Ok guys, some more information...
The RFI 6.5db is ground independant. Make no mistake, there's
NO SUCH THING as a fully ground indepentant antenna. All antennas including ground independant antennas use the ground plane to some degree to radiate the signal.
If you buy an antenna without a spring, (even ground independant ones), it'll usually perform better because a spring usually degrades the signal. The same applies to antennas mounted on the tailgate as the hinge in the door insulates the tailgate from the rest of the vehicle reducing the surface area of the ground plane. This is not as critical on the 477mhz cb band - i can get a solid 20klm from my tailgate mounted antenna, but i don't have a spring
My $200 GME 2.1 metre top of the range 6db collinear randome doesn't come close -> because it's got a spring.
The antenna you want is available from some Dick Smith stores, and it's in-store code is D4023. It outperforms most others because it's chrome plated brass and has a stainless steel whip. There's an antenna company called Rojone that specializes in base antennas and their flagship UHF CB base antenna is highly sought after because it's mostly made of brass and copper. It's considered by many enthusiasts a bargain at $300. I believe they are not making many of the D4023's anymore or have ceased production to make way for the new 'space age' looking model which has an extended feed which is now available at prestigecom or most radio comms outlets. It's pictured below:
I havn't used the above one but eventually i'll get one (without a spring, they're available too).
If you spend anymore than $79 on a mobile antenna, or bought something other than an RFI you've settled for secondbest, as far as range/performance goes.