I followed your article ("Forecast Rain Effects On Microwave Links," April, p. 78) in your attempt to show readers how to forecast rain effects in microwave terrestrial and satellite links. I have studied microwave propagation in the atmosphere with precipitation and know the theory behind it. I did an interesting science by using microwave radiometers in emission mode to obtain loss distributions over three years, to determine the necessary satellite-link parameters for 12, 18, and 35 GHz. Others similar studies were done for other bands.

Since 1988, I know that no theory can make any viable forecasts or predictions. International Telecommunications Union (ITU) recognized quite early that longtime experiments are the only way to obtain loss distributions at any place on the globe. Since the 1950s til now, many researchers have gradually collected a lot of experimental knowledge and facts about loss distribution over a year, which is, til now, the only known way to obtain link availability at any location. Nobody can forecast rain and other atmospheric effects upon microwave and mm-wave propagations. Nature does not follow our human theories. The only way to design a well-operating terrestrial or satellite link is to use ITU documents in which probabilities of loss distribution over a year can be found, to predict link availability. As declared many times, "theory may be wonderful but facts define how the nature works."

Best regards,
Jiri Polivka
Spacek Labs, Inc.

The Author Responds:
The object of the article was to present a general scattering theory that may be applied not only to hydrometers in the atmosphere (such as rain, snow, fog, etc.), but also applies to cases such as sandstorms, artificial lenses, composite materials like Teflon-based materials (e.g., Rogers 5880 and other materials), having random scatterers in them. The results of the article can be employed to calculate attenuation and depolarization phenomena in the above cases.

It is incorrect to state that nature does or does not follow our human theories. Nature exists and follows no theory. The theories developed are really there to try and explain physical and natural phenomena, not the other way around, so that we can understand them better.

I believe that true scientists and engineers are those workers that try to understand why and how physical and natural phenomena occur. By understanding these phenomena we will be able to apply our knowledge to various other field so that we may progress in those fields in a speedy manner.

Best regards,
Dr. John Howard
ET Industries

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