12.1 Introduction

It is important to understand why satellite communications have become popular in recent years and to what uses they are put. Satellite communications can be made available from almost any point on the earth's surface to any other point, in both an international and domestic environment. They are high in quality and reliability, and it is these attributes which have led to the popularity of satellite communications.

We are familiar with the televising of great international events via satellites as well as the convenience of worldwide telephone and data communications. We have also become more familiar, over the last few years, with an increasing number of data services and the development of low-bit-rate television for video-conferences and visual information transfer.

As system planners, it is our task to ensure that any earth-station design introduced into a satellite communications systems has the necessary virtues of giving reliable, high-quality communications. This Chapter will examine the ways of achieving these ends.

There may well be instances of marginal services where the quality and reliability may not be as important as the capital cost of supplying such a service. In these cases we may have to turn our ideas upside down in search of a cost-effective solution to this problem.

12.2 What is an Earth Station?

Let us first look at the types of communication covered by satellite, so that we can build up a picture of the services required from our earth station. These fall into a number of...