Mounting will be a bracket/rack fixed behind spare tire, with the mounting bracket to be projected toward the passenger side (with due observation to the rear door swing to ensure mount doe not impinge on body/taillight/etc and keeps the antenna roughly in line with tie down point).
So electrical bonding to mount assembly should be fine; it will be ensuring good, constant electrical conduction between mounting rack and the spare tire lugs/frame. There is probably where I will use star-type washers, if I can get them in a tire lug size.
Might also just go ahead and run a good size wire from one of those lugs under the washer to the rear bumper to ensure a reliable connection. Something around 12 gauge and just braze the lug to the bumper. Then I can paint over it.
So there are some matching circuits where the coax sheath also runs to ground instead of remaining only in the lower antenna element? Or is this matching circuit ground only to aid in reducing harmful interference from the body and enhance its role as a sort of ground reflector similar to radials used in horizontal dipoles and NVIS antennas (where they are not electrically connected to sheath but just serve as RF mirrors).
The whip antennas are generally dipoles (although how they do it - how it's wired, mechanically arranged - I don't know) and broadcast signals pretty effectively for their design and dimensions.
On the base of the antenna is a switching circuit to select the combination of matching circuit for the frequency range desired. A common misperception among ham radio guys is the idea that an "Antenna Tuner" actually allows 100% of the transmitted power from the radio to go out the antenna. What the "tuner" does is add capacitance or reactance to the inductive components to "fool" the radio amplifier into putting out its selected power and not "see" the mismatch. This power gets dissipated through the "tuner" (look at the specs on any "tuner" and you'll see power handling data and warnings about heat), not the antenna.
So where does that power go in an isolated truck?
In a perfect antenna, dipole (half positive, half negative), nearly 100 percent of the signal will be emitted - minus some loss due to resistance, reactance, in the cable, hardware, etc.
In any antenna, some current or voltage is going to be produced as "stray" emissions which need to be "choked" (by use of a BALUN - voltage or current as appropriate for the use) and the stray current bled off to ground so as not to travel around the circuitry from radio to mike, to knob, to Pretective Control Box or driver/operator leading to shocks, shorts, circuit damage or words inappropriate for (and banned from) this forum.
Since the actual truck is INSULATED from earth ground, the truck metal parts themselves become ground, or lowest electrical potential for all bonded circuits. It bleeds off, but not in EM bands likely to interfere with radio use, but mostly as voltage/current/static.
Some of the multiband antennas include 2 Meter bands, and these use the truck as a ground plane, like you might see with a classic 11 M citizen's band home tower antenna, one upright, and three or four more radials horizontally as "reflectors" although it's more complicated than than. Those antennas, like vertical multiband ham antennas radiate roughly 360 degrees the "dipole" being comprised of the upright (positive) and the radial(s) as ground - the more the more efficient and frequently the radials are of different lengths to maximize propagation within the band to lower the VSWR (another topic entirely), make the antenna system more efficient.
Oh, and the cable sheath IS connected to the radials, and to ground. For electrical AND RF ground. Braid carries RF better than solid wire.
I'm not an IEEE engineer, just a ham radio guy (Extra) and it's been a few years, but this is essentially correct.
Poke around on the web for information on antenna theory, or here:
http://www.arrl.org/how-antennas-work
or here:
https://www.dxzone.com/catalog/Antennas/Theory/
