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Second 3 mm SIS receiver available: first four receiver operation at Pico Veleta

A second 3 mm SIS receiver has been installed on October 18/19. This is the first time that four receivers (two 3 mm and two 1.3 mm receivers) can be used simultaneously at the 30m telescope. The 2 mm receiver can be used, as before, in combination with 3mm1 and 1.3 mm G1.

Figure 1: Single sideband receiver temperature of the newly installed second 3 mm SIS receiver (3mm2) at Pico Veleta. Temperatures were measured with the telescope calibration system and include optical losses and spillover. Image sideband rejection ranged from 25 dB to 40 dB.

The receiver construction was done mostly in Granada with components manufactured in Grenoble. Receiver temperatures (SSB) across the tuning band (82 - 116 GHz) are in the range 55 - 85 K (Figure 1). The receiver is tuned under remote control, and has very high sideband rejection (up to 40 dB). Laboratory measurements showed very good stability which seems to be reproduced at the telescope. No frequency switch test could be done so far.

Figure 2: Result of a pointing cross scan on Saturn using both 3 mm receivers. Note the excellent agreement of antenna temperatures and beam widths between the first 3 mm receiver (left hand side) and the newly installed second 3 mm receiver (right hand side). The relative alignment of both receivers is better than .

Figure 2 shows the result of a pointing scan across Saturn with the two 3 mm receivers. Antenna temperatures and beam widths of the first (``old'') 3 mm receiver (now called 3mm1) and the second (new) 3 mm receiver (called 3mm2) are almost identical. The relative alignment of the two receivers is better than 2.