Been thinking about something re: portable temporary antennas, particularly 80 and 40 meters. Say you can't put up a high dipole, so your antenna becomse a cloud-burner NVIS antenna. Good for short range, obviously.
Then consider a vertical. A full-size vertical would be prohibitive in a lot of situations, so then the question becomes...
How short can a vertical be and still be at least as good as a low dipole for distant communication? Especially if it's got a top hat?