  We present measurements of the effective surface impedance changes due to a
static magnetic field, $\Delta Z(H,T)=\Delta R(H,T)+\rmi \Delta X(H,T)$, in a
Tl-2212 thin film with $T_c>$ 103 K, grown on a CeO$_2$ buffered sapphire
substrate. Measurements were performed through a dielectric resonator operating
at 47.7 GHz, for temperatures 60 K$\leq T<T_c$ and magnetic fields $\leq0.8$ T.
We observe exceptionally large field induced variations and pronounced
super-linear field dependencies in both $\Delta R(H)$ and $\Delta X(H)$ with
$\Delta X(H)>\Delta R(H)$ in almost the whole $(H,T)$ range explored. A careful
analysis of the data allows for an interpretation of these results as dominated
by vortex dynamics. In the intermediate-high field range we extract the main
vortex parameters by resorting to standard high frequency model and by taking
into proper account the creep contribution. The pinning constant shows a marked
decrease with the field which can be interpreted in terms of flux lines
softening associated to an incipient layer decoupling. Small vortex viscosity,
by an order of magnitude lower than in Y-123 are found. Some speculations about
these findings are provided.
