[evlatests] A most spectacular failure of 'set-and-remember'?

[Rick Perley]

    More information:

    Remarkably, the IF 'A' jump times are *not* the same as the IF 'C' 
jump times.  Won't this invalidate the L302 theory?  In any event, if 
the L302 was wrong, there should be no discernible fringes during the 
time it was wrong.  But the fringes are strong and stable. 

    In no cases were the jump times aligned with source changes.  They 
all occurred in the middle of scans. 

    There is no change in the requantizer gains, so the correlator is 
exonerated. 

   

Keith Morris wrote:
> ea18 and ea19 both show the same behavior in the T304-a: the input power 
> and input attenuator were constant over the jump (at the nominal values) 
> and the output attenuator and power changed, to their nominal values. 
> This (and the AC-dependence) implies that the L302 was wrong, and became 
> correct, since the output detector is post-conversion.
>
> I can look into it further tomorrow.
>
>
>
> On 1/13/2014 5:17 PM, Rick Perley wrote:
>   
>>      I'm calibrating 20 S-band databases, taken from November 2013
>> through January 2014.    Five have been completed without any troubles
>> (other than the usual satellite RFI).  But one is 'special':
>>
>>      For this database, the gains of all antennas jumped up, by a factor
>> of ~ 2 to 10, at times roughly in the middle of the 90-minute run.  But ...
>>
>>      1) Only the A and C IFs jumped.
>>      2) Each antenna jumped gain at a different time.
>>      3) The new gain was in fact the correct one (judging from the
>> calibrated gain values and PSum values).  Hence, *the initial power
>> setup was too low by factors of a few*.  Somehow, this error was
>> corrected in the middle of the run.
>>
>>      This SB was under program 13B-316.  The data were taken on 06 Dec
>> 2013.
>>
>>      The time patterns of the jumps are curious:
>>
>>      1) Antennas 18, 19, 20, 22, 23 and 28 all jumped between 12:47 and
>> 12:51 (IAT).  All jumps were 'clean' -- no more than one intermediate
>> value is seen.
>>      2) All other antennas jumped between 13:20 and 13:45.  Some of these
>> jumps were not clean -- the system oscillated between the two states, or
>> (in one case) hopped around three states, before stabilizing.
>>
>>      The initial scan for this run was many minutes long -- more than
>> enough time for the system to find the 'right' level, and keep it.  But
>> it didn't, and it didn't ...
>>
>>      Any ideas?
>>
>>
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>>     
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