Gain is the factor by which an incoming signal is concentrated when it reaches the focal point. A higher gain dish would be required to receive signals from a weaker satellite. Gain is measured in decibels relative to an "isotropic antenna," one that would receive signals from all directions equally well. An isotropic antenna has a gain of 0 dBi, equal to a concentration factor of 1. A dish, for example, with a gain of 30 dBi, concentrates incoming signals by a factor of 1,000. The gain calculations, accessible from the CALCULATIONS and subsequently RECEIVE SYSTEM and ANTENNA PARAMETERS menus is measured in dBi.in increases as dish size increases since more signal can be intercepted, just like a larger bucket can collect more rain. Higher gain dishes are often required to receive the very weak signals from Intelsat global or hemispheric beams or from areas far off the boresight of spot or zone beams. For example, if reflective surface area is doubled, so is its gain. Gain also increases with signal frequency, actually the square of the frequency. A dish would thus have 9 times more gain at Ku-band than at C-band since the frequency is three times higher. The gain of a dish also depends upon its surface accuracy. Small distortions in the reflective surface, can cause substantial decreases in gain. Therefore, a dish that has a large number of deep welts or ripples will behave more poorly than one that is smooth and more closely approximates its designed shape. Signals striking a dent would be reflected away from the focal point. This loss of gain with surface imperfections becomes even more important at higher frequencies. Ku-band dishes must be more accurate than those for C-band reception.receive dish intercepts and concentrates signals from transponders with power outputs ranging from 6 to over 100 watts that have been attenuated by approximately 200 dB on their journey earthward. While system performance improves as dish gain increases, below a minimum gain, even the best LNB cannot compensate enough to adequately capture the signal essential to reconstruct a satellite broadcast.