Batboard

On a public safety crown vic installed a vhf high power spectra, with a permanent hole mount on the trunk, with a ground wire from the batteries ground to the trunk in place, now I need a suggestion on a 15 -25 inches vhf antenna that will perform the best for the radio on the same frequency. ¼ wave, gain, no ground plane? Any suggestion will be appreciated.

For your permanent mount on the trunk I would use the broadband VHF by Comtelco. A1151A it has a 18" .125 dia whip and a spring. Covers 24mHz in VHF.

Most if not all "gain" antennas do not have the frequency range, + or- 4 mhz at best.

If you haven't already drilled the hole for the antenna mount on the trunk lid consider this information. A 1/4 wave whip on the trunk lid will perform okay with some directivity due to where it's placed on the vehicle. If you were to mount the 1/4 wave antenna on the roof of the vehicle, the antenna will provide a good 360 degree RF radiating pattern and would be equivalent to a 5/8 wave antenna mounted on the trunk lid.

Within those height constraints, you're looking at a 1/4-wave unity gain antenna... which will be just fine.

I've had excellent results with the RadiallLarsen NMOWBQB:
http://www.tessco.com/products/displayP ... ventPage=2

Available in chrome or black, great power handling, etc.

I would remove the wire from the battery ground to the trunk lid. This is a Bad Idea. If you lose the straps from battery to frame or they become high-resistance, you'll end up seeing starter current running along this wire, creating a fire hazard among other problems. If you want to ensure a good ground, run some copper braid from the trunk lid to a hardpoint on the vehicle body or frame.