[evlatests] Phase Connection

[Rick Perley]

    Oops.  (It's a good thing we've got Barry around to remind us of our 
blunders ...)

    This effect requires a different calibration strategy.  Because 
antennas 13 and 18 have the modern L302s, with up-to-date firmware, we 
must use one of these (18 for this experiment) as the reference, in an 
investigation of phase stability of EVLA antennas.  Comparison with VLA 
antennas requires a VLA antenna as reference.  To ensure we make similar 
comparisons, I used antenna 9 as the VLA reference (it's adjacent to 
antenna 18), and compared 13's phase behavior with antenna 6 (adjacent 
to 13).  In this way, we are utilizing a similar baselines from adjacent 
antennas. 

    The result of this shows:

    Antenna 6 vs. 9 (VLA reference baseline) shows no significant phase 
changes between scans taken at the same frequency.  The time separation 
between such scans was 15 minutes. 
    Antenna 13 vs 18 (the EVLA baseline shows a gradual increase in 
phase -- identical on all four IFs -- of about 10 degrees over 15 
minutes.  The same slope was seen at all frequencies. 

    Looks like a baseline, or other such global phase effect, although 
if a baseline error, it is rather larger than I would expect for such a 
near-in pad (W12 = BW3). 

Barry Clark wrote:

>>    The 14-frequency experiment run yesterday to check on the L-band 
>>sensitivity relation vs. frequency permits a check of whether antenna 
>>phase returns after tuning to another frequency. 
>>    It does not, for any EVLA antenna, for any IF.  It does for all VLA 
>>antennas. 
>>    
>>
>
>As we keep saying, resetting the Fluke synthesizer frequency randomizes
>the phase between EVLA and VLA.  Are there two good L302s such that we
>can look and see if the phase returns on that baseline?
>_______________________________________________
>evlatests mailing list
>evlatests at listmgr.cv.nrao.edu
>http://listmgr.cv.nrao.edu/mailman/listinfo/evlatests
>  
>