Change: 26 November 1990
2. Natural radio noise is caused by atmosphere F layer storms and
cosmic radiation, which originates inside the atmosphere.
3. Fading of radio transmissions at 20 megahertz from an orbiting
satellite is due to the combined effect of the
Varying elevations of the earth's surface and the earth's
Ionization of gases and x-radiation from the sun.
4. What percent of the earth's environment surface is covered by
relatively highly conductive water?
Check your answers with the exercise solutions on page 100.
39. Line-Of-Sight Propagation.
within theoretical sight of each other. For ground-based terminals,
this implies a separation of 30 to 90 miles, dependent upon the
earth's curvature, antenna elevations, and the nature of the
The only distance limitations for paths
involving a satellite or a space probe are those imposed by such
factors as noise or limited radiated power.
In general, signal
strength decreases as range increases.