Satellites - Communications: Simple Antennas

This family of antennas is what people usually mean when they use the word "antenna"
This family includes the radio antenna on a car, or the antennas that are on older television sets
Simple antennas are just long thin pieces of metal that are can be in different shapes (eg. straight, looped, coiled)
The advantage of simple antennas is, of course, that they are simple; but, unfortunately, they have to be very long in order to be large enough to pick up signals
Long antennas are a problem in space because a satellite has to be as small as possible to make launching easier and cheaper
A satellites with a long antenna can store it within itself, and deploy it once in outer space
For example, STEM (Storable Tubular Extendible Member) antennas unroll once the satellite is in orbit, and remain rigid when deployed
Transmitting using simple antennas is very inefficient because, unlike a dish, the signal is emitted in a spherical fashion; this means that at least half of the radio waves are sent backwards into empty space (a dish allows the wave to be sent in one direction)
Simple antennas are very inexpensive

Produced by Galactics.
Comments: galactics@spacesim.org.
Last updated on: 8 August 1997.