Mobil install..Coax length??

[hammer0630]

Well I have very high swr 3.0 to 2.5.. I am bidding on some good grounding straps most important is they have terminals.

 

[Groundhog KSS-2012]

I am replacing my Cobra 29LTD radio and replacing my cheap oil coil antenna with a Wilson Trucker 18 inch shaft and a Galaxy DX959 modded out. What I am not sure of does Coax length make a big difference in mobile performance? I have right now in my Tacoma I believe is 18 feet of coax which is way to much causing me to coil it up under the truck. I bought 9 feet of coax that I think will be just long enough..am I doing the right thing here?

Another older thread. "Golden shovel time!"
Anyway, the "18 ft coax myth", is JUST THAT! A MYTH, PERIOD! And besides, if anyone is looking for a half wave of coax cable, they DIFFER depending on the VP. (Velocity Factor).
None are the same UNLESS, they have the same velocity factor. Period! When doing the calculation for a half wave of coax cable velocity factor MUST be factored in. If not, it will be wrong.