[evlatests] Phases on antennas 14 and 24

[Rob Long]

The antenna 14 B/D issue certainly looks like it may be hardware 
related.  If the phases in both IFs jump the same, is the magnitude 
identical from band to band?  What bands did you see this effect in and 
was X-band doing this also?

Rob

Rick Perley wrote:
>     I reported yesterday on phase changes seen on two EVLA antennas 
> during the 'modcomp-free' tests last Friday. 
> 
>     To Recap:
> 
>     14B and D showed two alternating phase states, separated by about 40 
> degrees. 
>     24, all IFs, showed multiple phase states. 
> 
>     For both antennas, phases are stable within any phase state.  The 
> transitions are abrupt, but always are such that an intermediate phase, 
> exactly halfway between the two, is seen.  Hence, the cause must be 
> linked to the fundamental integration time -- 0.417 seconds. 
> 
>     Vivek reported that likelihood that antenna 24's behavior was likely 
> due to a misbehaving RT phase.  Ken disabled this meter. 
> 
>     Data taken today, with Modcomps in control, show:
> 
>     Antenna 24 now has stable phase. 
> 
>     Antenna 14, IFs B and D are behaving as reported above. 
> 
>     Upon review, the following additional characteristics are seen on 14 
> B and 14 D:
> 
>     The transition always takes place following a 10-second 'tic'.  The 
> duration of the alternate phase is always 10.0, or in rare 
> circumstances, 20.0 seconds.  The two IFs always jump together, by equal 
> amounts. 
> 
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