On the VHF radio channel for the data exchange system via satellite (VDE-SAT); experimental results from the NorSat-2 Satellite Experiment

Measurements of the Very High Frequency (VHF) downlink from NorSat-2 has been analysed in the context of development of the waveforms for VHF Data Exchange via Satellite. Received carrier, noise and interference power were analysed and compared with theory and simulations. The received power levels are as expected for most of the time. Slowly varying fading is observed with peak-to-peak variations in the order of 20 dB and a standard deviation of 4.2 dB. The fading has a close to normal distribution (in dB) and is mainly caused by sea reflections and to a lesser degree shadowing by the ship structure. Although time periods with significant interference were observed, most of the time the noise floor can be classified as residential or city according to ITU-R Rec. 372 on Radio noise. The noise plus interference level measured did not represent white Gaussian noise, and it is beneficial if the waveform(s) is robust with respect to both narrowband and wideband noise. The received C/N0 showed a dynamic range of about 25 dB, exceeding 34.7 dBHz for 95 per cent of time.