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Sections  (top)

Installation (prior to 15feb02)

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History  (top)

• 28feb18: move platform up, down checking for best focus.
  
• 21sep17: hurricane maria
  
• 04dec12: polB Tsys jumps up be about 4k. Stayed high until 07dec12. denis found a loose rf cable from postamps.
  
• 04dec12 was the same day that lbw got brought down.. so the cable may have gotten twisted.
  
• 16aug12: installed new cal values that were measred ju12. (backdated to 01may12).
  
• 04jan10: cooling now on one of the alfa compressors (with 327).
  
• febmar04: receiver down. new cals installed, some cables replaced in dewar.
• 08jan04: xband receiver moved to new position on the turret floor.
• 05oct03: xbrcvr to antenna test range, measure cals, rcvtemp
• 03sep03: new xband horn installed, cal cables cleaned
• 03aug03: switched to use the 2 to 12 Ghz mixer rather than the 10 Ghz upconverter for the default first IF
• 06feb02:
• reshimmed horn to move it up .44 inches vertically, moved turret position .35 degrees (from survey).
• switched to pointing model 13. offsets still large.
• 27dec01: heater installed on wave guide for condensation.
• 19dec01: receiver installed.

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Calibration measurements  (top)

18mar04: Tsys vs frequency.
25jan04: xband gain curve using  data 05oct03 thru 25jan04.(GAIN CURVE)
05sep03: New horn performance: SEFD new horn,old horn.
05sep03: Compare (SEFDB/SEFDA) and (TsysB/TSYSA)
05sep03: Tsys vs frequency old and new horns.
03jun03: polb gain variations a1704 recomb lines
mar03: xband gain curves mar03 thru sept03  (GAIN CURVE)
21feb02:calibration runs on B0518+165(3C138),B1040+123,and B1328+307(3C286)
21feb02:beammaps (turret scans) J0237+288 after pointing offsets.

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Miscellaneous  (top)

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Installation:   (top)

180228: move platform up, down checking gain. (top)

    On 28feb18 the source B0428+205 (1.5Jy @ 9000MHz) was used to do calibration scans while the platform was moved vertically. The idea was to see if there was a large gain change as the focal distance was changed.
The setup was:

• xband rcvr.
• interim correlator.  25 Mhz bandwidths centered at 8500, 8800, 9000, and 9200 Mhz.
• tiedown tracking (with 3 distomat tracking enabled).
  

The sequence used was:

• Page 1: gain,tsys,sefd, beamwidth
• Page 2: coma, 1st sidelobe average height, efficiencies.
• The colors are different frequencies.
• The first pattern started on the left with the lowest za (the source was setting).
  

• each frame is a different frequency.
• The gains vs platform offset are plotted in color
• a positive offset moves the horn away from the primary.
• The black * are the standard heights.
• 1 lambda at 9000Mhz is 3.3 cm.
  

Summary:

• The standard offset gave the highest gain
• The +/- offsets were not symmetric.
• moving the platform down gave a higher gain than moving the platform up by the same amount, so the horn may be a little high.
• This was a very rough test.
  
• The sidelobes looked pretty ugly for all of the positions
• avg sidelobe height  -10db, peak sidelobe probably closer to -6db
  
• This should be repeated using a stronger source: 3C48, or 3C286..
• I need a faster way to move the td between patterns...

processing: x101/180228/xb_changehght.pro

09apr14: xmit tone from the control room.

• az=286,za=6.6
• xb receiver. 2-12 ghz mixer.
• xmit at 8351 using hp 20Ghz synth (amplitude about 0 dbm). It was locked to the station clock.
  
• xmit using xband helix
• use mock spectrometer to record data
• 160Mhz sampling freq, decimate by 1000 --> bw = 160Khz.
• 16 bit time domain sampling
• use 10 Mhz offset at a/d input, and -10Mhz shift in digital mixer to get rid of spikes at dc
• offset input band by an extra 10khz so echo returns 10Khz below center of downshifted band.
• Take data for 105 seconds (allows for a 16Megapnt xform).

• a single 16 million point (2^24) length transform was done on the data.
  
• The channel width is then .00954 Hz.
• PolA is black, polB is red (both are circular).
• The spectrum was normalized to the median value and then converted to a db scale.
  
• Top: spectrum showing +/- 50 Hz about the expected receive signal
• midlle: +/- 5 hz about the expected signal
• bottom: +/- .5 hz about the expected signal.

Summary:

• The upstairs if/lo is locked to the station clock.
• Most of the power in the tone is within 10 millihz (unresolved)
  

12jan06: check xband receiver after reinstallation.  (top)

• Fig 1: gain, Tsys, Sefd, Beamwidth: The 12jan06 points plotted with + while the 13jan06 values use an *. Colors are used to show the 4 frequencies used (8500,8800,9000,9200 Mhz). Tsys dropped by about 2 kelvins 12jan06 to 13jan06. The receiver was cool by 12jan06 (at least the tsys measurments done by the operators showed no decrease 12jan06 to 13jan06). The difference may have been the atmosphere.
• Fig 2:  Coma, first sidelobe height, beam efficiencies. The first sidelobe increase 12 to 5 degrees za corresponds to the gain drop. So were are probably going out of focus here.
• Fig 3: pointing errors. There is a 6 asec za offset (about .1 inches). With one source we can't tell whether this is a problem with the model itself or a residual of the reinstallation.
• Fig 4: The pointing errors for the last year (black)  over plotted with the current errors for these two days (red).  The length of the vector is proportional to the error (1 tick marck is 5 asecs). The direction of the error is the direction of the total error (the radial direction is za while the perpendicular direction is azimuth). These errors do not look any larger than the errors from the previous year. You'll notice that we have no previous sources that went through this same dec range.

13jun04: xband performance above 10 Ghz.   (top...)

• Fig 1: The gain and Tsys for 10.5 Ghz are too high. This is probably because the cal value used is too high. The Tsys for 11.1 Ghz looks a little low so its cal value is probably a little low. The sefd for all of the frequencies looks pretty consistant so the differences are probably coming from the cal values used.  The  cal values measured on the hill show a peak at 10.5 Ghz. This peak is probably not real.
• Fig 1: The SEFD for B1328+307 rises at za of 15 on the  setting track. The open loop for B1040+123 has a 120 degree periodicity in azimuth so it is coming from the 3 azimuth dependence of the optics. B1328+307 did not cover enough azimuth to determine if its loop was coming from the 3 azimuth term.
• Fig 1: The beam width also increases at za of 15 degrees (az=150).
• Fig 2: The coma is large. The first sidelobe gets up to about -11db. The beam efficiencies need to be scaled by the error in the cal.
• Fig 3: The rms pointing errors are 3.65 (za) and 6.01 (az). The 4.13 mean za error is similar to the mean error measured for the za error at lower frequencies.  The azimuth pointing error jumps by 10 arc seconds at an azimuth of 150 degrees. The tension in tiedown 4 was decreasing at this point, but it did not go loose until an azimuth of 135 degrees.
• Fig 4 shows the tracks across the dish. B1040+123 was done twice.

08jan04: xb rcvr moved to new position on turret floor.  (top...)

1. Fig 1: this is the azimuth za coverage for the 3 measurements. Black is before, red has tur=310.22, and green is with turret at 309.94 .
2. Fig 2: The pointing error for the 3 measurements. The median pointing errors were:

 

	MeanAzErr Asec	meanZaErr  Asec
pos1: before	1.42	-1.46
pos2: tur=310.22	-11.64	2.17
pos3: tur=309.94	2.08	2.54

1. Let Pos S have the  telescope pointing directly at the source.
2. Pos 1 is 1.42 asec greater than Pos S in az.
3. Pos 2 is 11.64 asecs less than Pos S in az.
4. To go from pos 2 to pos 1, you must move the azimuth 13 arc seconds (positive).
5. The turret coordinate system is counter clockwise with 45 asec/turretDeg. + 13asecs of azimuth is -13./45=.28. The new turret position is then: 310.22-.28=309.94.

17sep03: Resonances in the xband receiver. (top...)

05sep03: new horn performance. SEFD old and new horn.  (top...)

• Figure 1: The SEFD vs za for the 2 datasets. Black is the new horn, Red is the old horn. Each source has a separate symbol. The 4 boxes are the frequencies for the calibration data: 8500,8800,9000, and 9200 Mhz.
• Figure 2 Top: For each common source, the SEFD of the old horn was interpolated to the za's of the new horn measurements. The ratio SEFDOld/SEFDNew was then computed. The top plot shows this versus zenith angle. The colors are the 4 frequencies. The lines are linear fits to the data vs frequency.The zenith angle dependence of the ratio could be a pitch or roll change caused by a weight change of the dome. The variation in the data probably comes from Tsys changes caused by weather.
• Figure 2 Bottom: The linear fit for the ratio was evaluated at 10 deg za for  each frequency. The lower plot shows the change in SEFD (Old/New) for the 4 frequencies.

05sep03: Compare (SEFDB/SEFDA) and (TsysB/TSYSA) using x102 calibration data (top...)

    The x102 calibration data for sept 09,10,11  was used for this test. I  re analyzed the data since the normal processing combines the two polarization's and computes Tsys for stokes I. I refit the data using a 2d gaussian fitting for : Amp, offsets, major axis, coma, and coma angle. I did not try to fit for the sidelobes so the data is probably not as accurate as the default processing. The SEFD is Tsys in Janskies. It only relies on the source flux to be correct (the ratio sefdB/sefdA only depends on Tsys). You can compare the ratio of TsysB/TsysA using kelvins from the cal or Janskies from the source.

    The plots show the SEFD and Tsys for the 3 days of xband data.

• Fig 1 : SEFD vs za. Top is polA, bottom is polB. Each source has a separate symbol. Each color is a different frequency band.
• Fig 2: Tsys vs za. Top is polA, bottom is polB. Symbols are different sources, colors are different frequency bands. This data was taken after the new horn was installed (and after the cal cables were cleaned). It is using the cal values from jun03.
• Fig 3: The top plot is the ratio of SEFD'S : sefdB/sefdA. The center plot is TsysB/TsysA using the cal values. The bottom plot computes the average ratio by frequency (throwing out outliers). The black trace is TsysB/TsysA measured using the cal values. The red line is TsysB/TsysA using the source flux as the reference value.

05sep03: Tsys vs frequency with the new xband horn.  (top...)

• The frequency range 8 to 10 Ghz was covered 3 times.
• The high correlated cal was used (diode 1 to polA and polB)
• Blank sky was tracked during the measurement
• The same value for the cal was used in both cases (but see below...)

• sep03 used the new horn, jun03 used the old horn
• sep03 used the 2 to 12 Ghz converter, jun03 used the 10 Ghz upconverter.
• sep03 data was taken at 15:20 (clear weather) while jun03 was taken at 8:30 clear weather.

•  topPlot: This is Tsys vs frequency for both measurements. Black, Red are polA,polB with the new horn. Green,Blue are polA,polB with the old horn
• middlePlot: This is TsysB/TsysA for the newhorn (black) and the old horn (red). Above 9 Ghz the two curves are identical and close to 1 (tsysA the same as tsysB). Below 9 Ghz TsysB/TsysA for the new horn increases. This is probably happening because of tsysA being so low.
• Fig 1 Bottom:  This is the ratio of TsysHornNew/TsysHornOld. Black is pola, red is polB

I asked electronics if they had done anything with the xband cals. The only thing they could think of was that  they had "cleaned" the cal cables into the dewar on 04sep03.  The performance difference caused by changing the horns should be equal in polA and polB. The amount of cal signal getting into the dewar has probably changed for one of the cal cables so we need to recalibrate them.

jul03 update az,za pointing offsets from calibration scans.  (top...)

jun03 a1704 recomb lines, gain drifts.  (top...)

    While monitoring the xband total power  (25Mhz , 1 second samples) some variations in polB showed up. The plots show  total power vs time for 8 OFF src scans (no continuum). Each plot has the 4 sbc plotted bottom to top (with an offset between sbc for plotting). polA is black while polB is red. The total power has been converted to Kelvins (using the cals) and then the median value for each scan was removed.

•  Fig 1 pattern 1,2 are pretty good
• Fig 2 pattern 3 has a jump in polB (red) for all sbc at sample 250 of about .1 K (Tsys was about 50K). Pattern 4 has a jump at sample 110.
• Fig3 pat 5,6 both have drifts in polB
• Fig 4 pat 8 has a large jump in polB at sample 30.

    The second set of plots has the total power source deflection vs time for the 8 on/off patterns by. For each pattern (on-off) was compute for each 1 second record and then the total power was computed (in Kelvins). The plots show the srcDeflection vs time for the 8 patterns and the frequency of the oscillations.

•     Fig 1 Top. The src deflection vs time for the 8 patterns. The data is sampled at 1 hz. The y axis is in kelvins. Each color is a different on/off pattern. # of the sources had continuum while the other 5 had little continuum.
• Fig 1 Bottom. Each 300 second source deflection was fourier transformed and then the amplitude was plotted vs frequency.  The highest frequency is .5 hz. The power near .5 hz is probably aliased down from above .5 hz. The platform oscillations frequencies where measured to be .365 and .57 hz during hurricane georges.

    The slower drift may be weather or pointing. If they were pointing errors, then the oscillations that are sitting on top of the slow drift should decrease as the slow drift reaches a maximum (no longer on the edge of the beam). The data doesn't seem to do that. but..It could also be that the oscillations are dying out so that when there are no oscillations it doesn't necessarily  mean that we are on the center of the beam.

jul02 Tsys vs time. Dtsys/Tsys after integration. (top...)

1. The first plot shows Tsys vs sample for the 1200 samples by 14 drifts. The x axis is a complete set of samples for 1 day. The data has been smoothed by 3 (1.5 seconds) to reduce the size of the plotfile. Each 1200 points, the telescope would move to a new za (rise at the left , transit in the middle , and set on the right). Each color is a separate day (black1, red2, green3..). Each plot of the 4 plots is a separate frequency band. Within a plot, the upper set of lines is pol B (it has a higher Tsys) and the lower set is polA. The numbers 1-14 across the first plot are the 14 drifts done.  Some things to notice are:
• day 1 (black) strip 3,4 the gain in polA is varying.
• day 1 strip 3, day 2 strip 8 there is rfi at 8800 Mhz (2nd plot).The bumps in the total power (eg day2,strip 4) are    constant across frequency (all 4 sbc). They occur more at the edges (hi za). It is not rfi since it is wide band. It is probably not a source in the sidelobes since it did not repeat day to day. It is probably not a gain variation since it was identical in both polarization's (and they have different amplifiers etc ..(except the first lo is common).). It may be atmospheric variation of Tsys that is occurring on the order of minutes.
2. The second plot is a blowup of the first showing only the 8750Mhz data with no smoothing. Each day has been offset by 2 K for plotting. You can see that the weather is increasing the tsys by up to 2.5 K or about 5%.
3. The third set of plots shows spectral density (in units of Tsys) versus strip position and frequency. It has been  averaged over all of the strips off a day, all of the days, and both polarization's. The data has been weighted by 1/sigmaTsys^2 (no weighting for telescope gain was done). For each drift scan:

• The 1200 spectra are normalized in frequency by the average bandpass (excluding the continuum source).
• Each spectra is then divided by the total power (computed over channels 50:450). This is to remove any gain variation (and to some extent weather).
•  sigma^2 is computed over channels 50:450 and records 100:1200. The spectra are then multiplied by 1/sigma^2.
After accumulating all of the data, it is multiplied by 1/weights. An average bandpass is divided into this data and channels 50:450 are used to remove any time variation.
 The images have been scaled to 8 Sigma (min to max in the greyscale).  Each image is about 800Kbytes.
• averaged image 8750 Mhz
• averaged image 8800 Mhz
• averaged image 8850 Mhz
• averaged image 8900 Mhz
The rms was computed using strips 100 to 1200 and frequency channels 50 through 450. The expected rms is:
3Level/(50e6/512*han*.5secs*driftsPerDay*Ndays*npol)

Where driftsPerDay=14, Ndays=7, npol=2, Han=2, and 3level=1.23 for 3 level sampling.
Expected rms (7 days): .00028 dTsys/Tsys.

The measured values were a little less than this (see the plots).

The 2nd image (at 8800 Mhz) has interference that was there for 2 days. The large drift in frequency may point to a satellite in the sidelobes.

06mar02:HC3N,HC7N in TMC1.  (top...)

21feb02:calibration runs on B0518+165(3C138),B1040+123,and B1328+307(3C286).  (top...)

1. Fig 1. This has the pointing error in arc seconds for the azimuth and zenith angle directions. For the 3 sources there still appears to be an offset. Part of this is do to the calibration scans fitting for the coma while the turret scans don't. This moves the position a little. We also may need more calibration sources to get a better average.
2. Fig 2. plots the Gain (K/Jy) and Tsys(K), SEFD (Jy/Tsys), and average beam width (asecs) for the 3 sources (different symbols) and the 4 frequencies (different colors).  The SEFD at low za is well behaved (the 02jan02 data used 3C454.3 whose flux is not known but the shape seems to have improved).
3. Fig 3 shows the coma, 1st sidelobe height, main beam, and then main beam + 1st sidelobe efficiency. The first sidelobe heights has improved by maybe a db from the 02jan02 data.
processing: x101/020221/calib.plot

21feb02:HC3N lines at 9097,9098,9100 Mhz. possible detection?  (top...)

21feb02 beammaps (turret scan) J0237+288  (top...)

13feb02 beammaps J2253+161, 3C48.  (top...)

13feb02 pointing, beam squint, sefd, and beammaps. 3C48, J2253+161  (top...)

1. Fig 1. The top two plots are the pointing error in az,za versus az and za. This is using model13. The average offset is 27.4 asecs in az and 5.3 asecs in za. The model13 offset for xband will be updated by this amount. The bottom plot is the beam squint (pointErr PolA-PolB). It less than an arc second.
2. Fig 2. top is the normalized Tsys for polA (black) and polB (red). I normalized the curves by dividing by the average Tsys 0 to 12 degrees. Jumps in the plot may be from the fits or any gain changes (I assumed the gain remained constant for the entire set of observations). Apart from the jumps, tsys is relatively flat out to 15 degrees (unlike some receivers that show a linear ramp at low za).
3. Fig 2 center is the source deflection (as a % of Tsys for the 3 sources). The large hook for J2253+161 below 5 deg za is from the prf errors (see the next plot).
4. Fig 2 bottom is the SEFD versus za. 3C48 is the only source of the 3 with a well known flux (the other two are flat spectrum and probably variable). The fluxes used in K/Jy are next to the source names. The best value for 3C48 is 15 Jy/Tsys. With a 45 K Tsys this gives a best of 3 K/Jy gain. The pointing error of almost a beam will cause the gain to be down by  .5 to 1 db.  We will get this back when the pointing offsets are updated.

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02jan02 xband calibration run on J2253+161,3C48  (top...)

1. Fig 1. top is the Gain in K/Jy. The flux for B2253+158 (3C454.3) is probably off by up to 30 %. The next plots show the Tsys, SEFD, and average beam width.

Fig 2. top is the coma parameter that measures the asymmetry of the main beam. The next plot is the peak of the 1st sidelobe, followed by the main beam, and then the main beam plus 1st side lobe beam efficiencies.

27dec01 beammaps of J2253+161: (top...)

Pointing error and beam widths from turret scans: (top...)

1. Figure 1 plots the za error versus za and azimuth.
2. Figure 2 is the az error versus za and azimuth.
3. Figure 3 is the total error (az and za) added in quadrature and plotted versus za and azimuth.
4. Figure 4 is the beam widths in the za (top) and azimuth directions.

First (out of focus) light B1611+343:  (top...)

The tiedowns were not working so the platform was 2.5 inches low.

The source didn't come below 15 degrees za so the pitch, roll, and focus errors were large.

The source has a flat spectrum and is a low frequency variable so the flux is not real accurate.

The horn location still needs to be surveyed into position with the theodolite.

SEFD, Gain, and Pointing error. The flux used was 4 Jy at 8800 Mhz. The gain was computed using the source deflection/TsysDeflection and Tsys of 43K and 48K for polA and polB (taken from the tsys plots above). The pitch and roll error added in quadrature is probably close to .2 degrees. At 10 Ghz this would cause a 3db gain loss. The focus error is around 1"  which probably contributes a db. A 2 mm rms reflector surface would reduce the gain at 8800 MHz to 58% of theoretical. The pointing error on page 2 is about 38 asecs in az and 18 asecs in za. These offsets can be added to the xband pointing model offsets.

PolA beammaps of B1611+343. Each contour map is a 2 minute turret scan integration. The dome moves along the y axis +/- 1.5 arc minutes. The x axis is +/- 2 turret degrees (+/- 1.5 arc minutes on the sky). The contour colors are spaced by 3 db. The azimuth and zenith angle  is plotted at the top of each map

processing: x101/011220/doitcals.pro

20dec01: The cal values and Tsys versus frequency: (top...)

1. Figure 1 plots the cal values versus versus frequency for all of the cal types. The values were measured on the receiver range using liquid nitrogen as the load. The top plot is the low cals while the bottom plot shows the high cal values.
2. Figure 2 is Tsys versus frequency. Black is polA while red is polB. The telescope zenith angle varied from 12.5 to 9 degrees. At each frequency there are 4 separate measurements (*) plotted on top of each other.

20dec01: Power levels in the upstairs if/lo: (top...)

The top plot is the total power versus frequency at the input to the fiber optic transmitter with all of the adjustable attenuation removed (11 db before the mixer, 11 db after the mixer). The horizontal line is the total power level to give -103dbm/hz over 1 ghz bandwidth.

The middle plot is the gain needed in the postamps to bring the power levels up to -103dbm/hz at the FO xmter and still have 6 db attenuation in the rf attenuator (to allow for some adjustment). The spectral density was computed from the total power by assuming 1 Ghz of constant spectral density about each total power measurement. This will underestimate the spectral density on the edges (since there is not 1 Ghz of total power).

The bottom plot shows the power levels at the input to the IF1 mixer chassis if 12 db gain is added to the postamps. It assumes a 35 db gain for the mixer chassis.

Rfi seen using the xband feed: (top...)

Peak spectral density versus frequency for the two bands with rfi. The vertical scale is linear in power. Red is polA and green is polB.

Spectral density image at 8120 Mhz (time versus frequency).

Spectral density image at 9350 Mhz (time versus frequency).

19dec01: Measuring the turret position of the feed: (top...)

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