R&D Report 1973-05 : Ionospheric non-linearity: Protection ratios required against cross-modulation interference (Luxembourg Effect) D.J. Whythe, C.R.G. Reed Studies of intermodulation of a weak signal by a strong signal in the ionosphere have defined the degree to which the level of intermodulation varies as a function of modulation frequency of the strong signal. This report describes experiments which show that, as a result, a 6 dB relaxation, relative to co-channel interference, may be allowed in the permissible level of cross-modulation interference, measured at a modulation frequency of 300Hz.
