The 5/8 wave antenna consists
of a vertical radiator which is fed at the base.
A matching device must be added between the antenna and the feed line if you wish to feed it with coax.
Adding a coil at the base in series with the antenna
works quite well for mobiles antennas.
I have a good Detailed 5/8 wave mobile antenna Excel Program that will
calculate all the dimensions and coil taps for you. Download File 5/8 mobile ant.