@338_MtRushmore:
I referred to that set up as a "vertical dipole", when I was speaking to my HAM cousin, the day I did it, and he questioned the accuracy of that term. I'm kind of learning things, still; I don't know what to call it, I just know it's working, lol.
But, yeah, the Volvo is mostly fiberglass, and poorly grounded. There are other antenna set ups that I could try, if I owned the truck. But, it's a company vehicle, so I have limits on what I can do.
My next step, I think, is to cophase dual "dipoles", because the flaw that I expected manifested the other day, when I passed the guy that I was talking to. The passenger side of my truck has a big "deaf" spot. But, as I said, I expected that.
As to the resonance, I want to see that, myself. An antenna analyzer is on the top of my wish list. Two of them are, actually. There is an MFJ model that I want, mainly because it seems to be a very widely trusted brand and model. But, I also want the "Mini60" Sark100 clone with Bluetooth. The various graphs and all look fun; and the technology of the thing appeals to my inner geek, lol.