Craig,
I think there is some good information here. Thanks for taking the time to put it out here for us.
I do not claim to be an expert but I do question the negative gain on a 1/4 wave. Specifically that half the wire in the air necessarily means 3db loss.
Removing half of the antenna metal reduces the "antenna apeture" by 50%, which results in a 3db loss. Subtract 3db from the dipole gain of 2.15 and you have -0.85 db gain (a loss of .85 db below zero). It's not only half the performance of a dipole, it's below the zero point of that theoretical isotropic radiator.
...The other half of the signal is "thrown away" as ground...
Where does the power go? If it does not come back down the coax (bad SWR), where is it going? Law of conservation of energy and all. Absorbed by the ground plane and turned into heat? The plane must be reflective to work. If all it is doing is, as you posit, "throwing away" or absorbing half the signal, would not the antenna work better without a ground plane? Surly it is being reflected in order to achieve a workable standing wave by "mirroring" the other half of the waveform. Does not the ground plane then becomes part of the aperture? It seems to me that a theoretically perfect plane would not have the 3db loss you assert, but rather that the loss would be a function of the planes inefficacy in reflecting the image of the driven element.
On a somewhat unrelated note; from Personal experience, I can say that higher gain verticals are not always preferable. I generally run the Comet SS-680SB (listed as 2.1 dBi 1/2 wave) on my jeep because it is physically short and the spring makes it very robust but I also carry the longer, higher gain SBB-7 (listed as 4.5dBi 6⁄8 wave center-load) both for redundancy and for mountain top simplex work. From a clear vantage point, the SBB-7 is remarkably better at reaching distant stations but as soon as I come off the mountaintop, it is noticeably less effective at reaching even nearby repeaters. Driving next to a hill will completely block a repeater that I could reach from that same spot with the shorter antenna for instance. My theory is that because the higher gain radiates in a lower, narrower pattern it is causing more power to be absorbed by the near field terrain such as hills and trees. The lower gain half wave sends more power up and over the hills where they have a chance to be reflected or refracted back down toward the listening repeater. In my testing, in addition to being much more practical due to its length, it is a much better radiator for everyday use in the woods.
