Tsys for Mathew's 430Mhz test feed
The driver circuit for the cal diode was modified
to get rid of a cal instability (more
info). The cal deflection was remeasured on 14oct05. The
stability was checked, and the average Tsys was computed. The setup was:
The plots show the
cal deflection and the system temperature (.ps) (.pdf):
The telescope was parked at az=37 (dome side) ch=8.8 degrees (the lst was
around 16:20 Hr).
The cal was toggled on 1 sec, off 1 sec. This continued for 1050 seconds.
1 Mhz around 430 was detected with a 2 millisecond time constant and sampled
at 1 khz.
The median value for each 1 second was then used for the cal on, off
Tsys for the receiver is 165 K. The cal value now looks
Fig 1 top: Total power vs time for the cal on. These are the 1 second medians.
The units are linear in power (A/D counts). The spikes are caused by
Fig 1 2nd plot: Total power vs time for the cal off.
Fig 1 3rd plot: (CalOn-calOff)/(median(calOff). This shows the variation
of the cal deflection in units of Tsys.
Fig 1 bottom:Tsys vs time using 42.1 for the cal Temperature.