  We discuss experimental results obtained using a tunable cylindrical coaxial
cavity constituted by an outer Cu cylinder and an inner Pb-BSCCO wire. We have
used this device for investigating the microwave response of the
superconducting wire, both in the linear and nonlinear regimes. In particular,
by tuning the different modes of the cavity to make them resonant at exactly
harmonic frequencies, we have detected the power emitted by the superconducting
inner wire at the second- and third-harmonic frequency of the driving field.
The results obtained in the nonlinear regime, whether for the microwave surface
impedance or the harmonic emission, are qualitatively accounted for considering
intergrain fluxon dynamics. The use of this kind of device can be of strong
interest to investigate and characterise wires of large dimensions to be used
for implementing superconducting-based microwave devices.
