On Jun 3, 10:57*am, dykesc wrote:
I am trying to validate impedance values I am measuring with my
MFJ-259B. I want to do this by using my MFJ-993B auto tuner. The tuner
uses a simple L network to create the conjugate match. I want to take
the final inductance, capacitance and swr values from the auto tuner
digital display after matching is completed and back calculate the
impedance that the tuner is seeing. Is there an online calculator that
will do this?

Many thanks for replys.

In a quick scan of the replies, one thing I didn't see mentioned is
that if the indicated SWR is not 1:1, then there's an uncertainty in
your answer. For example, a 1.1:1 indicated SWR, taken with a meter
calibrated accurately to 50 ohms, could represent 55 ohms or 45.5
ohms, or any other impedance with the same magnitude of reflection
coefficient relative to 50 ohms. If you start at 55 ohms, you'll get
a different answer for a particular L and C than if you start at 45.5
ohms. Of course, each of those will be different than the answers for
other phase angles of the same reflection coefficient. You can get
rid of that particular uncertainty by adjusting to 1:1 SWR. Of
course, you're still left with other uncertainties, but since you have
control over that particular one (presumably), at least get rid of it.

I'd use WinSmith to do the calc you mention, or hack a simple
spreadsheet if I had several to do, or put the values into Matlab or
Scilab.

Cheers,
Tom