Radyne: Tropo Modem

Radyne:

Troposcatter Communications

Troposcatter communications refers to a method of establishing a link between two stations that are beyond line of sight of each other due to the earth's curvature. It relies on properties of the troposphere that "scatter" some of the energy in the beam that allows a receiving antenna that isn't in the beam of the transmitting antenna to receive the signal. The phenomenon has been well studied. It has been used for decades, mostly by the military, for links in the range of 50 to 300 miles. Excessive path loss limits the distance to approximately 300 miles. The challenge of tropo is the fact that the troposphere does not provide a fixed reflection of the signal. The scattering of the signal that happens in the common volume of the antenna pattern results in a signal that varies rapidly and dramatically over time. This is referred to as frequency selective fading. Changes occur over the span of a few milli-seconds.