An Easy Method of Receiving Picture Signals from Satellites

Abstract : Experiments were carried out to obtain an easy method of receiving picture signals from ESSA4 NIMBUS, and ATS satellites and to determine the quality of apparatus required for the purpose. The experiments involved measurement of the electric field intensity from the satellites and examination of the contrast, resolution, and fineness of the reproduced pictures that were sent back to the earth by the satellite's automatic picture transmission system whose signals were carried at a frequency of 136 MHz and modulated to AM-FM by video signals. The signals, received by simple antennas such as the doublet, turnstile or helical antenna and through an FM receiver, were reproduced by a facsimile machine. It was necessary to insert a modulation-increasing circuit between the FM receiver and the facsimile reproducer when the modulation index of the video signals was as low as the NIMBUS signals. Faraday fading, scintillation fading, the environmental effect on the antennas interruption of interference, and external noises were also considered. (Author)