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<p>What Rick mentioned is correct. Unfortunately, it is difficult to
keep the dipole aligned "perfectly", dependent on which direction
the sub-reflector was last rotating. There are nylon guide blocks
at the apex of the antenna trombone assembly which do loosen/wear
over time and allow more slop in the dipole orientation. CCW vs CW
rotation of the sub-reflector can leave the dipole in slightly
different positions. Usually, this is within a couple of degrees.</p>
<p><br>
</p>
<p>Rob<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 9/11/2024 10:12 AM, Rick Perley via
evlatests wrote:<br>
</div>
<blockquote type="cite" cite="mid:CH3PR14MB71379D84BBD8E4F66B506D6FD79B2@CH3PR14MB7137.namprd14.prod.outlook.com">
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<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
I noted yesterday some discrepant dipole orientations, and noted
that I had the impression these were worse than at earlier
times. </div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
By happenstance, I'm calibrating some old (2019) P-band data for
Tracy Clarke, which allows me to judge the correctness of that
statement.</div>
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<br>
</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
The statement is <b>wrong</b>. Misorientations were worse in
2019 than now. </div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Tracy's data were taken twice – in March and in September of
2019. The distribution of orientations were in fact worse than
now, and also were very different. Antennas misoriented now
were better (or worse) in 2019. Indeed, the correlation between
the two 2019 observations is not very strong. </div>
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<br>
</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
I believe these conclusions are not surprising, as the dipoles
are known to be subject to rotation caused by the rotating
subreflector. Perhaps Rob Long can confirm this statment. </div>
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<br>
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Rick</div>
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