Radio transmission works with or without line of sight. If line of sight is possible then transmission can take place between sending antenna and receiving antenna. The placement of antenna has to take into account the curvature of the Earth with antenna being built taller accordingly. This will also allow for greater transmission distances. If line of sight cannot be implemented then signals can be broadcast to the upper layers or the atmosphere or space and then transmitted back to Earth.
The electromagnetic spectrum used for radio communication consists of eight distinct ranges which are regulated by government authorities:
|VLF||Very low frequency||3 - 30KHz|
|LF||Low frequency||30 - 300KHz|
|MF||Middle frequency||300KHz - 3MHz|
|HF||High frequency||3 - 30MHz|
|VHF||Very high frequency||30- 300MHz|
|UHF||Ultra high frequency||300MHz - 3GHz|
|SHF||Super high frequency||3 - 30GHz|
|EHF||Extremely high frequency||30 - 300GHz|
Click on this link to review the wikipedia resource on radio.
Next: Satellite Transmission