Satellite communication systems are subject to international agreements and regualtions. The International Telecommunication Union (ITU) regulates frequency use and defines "bands"
The following bands are commonly used:
C-band was the first band to be used for satellite communication systems, inc DTH (Direct To Home Satellite Services, TV Distribution, Subscription, Free to Air). However, when the band became overloaded satellites were built for the next available frequency band, the Ku-band. The C-band frequency range has one significant problem. It is the frequency region assigned to terrestrial microwave radio communication systems. Larger Dishes were required. At the current point of time - C Band nevertheless is still used.
3.7 – 4.2 GHz
Advantages:
Less disturbance from heavy rain fade
Disadvantages:
Needs a larger satellite dish (some signals are now powerful enough for smaller dishes)
Possible Interference from microwave links
Ku-band is now typically used for broadcasting, inc DTH and 2-way Internet connections. The Ku-band frequency range is allocated to be exclusively used by satellite communication systems, thereby eliminating the problem of interference with microwave systems. Due to higher power levels at new satellites Ku-band allows for significantly smaller dishes.
Low Band: 10.7 to 11.7 GHz. High Band: 11.7 to 12.75 GHz
Advantages:
No interference from microwave links and other technologies
Operates with a smaller satellite dish (diameters from 90cm) -> cheaper and more easy installation
Disadvantages:
Sensitive to heavy rain fade (significant attenuation of the signal) / possibly can be managed by appropriate dish size etc.
The myth: At the inception of satellite communications in C-band was the only option. It has been the long held belief that Ku-band could not be deployed due to the torrential rains in regions like in Africa. However, with the technology progress in the satellite industry (invention of better LNBs, Dishes, Low threshold receivers), and the more powerful satellites. This thereby eliminates the impact of heavy showers. Its all a matter of correct design and proper equipment to make Ku-band same stable than C-Band to rain factor influence.
The newest band being Ka-Band...... used by Saorsat (a free-to-air satellite service in Ireland) on 9E, but now there are a few satellites with Ka-Band Frequencies/Beams over the frequencies of 26.5–40 GHz.
edited (shortened, yup it was longer!!!, lol) as our friend above beat me to it