[evlatests] Fwd: Re: Antenna 5 Bandpass (cont).
Jim Jackson
jjackson at nrao.edu
Fri Nov 4 13:20:39 EDT 2011
Dan Mertely is asking about the effect of
disconnecting the W8 RFI monitor on Antenna
5. This has now been disconnected for nearly a
month. Can we tell if this has made a difference
in the long standing ripple problem that was
being seen in L-band on this antenna? We really
need to get the W8 monitor back up and running -
either by simply reconnecting it if its not the cause, or fixing it if it is.
Thanks,
Jim
>Hi Jim. Would you try to organize a definitive
>test of the L-band bandpass of ea05, searching for
>the ripple written up in C127766? As you can see
>in the message at the top of this email chain, the
>W8 monitor tap was removed back on Friday, 07 Oct,
>2011, so a test at this time should determine
>whether the ripple problem (only seen in
>correlated observations--see Urvashi's 27 Oct,
>2010 email at the bottom of this email chain) is
>in fact due to the W8 monitor tap.
>
>The W8 monitor is quite a useful tool, used by not
>only the VLA IP group, but also non-NRAO astronomers
>and observatories. I would like to get it back on-
>line. Since all the ea05 ripple reports varied as
>to polarization and occurrence, and since the W8mon
>tap hardware has changed a number of times (without
>a correlated change in ea05 ripple reports), I think
>we need to determine whether it was the cause, now
>that it has been totally disconnected for nearly a month.
>Thanks.
>
>-Mert
>
>
> > -------- Original Message --------
> > Subject: Changes to ea05 L-band RCP delays?
> > Date: Fri, 07 Oct 2011 12:22:46 -0600
> > From: Dan Mertely <dmertely at aoc.nrao.edu>
> > I removed the W8 Monitor tap from the RCP output
> > of the L-band FE on ea05 this morning. The tap
> > had a 3 inch long 90 deg hybrid, plus a number of
> > coax adapters on it. I would recommend checking
> > L-band delays as a result of the shortening of the
> > RCP signal path.
> >
> > I removed it in order to debug the wide-band noise
> > hump seen in some observations since Oct 2010. It
> > would be useful to re-check the correlated bandpass
> > in the same way the bump was discovered, in order
> > to determine whether it has now gone away.
> >
> > Ref: The L-band noise bump described in C127766.
> >
> > -Mert
>
> > -------- Original Message --------
> > Subject: Re: [evlatests] Antenna 5 Bandpass
> > Date: Mon, 10 Oct 2011 12:27:52 -0600
> > From: Dan Mertely <dmertely at nrao.edu>
> > Organization: NRAO
> > To: Ken Sowinski <ksowinsk at nrao.edu>
>
>Certainly about the right length (~100 ft for
>1/2 wavelength). There are a lot of other
>splices and connectors along the way, however.
>In addition, the tap was a -10 dB hybrid as a
>splitter, going into 2 of the old blue Miteq
>L-band post amps (in series) via a isolator,
>before hitting the long stretches of 1/2 inch
>heliax. The main (EVLA) signal path shouldn't
>have seen any back reflections through all that!
>-Mert
>
> > -------- Original Message --------
> > Subject: Re: [evlatests] Antenna 5 Bandpass
> > Date: Mon, 10 Oct 2011 12:11:10 -0600 (MDT)
> > From: Ken Sowinski <ksowinsk at nrao.edu>
> >
> > About the length of a cable from the vertex room to
> > a connector at the gound?
>
> > Rick Perley wrote:
> > In reviewing my L-band 'Herc A' data, I fine the fine-scale ripple
> > present in the data taken last March, but apparently absent in the data
> > taken last December 17. The only caveat (and the reason for
> > 'apparently') is that the data taken on 17 December had a coarser
> > resolution -- 2 MHz -- rather than the 1 MHz of the other data sets.
> > The frequency period of the ripple is about 5 MHz, so it is just
> > possible that the 2 MHz resolution smoothed the ripple in the 17
> > December data. I regard this as unlikely.
> > _______________________________________________
> > evlatests mailing list
> > evlatests at listmgr.cv.nrao.edu
> > http://listmgr.cv.nrao.edu/mailman/listinfo/evlatests
>
> > -------- Original Message --------
> > Subject: Fwd: may be i stand corrected
> > Date: Tue, 4 Jan 2011 22:02:58 -0700
> > From: Joseph P. McMullin <jmcmulli at nrao.edu>
> >
> > Sorry, not quite done perhaps. The original plots did not use continuous
> > lines as we'd done
> > before; when you do that you see ea05 is spikier (at around a 10% level)
> > in the R feed in both spws...
> >
> > --
> > Dr. Joseph P. McMullin
> > EVLA
> > Ph: +1 575 835 7315
> > E-mail: jmcmulli at nrao.edu <mailto:jmcmulli at nrao.edu>
> > http://science.nrao.edu/evla/
>
> > -------- Original Message --------
> > Subject: C127766
> > Date: Thu, 30 Dec 2010 12:47:53 -0700
> > From: Jim Ogle <jogle at aoc.nrao.edu>
> > Organization: NRAO
> > To: <nrao-rfi at aoc.nrao.edu>, <echavez at nrao.edu>, <jjackson at nrao.edu>,
> > > <rlong at aoc.nrao.edu>
> >
> > Work status on work order number C127766 is CLOSED on 12/30/2010
> >
> > Work Requested: Failure - from JIRA, all baselines with ant05 at L-band
> > showing severe bandpass ripples. Seen during RSRO.
> > 10/28/10 - only RCP, both IFs.
> >
> > Corrected Action: Adjusted or Completed. Ripple was previously found to
> > move from RCP to LCP with move of W8 monitor tap. Today (12/30) I
> > replaced the -10 dB directional coupler and added an isolator to the
> > tapped output (ahead of the 2 W8 monitor Miteq amps). The entire tap
> > circuit was moved back to RCP. RCP should be checked again for the
> > ripple. The IFA & IFB bandpasses look "normal" afterward, using the
> > bandpass plotter to verify correct installation. -Mert
>
>
> > -------- Original Message --------
> > Subject: Re: L band
> > Date: Mon, 29 Nov 2010 15:25:34 -0700
> > From: Rob Long <rlong at aoc.nrao.edu>
> > Organization: NRAO
> > To: Dan Mertely <dmertely at aoc.nrao.edu>
> >
> > Do you have an amp between the coupler and the building?
> >
> > Rob
>
> > Dan Mertely wrote:
> > Hi Guys. I appreciate the ideas, but at this time I
> > think there is no need to get too fancy. In the next
> > day or so I'll get up there & replace the short RF
> > cables used, and clean-up all the connectors. If that
> > doesn't eliminate the ripple, I can change out the old
> > directional coupler for another--perhaps one with better
> > isolation. It's a simple system, I'd hate to complicate
> > it.
> >
> > -Mert
> >
> >
> > Rob Long wrote:
> >> I just checked with ALMA after lunch to see if they have an older
> >> optical TX/RX pair that we could try out with Dan's setup. I have a
> >> box of parts to look through and I'll let you know what I find.
> >>
> >> Rob
> >>
> >> Jim Jackson wrote:
> >>> Dan,
> >>>
> >>> Is this something that may be easy to fix by adding filters, DC
> >>> blocks, isolators, etc to the W8 monitor cable?
> >>> The other option is to move the W8 monitor to fiber using a pair of
> >>> 2 GHz analog optical transmitter/receivers. This might be nice since
> >>> it could be moved to any antenna location, not just W8.
> >>>
> >>> Cheers,
> >>> Jim
> >>>
> >>> At 05:27 PM 11/24/2010, Joseph P. McMullin wrote:
> >>>> Hi,
> >>>>
> >>>> Sorry for the long delay but we finally got our homework done on L
> >>>> band (I ran a 30 minute
> >>>> L_osro yesterday to make sure I had adequate time on source to
> >>>> review the pattern).
> >>>> Both Urvashi and I looked at the data and the quick summary (from
> >>>> her; I did a longer integration cycle and still
> >>>> see a dramatic difference with the LCP):
> >>>> ---
> >>>> Now, the 'L' polarization shows a ripple, and 'R' does not. I think
> >>>> this is consistent with what you described was done.
> >>>>
> >>>> I looked only at scan 30, spw 0 and did 5-second calibration
> >>>> solutions. I plotted amp(gain) vs channel . Each plot consists of
> >>>> an overlay of several 5-sec gain solutions - they overlap => no
> >>>> time-variation within the scan.
> >>>>
> >>>> Attached plots :
> >>>> EA05 : Orange = R pol, Blue = L pol. Ripple is only in L pol.
> >>>> EA10 (just for comparison) : same as above - no ripples.
> >>>> ---
> >>>> Plot is attached.
> >>>>
> >>>> Joe
> >>>> --
> >>>> Dr. Joseph P. McMullin EVLA Ph: +1
> >>>> 575 835 7315
>
> > -------- Original Message --------
> > Subject: Re: EA05 L-band ripple
> > Date: Wed, 27 Oct 2010 14:20:35 -0600
> > From: Urvashi R.V. <rurvashi at aoc.nrao.edu>
> >
> > Hi Dan,
> >
> > - Both IFs, "R polarization" only (seen after making gain solutions).
> > - Vertical scale is linear in plot_bandpass_ea11_ea05_ripple.png
> >
> > Two more plots are attached:
> > - Amp (gain solutions) vs channel-number for EA05, spw_04 (AC) and
> > spw_13 (BD), (leaving out first 3 and last 3 channels in each spw).
> > - Linear scale for the y-axis.
> > - Ripples are in the R polarization only.
> > - Plot panels are 10 seconds each (left-to-right, top-to-bottom) - to
> > show that these don't change much with time.
> > - Phase vs Frequency shows a similar ripple, about +/- 20deg (from
> > gain solutions)
> > - Calibration corrects for this, although residuals on EA05 baselines
> > (after imaging) are about 40% higher than the others.
> >
> > Please let me know if you need more info on this.
> >
> > Thanks.
> > Regards
> > Urvashi
> > (उरà¥à¤µà¤¶à¥€)
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