  We report the radio observations of a sub-sample of the 428 galactic compact
bubbles discovered at 24 $\mu$m with the MIPSGAL survey. Pervasive through the
entire Galactic plane, these objects are thought to be different kinds of
evolved stars. The very large majority of the bubbles (~ 70%) are however not
yet classified. We conducted radio observations with the EVLA at 6 cm and 20 cm
in order to obtain the spectral index of 55 bubbles. We found that at least 70
per cent of the 31 bubbles for which we were effectively able to compute the
spectral index (or its lower limit) are likely to be thermal emitters. We were
also able to resolve some bubbles, obtaining that the size of the radio nebula
is usually similar to the IR size, although our low resolution (with respect to
IR images) did not allow further morphological studies. Comparisons between
radio flux densities and IR archive data from Spitzer and IRAS suggest that at
least 3 unclassified bubbles can be treated as planetary nebula candidates.
