Grounding aerials/antennas?

[gavinwibrow]

My D4 came with a heavy duty alloy roof rack, to which were attached CB and mobile phone aerials each on tiltable bases to fit into a domestic garage.

I have removed the platform and restored a pair of surf racks. The platform was attached to the car via the inbuilt LR roof nuts.

I now want to refit the aerials via making up a steel frame which will be bolted under the pair of cross bars.

Question - will I need to ground the steel frame to the roof?

[pop058]

Some are ground independent so the earth could be provided by the earth shield on the coax. Maybe a google on the model number might be the go.