CB radios

CB antennas require a metal ground plane to work correctly. So as we've moved away from metal vehicles a NGP antenna which uses the coax as a ground has become popular, but they are usually very marginal. You may have a NGP antenna and per above whatever you have the SWR has to be set.

I suspect that many of the antennas installed by the mfg are like the tank monitors and have only one purpose - for the salesman to sell you the rig - "You've got a CB antenna and you can monitor your tank levels..."