  We report on the anisotropy of the vortex motion surface impedance of a \fst
thin film grown on a CaF$_2$ substrate. The dependence on the magnetic field
intensity up to 1.2 T and direction, both parallel and perpendicular to the
sample $c$-axis, was explored at fixed temperature at two distinct frequencies,
$\sim16\;$GHz and $\sim27\;$GHz, by means of bitonal dielectric resonator. The
free flux flow resistivity $\rho_{ff}$ was obtained by exploiting standard
models for the high frequency dynamics, whereas the angle dependence was
studied in the framework of the well known and widely used
Blatter-Geshkenbein-Larkin (BGL) scaling theory for anistropic superconductors.
Excellent agreement with the scaling law prescription by the fluxon flux flow
resistivity was obtained. From the scaling analysis, a low-field mass
anisotropy $\sim1.8$ was obtained, well within the value ranges reported in
literature. The angular dependence of the pinning constant suggests that
pinning is dominated by random, isotropic point pins, consistently with
critical current density measurements.
