All,

This is a follow up to a dialog several months back on impedance
measurements. The question relates to smith charts and an HP 8407a with
a polar display. I was under the impression that the polar display and
the smith chart were pretty closely related. In fact hp made smith chart
overlays for the screens.

The smith chart predicts a variable capacitor connected across a source
will be represented by an impedance semicircle in the capacitive domain,
one of the points on the semicircle passes through the 50 ohm center. I
would expect to be able to create this using the 8407.

The 8407 creates a circle around the outside edge of the display. It is
a circle, however it does not pass through the center.

Why are these different? What above is incorrect?

thanks - Dan