard only while above the horizon. Their signal shifts in frequency during a pass (Doppler), most on the higher bands; see [[SimTX Guide/Satellites|Satellites]].