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Sections:

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History:

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Calibration measurements:

• 05feb14: ratio of backscatter gain to on axis gain.
  
• 13jan13: calibration results: jun12-dec12. updated pointing offset.
• 16aug06: fit gain vs frequency.
• mar03  -  oct03: GAIN CURVE.

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Measurements in date order:

• 29aug19: Tsys   change as aeronomy receiver goes from cooled receiver to warm receiver.
  
• 23apr19: polB jennings relay give high tsys.
  
• 05feb14: ratio of backscatter gain to on axis gain.
  
• 13sep13: ripple seen in polA bandpass. Tapping on plumbing causes polA jumps (again).
  
• 09sep13: polA cavity filter repaired an reinstalled.
  
• 05sep13: polA cavity filter (before amp) bad. removed. Was causing jumps in tsys polA
  
• 05sep13: polA jennings relay bad. switched  with polB relay (at least for radar run).
  
• 27aug13: new turnstile damaged. replaced by old turnstile. Jennings relay polA also replaced.
• 05aug13: "new" turnstile damaged. replace by old turnstile 27aug13.
  
• 03apr13: polA Tsys jumps to 400 K in the afternoon.
  
• 13jan13: calibration results: jun12-dec12. updated pointing offset.
  
• 02dec12: sweep notched filter in front of dewar
  
• 30nov12: az swings with polA filter removed tv station intermods,az dependence, time periodic birdies
• oct-dec12: a2704 total power mapping shows polA ripples for > 1/2 the runs
• 19nov12:take spectra while moving radar,radio astronomy switch. Ripple in both positions.
  
• oct-nov12: x111 data shows polA  ripple coming and going.
• 19oct12: polB jennings relay removed. Little power from sky was getting to polB.
  
• 15oct12: 430 dome polB gain is 10% of the expected  value.
  
• 19sep12: TsysPol A is jumping around. Also plot Tsys vs Freq.
  
• 05sep12   atm power profiles show cal dropouts.
• 30mar12: terminate different positions before dewar looking at polA ripple
  
• 26mar12 - looked at polA ripple while on load.
• 17mar12: polA ripple continues ..
  
• 11aug11:polA ripple remains when radar/radioastronomy switch bypassed.
  
• 01aug11: proj a2599 dps sees polA bandpass irregularities.
  
• 28jul11,23jun11,17may11: polA shows irregularities in its bandpass 
• 2011 - 2012 ripples in polA 
• 24oct09: polB had normal gain. So polB jennings relay ok here.
  
• 27sep10: check 430 stability.. looks ok. dynamic spectra, avg spectra, rms/mean, total power vs time.
  
• 10aug09: polA unstable
  
• 23apr09: Noise at 439 MHz in dome system when Tx Hv on.
  
• 06apr09: peak hold spectrum at dewar output during az swing.
  
• 16aug06: fit gain vs frequency.
• 19jul06: reflection from new turnstile (.jpeg)
• 14jul06: reflection from old turnstile (.jpeg)
• 11jan04: (TsysPolA - TsysPolB) drift for 2003, 2004
• jun04: tv stations 14,22 causing intermods in both ch and dome dewars.

190829 430 warms up during aeronomy run.

    We were running an aeronomy experiment (using the sterling cooled amp) on 29aug19 when the system warmed up.
I computed the Tsys for the start of each ri file using 10secs of cal measurements for each point.

The plot shows the change in Tsys from cold to warm receiver (.ps) (.pdf)

• Tsys went from about 180 K cold to 200K warm.
  
• The bump at 21 hours is the galaxy passing overhead (19:00 lst).

processing: x101/190830/gr430warmup.pro

05feb14 ratio of backscatter gain to on axis gain.

    Herb  carlson and frank djuth wanted the backscatter gain for the 430 dome.
15 heiles calibration patterns on B0316+162 (CTA21.. point source with a flux of 8.7 Jy) were used. Carl's patterns consist of:

• 4 passes through the source. Each pass is 6 fwhm beams long
• az  strip through source
  
• za strip through source.
  
• -45 degree strip through source
• +45 degree strip through source.
• A 2-d gaussian with sidelobes is fit to each pattern. The fit includes:
• offset, peak, widths in 2 directions, rotation angle for ellipse, coma parameter
  
• the sidelobes are fit as gaussians. an 8th order harmonic fit is done at the sidelobe distance
  
• Each pattern had 4 separate measurements:
• 25Mhz bw centered at 430 Mhz
• 12.5 Mhz bw centered at 430Mhz
• 1.56 Mhz bw centered at 429 Mhz
• 1.56 Mhz bw centered at 431 Mhz
• The variations are to check for interference.

Computing the back scatter gain:

• The image covers +/-35.4 arc minutes
• The contours are spaced by 3db.
• This pattern was taken at za = 16.8 deg.

• Page 1:
  
• top: az,za for the 15 patterns . The left side has the source rising, the right have is the source setting.
• Bottom: Point source gain vs za for the measurements.
• the colors show the 4 bands taken for each pattern
• The 25Mhz band was lower than the other 3. this probably includes the gain dropoff with freq.
• Page 2: over plot the central strips for each pattern
• Black is the azimuth strip through each map.
• red is the za strip through each map.
• the azimuth width is narrower because of the elliptical illumination of the primary (extended in the az direction).
• Page 3: ratio of integral(bmap^2)/integral(bmap)
• Top all patterns. average value: .423
• Bottom: limit patterns to za > 10 (the dome sits above za=10 for most world day runs). Average value .420.
• The integral was done over a radius of 35 arc minutes from the beam center
  

13sep13: polA ripple aug13-sep13   (top)

    On 13sep13 we tested polA of 430 dome because the tsys had started to jump around again. The test was:

• On the oscilloscope we could see jumps in the total power when denis lightly tapped on different parts of the plumbing between the turnstile and the amp. He tapped on : the jennings relay, ra switch, elbows, filter, cable to dewar.
• The jumps seemed to be stronger closer to the filter. They were up to Tsys (while on sky).
  
• When the jenning relay was switched to load, tapping caused jumps that were about the same size as on sky (even though Tsys had increased by a factor of 5).

• 25 Mhz, 1 sec dumps, center at 430 Mhz with the interim correlator using 9 level sampling
• The spectra showed bandpass ripple in pola.
• The ripple was always present (with and without the tapping).

• Page 1: 1 second spectra taken 13aug13.
• Black is polA, red is polB
• Top: spectra on sky
• Bottom: Spectra on load (jennings relay closed) and sky.
  
• upper spectra on load shows no ripple
• bottom spectra is the spectra from the top frame plotted replotted.
• The ripples go away when on load.
• Page 2,3 - overplot x111 spectra 01aug13 -> 13aug13
• Page 2 is polA
• Page 3 is polB
• The spectra are plotted with offsets (for display). 01aug is at the bottom,
  
• Colors show different configurations for the 430:

• Date	amp	filter	turnstile	Notes
  01aug-05aug	astro	polA bad	New	polA filter bad
  06aug-27aug	astro	polA bad	polA New damaged	polAfilter bad
  27aug-05sep	astro	polA bad	polA old turnstile
  05sep-09sep	radar	out	polA old turnstile	the ripples are gone
  09sep-13sep	astro	fixed	polA old turnstile

Summary:

• PolA has had ripple in the bandpass since at least aug13. PolB does not have this ripple
• broken wires were found in the polA cavity filter on 05sep13.
• In the lab, tapping the filter with the wire broken caused large jumps in the filter transmission.
•  It was fixed and replaced on 09sep13.
  
• In the lab, tapping on the filter did not change the transmission properties (after the fix).
  
• The ripple was present before the turnstile was damaged.
• The turnstile damage did not make the ripple worse.
• putting in the old turnstile seems to have increased the ripple
• Using the radar receiver without the filter made the ripples go away.
• This means that the problem is not the jennings relay
• repairing the filter did not fix the ripple problem.
• tapping on the plumbing after the filter fix caused jumps in the power after installation in the dome (although this was not checked until 13sep13).
  

05sep13: polA cavity filter removed. polA jennings replaced.  (top)

    On 05sep13 around 10:00 the aeronomy experiment was stopped to switch the radar  room temp miteq amp with a cooled version.

• Prior to the replacement we were getting tsys around 175K
• after the replacement we got Tsys values that varied from 105 to 150K.
• Switching from load to antenna and back caused the antenna level to jump by up to 3db.
  
• After some more tests it was decided that the polA jennings relay (installed 27aug13) was not working.
  
• A spare relay driver was tested, but the problem remained.
• The jennings relay on polB was switched with the polA jennings relay. during radar runs, polB is not used.
• We measured a tsys of about 150K after the jennings relay was replaced.
  
• After the switch we was saw large jumps in tsys when the plumbing between the turnstile and the dewar was touched/banged. The jumps were especially strong when areas near the cavity filter were hit.
• We removed the cavity filter. the miteq amps have more dynamic range than the cooled amps.
• After removing the cavity filter:
• Tsys was 95K in polA
• Tsys did not jump when we banged on parts of the plumbing.
• The filter was brought down to the lab and checked:
•  on the network analyzer, lightly tapping the filter or connectors caused level jumps of up to 5 db.
• This filter is probably why tsys PolA had been jumping around (for many months).
• Results:
• A loose solder joint was found inside the cavity filter. It was fixed and then reinstalled in the dome 09sep13.
• the jennings relay on polB (originally from polA ) was exercised (after the radar run). No problems were found. The problem must have been that the polA relay was shaking the filter a little more than the polB. The jennings relays remained swapped.
  

05aug13: turnstile damaged (top)

    The turnstile (install 2006) was damaged on 05aug13 while removing ao19. The winch was left hanging and hooked the adjustable backshort on the edge of the  turnstile when the rotary floor was moved. This bent the turnstile.

• when it occurred:
  
• 05aug13 7:12 am. tsys 80.7,79.3 K
• 05aug13 11:24 am. tsys: 323.3, 60.4 K

• the "old" turn stile does not have a tuning stub. it's centerfreq is lower than 430 Mhz.
• Tsys polA had jumped up to 250-300 K after the problem  The jennings relay polA was found to have large impedance.. It was also replaced on 27aug13 when the old turnstile was installed. Tsys went back down to around 60K.
  

03apr13: polA Tsys jumps high in afternoon.  (top)

04apr13: resolution: polB jennings relay had been installed backwards. It was switching sky between load and lna instead of lna between load and sky. reinstalled correctly.  This means that the high polA Tsys was probably both were on load.

    Since around the 31mar13 some afternoon tsys measurements have shown TsysPolA to be much higher than polB (250 to 400 K vs 100)
Plots were made of the hcorcal tsys for 430 using data 21mar13 through 03apr13(am).
The plots show tsys vs date, hour, and lst (.ps) (.pdf):

• PolA is black, polB is red.
• Top: 430 dome Tsys vs date .. starting at 21mar13 thru 03apr13 am.
• The two largest polA tsys' occurred on 31mar13,and 01apr13
  
• middle: Tsys vs hour of day (AST)
• The large Tsys occurred at 15:30 and 16:00 hours
• Bottom: Tsys vs local sidereal time.
• Tsys will increase at 6:00 (galactic anti center) and 19:00 (galactic center).

Comments:

• PolA,B will not differ this much because of polarized power from the sky..
  
• The two high measurements have nearly identical values even though they are separated by 24 hours.
• if this was rfi i would expect the differences to jump around
• I think the high value is close to Tsys with the receiver on load.
• My guess this is a problem with the load switch for polA.
• If the operator accidentally left the load switch on load, then polB should also be high (need to check polB load)
• There may be problem with the load switch  or the signal going to it.

02dec12: sweep notched filter in front of dewar. (top)

• the filter was swept 3 times.
  
• Each had a differing tension on the  filter connector to see how much it would change.
• black,red,green show the 3 different measurements.
• The 4 frames show S11, S22, S21, S12
• S11 is the reflection from the damaged connector. This was connected to the antenna
• S22 is the reflection from the dewar side of the filter
• S21 is the transmission from the antenna to the dewar
  
• S12 is the transmission from the dewar to the antenna
• Page 1:
• The entire freq 180 to 680 MHz
• Page 2: blowup  showing  400-450 MHz
• Page 3: blowup 460 to 530 MHz
• The dashed vertical lines are the tv station bands.
• Chn 14 and 22 were the analog stations causing the intermods in the dewar.
• With the switch to digital tv, these stations are no longer very strong (22 in not present at all).
• Chn 15 and 23 (digital stations) are now causing intermods in the dewar.
• Then notch near chn 15 changed a lot when for the sweeps with different amounts of  stress.
• chn 23 is not cut off very much by the old notches.

27sep10: check 430 stability  (top)

• Telescope sitting at az=285, za=9.
• mock spectrometer took 21 MHz centered at 430MHz. The 422-442 filter was in.
• 300 seconds of .1 sec averages were taken.

data images, plots:

• Dynamic spectra for 300 seconds with .1 second resolution (.gif)
• The bright horizontal lines are lightning.
• There is not much signal below 422.5 MHz.
• Average spectra, rms/mean by chan , total power vs time (.ps) (.pdf)
• Page 1
• top 5 minute average spectra.
• bottom: rms/mean for the 3000 .1 second records.
• The green lines is the expected rms. the measured value is large because of the continuum sources.
• Page 2:
• top: total power vs time. The rfi was removed before computing the total power.
• 2nd: ratio pola/PolB
• 3rd: The spectra of the total power. 5 hz max bandwidth (since 10 hz samples)
• bottom: blowup spectra of total power.

Summary:

• There are no large jumps or drifts in the total power vs time for polA, or polB (unlike aug09).
• the 1.2 hz spike in polA  total power spectra is gone (crosshead frequency).

10aug09: 430 polA unstable (top)

• az,za=270,1.09 sitting.
• mock spectrometer: 8k channels, 34 MHz Bw, and .1 second sampling.
• Data taken for 300 seconds.

• Black is polA, red is polB
• Top: total power vs time
• Middle: The spectrum of the total power was computed and plotted. The 1.2 hz and harmonics come from the dewar refrigerator cycle.
• Bottom: blowup of the spectrum of the total power (0-1 hz). There is no obvious 15 second periodicity (.066 hz). Maybe what people saw is not  very stable in time.

Summary:

• Pol A has a large 1.2 hz periodicity in its total power. This is coming from the refrigerator. We should probably bang on the can to see if something is loose inside...

mar03 thru oct03 GAIN CURVE. (top)

11jan05:  TsysPolA - TsysPolB drift for 2003 and 2004 (top)

     Fig1-  Top: Tsys for 2003. Black is polA, red is polB, Bottom: TsyspolA-tsysPolB
     Fig2:- Top: Tsys for 2004. Bottom: TsysPolA-TsysPolB

    From the plots you can see that the difference TsysPolA-TsysPolb has been changing. In july 2003 the difference started to increase (TsysA larger then TsysB). Around 17nov03 the difference jumped by 10 degK so that TsysB was larger then tsysA by about 10 degK.   It stayed at this level until august 2004 when it started to increase gradually.
      The tsys measurements tend to be taken at 16:30 AST so the RA of the measurement will move during the year. It seems unlikely that the gradual drift  in TsysPolA - TsysPolB is coming from the sky since the receiver is circularly polarized (and there are no extended sources of circular polarization that i know of).   Looking at the src deflections over this time period the polA,polB ratio remained fairly constant, so my guess is that Tsys was changing (and not the cal size).

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