Experimental verification of asymmetrical short-term scintillation distribution model

The theory that tropospheric scintillation is associated with turbulence in clouds leads to an asymmetrical distribution of signal level fluctuations in decibels, in contrast to the commonly used symmetrical model. The asymmetry of measured signal fluctuations from Spino d'Adda is evaluated and it is found that the measured short-term distribution is in good agreement with the asymmetrical mode

Spectra of equatorial total electron content derived from GPS signals

High cadence GPS TEC signals collected on Ascension Island, South Atlantic Ocean, during sunspot minimum, and in Vanimo, Papua New Guinea, over half a solar cycle, have been analysed for their spectral properties. A new parameter <I>T<sub>k</sub></I> has been introduced to quantify the strength of TEC irregularities at a scale size of 1 km. The scintillation strength and the spectral index have been analysed as functions of each other, and of local time, season, location and sunspot number. The scintillation strength is highest in autumn and spring in both locations, although the quietest period is summer in Ascension and winter in Vanimo. The scintillation strength decreases with decreasing sunspot number, but is consistently lower in Vanimo than in Ascension. The spectral index decreases with scintillation strength, and increases during the hours of the evening. A method is developed to estimate <I>T<sub>k</sub></I> from the large data base of <I>S</I><sub>4</sub> measurements

Axial crosspolarization in reflector antennas due to asymmetric cross-polar feed patterns

\u3cp\u3eThe on-axis cross-polarisation of a reflector antenna illuminated by a feeding system with an asymmetric cross-polar radiation pattern is examined. A graph is presented from which the cross-polarisation discrimination (XPD) of the reflector antenna can be simply obtained.\u3c/p\u3