[Repeater-Builder] New Transmitting Antenna SWR Question

[agrimm0034]

Currently just upgraded my home built GMRS Maxtrac repeater to a new 6.5db Gain 
Tran-Max antenna. Says SWR should be 1.5 - 1 or less and I have a reading of 
2.5 - 1. I'm using LMR 400 ultra low loss cable at 40 ft putting in 40 watts of 
power. The antenna is mounted on 40 ft tower old 3 legged style. Nothing is 
around the antenna and check cable to make sure it wasn't shorted and 
everything seems to be fine. Any ideas on how to make the Standing Wave better?