honestly I haven't been where your at. or i should say in a long long while.. everybody pretty much runs the predator antenna with either the 22" or 27" length shaft... gets the antenna up and away from the truck and much less reflection.....7ft.skipshooter and 7ft. firestiks are out there too. in the fiberglass option. ...
most predators are set by many at a 1:2 1:3 or 1:4 pretty easily on the crapcadias....like ridgeline said needs to be checked by a external swr analyzer a mfj or rig expert or along those lines....
Experimenting with cable length is masking a problem but not fixing it. A 50 ohm dummy load will show a perfect match regardless of cable length. If changing cable length fixes something, it means you don't have a perfectly tuned antenna.
This is not gonna fix your issue BUT it will help seeing a predator was mentioned..IF you go that route and you hear a lil more than enuf static.......Heat shrink the base shaft and mast above the coils...Just covered mine with goralla tape just to see.,shockinly it helped....Doesnt do nothing on fibreglass ant.. Give up on anything less that 5.5 ft on a crapcadia..
didn't exactly want to come out and say that but that's a true statement.... less than 5.5 ft. on these trucks is a waste of time and yer $$$$$
bought an external tester. showing 2.3 on 01, 1.8ish on 19, 1.6 on 40 still showing cb antenna warning on all channels when truck is running
those high swr numbers usually mean a rf ground issue on a lot of crapcadia trucks... I've seen it many times and some trucks are a lot worse off than others ......