To tune your coax, here is the formula: 492 X (Velocity Factor) divided by Frequency (MHz) = Full Wavelength divided by 2 = Half wavelength. Velocity Factor for Coax 8X is .82, Coax 8U is .84, Coax LMR 400 is .85 5/8 wavelength = 0.625
Tune your coax to the most used frequency and you will drive all of your power out with no return to the radio. This is the secret for a 1:1 SWR! Enjoy!