[evlatests] Phase jumps, and holography

[Rick Perley]

    The relation between holographic scans, and the phase behavior, is 
not a simple one (although it may have a simple solution!)  Below is a 
log of the scan boundaries, and observed phase behavior for antenna 16, 
IF 'B' (at 1275 MHz) from last night's run. 

Time               Event or phase change
----------------------------------------------------
22 57 50         Calibrator scan starts
22 59 30.4      -180
22 59 31.0      Calibrator scan ends
22 59 40         Holography scan starts
22 59 52.5      -48
23 00 02.1      +225 (we have returned to the original phase)
23 01 31         Holography scan ends
23 01 40         Holography scan begins
23 01 43.8      -135
23 01 52.1      +135
23 03 31        Holography scan ends
23 03 40        Holography scan begins
23 03 43.8      + 20
23 03 51.7      -198  (note -- we're now in the 'inverted' phase state)
23 05 31.0        Holography scan ends
23 05 40.0        Holography scan begins
23 05 42.9        +180
23 05 51.2        -180  (NB  this one breaks the rule of +/- 180 being 
uniquely associated with holography scans)
23 07 22.5        +180
23 07 31            Holography scan ends
23 07 40            Holograph scan begins
23 07 43.3        -135
23 07 52.1        +135
23 09 31            holography scan ends
23 09 40            holography scan begins
23 09 43.7        -242
23 09 51.7        +65 (NB We're back in the 'inverted' state)
23 11 31.0         holography scan ends
23 11 40            Calibrator scan begins
23 12 51            Calibrator scan ends
23 13 00            holography scan begins
23 13 10.8         +180
23 14 43.3         -180
23 14 51            holography scan ends
23 15 00            holography scan begins
23 15 04.2         +200
23 15 12.1         -20 (so we're now in the 'normal state')
23 15 22.5         +40
23 15 32.1         -40
23 15 42.1         +40
23 15 42.1         -40
23 16 43.3         -180
23 16 51            holography scan ends
23 17 00            holograph scan begins
23 17 03.7         +65
23 17 11.7         -65
23 18 42.5         +265
23 18 51            holography scan ends
23 19 00            holograph scan begins
23 19 00             -265
23 19 11.7         +180
23 20 51            holography scan ends
23 21 00            holography scan begins
23 21 00            -180
23 21 04.0         +245
23 21 12.5         -70 (NB -- back at 'normal phase')
23 22 51            holography scan ends
23 23 00            holography scan begins
23 23 03.5         +85
23 23 11.7         -85
23 24 51            holography scan ends
23 25 00            calibrator scan begins
23 25 00            -180
23 26 51            calibrator scan ends

    There are two different families of phase jumps:

    Type A)  Short duration ones -- nearly always 10 seconds (or a bit 
less) long, of variable sign.

    Type B)  Long duration ones -- always 180 degrees.  The transitions 
often, occur within 10 seconds of a scan boundary.