While the causes for QRM were well understood, mostly man-made, and could be dealt with through cooperation and tuning techniques, other disruptive on-air phenomena were clearly beyond such controls: those caused by nature. Some, such as static (QRN, also called strays), although understood to a large degree, had no known effective remedy.  Others, such as fading, were not understood at all. At constant transmitter power, what natural phenomena could possibly cause a signal to fluctuate in strength? Why wasn’t a … Continue reading →