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<p>All:</p>
<p>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. <br>
</p>
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-------- Forwarded Message --------
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<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Subject:
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<td>RE: [evlatests] One phenomenon explained ...</td>
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<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Date: </th>
<td>Thu, 16 Nov 2023 23:22:17 +0000</td>
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<th valign="BASELINE" nowrap="nowrap" align="RIGHT">From: </th>
<td>Bruce Mues <a class="moz-txt-link-rfc2396E" href="mailto:bmues@nrao.edu"><bmues@nrao.edu></a></td>
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<th valign="BASELINE" nowrap="nowrap" align="RIGHT">To: </th>
<td>Rick Perley <a class="moz-txt-link-rfc2396E" href="mailto:rperley@nrao.edu"><rperley@nrao.edu></a>, Catarina Ubach
<a class="moz-txt-link-rfc2396E" href="mailto:cubach@nrao.edu"><cubach@nrao.edu></a>, Doug Whiton
<a class="moz-txt-link-rfc2396E" href="mailto:dwhiton@nrao.edu"><dwhiton@nrao.edu></a></td>
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<br>
<br>
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.<br>
<br>
Bruce Mues - FOI, FOT-OSP<br>
Technical Manager: Servo-Fiber<br>
NRAO-VLA<br>
New Mexico, USA<br>
P: 575-835-7417<br>
E: <a class="moz-txt-link-abbreviated" href="mailto:bmues@nrao.edu">bmues@nrao.edu</a><br>
<br>
-----Original Message-----<br>
From: Bruce Mues Sent: Thursday, November 16, 2023 1:32 PM<br>
To: Rick Perley <a class="moz-txt-link-rfc2396E" href="mailto:rperley@nrao.edu"><rperley@nrao.edu></a>; Catarina Ubach
<a class="moz-txt-link-rfc2396E" href="mailto:cubach@nrao.edu"><cubach@nrao.edu></a>; Doug Whiton <a class="moz-txt-link-rfc2396E" href="mailto:dwhiton@nrao.edu"><dwhiton@nrao.edu></a><br>
Subject: RE: [evlatests] One phenomenon explained ...<br>
<br>
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.<br>
<br>
Thanks,<br>
<br>
Bruce Mues - FOI, FOT-OSP<br>
Technical Manager: Servo-Fiber<br>
NRAO-VLA<br>
New Mexico, USA<br>
P: 575-835-7417<br>
E: <a class="moz-txt-link-abbreviated" href="mailto:bmues@nrao.edu">bmues@nrao.edu</a><br>
<br>
-----Original Message-----<br>
From: Rick Perley <a class="moz-txt-link-rfc2396E" href="mailto:rperley@nrao.edu"><rperley@nrao.edu></a><br>
Sent: Thursday, November 16, 2023 9:51 AM<br>
To: Catarina Ubach <a class="moz-txt-link-rfc2396E" href="mailto:cubach@nrao.edu"><cubach@nrao.edu></a>; Doug Whiton
<a class="moz-txt-link-rfc2396E" href="mailto:dwhiton@nrao.edu"><dwhiton@nrao.edu></a><br>
Cc: Bruce Mues <a class="moz-txt-link-rfc2396E" href="mailto:bmues@nrao.edu"><bmues@nrao.edu></a><br>
Subject: Re: [evlatests] One phenomenon explained ...<br>
<br>
... and I note that these two are the two most recent ACU
upgrades. Perhaps these are not 'tuned' as well as the others?<br>
<br>
Rick<br>
<br>
On 11/16/23 09:47, Catarina Ubach wrote:<br>
<blockquote type="cite">EA06 ACU Upgrade 6/14/2023<br>
EA10 ACU Upgrade 5/18/2023<br>
<br>
Catarina<br>
<br>
-----Original Message-----<br>
From: evlatests <a class="moz-txt-link-rfc2396E" href="mailto:evlatests-bounces@listmgr.nrao.edu"><evlatests-bounces@listmgr.nrao.edu></a> On
Behalf Of Rick Perley via evlatests<br>
Sent: Wednesday, November 15, 2023 7:44 PM<br>
To: Doug Whiton <a class="moz-txt-link-rfc2396E" href="mailto:dwhiton@nrao.edu"><dwhiton@nrao.edu></a><br>
Cc: <a class="moz-txt-link-abbreviated" href="mailto:evlatests@listmgr.nrao.edu">evlatests@listmgr.nrao.edu</a>; Bruce Mues
<a class="moz-txt-link-rfc2396E" href="mailto:bmues@nrao.edu"><bmues@nrao.edu></a><br>
Subject: Re: [evlatests] One phenomenon explained ...<br>
<br>
Doug:<br>
<br>
Thanks for this — very good to know.<br>
Ea06 and 10 act like the ‘old’ systems. Are we sure they have,
in fact, new ACUs?<br>
<br>
Rick<br>
<br>
Sent from my iPad<br>
<br>
<blockquote type="cite">On Nov 15, 2023, at 7:04 PM, Doug Whiton
via evlatests <a class="moz-txt-link-rfc2396E" href="mailto:evlatests@listmgr.nrao.edu"><evlatests@listmgr.nrao.edu></a> wrote:<br>
<br>
Rick,<br>
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.<br>
<br>
Doug<br>
<br>
<br>
<blockquote type="cite">An addendum to the previous post:<br>
In examining the DFTIM 'waterfall' plots carefully, I think
I can<br>
</blockquote>
explain the apparent 'bad data' for the moon for the 'speedy'
antennas.<br>
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.<br>
<blockquote type="cite">The attached screenshot shows just the
first scan -- this is the V<br>
</blockquote>
vector sum, with frequency on the horizontal axis, time on the<br>
<blockquote type="cite">vertical. The bright circularly
polarized reflection is easily seen<br>
</blockquote>
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<br>
visible) data prior to<br>
<blockquote type="cite">the bottom row, this V signal is not
present.<br>
The sudden transition to better data is easily seen, 40
seconds up from<br>
</blockquote>
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).<br>
<blockquote type="cite">So I think the only 'mystery' is how
16 'new ACU' antennas can arrive at<br>
</blockquote>
the target source, after so long a journey (nearly 180 degrees
of azimuth rotation) at exactly the same time.<br>
<blockquote type="cite">Rick<br>
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</blockquote>
<br>
--<br>
Doug Whiton<br>
Hancock VLBA<br>
National Radio Astronomy Observatory<br>
603-525-4332<br>
<br>
<br>
<br>
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