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<p>Some comments below.</p>
<p>Rob<br>
</p>
<br>
<div class="moz-cite-prefix">On 9/22/2017 11:00 AM, Frank Schinzel
wrote:<br>
</div>
<blockquote cite="mid:bc10a198-57ba-6aca-4e10-2eff73192e2f@nrao.edu"
type="cite">
<br>
<br>
On 09/22/2017 10:55 AM, Rick Perley wrote:
<br>
<blockquote type="cite"> Some P-band data were taken earlier
this week. Frank asked me to check on the quality:
<br>
<br>
I extracted the four scans of 3C147, and used five spectral
windows (5 through 9). I find:
<br>
<br>
1) Antenna 28 was in the barn, and antennas 13 and 14 were
both out of service during these observations.
<br>
<br>
2) Antenna 23 was in a peculiar state -- the 'Y' channel
oscillated in delay on a fast (few seconds) timescale. The 'X'
channel also had irregular delays, but only for the first two
calibrator scans -- it seemed fine for the last two (two hours
later).
<br>
<br>
</blockquote>
This is probably a DTS issue. It has been doing funny things.
<br>
<blockquote type="cite">
<br>
3) Requantizers seemed to be working (meaning, they changed
level between the second and third calibrator observation).
<br>
<br>
4) CALIB gains (after applying the RQ correction) showed a
wide range of antenna correlated power -- a factor of four
between highest and lowest for a given SPW.
<br>
<br>
5) The 3 MHz bandpass ripple is strong on: 7X (2dB, pk-pk
in power), and 17X (2 dB). All others are less than 1dB.
<font color="#009900">We looked carefully at these two antennas
and found that the ripple problem exists mostly at the higher
end of the band (and somewhat at the lower end.) When we
terminated the receiver inputs with a 50 ohm load, bandpass
was flat across the entire range. We also replaced the dipole
to receiver cables on ea17 as the semi-rigid had broken solder
joints. However, VSWR on the dipoles show good return loss in
the narrow region around 327 but terrible VSWR above about 350
MHz. Maybe we need to pull these dipoles and have a closer
look, but their performance is fairly similar to other
antennas in the array.</font><br>
</blockquote>
</blockquote>
<blockquote cite="mid:bc10a198-57ba-6aca-4e10-2eff73192e2f@nrao.edu"
type="cite">
<blockquote type="cite">
<br>
6) With respect to 'golden antenna 24', the
cross-polarization is high (above 10%) on: ea03, ea10, ea14,
ea16, ea17, ea18, ea19, ea21, ea22, ea27. These are likely to
to dipole orientation. A confirmation check would be useful. <font
color="#33cc00">
<font color="#009900">I have noticed that the P-band dipoles
move around a bit during sub-reflector movement. I would be
interested in knowing if cross-pol is higher or lower
depending on if the sub is moved into position from CW or
CCW movement or any other sub movement. It just seems that
we have a large number of antennas with high cross-pol.</font><br>
</font><br>
</blockquote>
Note ea24 DTS was flaky when the data was taken, if you don't see
anything crazy in the phases or delays then it might have been ok.
<br>
<blockquote type="cite">
<br>
Rick
<br>
<br>
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