The dual-frequency receiver of antenna 4 (which was the first of the series and suffered from a focus offset between both channels) has been replaced by a new one. The co-alignment of the 2 channels was set up in the laboratory, and has been checked to be better than 2'' on astronomical sources. The new receiver provides significantly better performance than the previous one, specially in the 1.3mm band: is below 40 K DSB over most of the band (32 K DSB at 230 GHz).
The old receiver is being refurbished in the laboratory. It will serve as a spare, or will be used to replace the receiver of Antenna 1 which has a high near 245 GHz.