Tropospheric Fading

Tropospheric turbulence and small changes in the weather are responsible for most fading at VHF and higher. Local weather conditions, such as precipitation, warm air rising over cities and the effects of lakes and rivers, can all contribute to tropospheric instabilities that affect radio propagation. Fast-flutter fading at 28 MHz and above is often the result of an airplane that temporarily creates a second propa- gation path. Flutter results as the phase relationship between the ordinary tropospheric signal and that reflected by the airplane change with the airplane’s movement.