[evlatests] slow attenuator setting on ea16 IF D

[Keith Morris]

The monitor data archive shows that the total power in ea16-t304-d 
continued to change after the attenuator had been set (see attached 
plot).  Ken's subreflector hypothesis sounds reasonable.



Claire Chandler wrote:
> Yes, all other IFs look like ea15 and ea17 in the plot.  This only affects 
> IF D.
> 
> Claire
> 
> On Mon, 8 Aug 2011, Ken Sowinski wrote:
> 
>> On Mon, 8 Aug 2011, Claire Chandler wrote:
>>
>>>  Steps in the amplitudes on ea16 IF D (L-pol) indicate that it's taking
>>>  several minutes to find the correct attenuator setting at the beginning of
>>>  an observation (the attached plot is for Ka-band).  I have seen this in
>>>  several recent datasets; the attached is from July 15, but I also saw it
>>>  in data taken on Sunday morning.
>> I hesitate to blame mis-set attenuators for this because the
>> steps are not consistently 1 dB or multiples.  If it were not
>> for the fact that the other IFs were fine (is that really true?)
>> I would consider a sticky subreflector that moves a little further
>> each time it is commanded until it finally gets there.
>>
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-- 
Keith Morris
National Radio Astronomy Observatory
1003 Lopezville Rd.
Socorro, NM 87801
575-835-7060 (phone)
575-835-7027 (fax)
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