Total posts : 45366
MRAM made the observation that this thread asked one question but branched into many more, and that’s true, but I argue that everything that’s been said is related to the original question. I see the top L-bends into horizontal branches as having the same net effect as a top hat.
Another observation, probably obvious, is that it becomes often necessary to discuss the larger scale of licensed technology and then try to reduce the size to fit Part 15 limitations.
One question buried in this ongoing dialogue which has not been directly confronted is my posing the “cage monopole” (a term only now being introduced to this thread), consisting of four parallel 3-meter antennas all fed from a single transmitter, as being equivalent to a single 3-meter wire, except lower in impedance. I likened it to a Litz wire for its multiple-wires-in-one.
The paper on the Star-H says, “It is well known that creating a cage monopole of vertical wires to increase the diameter of the radiator can increase the bandwidth of a short vertical antenna.” That comment gives an especially appealing reason to consider the cage monopole as a realistic Part 15 design.