[evlatests] P-band status, cont.

[Paul Harden]

On 1/28/2014 9:43 AM, Rick Perley wrote:
>      After a bit of analysis, a more detailed status report:
>
>      1) Reversed Polarizations:
>
>      ea06, ea17

We worked on EA17 today and fixed the problem with low output power (a 
loose connector in the LO/IF distribution).  I forgot to swap the 
polarization.  We'll swap EA06 and 17 as soon as we can (next day or two).

Also, EA22 moved from the master pad to north arm.  P-band dipole 
installed and appears to be about 5 degrees off optically.  Receiver 
installed today (Tuesday) and all checks OK.  Should now be fully 
functional.

EA14 now in the barn.  Receiver and P-band dipole pulled so they can 
work on the subreflector.  Will be out of the array for a while.

>      2) Low Power:
>      ea06 'R':  Low in power by 13 dB
>      ea16 'R':  Low by 15 dB
>      ea20 'R':  Low by 3 dB
>      ea25 'L':  Low by 23 dB

Will check.  Low band specifications call for output power to be within 
3dB between all receivers, and no more than 3dB difference between 
polarization channels.  EA20 seems right at specifications.  13-23dB low 
is clearly a problem, however, and will check.

>      3) High Cross Polarizations  (> ~ 10%)
>      ea04, ea06, ea11, ea17, ea20.

Will check EA06 and 17 optical alignment when we swap polarizations, and 
the others as we can get to them.

As observed, when the subreflector moves in rotation, the P-band dipoles 
tend to move 3-5 degrees (mechanical slop), depending on direction of 
subreflector travel.  We may not be able to guarantee axis alignment any 
better than this 3-5 degrees.

>      All else looks very good.

Thanks.  We're zeroing in on a 100% functional low band system.

Paul