VSAT Frequency Band
There are five radio frequency bands that communication and military satellites operate within, these frequency bands determine the link quality and coverage area. As described on www.iDirect.net, these frequency bands can be defined as follows:
MSS Frequency Bands
Uplink 1.6 GHz
Downlink 1.5 GHz
L band is primarily used for Mobile Satellite Services, like Inmarsat and Iridium. Being a relatively low frequency, L-band is easier to process, requiring less sophisticated and less expensive RF equipment, and due to a wider beam width, the pointing accuracy of the antenna does not have to be as accurate as the higher bands.
Only a small portion of L-Band is allocated to satellite communications on Inmarsat. Inmarsat uses L-band for its FleetBroadband, Inmarsat-B and Inmarsat-C services. The older Inmarsat A and B antennas were typically 1 meter in diameter, but, with the launch of more powerful satellites and the use of steerable spot beams, FleetBroadband antennas are down to less than 30cm (12 inches).
VSAT Frequency Bands
Uplink 5.925-6.425 GHz
Downlink 3.7-4.2 GHz
C-band is primarily used for voice and data communications as well as backhauling. Because of its weaker power it requires a larger antenna compared to Ku-band, usually 2.4m for maritime use. However, due to the lower frequency range, it performs better under adverse weather conditions on the ground. In addition, C-band typically has large beams and makes it possible to provide ‘Global’ coverage with only three satellites.
Uplink 7.9- 8.4 GHz
Downlink 7.25 – 7.75 GHz
X-band is used for military communications and Wideband Global SATCOM (WGS) systems.
Uplink 14 GHz
Downlink 10.9-12.75 GHz
Ku-band is used typically for consumer direct-to-home access, distance learning applications, retail and enterprise connectivity in addition to maritime. The antenna sizes are much smaller than C-band because the higher frequency means that higher gain can be achieved with smaller antenna sizes. Networks in this band are more susceptible to rain fade, especially in tropical areas.
Downlink 18-20 GHZ
Ka-band is primarily used for two-way consumer broadband and military networks. Ka-band dishes can be much smaller and typically range from 60cm-1.2 metres (2′ to 4′) in diameter. Transmission power is much greater compared to the C, X or Ku-band beams. Due to the higher frequencies of this band, it is more vulnerable to signal quality problems caused by rain fade.
Illustration : The five radio frequency bands.