[evlatests] P-band checkup

[Rick Perley]

     Thanks to Paul and crew for attending to these issues so quickly.

     Regarding the polarization of ea01.  It's good that the cause was 
easily found and corrected.  Misaligned dipoles is the most obvious -- 
but not the only -- way to get high cross-polarization. This is one of 
the antennas which has the modified mounting system -- so I think it's 
important to understand how it got misaligned by ~30 degrees.  Any ideas?

     For ea08, we'll need to run another on-sky test to see if the 
connector correction has made the polarization better.  Probably best to 
wait until the switched power issue for ea01 is resolved -- next week?

     Rick

On 07/14/2016 06:21 PM, Paul Harden wrote:
> Made some low band progress at the site on Thursday.
>
> On 7/11/2016 7:49 PM, Rick Perley wrote:
>> 1) All antennas *except* ea08Y worked well.  The sensitivity of this 
>> polarization channel is less than half of the others.
>
> We fixed this low band antenna.  A bad connector-adapter gobbling up 
> the power on the RCP side.  Bandpass plots shows all IF's now at 
> proper power and passbands.
>
>> 4) Very large cross-polarizations are seen on some antennas.
>>
>>          a) The worst (by far) are:  ea01,ea06, ea08, ea17, ea27. 
>> (ea01 is nearly 50% cross-polarized!!!).
> EA08 alignment looks pretty good.  Nothing really to realign.
> EA01 indeed was misaligned by about 30 deg.  Dan Mertely and Brandon 
> got it realigned and reported the mounting hardware was all tight with 
> the new mounting collar and no real explanation on why it had moved so 
> far.  We'll see what happens over the next few months.  At the moment 
> anyway, it is properly aligned to the quadrapod legs.
>
> We didn't get a chance to check P-band dipole alignments on EA06, 17 
> or 27.  Will catch next maintenance day.
>
> Also worked on the no CAL switching on EA01.  Problem is the CAL term 
> from the F318 to the low band system is switching at 20Hz vs. 10Hz.  
> Put in a new F318, no change, so obviously an input problem 
> somewhere.  Jim Jackson thinks he knows what the problem might be in 
> the fiber interface, so will likely be fixed very soon.
>
> Paul, Sandra, Dan, and Brandon
> The Low Band Brigade, San Augustin Chapter
>
>
>
>
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