[evlatests] Tcal accuries at P-band

[Frazer Owen]

     The scatter is expected. Actually the scatter is pretty small. The 
ability to measure the T_cals in the lab is limited. We needed to have 
done this sort of on-the-sky calibration.

---Frazer

On 9/2/14 6:06 PM, Rick Perley wrote:
> A recent test at P-band observed both Cygnus A and some good 
> calibrators (3C48 and 3C380).  The primary goal was to test linearity 
> of the system -- results for this will be presented later (but the 
> news is very good).
>
>     Here I report on the accuracy of the Tcal values.
>
>     All antennas except ea13 and ea18 had good values of PDif.  If the 
> Tcal values are correct, and the efficiencies utilized are correct, 
> the visibility data for the calibrators, following application of the 
> switched power should equal the known source flux densities.
>
>     For this test, I chose a single subband, at 312 MHz.  (Reason -- 
> this subband had the least RFI).   After basic editing, the switched 
> powers were applied, and CALIB run on the two calibrators listed above.
>
>     The mean solutions (for 'R' and 'L') were within 5% of 1.0. That's 
> the good news.
>
>     The not-so-quite good news is that there is a large scatter. Below 
> are the CALIB gains needed to bring the data into alignment with the 
> correct flux densities.  Presuming the utilized efficiencies are 
> correct, and are the same for every antenna, the error is in the 
> values of the Tcals.  The needed correction to the Tcal values is the 
> square of the gain factor listed.  Hence, if the gain factor is 1.1, 
> then the Tcal value should be increased by 1.21.
>
> Antenna      Gain Factor
>
> 1R                     1.08
> 1L                      1.07
> 2R                     1.03
> 2L                      0.87
> 3R                     1.05
> 3L                      0.95
> 4R                     1.02
> 4L                      0.75
> 5R                     0.90
> 5L                      0.86
> 6R                      0.98
> 6L                      1.06
> 7R                     1.02
> 7L                      0.92
> 8R                     out
> 8L                      out
> 9R                     1.09
> 9L                      0.84
> 10R                    1.50
> 10L                    1.30
> 11R                    out
> 11L                     out
> 12R                    1.23
> 12L                    1.36
> 13R               no PDif
> 13L                no PDif
> 14R                   0.97
> 14L                   0.72
> 15R                   1.20
> 15L                    0.84
> 16R                   1.20
> 16L                    0.95
> 17R                   0.92
> 17L                    1.00
> 18R                   1.04
> 18L              PDif broken
> 19R                   1.08
> 19L                    0.67
> 20R                   1.10
> 20L                    1.17
> 21R                    1.14
> 21L                    1.03
> 22R                   0.94
> 22L                    0.90
> 23R                    1.05
> 23L                    1.07
> 24R                   1.12
> 24L                     1.13
> 25R                    1.27
> 25L                     1.50
> 26R                    0.90
> 26L                     0.97
> 27R                    0.93
> 27L                     1.05
> 28R                    0.93
> 28L                     0.91
>
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