You might improve signal strength with a simple "T" dipole inside, or a 1/4 wave auto rod type (30.5") outside. Be careful of overall height so it doesn't hit anything. Obviously the higher the better for reception. Perhaps a small rubber-duck could help, they tend to be marginal.
DRV Suites ES-38RSSA #9679
GM Denali 3500HD-Max 4x, CC, 8' DRW