  A method is presented to measure the absolute value of the London penetration
depth, $\lambda$, from the frequency shift of a resonator. The technique
involves coating a high-$T_c$ superconductor (HTSC) with film of low - Tc
material of known thickness and penetration depth. The method is applied to
measure London penetration depth in YBa2Cu3O{7-\delta} (YBCO)
Bi2Sr2CaCu2O{8+\delta} (BSCCO) and Pr{1.85}Ce{0.15}CuO{4-\delta}$ (PCCO). For
YBCO and BSCCO, the values of $\lambda (0)$ are in agreement with the
literature values. For PCCO $\lambda \approx 2790$ \AA, reported for the first
time.
