12meter  cal values measured 20jun23


Links to PLOTS:

Links to SECTIONS:

Why the cals were remeasured.
The model used to compute the cal values
The parameter values used in the computation
Taking the data
Processing the data
rms/mean spectra.
     calRatio (caldif/caloff) vs freq
     Computed Tcal
     compare Tcal with 2" shims and Tcal with 4"shims

Why the cals were remeasured.

    The cooled wideband receiver was installed on the 12m on 16may23. The cals were originally measured on 30may23 with  2" on shim used.  During the first part of june we experimented with different number of shims. On 20jun23 we arrived at the final configuration of 4 1" shims (2 inches closer to the secondary than the 30may23 measurements). On 20jun23 we then remeasured the cal values.

Parameters used for Tcal computation

    The values i ended up using for the computations (see below for explanations) were:

value Notes
Tabsorber 297.8K
The tabs was 75.3F when we started and 78.1F when we finished.mp.
Tsky 5k-11K
From paul Goldsmiths memo. 5K at 1GHz, 11K at 12GHz using a 2nd order fit. These values should be for zenith. I made no correction of the elevation
best guess. brought Tsys Yfactor and Tsys abs closer together.
Treceiver 20k
from values measured at the test range.
horn cooled
horn cooled

 Taking the data:

Processing the data:

    For  each 3calon,3caloff's at a given freq range

The Results

rms/mean for 3sec*3loops of data

    The rms/mean for the measured data (.png)

Calratio (calDif/calOff) vs frequency

    The 2nd image shows the cal ratio (calOn-calOff)/caloff (.png)

cal value

    The plots show the computed cal values in degK (.ps)  (.pdf)

Comparing Tcal with 2" and 4" shims

    The Tcal values measured on 30may23 with 2" shims are compared to the 20jun23 4" shim values (.ps) (.pdf)


processing: x101/230620/cals/doit.pro  .. and routines within it.

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