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Sections:

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History:

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Calibration measurements:

• 13jan13: calibration results: jun12-dec12. updated pointing offset.
  
• mar03  -  oct03: GAIN CURVE.

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Measurements in date order:

• 03par13: 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.

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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