Editing Satellite Internet access (section)

===Interference===
[[File:Bigpond internet Satellite.jpg|thumbnail|right|A foldable [[Bigpond]] satellite Internet dish]]

Satellite communications are affected by moisture and various forms of precipitation (such as rain or snow) in the signal path between end users or ground stations and the satellite being utilized. This interference with the signal is known as ''rain fade''. The effects are less pronounced on the lower frequency 'L' and 'C' bands but can become quite severe on the higher frequency 'Ku' and 'Ka' band. For satellite Internet services in tropical areas with heavy rain, use of the C band (4/6&nbsp;GHz) with a circular polarisation satellite is popular.<ref>{{Cite news|url=https://www.linksystems-uk.com/c-band-ku-band/|title=C Band Ku Band Comparison|date=2004-07-30|work=Link Communications Systems|access-date=2018-02-10|department=Technical|language=en-GB}}</ref> Satellite communications on the K<sub>a</sub> band (19/29&nbsp;GHz) can use special techniques such as large ''rain margins'', ''adaptive uplink power control'' and ''reduced bit rates'' during precipitation.

''Rain margins'' are the extra communication link requirements needed to account for signal degradations due to moisture and precipitation, and are of acute importance on all systems operating at frequencies over 10&nbsp;GHz.<ref>Takashi Iida [https://books.google.com/books?id=v-OuSc4t7IQC Satellite Communications: System and Its Design Technology], IOS Press, 2000, {{ISBN|4-274-90379-6}}, {{ISBN|978-4-274-90379-3}}</ref>

The amount of time during which service is lost can be reduced by increasing the size of the [[satellite dish|satellite communication dish]] so as to gather more of the satellite signal on the downlink and also to provide a stronger signal on the uplink. In other words, increasing antenna gain through the use of a larger parabolic reflector is one way of increasing the overall channel gain and, consequently, the signal-to-noise (S/N) ratio, which allows for greater signal loss due to rain fade without the S/N ratio dropping below its minimum threshold for successful communication.

Modern consumer-grade dish antennas tend to be fairly small, which reduces the rain margin or increases the required satellite downlink power and cost. However, it is often more economical to build a more expensive satellite and smaller, less expensive consumer antennas than to increase the consumer antenna size to reduce the satellite cost.

Large commercial dishes of 3.7&nbsp;m to 13&nbsp;m diameter can be used to achieve increased rain margins and also to reduce the cost per bit by allowing for more efficient modulation codes. Alternately, larger aperture antennae can require less power from the satellite to achieve acceptable performance. Satellites typically use [[photovoltaic]] solar power, so there is no expense for the energy itself, but a more powerful satellite will require larger, more powerful solar panels and electronics, often including a larger transmitting antenna. The larger satellite components not only increase materials costs but also increase the weight of the satellite, and in general, the cost to launch a satellite into an orbit is directly proportional to its weight. (In addition, since satellite launch vehicles [i.e. rockets] have specific payload size limits, making parts of the satellite larger may require either more complex folding mechanisms for parts of the satellite like solar panels and high-gain antennas, or upgrading to a more expensive launch vehicle that can handle a larger payload.)

Modulated carriers can be dynamically altered in response to rain problems or other link impairments using a process called adaptive coding and modulation, or "ACM". ACM allows the bit rates to be increased substantially during normal clear sky conditions, increasing the number of bits per Hz transmitted, and thus reducing overall cost per bit. Adaptive coding requires some sort of a return or feedback channel which can be via any available means, satellite or terrestrial.