12meter xband cal values measured 17jan22


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
Total power vs time by freq band.
     calRatio (caldif/caloff) vs freq
     Fitting to calRatio vs freq
     Computed Tcal and  tsys vs freq

Why the cals were remeasured.

    The xband cal diode was stabilized with a peltier cooler on 08Nov21. On 17jan22 we were finally able to access the horn to do a sky and absorber measurement to measure the cal value.

Parameters used for Tcal computation

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

value Notes
Tabsorber 301.3K 83 F from temperature sensor in absorber
Tsky 15K includes any scattered energy. see below
Treceiver 74,68K
 polA,B  see below
omt temperature.. a guess.
reflection coef for horn/omt see below
omt absorption

 Taking the data:

Processing the data:

    For each scan the following is done:

The Results

Total power vs time by freq band

    Plotting the cal Deflection total power vs time (.pdf)

Calratio (calDif/calOff) vs frequency

    The 2nd set of plots shows the calRatio vs freq plotted for each scan (.pdf)

Fitting a curve to the calRatios.

   A harmonic fit was  done  to the calRatio vs freq and then the fit was used to compute TCal.

The plots show a fit to the CalRatio measurements (.pdf)

Computed Tcal and Tsys using the cal values.

    The  plots show the computed Tcal and tsys in deg K using the new cal values (.pdf)


processing: x101/220117/measure_cal.pro

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