[evlatests] P-band Dipole Orientations {External}

[Ephraim Ford]

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:



[cid:image001.png at 01DB09E0.4ABD5D10]



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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