  We have obtained a deep radio image with the Very Large Array at 6 cm in the
Lockman Hole. The noise level in the central part of the field is about 11
microJy. From these data we have extracted a catalogue of 63 radio sources. The
analysis of the radio spectral index suggests a flattening of the average radio
spectra and an increase of the population of flat spectrum radio sources in the
faintest flux bin. Cross correlation with the ROSAT/XMM X-ray sources list
yields 13 reliable radio/X-ray associations, corresponding to about 21 per cent
of the radio sample. Most of these associations (8 out of 13) are classified as
Type II AGN. Using optical CCD (V and I) and K' band data we found an optical
identification for 58 of the 63 radio sources. This corresponds to an
identification rate of about 92 per cent, one of the highest percentages so far
available. From the analysis of the colour-colour diagram and of the radio flux
- optical magnitude diagram we have been able to select a subsample of radio
sources whose optical counterparts are likely to be high redshift (z>0.5)
early-type galaxies, hosting an Active Galactic Nucleus responsible of the
radio activity. We also find evidence that at these faint radio limits a large
fraction (about 60 per cent) of the faintest optical counterparts (i.e. sources
in the magnitude range 22.5<I<24.5 mag) of the radio sources are Extremely Red
Objects (EROs) with I-K'>4.
