[evlatests] Tcal accuries at P-band

[Bryan Butler]

i also wouldn't be so sure that the efficiencies are all the same.


Frazer Owen wrote, On 9/2/14 18:23 :
>      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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