[evlatests] the P band polarization saga

[Wes Grammer]

I agree with Rick, but as long was we know what they are at the output, 
regardless of where the reversals are in the chain, that seems good 
enough for now.

A cable swapping & labeling campaign could be done in July, when we are 
back into the D-array. I can add this to the list I'm compiling.

-Wes

On 3/12/2014 3:45 PM, Paul Harden wrote:
>
> On 3/12/2014 3:14 PM, Ken Sowinski wrote:
>> On Wed, 12 Mar 2014, Ken Sowinski wrote:
>>> So, what we really have is:
>>>
>>>      RCP path =~ H =~ Y
>>>      LCP path =~ V =~ X
> This is indeed what we verified today.
>
> RCP = IF A/B = Horizontal dipole (P-band)
> LCP = IF C/D = Vertical dipole
>
> The entire array is currently polarized the same (consistent) per the
> above.  This is the result of having an even number of cable swaps in
> some antennas.  In most cases, we have a cable swap in the vertex room
> (that discovered today), and the feed cables in the apex have been
> swapped over time to make it right -- i.e., an even number of swaps.
> Dan nor I know how many antennas have the swapped vertex room cables.  I
> am guessing quite a few, since these heliax cables were built and
> installed during the EVLA build.  It is a pair of heliax, mismarked,
> tucked up in the cable trays, you would never suspect would have one end
> marked differently than the other.  But, easily fixed, and we now know
> how to test and suspect them.
>
> As Dan and I frequent the array, we will keep a log of those antennas
> with the incorrectly labeled cables.  Those would also be the antennas
> with swapped feeds at the apex.  If the decision is made to correct the
> cabling, we'll do it, and we should know which antennas need the work.
> A matter of swapping cables at the apex, and vertex room, at the same
> time and verifying the polarization remains correct.  If this cable
> swapping is deemed the right path, I do recommend waiting a few months
> until we are in the D-array (at least not the A).
>
> Thanks Rick and Ken for helping us finally figure out where this many
> years-old polarization swap has been occurring.  It's been driving us
> nuts as well.
>
> Just 8 more receivers per antenna to check!  Can't wait.
>
> Paul (and Dan and Greg)
>
> PS RICK: The P-band dipole on EA22 looks about 3 degrees skewed from ideal.
>
>
>
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