  We present VLA radio continuum measurements of SN1993J in M81 at the
frequencies of 0.32 (P-band), 1.3 and 1.7 (L-band), 4.9 (C-band), 8.5 (X-band),
and 14.9 (U-band) GHz carried out on December 17 and 21, 2000, about 2820 days
after the supernova explosion. We find that a power-law spectrum, free-free
absorbed by an homogeneous, or clumpy, distribution of ionized gas yields the
best fit to the radio data. A combined homogeneous-clumpy model is not favored,
but neither totally excluded. This result contrasts with the modeling of the
early ($t \lessim $230 days) radio emission from SN1993J, where a mixture of
homogeneous and clumpy absorbers appeared to be necessary to adequately
describe the behavior of the light curves. The radio spectrum of supernova
SN1993J between 0.32 and 14.9 GHz is well characterized by $\alpha = -0.67 \pm
0.02 $ ($S_\nu \propto \nu^\alpha$), typical of an optically thin radio
supernova. A fit to the radio spectra of SN1993J from $\sim$ 70 up to 2820 days
shows that the observed spectral index of SN1993J has been slowly evolving
since $t\sim$1000 days on, with the observed spectral index changing from
$\alpha \approx -1$ to $\alpha=-0.67$. This spectral evolution seems to suggest
that, in addition to the radiative (synchrotron) losses, adiabatic cooling and
ionization (Coulomb) losses at the lowest frequencies might be contributing
significantly to the integrated electron spectrum.
