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  • In telecommunication, antenna noise temperature is the temperature of a hypothetical resistor at the input of an ideal noise-free receiver that would generate the same output noise power per unit bandwidth as that at the antenna output at a specified frequency. In other words, antenna noise temperature is a parameter that describes how much noise an antenna produces in a given environment. This temperature is not the physical temperature of the antenna. Moreover, an antenna does not have an intrinsic "antenna temperature" associated with it; rather the temperature depends on its gain pattern and the thermal environment that it is placed in. Antenna noise temperature has contributions from several sources: Galactic radiation Earth heating The sun Electrical devices The antenna itself Galactic noise is high below 1000 MHz. At around 150 MHz, it is approximately 1000K. At 2500 MHz, it has leveled off to around 10K. Earth has an accepted standard temperature of 290K. The level of the sun's contribution depends on the solar flux. It is given by where is the solar flux, is the wavelength, and is the gain of the antenna in decibels.