  We emphasize the importance of observations of young supernovae in wide radio
band. We argue on the basis of observational results that only high or only low
frequency data is not sufficient to get full physical picture of the shocked
plasma. In the SN 1993J composite spectrum obtained with Very Large Array (VLA)
and Giant Metrewave Radio Telescope (GMRT), around day 3200, we see
observational evidence of synchrotron cooling, which leads us to the direct
determination of the magnetic field independent of the equipartition
assumption, as well as the relative strengths of the magnetic field and
relativistic particles energy densities. The GMRT low frequency SN 1993J light
curves suggests the modification in the radio emission models developed on the
basis of VLA data alone. The composite radio spectrum of SN 2003bg on day 350
obtained with GMRT plus VLA strongly supports the internal synchrotron self
absorption as the dominant absorption mechanism.
