Mobile Ant. Ground plane question

[GrouserPad]

Scenario: Pickup truck with a full fiberglass cap that has steel luggage mount bars running across the front and rear of fiberglass cap. If mounting a VHF antenna directly on the center of the steel front most luggage bar which is approximately 10” from the trucks cab, would the antenna be able to adequately utilize the truck cab for groundplane? Or would it not recognize the steel surface not being mounted directly? using a 5/8 over 5/8 antenna.

 

[slowmover]

You’ll have to follow what metal structure framing is inside topper down to bed rail. Uncover bare metal on both to RF Bond.

There are mounts (BREEDLOVE) which accommodate bed toppers. Easier solution.

 

[prcguy]

An antenna wants lots of flat sheet metal at least 1/2 wave diameter right under the antenna and that would be about 36in diameter at VHF. Raise the antenna above the sheet metal and it will complain. Mount it to a metal bar and it will not be happy and will not make use of the metal cab nearby. Bond the metal bar to the bed rail and it won’t fix the problem except the wire going downwards will add a tiny bit of ground plane but not enough to make it happy.