ALMA Memo #461

The Amplitude Calibration System revisited

S.Guilloteau (IRAM / ESO)
A.Bacmann (ESO)

16 Sep 2003

Keywords: Amplitude Calibration, Receiver Saturation

Different strategies of use of a semi-transparent device combined with two temperature loads
for calibration are explored. It is shown that a system with an ambient load, a hot (100
Celsius or so) load, and a semi-transparent grid with 50 % transmission allows to reach a
1 % accuracy on the receiver gain even in presence of saturation. The best precision
requires a device which offers the 5 major combinations: Sky, Sky+Ambient, Sky+Hot,
Ambient, Hot. If saturation is negligible, the system can be used as a standard dual load
calibration device, with better accuracy.