T3B: Tropospheric ducting or bending; amateur satellite and EME operations

Ducting occurs in the region of the atmosphere called the Troposphere. Tropospheric bending lets you contact stations farther away on the 2-meter band.

Tropospheric ducting is caused by a temperature inversion. A stable high-pressure system weather condition can cause tropospheric ducting. A widespread temperature inversion causes VHF radio waves to be propagated several hundred miles over oceans. It occurs most frequently in the UHF bands.


The signal loss for a given path through the troposphere increases as the frequency increases.

High-gain antennas are normally used for EME (moonbounce) communications to overcome the extreme path losses of this mode. A high-gain array of Yagi antennas would be the best choice for an EME (moonbounce) station.

Before two stations can conduct real-time communications through a satellite, it must be in view of both stations simultaneously. It is necessary to use higher transmitter power when conducting satellite communications via a satellite that is low to the horizon.