Q 1.15 Are K-band (18-27 GHz) satellite links affected by rain, time-of-day, clouds and sandstorms?
K-band satellite links are severely affected by rain. As an example, for the temperate continental climate regions of the USA the link margin required for 99.9% link reliability is 10 dB at 20 GHz, increasing to 20 dB for 30 GHz link at moderate elevation angles. Rain attenuation is inversely related to elevation angle. Cross-polarization discrimination is also affected by rain – its magnitude being influenced by frequency, co-polar attenuation and polarization.
Time-of-day has a strong correlation with ionospheric scintillation, which is very weak at such frequencies. Tropospheric scintillation does not correlate with time-of-day. Satellite movement is a time-of-day variable that can cause minor variations in received signal in large antennas unless tracked out.
Attenuation by clouds and fog depends on their liquid content. The largest attenuation from clouds in fair weather is equivalent to that caused by light rain (~10 mm/hr). The attenuation from fog can be considered negligible for practical purpose as the liquid content is low and their radio path length through path is small (~50-100 m).
Attenuation caused by sand storms depends on the frequency, type and density of dust particles, length traversed by radio waves in the sand storm, height of the user terminal. As an example, one theoretical study estimates the average attenuation as about 0.2 dB/km in an African region, observing that attenuation increased significantly as dust density increased.
The reader should refer literature for more details.