[evlatests] Referenced Pointing, Modcomp Free

[Rick Perley]

    Some good news to report. 

    The Friday test included a referenced pointing observation, plus 
pairs of observations at the higher frequency bands, one of which had 
the correction applied, the other not.  Enough VLA antennas are 
unaffected by the 'pulsing' problem (and all the EVLA antennas are 
unaffected) to permit a judgement of whether referenced pointing is 
being applied under Modcomp-free operation. 

    The Answer:

    Referenced pointing is working. 

    Details:

    I checked the 'on' and 'off' amplitudes for X and K bands, where the 
SNR is good. 

    At X-band, only three antennas showed a notable change in amplitude 
-- 15, 16, and 23.  These are the three (non-pulsing) antennas with the 
largest (by far) pointing errors found by the referenced pointing 
scan.   For all three, the amplitudes went up by an amount reasonable on 
the basis of the pointing error.

    At K-band, seven antennas showed no measureable change in amplitude, 
four showed distinct improvement, and one got distinctly worse.  The 
seven unchanged antennas (4,10,13,18,19,21,26) all had small (less than 
0.2 arcminute) errors.  The four antennas which improved (15, 16, 23 and 
24) had the largest offset errors.  Antenna 14 was the wayward one -- no 
explanation is offered (but I note that there is large asymmetry in the 
amplitude between the RCP and LCP  channels).