[evlatests] EVLA Misbehavior Last Nigh

[Ken Sowinski]

On Fri, 4 May 2007, Barry Clark wrote:

> Oh, I forgot to mention.  Antenna 24 was also doing that during the day
> yesterday.  It was totally freaking out Telcal, which I was using heavily,
> so I stopped including it.
>
>>     1) Antenna 24 is seriously misbehaving.  The A and C IFs have
>> perhaps a dozen abrupt drops in amplitude, by about 30%.  The drops are
>> simultaneous in both IFs, but are always 'single' -- the next 1.67
>> second record is at the proper level.  The B and D IF behavior shows the
>> same drops (simultaneously with the A and C), *** and in addition***
>> have major and long-lasting changes in amplitude -- by a factor of two.
>> The phase behavior of this antenna is terrible -- large (> 50 degree)
>> jumps, probably coincident in time with the amplitude jumps.  The phase
>> jumps are never 'single' -- the jump in phase is retained for tens of
>> seconds until another jump -- which rarely returns to the same phase.

And I saw it this morning.  Narrow band, L band line in 2AC mode.
Rick's plots suggest that all 4 IFs do similar things at the same
time, so it is liley a timing issue in the antenna rather than a
simple L302 (or two) problem.