Batboard

I know it's a little off topic but was hoping someone might offer their opinion.

I have a UHF and a VHF antenna mounted on the cab roof of my pick-up. I used to have a roll bar with a CB antenna mounted to it and it performed excellent with a low SWR of 1.5:1...... I got rid of the roll bar and bought a fiberglass cap for the bed and mounted the CB antenna in the center of the cap. I have a 3 ft X 2 ft of flat sheet metal mounted to the underside of the truck cap to act as a ground plane for a Wilson 1000 antenna (the same one I had on the roll bar) and my SWR readings are above 3 on all channels, which makes me think I don't have enough ground plane.

I have 18 ft of RG 8X cable and have checked that I have no shorts in the cable or mount. I have continuity from the antenna ground to the sheet metal and I grounded the sheet metal to the chassis of the truck...

I'm no expert but is there any way I can bring my SWR down without having to get more sheet metal??

I would have thought you would have used a circular piece of metal in a 3 foot diameter and also grounded the metal to chassis also in insure a good ground.

your ground plane is too small that what essentially low-band.

Could I extend my ground plane by using 4 to 6 ft lengths of wire from the center of the mount and radiating in each direction?

Ideally your counterpoise wires should be 1/4 wave on the lowest frequency. That means 9' for CB. The more wires the better but whatever you can reasonably manage will have to do.

Would copper or aluminum foil tape work for this application of creating a ground plane on the underside of a fibergalss truck cap? If so, would 1/2" be wide enough, or should I try to fine something wider?

Thanks

Should be fine. As long as you get a good electrical connection with the ground side of the mount it'll work.