Satellite antenna propagation involves a number of techniques and different ranges for sending and receiving signals. New measurement techniques for testing antennas ar also being developed and implemented to analyze the propagation field and to understand what happens to the signal under different conditions. An examination of the issues raised with reference to antenna propagation and the measurement of performance shows the nature of the field today and some of the directions in which it is moving. The discussion below shows how technicians analyze existing antenna configurations and determine new ways of assuring that signals are sent and received with as little distortion as possible. One important function of these researches is to develop technology to pinpoint the direction of signals and so to determine the location from which they are emanating. Such technology also makes it possible to send signals more precisely to a specific location.
NASA's Advanced Communications Technology Satellite (ACTS) Program is one important technological system being used by more and more companies and the U.S. government to place satellites in orbit, to identify and secure those orbits, and to communicate on various levels. The transmission of electromagnetic waves through space has become common over the past century. The antenna is the critical interface between the hardware and space, and antenna testing is a major field to assure that the antenna performs the desired task and does so at the proper levels, in the correct range, and so on: "Antenna design and propagation predictions are the key to successful HF communication" (www.gordon.army.mil/acd/tcs/hf/propag8n.htm).
HF transmissions (sky waves) are affected to a great degree by the earth's atmosphere. HF communications would be easy if the atmosphere were static, but in fact the atmosphere varies with altitude, location, time of day, season, and year. The layers of th...