A stability problem of the 1.3 mm receiver G2 - manifesting itself in poor baselines - could be solved by replacing the cold HEMT amplifier.
Lately, the 1.3 mm receiver G1 occasionally showed a broad feature (about 80 MHz wide) in the baseline. This feature occurs erratically and can severely degrade the spectrum. However, most of the time the baseline is ok. The cause for this feature is not known at this point. The problem is being investigated.