System noise temperature reflects how much noise is added to a satellite signal by a reception system. Sources include noise detected by the dish and produced in the LNB, cable runs and remaining electronic circuitry.tellite reception systems are sensitive to very weak noise sources including both galactic noise and that introduced by radiation from the warm earth. Galactic noise detected by a dish pointed directly into deep space is typically about 6°K. However, noise from the warm earth that is at an average temperature of 290°K is much higher. This noise is detected via dish side lobes and depends upon its elevation. As a dish is lowered towards the horizon it detects more ground noise. Since elevation to satellites at the center of the geosynchronous arc is higher than that of those at the easterly and westerly portions, system noise is lower when the most southerly satellites (or most northerly in the southern hemisphere) are targeted.e noise performance of an antenna can be improved in a number of ways. A higher quality dish of a given aperture has lower side lobes and is therefore less susceptible to noise. A larger diameter dish also has a better side lobe pattern and a more narrow main lobe so it generally contributes lower amounts of noise. Similarly, a deeper antenna having a lower f/D ratio, all else being constant, would detect lower amounts of ground noise.e noise introduced by the LNB is simply expressed by its noise temperature or figure. Therefore, for example, a 25°K LNB adds 25°K of noise. The noise contributed by the cables and satellite receiver is low by comparison because the LNB amplifies both the noise and signal detected by the antenna/feed. Its output signal is substantially higher in power than the noise added by cables, connectors and the satellite receiver. Therefore, the balance of system components has only a small effect, typically at most 5°K, on system noise temperature. G/T, the figure of merit for an earth station, can therefore be closely approximated by replacing T, system noise temperature, with the noise contribution of just the antenna and low noise amplifier. The signal at the output of the LNB is thus the key determinant of overall performance quality of satellite reception system.