DB,
The only thing that led me away from thinking about amp tuning and harmonic content was that groundwire stated that he gets a 1.6 SWR when running the Yaesu right to the antenna.
If we trust that the SWR meter being used isn't itself part of the problem, then this leads me to an antenna installation issue, or more likely a grounding issue.
Yeah, at this point i am just guessing.
I thought I read that with low power his SWR looks fine... Looking back I may have mistook something Beetle said on the first page as coming from him... I am not seeing anywhere where he says his rigexpert reads a lower SWR. If that is the case, my mistake. That being said, if SWR does look fine with his RigExpert, and is higher with his radio and other gear... Your next few lines interest me actually.
If it were my vehicle i would do a quick test to help isolate this possible problem.
take that yaesu out of the vehicle, put it on a table right outside of it, and power the yaesu with an external power supply that has zero connections to the vehicle.
this ensures that your vehicle is nothing more than one antenna and whatever groundplane you have made for it by bonding your vehicle together.
the radio's only connection with this system is the coaxial cable that goes from the radio to the antenna through an SWR meter (make sure that SWR meter isn't touching any metal in the vehicle just to be sure).
if testing with the radio isolated from the vehicle produces a lower SWR, then this would point to some sort of grounding issue between the way the radio is installed in the vehicle and the grounding of the antenna.
LC
If this happens this would likely be the result of a ground loop, which is something that can cause all kinds of problems, some of them appearing to be strange or even intermittent, many of which hide themselves very well and simply cause your equipment to let out the magic smoke at higher rates than would otherwise happen, even when running well within safe power levels and SWR readings. Ground loops are something that almost no one ever considers, but can and does happen in mobile setups, although admittedly fairly rare. Of course, if his rigexpert were were used to test the antenna, and it were run on internal battery power, and he got a lower SWR, (essentially the same thing you recommend only with different equipment) that could also be a sign of a possible ground loop.
On the other hand, if everything is reading an SWR of 1.6, the first thing I would do is remove the passive element on his setup and see how the single so called "hot" element tunes by itself. (I have quickly scanned through ever post and don't recall seeing that this has been done).
I highly doubt that the antenna itself is the issue, I have worked with and seen several of Kale's masterpieces over the years, and not one failed, or caused me to ever question its capabilities. I have seen more than one of these handle more than the advertised 10KW of power with no problems.
But seriously, even if any of this was the case, I would want to see the system myself before making any determination, or calling anything running this much power good. I agree with him that it is a different world, a world that if you are lucky a problem will only be an expensive and timely fix, and if your not lucky...
Of course, I also don't like how these amps are built, but thats another story...
The DB