KC8ICI Alan Kaylor Truck "Screwdriver" Antenna
Alan Says its ugly but it works
The capacity hat is made of sheet aluminum & the rod is a conventional CB whip shortened to clear underpasses. A toridal down auto transformer at the base helps provide a match.
This type of mobile vertical antenna is called a "Screwdriver" because the first home brew ones used a power screwdriver motor to adjust the position of finger stock that contacted a helical inductor in the tube to adjust the inductance and hence the frequency there the unit would match the transceiver's 50 ohm source impedance.