band (4/6 GHz) with a circular polarisation satellite is popular. Satellite communications on the Ka band (19/29 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 GHz. The amount of time during which service is lost can be reduced by increasing the size of the 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 m to 13 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