[evlatests] Results from Today's P-band Test

[rperley]

We ran a test to confirm the identification of the signals from the 
P-band dipoles.

The test consisted of observing 3C48, and terminating the outputs from 
the *vertical* dipole on ea28.  The termination was done sequentially in 
two places:
     a) At the input to the amplifier (at the vertex) for the cable which 
was visually confirmed to be from the vertical dipole.
     b) At the input of the T301 for the cable labelled 'L' -- which is 
believed to be the cable carrying the 'V' dipole signals.

The observations went thusly:

1) Started at 09:27 (local) with all available antennas on source.
2) ea28 stowed at 09:31.  Vertical feed cable terminated at the input to 
the amplifier.
3) ea28 back on source at 09:54.
4) ea28 stowed at 09:57.  Vertical feed cable restored.  Cable labelled 
'L' terminated at input to T301.
5) ea28 back on source at 10:22.
6) ea28 stowed at 10:25.  Cable labelled 'L' restored to T301.
7) ea28 back on source at 10:44.
8) Observations ended at 10:47.

Results:

Monitoring in the 'war room' showed the correlations went to zero for 
both cable terminations in IF channel 'C'.

Loading the data into AIPS showed that the correlations went to zero for 
both cable terminations in the channel identified as 'X'.

Hence, the assignments are:

Horizontal dipole = A/B side = 'R' labelled cable = 'Y' channel in AIPS
Vertical dipole   = C/D side = 'L' labelled cable = 'X' channel in AIPS.

It will be useful for some to know that in the MeerKAT datasets, the 'X' 
and 'Y' channels (as seen in AIPS) are opposite to the VLA:  'X' = 
horizontal dipole, 'Y' = vertical dipole.

Rick Perley