Zona4r

So i searched and found people having an excessivle high swr, but not a constant one. i'm guessing this is a grounding problem, but would like others opinions.

So i finally got around to tuning my antenna (5' Firestik II) and I can't get the SWR below 1.6 (it's the same on all channels). What gives? I know 1.6 is acceptable, but I'd like to get it lower. I have the screw on top all the way down.

Is this a grounding issue? At first I was having trouble getting the swr below 3. I shortened the ground wire running from the cb. Should i shorten this more? Should I adding a ground wire to the mount.

CB: Cobra 75 wx st mounted under driver's seat.
Antenna: 5' Firestick II mounted on rear.

I'm also running the 18' Fireflex coax. What did everyone else do witht he extra cable. I know not to cut it or coil it. Just thinking this might have something to do with it.