  We describe a new high sensitivity experiment for observing cosmic microwave
background (CMB) anisotropies. The instrument is a 2-element interferometer
operating at 33 GHz with a ~3 GHz bandwidth. It is installed on the high and
dry Teide Observatory site on Tenerife where successful beam-switching
observations have been made at this frequency. Two realizations of the
interferometer have been tested with element separations of 11.9 lambda and
16.7 lambda. The resulting angular resolution of ~2 deg was chosen to explore
the amplitude of CMB structure on the large angular scale side of the Doppler
(acoustic) peak. It is found that observations are unaffected by water vapour
for more than 70 per cent of the time when the sensitivity is limited by the
receiver noise alone. Observations over several months are expected to give an
rms noise level of ~10 - 20 micro K covering ~100 resolution elements.
Preliminary results show stable operation of the interferometer with the
detection of discrete radio sources as well as the Galactic plane at Dec = +41
deg and -29 deg.
