Communication Satellites
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All companies putting a communication satellite constellation into the sky have to consider what portion of the electromagnetic spectrum their signal will occupy. The electromagnetic spectrum is the range of electromagnetic radiation from waves of high frequency and short wavelengths to waves of low frequency and long wavelengths. Starting at the high frequency, the electromagnetic spectrum consists of Gamma rays, x-rays, ultraviolet radiation, visible light, infrared radiation, microwaves, and radio waves. Communication satellites use microwaves, which are at the high end of the radio portion of the spectrum.

New satellite systems have to apply for spectrum use. In America, permission has to be gotten first from the FCC. In 1997 the FCC granted 13 companies Ka-band licenses. The International Telecommunications Union gives international permission to spectrum use.

The problem of allocation of the spectrum for telecommunications use is similar to allocation of radio bands. If you have two stations too close to each other on the dial, you are going to get interference and an unclear signal. So satellite companies need to give themselves enough space to operate on the spectrum. Finding space on the spectrum becomes more difficult when you are working on a global scale.

Most new satellite systems are looking for space in one of three areas of the spectrum: L-band, Ku-band or Ka-band. Each of these bands represents an area of the EMS and each has its own positive and negatives.

frequency range positives negatives
L-band 1.53-2.7GHz long wave lengths can penetrate many structures; requires less powerful transmitters largely allocated
Ku-band 11.7-12.7 GHz Download; 14-17.8GHz uplink medium wavelengths penetrate many obstacles and carry lots of data largely allocated
Ka-band 18-31 GHz a lot of available spectrum and shorter wavelengths carry a lot of data requires powerful transmitters; short wavelengths subject to rain fade

The new satellite broadband corporations will mostly be using the Ka-band for their transmissions. Note: The band names for area of the spectrum were created during WW2 and each name was created to confuse anyone trying to understand radio broadcasts.

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