just for the record

It would probably take 375 ground straps to bond all the different sections together on that truck

 

It's only a pain if you insist on not using a dipole otherwise it's quite simple.

 

An antenna with a tunable counterpoise.
Something along the lines of this picture with a tunable ground and tunable hot element .
On a truck both sides would have to be shortened for practicality.

 

The different readings we're not the reason I suggested the dipole. The way the truck was constructed using glued metal panels is the reason I suggested the dipole.
Ridgeline got that truck dialed in but he had to rip the whole truck apart in order to do it and that is out of the question for most company drivers. I suggested the dipole from a company driver perspective since it's quick and easy and requires no modification to the truck.


That's one I built out of desperation for an International that had electrical current flowing through the sheet metal of the body.
The truck wasn't mine and I had no interest in fixing the problem .

 

Sometimes the easiest thing to do is isolate the antenna system from the body of the truck electrically for trucks with bonding issues or electrical issues.
I spent about 2 weeks dicking around with that International truck trying to use the body as a counterpoise and I finally gave up. It took me 5 minutes to add the tunable counterpoise and electrically isolate the antenna system from the mirror bracket.