[evlatests] Modcomp-Free Tests, 18 May

[Rick Perley]

    In answer to Ken's query (below):

    These drops are both similar, and different ... 
    Their duration and amplitude were similar to those reported on EVLA 
antennas before.  They are different in that they *always* affect all 
four IFs identically. 

    Given the unsteadiness of all the gains of the inner 
(D-configuration) antennas on this test, and that this was only notable 
at the beginning test (with Modcomps in control), and virtually gone by 
the time the Modcomp-free tests ran, (do minutes later), I'm speculating 
these little drops are due to some external source -- like lightning?  
Some evidence for this is found in the fact that all these drops for the 
inner antennas occurred at the same time (while those seen on the 
distant ones were seen with a different pattern). 



Ken Sowinski wrote:
> On Sun, 20 May 2007, Rick Perley wrote:
>
>>    We are seeing many 'short drops' on ALL antennas.  In all cases,
>> these affect all four IFs simultaneously and identically.  These were
>> much worse during the 'Modcomp-on' data.
>
> Is this the same as what you used to call the "short, shallow
> drops"?  If it is really seen with the Modcomps too, then I will
> have to start thinking about ways to make it in the correlator.
> If it is really true that we continued to see it with phase
> switching off then explanations are hard to come by.
>