Hey Fausto79, here is a pic of my UHF install, there is a plug behind panel that you can pick up both earth and power, UHF anntennae generally dont need ground plane but putting ant on rear wheel carrier will generally transmit forward and to the left, mounted on bullbar generally will transmit moreso backwards, centre of roof is ideal but not generally practical unless mounted on roofrack,
cheers
ken
https://www.aulro.com/afvb/

