On 31 Jul 2005 21:01:19 -0700, "
wrote:
I have a pi-network, or at least I believe it is a pi-network in my
antenna tuner. It has two caps to ground and one in series inductor.

If I tune my SWR for 1:1 and go back and measure each value of the
capacitors and inductor, is there a equation or computer program I can
use these measured values to obtain my complex impedance at the input
of the coax cable?

Hi OM,

Good time to learn the Smith Chart. The components in that network
are simply arcs moving the presented Z to the transformed Z (50Ohms).
Unfortunately this is easier said than done - or understood. Like all
skills, time and practice are necessary.

As for understanding, the Smith Chart will bring that quicker than any
software - which simply dumps an answer in your lap, the quality or
actual utility of which is as much a mystery as the problem you wanted
to solve. There are a multitude of network settings that will satisfy
the matching and software or equations will do little more than say
"yup, that setting does exactly as you observed." Not very filling,
but when you do the same thing on the Chart, you can see where you are
going before you get there. This means you also have the choice of
choosing the best path (shortest). It would be a rare piece of code
that could do that - from a mountain of formulas.

73's
Richard Clark, KB7QHC