[evlatests] P-band Dipole Orientations {External}

[Rob Long]

This looks off to me. I'll talk to my team tomorrow.

Rob

On 9/18/2024 3:34 PM, Ephraim Ford via evlatests wrote:
>
> This looks about the same as the photo I took, just from the different 
> direction.
>
> *From:* evlatests <evlatests-bounces at listmgr.nrao.edu> *On Behalf Of 
> *George Moellenbrock via evlatests
> *Sent:* Wednesday, September 18, 2024 2:02 PM
> *To:* evlatests at listmgr.nrao.edu
> *Subject:* Re: [evlatests] P-band Dipole Orientations {External}
>
> Hi Rick, Rob-
>
> Climbed ea11 today with some visitors, and mused about the P-band 
> dipole orientation. FWIW...
>
> Get out your protractors:
>
> Notwithstanding Rob's assertion below (about ea11), the above looks a 
> tad off-set clockwise-ward (looking up at it), relative to the quad 
> legs.  Of course, I'm not looking straight up from the center of the 
> dish, and it was best-efforts aligning myself with the quad legs (and 
> the sun was bright!).    I'm not sure this looks like as much as 10 
> deg (as Rick reports), but it is easily 5 deg, I think, and Rick's 
> measurement would be consistent with ea01 being at -5 deg (and Rob's 
> assertion that ea01 is a bad reference), and most of the others in his 
> table would be closer to zero.   Of course, there are 20+ other 
> antennas that are well-aligned with ea01...
>
> Cheers,
>
> George
>
> On 9/18/24 11:43, Rob Long via evlatests wrote:
>
>     Hi Rick,
>
>     It looks like our main dipole culprit is ea01. The dipole itself
>     is not orthogonal (elements twisted) and we are going to have to
>     get with the mechanics to get it removed so we can align it or
>     install the spare.
>
>     ea11 (on the other hand) looks to be aligned well (if you wanted
>     to use it as a reference).
>
>     Rob
>
>     On 9/10/2024 3:43 PM, Rick Perley via evlatests wrote:
>
>         Ther results of a polarization calibration of a recent P-band
>         dataset (obtained via VLITE) indicate a significant number of
>         antennas with apparently misaligned feeds.
>
>         As this was a VLITE database, there were only 18 antennas
>         included, one of which was out of service.  For the seventeen
>         others, the calibration shows seven antennas misaligned by
>         more than 5 degrees w.r.t. the reference dipole (ea01).  They are:
>
>         ea17  5.7 degrees
>
>         ea07  8.6
>
>         ea11  10.3
>
>         ea20  5.7
>
>         ea23  5.2
>
>         ea27  8.0
>
>         ea21  8.6
>
>         It is my impression (but I do not have the data in hand to
>         prove it) that this is worse than what was seen a few years ago.
>
>         These misorientations should be easily visible from the
>         antenna surface.  It would be good to know if visual
>         inspection agrees with the observations.
>
>         Rick
>
>
>
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