Gap Analysis of Ambient Electromagnetic Noise Measurements Stored in the ITU Data Banks.

For any radio frequency (RF) sensor (receiver) to function optimally, the ambient noise field strength, converted to electrical power by the transducer (antenna), must be lower than the in-ternal noise of that sensor. Therefore, knowledge of the expected ambient noise level is essential for the design of sensors for earth observation, atmospheric research, radio astronomy or navigation. The International Telecommunication Union (ITU) provides a model that predicts ambient man-made noise levels, differentiated by frequency, origin and environment.

Design and Validation of Probes and Sensors for the Characterization of Magneto-Ionic Radio Wave Propagation on Near Vertical Incidence Skywave Paths.

This article describes the design and validation of deployable low-power probes and sensors to investigate the influence of the ionosphere and the Earth's magnetic field on radio wave propagation below the plasma frequency of the ionosphere, known as Near Vertical Incidence Skywave (NVIS) propagation. The propagation of waves that are bent downward by the ionosphere is dominated by a bi-refractive mechanism called 'magneto-ionic propagation'. The polarization of both downward waves depends on the spatial angle between the Earth's magnetic field and the direction of propagation of the radio wave.