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<font size="-1"><font face="Century Schoolbook L">Good thing Vivek
thought about this. I wouldn't have.... but<br>
in hindsight, shadowing certainly fits your description of the<br>
issue.<br>
<br>
Mark<br>
</font></font><br>
<div class="moz-cite-prefix">On 5/26/20 10:12 AM, rperley via
evlatests wrote:<br>
</div>
<blockquote type="cite"
cite="mid:5edaa7a2d60b07ba2816075827707dab@nrao.edu">And indeed,
this is exactly what was wrong. Only this antenna was shadowed --
by ea12, sitting on N01.
<br>
<br>
Sorry for the red herring. Shadowing in C configuration is rarely
an issue...
<br>
<br>
Rick
<br>
<br>
On 2020-05-26 11:54, Vivek Dhawan wrote:
<br>
<blockquote type="cite">ea09 is on W02. Shadowing?
<br>
<br>
On Tue, May 26, 2020 09:18, Ken Sowinski via evlatests wrote:
<br>
| I haven't looked at pointing results recently because it hard
to do from
<br>
| home. But, on the face of it an effect that large suggests
there might
<br>
| be someting loose up at the apex. As a pointing model error
is has to
<br>
| be well over an arc-min to cause consistent failures at X
band.
<br>
|
<br>
| Ken
<br>
|
<br>
|
<br>
| On Mon, 25 May 2020, rperley via evlatests wrote:
<br>
|
<br>
|> We ran the 'gain-elevation' script last night. The
purpose is to remeasure
<br>
|> the gains as a function of elevation, from X through Q
bands. The method
<br>
|> uses 'double-referenced pointing' -- referenced pointing
is done first at
<br>
|> X-band, and these results are used to 'peak up' Ku-band,
then K-band, then
<br>
|> Ka, and ending with Q-band. This is to ensure the
antennas as peaked up on
<br>
|> the source for each band and elevation.
<br>
|>
<br>
|> Observations started with the source (J2007+4029) at 11
degrees elevation,
<br>
|> and proceeded cyclically through the bands until meridian
transit. For
<br>
|> each
<br>
|> cycle, the old referenced pointing solutions were
'forgotten' when X-band
<br>
|> was
<br>
|> next scheduled. This procedure worked very well for
nearly all antennas.
<br>
|> But not ea09...
<br>
|>
<br>
|> Something is seriously amiss with this antenna, for
elevations below 30
<br>
|> degrees.
<br>
|>
<br>
|> All referenced pointing attempts failed, including the
initial X-band one,
<br>
|> until the antennas reached 23 degrees elevation. At this
elevation, the
<br>
|> solution offset parameters looked good, but in fact were
not, as the gains
<br>
|> (at X-band!) were low by 40%. As the antenna rose, the
gains rapidly
<br>
|> increased until, at elevation 34 degrees, all looked
normal at all bands.
<br>
|> From then until meridian transit, all was well.
<br>
|>
<br>
|> I have no idea what is wrong here. Any ideas?
<br>
|>
<br>
|> Rick
<br>
|>
<br>
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