Motorcycle Installation

I am currently trying to instal a CB onto my motorbike.

I have done the easy bit of installing the rig, but I am having problem with the attenna, or getting a decent SWR anyway.

The attenna I have is a PNI S75 Mag mount. Now a mag mount aint much use on a bike, so I have removed the aerial & coax from the magnet & attached to a home made bracket, whic from what I can see is no different to mounting using a gutter or mirror bracket on a car.

However the SWR readings wont come doen an stay in the red. I have checked for coax shorts etc, no probs there.

However if I reassenble the antenna into its orignal magmount & place on a metal table the SWR is fine.

Any ideas where I am going wrong ?

You need to get an antenna that doesn't need a ground plane, a quick search on DuckDuckgo will tell you your options and go into more detail about the no ground plane issue.