This would be run from the bolts on the CB mount. then one of the bolts holding the roofbar mount fixing plate onto the mounting points on the car.
Using the wire, which is stranded, I got two low-SWR points either side of the CB allocations (SWR remains high within the band) once the mount was bonded, with the wire at the full spool length (2-meters or so) the SWR was much lower but it really needs bonding.
The 2/70 colinear antenna is offset from the centre towards the driver's side of the car, early tests on the VNA suggested that on 2-meters this antenna is working fine so I do not know where the antenna is getting its ground from on that band, I've not checked this on 70cm as yet.
As the VNA battery ran out during tests today I tried to power it from the car charger, this created a ground loop because the car electrical system has its negative grounded to the body as well as is the case in many modern vehicles.
Tomorrow I will pick up a braided earth strap of suitable length and try this on the car to bond the CB antenna as I suspect this copper DC cable I've used may not be working as expected.
73 de M0WNU/26CT730