xband cal values measured 06jun03


Links to PLOTS:
hcorcal value versus freq from sky and absorber
spectra of hcorcal on/off-1 on sky
power levels during hcorcal measurements

Ratio of other cals to hcorcal tracking blank sky.
Compare old and new xband cal values.

Links to SECTIONS:
Measuring the high correlated cal using blank sky and absorber
Measuring the other cals on blank sky relative to the high correlated cal.

Measuring the high correlated cal using sky and absorber: (top)

    The high correlated  cal value (diode 1 going to polA and polB) for xband wide was measured 06jun03 on the telescope using  the sky/absorber technique. The telescope tracked  blank sky and used 3 second cal on/offs.
    The cals values had also been measured at the receiver test shack in dec01. These measurements included the measurement of Treceiver across the band. The Treceiver measured was used in the 06jun03 reduction.

    The temperatures used in the computation were:
Tabsorber 299. K
Tsky+Tscattered 18 K
Treceiver from test shack

Each frequency band was measured 6 separate times on the absorber and 6 separate times on the sky. For each measurement the calon/off-1 spectrum was  computed.   A 5th order polynomial was fit to this data to generate the cal values (throwing out any datapoints greater than 2sigma on the first iteration of the fit). The calValue versus frequency plots show the results.

    The spectra of calOn/Caloff-1 for the 6 sky measurements  shows the spectra for the on sky measurements. 100 Mhz junks at a time were taken.     There are ripples in the spectra. At the high end the period is about 80 Mhz. This would be a cable length of  150/80. *.6 = 1.1 meters.

    The final plot has the power levels during the measurements.

processing: x101/030606/hcorcal/xbinp.pro,xbcal.pro,xbspec.pro,xbdiag.pro

Measuring the other cals using sky and the high correlated cal from above.  (top)

    The high correlated cal was measured above using sky and absorber as the hot and cold load. On 18jul03 the other cals were measured relative to the high correlated cal. This went from 8:15  to about 10:30 am. Three  passes were done through the frequency range. The first two passes went from a za of 10 deg rising to 11 degrees setting tracking blank sky. The 3rd pass started at 10 degree rising tracking the same declination but a different ra. The sky was clear the entire time.  The cal sequence was:     100 Mhz at a time was measured (4 by 25Mhz) going from 8000 to 10000 Mhz. The cal was cycled on/off for 3 secs at each step.  The entire frequency range was repeated 3 times.

    The calOn/calOff -1  spectra was computed for each measurement (giving cal in units of calOff or Tsys).  Each of these 25 Mhz band passes was cumfiltered. This was done on the 3 loops of the same freq band (256 channels *2 numbers). The total power was computed and then the ratio of each cal value relative to the hcorcal was computed (via interpolation of the 3 hcorcal measurements). These values were used to generate the cals table (after multiplying by the hcorcal in kelvins). An 11 order polynomial fit to the data was  done for display purposes (but it was not used to generate the cal values).  The figures show the other cals relative to Tsys and the hcorcal:

The final plot shows how the measured cal values have changed.