[evlatests] Antenna 1 at Ka-band

[Bob Hayward]

More accurate details to Chuck's description below.

It was the RCP downconverter that failed (not the LCP). It was the first 
prototype MMIC unit we had received from Caltech. One of the bonds had 
in the IF path had lifted and was quickly rebonded here. However, as the 
receiver was our first prototype (S/N 01), it had several other issues 
that needed to be addressed before returning it to the Array. Theses 
improvements include...

- Helicoils inserted into the stripped feed flange holes on the top 
plate in order to allow the horn be tightened down snuggly again.

- Replacing the early fixed gain LO Ref amp with the newer limiting 
amplifier version.

- Since we had the Dewar open, we rearranged and replaced some of the 
waveguide and coax plumbing to make it look more like our later 
production units.

- Replacing the early version of the Diode Protection Card with the 
latest version so it will provide proper Serial Number read-back.

There are bigger upgrades that the receiver will eventually need 
(improved downconverters, a new top plate and thermal transition) but 
these will be implemented in 2012 or later.

-Bob


Chuck Kutz wrote:
> Rob Long wrote:
>> Did the Ka-band receiver get fixed on ant 1?  I know there was a problem 
>> with ant 1 and the FE guys were working on it, but I don't know what the 
>> conclusion was.
>>
>> Rob
>>
>> Rick Perley wrote:
>>   
>>>     I believe there has been some discussion about what is wrong with 
>>> antenna 1 at Ka-band. 
>>>
>>>     From the data taken last weekend, it is clear that the problem with 
>>> the data lie with the system temperature calculation.  The raw 
>>> visibility data (correlation coefficients) are just fine.  But the Tsys 
>>> values are either missing or utterly absurd. 
>>>
>>>     Of course, there is no diagnosing the problem possible now -- we'll 
>>> await the rise of WIDAR to see what happens ...
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>>   
> No, the Ka in antenna 1 is not fixed yet. It is next in the que though 
> (we have been working antenna 4's Ka)
> 
> The LCP down converter in antenna 4's Ka failed and is almost finished 
> with the rework. The down converter fix was a lifted wire bond, so the 
> repair did not consume any critical components (sigh of relief). Still 
> need to run the soida tests and will finish up next week.
> We will bring in the Ka from antenna 1 next week.
> 
> Chuck
> 
> 
> Chuck
> 
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