[evlatests] Hysteresis in Tuning failures

[Claire Chandler]

Does "fail to tune" mean no fringes (noise) or is there an actual M&C flag 
that says IFs A+C failed to tune?  Can you really disentangle this from 
the problem caused by the bug in the executor?  Shouldn't we just repeat 
this with the new executor?  Joe ran some tests today that showed the new 
executor seems to be behaving much better.

Claire

On Thu, 17 Jun 2010, Rick Perley wrote:

>    An extraordinary phenomenon has been noted.
>
>    In the Cygnus A observations taken last Friday, I noted that antenna
> 9, in IFs A and C, consistently failed to tune to 2500.0 MHz (in OSRO
> mode 1 with 128 MHz subband width) -- but *only* for the scans on Cygnus
> A.  Observations of the nearby calibrator J2007+4029 always fringed.
> How can the LOs 'know' the antenna is on Cygnus A, rather than the
> calibrator?
>
>    It seems the answer depends on what was observed on the previous
> scan.  In all cases, the observation of J2007+4029 at S-band was
> preceded by an observation (on that same source) at X-band (at 8100.0
> MHz).  But for all observations of Cygnus A at S-band, the preceding
> observation was at C-band (at 4500.0 MHz).
>
>    It would be very good to understand and eliminate this phenomenon.
>
>
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