  We experimentally investigate theoretical predictions of universal impedance
fluctuations in wave chaotic systems using a microwave analog of a quantum
chaotic infinite square well potential. Our approach emphasizes the use of the
radiation impedance to remove the non-universal effects of the particular
coupling from the outside world to the scatterer. Specific predictions that we
test include the probability distribution functions (PDFs) of the real (related
to the local density of states in disordered metals) and imaginary parts of the
normalized cavity impedance, the equality of the variances of these PDFs, and
the dependence of the universal PDFs on a single control parameter
characterizing the level of loss. We find excellent agreement between the
statistical data and theoretical predictions.
