[evlatests] Fwd: One phenomenon explained ...

Mon Nov 20 18:45:03 EST 2023

All:

Bruce Mues sent a few of us the explanation for the odd result that two 
of the upgraded antennas were still showing 'old ACU' antenna behavior.  
I forward his report, so that all can see the easy explanation.

-------- Forwarded Message --------
Subject: 	RE: [evlatests] One phenomenon explained ...
Date: 	Thu, 16 Nov 2023 23:22:17 +0000
From: 	Bruce Mues <bmues at nrao.edu>
To: 	Rick Perley <rperley at nrao.edu>, Catarina Ubach <cubach at nrao.edu>, 
Doug Whiton <dwhiton at nrao.edu>

The MaxVelocity setting for AZ and EL was not correct on these two 
antennas compared to the other new ACU's. The configuration setting has 
been updated on these two ACU's. This will be checked on future upgraded 
antenna's before they are turned over to OP's.

Bruce Mues - FOI, FOT-OSP
Technical Manager: Servo-Fiber
NRAO-VLA
New Mexico, USA
P: 575-835-7417
E: bmues at nrao.edu

-----Original Message-----
From: Bruce Mues Sent: Thursday, November 16, 2023 1:32 PM
To: Rick Perley <rperley at nrao.edu>; Catarina Ubach <cubach at nrao.edu>; 
Doug Whiton <dwhiton at nrao.edu>
Subject: RE: [evlatests] One phenomenon explained ...

I will need to check the config screen on the ACU in these two antennas 
to make sure the parameters are correct. I will report back when I have 
completed that check.

Thanks,

Bruce Mues - FOI, FOT-OSP
Technical Manager: Servo-Fiber
NRAO-VLA
New Mexico, USA
P: 575-835-7417
E: bmues at nrao.edu

-----Original Message-----
From: Rick Perley <rperley at nrao.edu>
Sent: Thursday, November 16, 2023 9:51 AM
To: Catarina Ubach <cubach at nrao.edu>; Doug Whiton <dwhiton at nrao.edu>
Cc: Bruce Mues <bmues at nrao.edu>
Subject: Re: [evlatests] One phenomenon explained ...

... and I note that these two are the two most recent ACU upgrades. 
Perhaps these are not 'tuned' as well as the others?

Rick

On 11/16/23 09:47, Catarina Ubach wrote:
> EA06 ACU Upgrade 6/14/2023
> EA10 ACU Upgrade 5/18/2023
>
> Catarina
>
> -----Original Message-----
> From: evlatests <evlatests-bounces at listmgr.nrao.edu> On Behalf Of Rick 
> Perley via evlatests
> Sent: Wednesday, November 15, 2023 7:44 PM
> To: Doug Whiton <dwhiton at nrao.edu>
> Cc: evlatests at listmgr.nrao.edu; Bruce Mues <bmues at nrao.edu>
> Subject: Re: [evlatests] One phenomenon explained ...
>
> Doug:
>
> Thanks for this — very good to know.
> Ea06 and 10 act like the ‘old’ systems. Are we sure they have, in 
> fact, new ACUs?
>
> Rick
>
> Sent from my iPad
>
>> On Nov 15, 2023, at 7:04 PM, Doug Whiton via evlatests 
>> <evlatests at listmgr.nrao.edu> wrote:
>>
>> Rick,
>> We should expect the antennas with new ACUs to move with precision 
>> (within several milliseconds). The biggest mystery for me is why 6 
>> and 10 were not behaving as expected. I'm sure Bruce will want to 
>> look into that. We are aware of the fact that the old ACU antennas 
>> are running on upper edges of the slew speed spec and setting their 
>> slew speed is far from precise.
>>
>> Doug
>>
>>
>>> An addendum to the previous post:
>>> In examining the DFTIM 'waterfall' plots carefully, I think I can
>> explain the apparent 'bad data' for the moon for the 'speedy' antennas.
>> I notice that the reflected circularly polarized signal is visible, 
>> at the normal strength, for the 40 seconds of data preceding the 
>> apparent arrival of the 16 new ACU antennas. For these 40 seconds, 
>> only the 'speedy' antennas are claimed to be on source. What I 
>> thought was evidence of bad data for these 40 seconds -- easily 
>> visible at the bottom of the attached screenshot, is actually just 
>> higher noise, as there were only nine antennas on source at the time.
>>> The attached screenshot shows just the first scan -- this is the V
>> vector sum, with frequency on the horizontal axis, time on the
>>> vertical. The bright circularly polarized reflection is easily seen
>> throughout. The bottom 40 seconds shows notable noisier residuals -- 
>> which I originally thought represented bad data, but which is now 
>> interpreted to be just the higher noise due to the reduced number of 
>> antennas contributing to the vector sum. The evidence is the 
>> continuance of the V signal. For the (flagged, therefore not
>> visible) data prior to
>>> the bottom row, this V signal is not present.
>>> The sudden transition to better data is easily seen, 40 seconds up from
>> the bottom row, and is caused by the amazingly simultaneous arrival 
>> of all the other antennas (or, perhaps more likely, the on-line 
>> flagging deciding this was a good time to declare things normal).
>>> So I think the only 'mystery' is how 16 'new ACU' antennas can arrive at
>> the target source, after so long a journey (nearly 180 degrees of 
>> azimuth rotation) at exactly the same time.
>>> Rick
>>> _______________________________________________
>>> evlatests mailing list
>>> evlatests at listmgr.nrao.edu
>>> https://listmgr.nrao.edu/mailman/listinfo/evlatests
>>
>> --
>> Doug Whiton
>> Hancock VLBA
>> National Radio Astronomy Observatory
>> 603-525-4332
>>
>>
>>
>>
>> _______________________________________________
>> evlatests mailing list
>> evlatests at listmgr.nrao.edu
>> https://listmgr.nrao.edu/mailman/listinfo/evlatests
>
> _______________________________________________
> evlatests mailing list
> evlatests at listmgr.nrao.edu
> https://listmgr.nrao.edu/mailman/listinfo/evlatests
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listmgr.nrao.edu/pipermail/evlatests/attachments/20231120/2599aabb/attachment.html>