[evlatests] ea24 problem

[Ken Sowinski]

On Tue, 8 Mar 2011, Rob Long wrote:

> Pointing and sub-reflector were asked about right away. How did we determine 
> it was OK at first?

By noting that the FRM parameters for ea24 had not been changed
in the database for a long time.  We never expect the hardware
to change.

A real test should have been done and was not.


> Ken Sowinski wrote:
>> On Fri, 4 Mar 2011, Emmanuel Momjian wrote:
>> 
>>> Yesterday, test observations at Ku-band showed noisy phases and amplitudes
>>> on ea24. To look into this in more detail, today we ran multi-frequency
>>> observations spanning all the bands from X to Q using the calibrator
>>> J2202+4216 .
>>> 
>>> While there is nothing obvious at X-band, the data show that the phases 
>>> and
>>> the amplitudes degrade progressively from Ku to Q band.
>>> 
>>> Pointing looks OK on ea24. Therefore we think that the problem may be in 
>>> the
>>> L301 or its reference signal, although L302 and the round trip phase look
>>> good.
>> 
>> The problem was just found to be focus.  The focus zero point changed
>> by about 2 cm sometime last week.  I have adjusted the focus settings
>> for all the high frequency bands as well as X and C bands.  A more
>> careful measurement will be made in the next day or so.
>> 
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>