This receiver has been used for observations at the 30m
telescope on February 1--15, 1994. The 30m telescope
is equipped with a multiplexing quasi optical system for
parallel observation in 3 frequency bands. It was possible to operate
in parallel in the 0.8 mm, 1.3 mm and in 3 mm bands. The telescope
system noise temperature in the 0.8 mm band is strongly dependent on
frequency, weather and the telescope orientation. The best
SSB system noise temperature during the observation period was 500 K
at 330 GHz when the opacity was about 0.17.
When the automatic calibration loads are used for the measurements
of the receiver noise the losses between the receiver and the standard
reference plane have to be taken into account. The noise temperature
measured in the reference plane of automatic calibration (
) may
be 30--40 K higher than the receiver noise temperature due to the 
loss in the multiplexing system.
Fig. {8
gives a sample result: the 
CO(3-2) transition spectrum
in IC 342, measured with the new receiver at the telescope.
Figure 5:
Receiver DSB noise temperature. The frequencies in the black
part of the curve are available with the present LO remote control.
Noise temperature is measured immediately in front of receiver.
Figure 6:
Receiver sensitivity in photons.
Figure 7:
Receiver DSB noise temperature in the 500 MHz IF band, measured with
the autocorrelator
Figure 8:
The 
CO(3-2) transition spectrum of the galaxy
IC 342 measured with
the new receiver at the telescope (by courtesy of Andreas Schulz et al.)
Acknowledgements. The construction and installation of the new G2 mixer and of the 345 GHz receiver benefited from valuable support from several members of IRAM's technical staff, among whom : M.Voss and D.Billon for the fabrication of the junctions, J.L.Orecchia and J.Sendra for the machining, J.Blondel, C.Boucher, and J.Y.Chenu for the cryogenics and support of laboratory tests, and H.Hein for the on-site installation and tests.
Alexandre KARPOV