A few afternoons ago, I watched the signal from TouCans fade from an s9 into the Utah SDR to nothing in a matter of minutes. There was nothing wrong with the rig. I was literally getting to observe the effect the F2 layer has on propagation on twenty meters. Schedule 00:02 UTC/16:02 PST: Almost at S9 into Utah 00:32 UTC/16:32 PST: Running at S9 into Utah 00:36 UTC/16:36 PST: Already down to S5 00:37 UTC/16:37 PST: The signal is all but gone What Happened? Here's the F2 critical frequency, (fof2), along the path to Utah at each of the above time steps. The critical frequency is the maximum frequency that will be reflected straight back down to the ground at any point rather than piercing the ionosphere and propagating out into space. When I say along the path, I mean the value for fof2 reported by GloTEC at that time. GloTEC collects a number of ionospheric data sources and assembles them into a model of what the F2 layer looks like at any location on Earth at a give...