Hi Ed,Many thanks for your reply! You’ve provided the key missing link for me: that the equal but opposite in direction currents on the 2 sides of the top hat wires of a T-antenna will cause any RF radiated from the top hat wires to cancel out at far field distances (ignoring asymmetries as you note). It’s quite remarkable actually but brilliant considering this was all figured out more than a hundred years ago in the early days of wireless telegraphy.
I also appreciate both of the URL links you provided. Especially, the Wikipedia article on T-antennas is a terrific and informative read, not to mention the great photos of some historic and impressive VLF/LF/MF antennas of yesteryear (the 1.2 mile long Grimeton 17 kHz one being particularly stunning). Also, the capacitance calculator link you provided confirmed what I suspected: that the actual amount of capacitance created by the top hat over ground (at least at the NDB I visited) is not all that much—a few uF’s at most. But I guess when you’re trying to push some “reluctant” RF up into a vertical wire that’s far shorter than 1/4 wavelength, any added capacitance at the top will improve things considerably.
Thanks again, Ed. Really appreciate it. Yes, great discussion.
Bruce WA1HGJ