Old receiver systems

The above description refers to the ``new generation'' receivers installed during the winter 2006-2007 (3 and 1.3 mm bands) together with the new IF processor. The system was completed in 2007-2008 with the 2 mm band, and should be further developed in the next years (0.8 mm band, new wide-band correlator). The LINE command allows one to produce plots using the old receiver and backend system, to be able to check old Plateau de Bure data. The command SET PDBI 1995|2000|2006 is used to select the status of the instrumentation in the year:

• 1995: 3 and 1.3 mm receivers, 500 MHz bandwidth (from IF 100 to 600 MHz).
• 2000: 3 and 1.3 mm receivers, 580 MHz bandwidth (from IF 100 to 680 MHz).
• 2006: new generation receivers and new IF processor (this is the default)

For the old receivers (1995 and 2000), the NARROW, SPECTRAL, and PLOT commands are not relevant. Instead, the LINE command has a series of options, the most important one being LINE /SPECTRAL iunit bandwidth fcenter to plot the position and width of the correlator spectral units (see on-line help for all options). The plots that are produced are always DSB-like. Note that the doppler correction is of some importance for the old receivers, because these receivers were (or could be tuned) DSB. Indeed, doppler tracking is correct only in the signal sideband. The doppler correction is correct in the image sideband when the frequency is loaded by OBS at the Plateau de Bure, but subsequent tracking is computed for the signal side band only. The tracking error in the image side band is 0.04 km/s at 86 GHz, in the worst case. This is now unrelevant for the current Plateau de Bure receivers, which are SSB.