Hi Jerry,

The Z-Theta Chart has actually been around a long time, well known as the
'Carter' Chart, developed by Philip Carter, an early RCA transmission-line and
antenna inventor, around the same time as Philip Smith developed the Smith
Chart. In one of HP's Application Notes it is incorrectly called the 'Charter
Chart'. But you are correct, overlaying those two charts is often very helpful.

Walt, W2DU