Communications & Defense Beyond the line of sight HF communications propagate via the ionosphere. Many different modes of propagation may be supported and each may arrive at different time delays, and may be subjected to Doppler shift and spread due to bulk motion and turbulence in the ionosphere. All of these parameters, and the received signal-to-noise ratio (SNR), can have an effect on HF communications systems. By measuring the HF channel, we provide data to facilitate HF simulator and modem development, with the goal of developing communications systems that are more reliable and can use increased data rates. Qinetic Space wars Ionospheric tomography provides a high-resolution image of the electron density distribution in the vertical, meridional plane using only a small number of satellite receivers on the ground. Polar orbiting satellites of the Naval Ionospheric Measuring System (NIMS) transmit phase-locked radio carrier waves at 150 MHz and 400 MHz and these signals are measured at five ground stations along the length of the UK. The total electron content (TEC) along each ground-satellite path is calculated. A computerised algorithm then reconstructs an image of the ionospheric electron distribution from the TEC measurements.
Posted on: Fri, 28 Nov 2014 13:12:28 +0000
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