Radio Transmission
Its frequency is between 10 kHz to 1GHz. It is simple to install and has high attenuation. These waves are used for multicast communications.
Types of Propogation
Radio Transmission utilizes different types of propogation :
- Troposphere : The lowest portion of earth’s atmosphere extending outward approximately 30 miles from the earth’s surface. Clouds, jet planes, wind is found here.
- Ionosphere : The layer of the atmosphere above troposphere, but below space. Contains electrically charged particles.
Microwave Transmission
It travels at high frequency than the radio waves. It requires the sender to be inside of the receiver. It operates in a system with a low gigahertz range. It is mostly used for unicast communication.
There are 2 types of Microwave Transmission :
- Terrestrial Microwave
- Satellite Microwave
Terrestrial Microwave
For increasing the distance served by terrestrial microwave, repeaters can be installed with each antenna .The signal received by an antenna can be converted into transmittable form and relayed to next antenna as shown in below figure. It is an example of telephone systems all over the world
Satellite Microwave
This is a microwave relay station which is placed in outer space. The satellites are launched either by rockets or space shuttles carry them.
These are positioned 36000KM above the equator with an orbit speed that exactly matches the rotation speed of the earth. As the satellite is positioned in a geo-synchronous orbit, it is stationery relative to earth and always stays over the same point on the ground. This is usually done to allow ground stations to aim antenna at a fixed point in the sky.