Greetings antenna users Are all Un-Uns current devices ?? I am trying to understand the principles for using one as an impedance matching device on a shortened vertical ( mobile ). Anyone with a simple explanation ?? (I have trouble with large, complicated math formulas). I have Sevik's, Maxwell's, and ARRL Antenna books and have done Net searches without finding what I need. Help PSE ??? Vy Tnx and 73, Tom AA1NZ