ATMOSPHERIC NOISE POWER AVAILABLE AT THE OUTPUT OF AN ELEVATED RADIOMETER ANTENNA.
NAVAL RESEARCH LAB WASHINGTON D C
Pagination or Media Count:
Formulae are developed for the atmospheric noise power available at the output of an airborne radiometer antenna of narrow beamwidth. The theoretical model chosen for the antenna possesses characteristics which are fairly representative of the radiators met in practice. In a numerical example, in which the beam-depression angle is taken to be 30 degrees, the theory is applied to the calculation of the atmospheric path attenuation and the effective atmospheric noise-temperature of the elevated antenna for a number of frequencies and antenna heights. The path attenuation varies from 0.2 db at 5000 feet of altitude and a frequency of 35 gc to 1.7-2.5 db at heights of 30,000 feet or more and at frequencies of 80 to 100 gc. The effective noise-temperature of the antenna is 20 K at 10,000 feet altitude and at a frequency of 35 gc. As the frequency is elevated to 75 gc, the altitude remaining at 10,000 feet, the noise-temperature of the antenna increases to 80 K. Author