When a question is migrated, does it still show up in the original site @MikeWaters? @hobbs-KC2G and I both posted similar answers, except his has a spectacular graphic from software he wrote himself! We both wrote our answers for a non-technical audience (regarding radio technology). If the question had been asked on ham.SE, I wonder if I would have written the same answer that I did. Maybe I would have, if the OP emphasized that he or she wasn't a ham and knew nothing about HF propagation.
