The 327 Mhz receiver is a dual linear receiver with room temperature amplifiers and a 30 Mhz wide filter.

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Sections:

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History:

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Calibration measurements:  (top)

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Rfi  (top)

05nov05: azimuth dependence of birdies in the 327 rcvr.
21oct05: output of 327Mhz rcvr after the 1st amp (and before the rf filter).
16oct05: 1 Mhz comb coming from dome AC units.
27aug05: the 16Khz comb in the 327 rcvr comes from the alfa motor controller.

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Miscellaneous  (top)

07may09: tsys vs sky position for jun2008 to may09
16jul08: tsys vs date,hr,ra,dec with cold receiver
07may07: Strong 60 Hz in p1693 pulsar data using the 327 receiver and the wapps.
 07jan04: 327 receiver moved to new turret position.
jul02      :Room temperature receiver installed
29sep00:Turret position

All measurements in date order  (top)

09feb10:p1693 drift scan:

• cfr: 327, bandwidth: 50Mhz, 3lvl sampling, 200Usec dumps, addpols
• az,za:275,15.49

• spectra were hanning smoothed and averged  to .5 seconds.

• Top: the 220 second average spectra. The vertical scale is linear in power.
• Bottom: the rms/mean by channel for the first File. The rms was computed after averging to .5 seconds.
• The expected rms (from the radiometer equation) is show in red.

07may09: Tsys vs ra/dec and Tsys vs galLong/galLat.  (top)

• PolA is plotted in black
• PolB is plotted in red
  

• Page 1: tsys vs ra,dec
• Top: ra,dec positions where the measurements were made.
  
• We normally sit at az=270,or 285 and za=around 10.
• Center: Tsys vs Ra.
• Places with elevated Tsys
• ra=6 galactic anticenter
• ra=15-17 north polar spur
• ra=19 : galactic plane
  
• Bottom: Tsys vs Declination
  
• Not much info since most decs are 15 or 18 Deg.
• Page 2: tsys vs galactic longitude and latitude.
• Top: galactic latitude and longitude for the measurements
• Center: Tsys vs gal Longitude
• Places with elevated Tsys
• long=35  North polar spur
• long=50 galactic plane
• long=190 anticenter
• Bottom: Tsys vs galactic latitude
• lat -5 anticenter
• lat=5 galactic plane
• lat 30-70 top set, north polar spur
• Page 3: TsysB - TsysA vs ra, galactic latitude
• The top plot is vs Ra, the bottom plot is versus galactic longitude.
• There is not a lot of structure vs ra or longitude. Polarization is probably not playing a major part.
• The median value is 8.9 Kelvins with an rms of about 5K
  

• The lowest Tsys for polA was about 85 K around ra=9-12 hrs
• Tsys can increase to > 160 K on the plane
• PolB is 8.9K warmer than polA.
  

16jul08: tsys vs date,hr,ra,dec with cold receiver  (top)

• Top: tsys vs date.
• 2nd: tsys vs Hour of day.
•  tsys before 10 am seems to be higher than than after 10am. Could it be sunrise??
• 3rd: tsys vs za. we usually do tsys around za=10.
• 4th: tsys vs ra.
  
• The high points at ra=15 are the north polar spur. At 408MHz it is about 20K higher than the ra=10 data  (327 will be higher).
• The points at 2-4 hours with tsys =100 do not have a lot of continuum. These are the 7-10am points in plot 2.
• 5th: tsys vs dec. Most points are taken between decs of 15-20 degs..
  
• The high point at dec=2 corresponds to ra=15. The continuum here is not that large (the north polar spur picks up at ra=15, dec=10-20) So i'm not sure why this is so high.

• Tsys can vary by 20-30 kelvins with sky position
• 8am-10am seems to be higher than 12-19 pm.
  

21jun08: Ratio SEFDA/SEFDB shows Tsys B > TsysA  (top)

• source CTA21  is  unpolarized
• 03 hours is far enough away from the north polar spur that the background should not be polarized.
  
• Bandwidths of 25, 1.5, .78 Mhz were measured all centered at 326 Mhz.
• SEFD=Tsys/Gain or SEFDA/SEFDB = (TsysA/TsysB)*(GainB/GainA)
• since both Tsys and Gain depend linearly on the cal, the cal is cancelled by the ratio. The sefd is not affected by errors in the cal

• Top: TsysA and TsysB vs za.
•  TsysB is 10 to 15 Kelvins higher than TsysA
• The 25 Mhz band of polb is about 5K higher than the 1.5 and .78 Mhz bandwidths. This may partly come from using the cal value at the center of the band for the entire band.
• Middle: Tsource A and T source B.
• PolA and polB both give close to the same source temperatures so the cal values are not wrong by much.
• PolB gives the same source temperature for all of the bandwidths so using the cal value at 326 MHz is not the reason why the top plot showed a difference in the polB bandwidths.
• Bottom: SEFDA/SEFDB
  
• The ratio is 90 to 93% so TsysB is really higher than TsysA.

Conclusion:

• Tsys polB is about 10% higher than Tsys polA.
• Tsys (measured at 326Mhz)  for polB 25 Mhz is about 5% higher than Tsys measured with 1.5 or .78Mhz bandwidths

28feb05: gain curve for data taken mar03 to feb05  (top)

• 6 < gain < 11.5 K/Jy
• Sefd < 18
• average beam width between 800 and 950 arc seconds.

     g(za)=c0 +c1*za + c2*(za-14)^2 +c3*(za-14)^3

where the ^2 and ^3 terms are only applied for za ge 14 degrees.
     The plots show the gain curve and the residuals (.ps)    (.pdf):

• Fig 1: the azimuth , za coverage for the data.
• Fig 2 top: Red is the data, black is the fits. The fit coefficients are listed on the plot. The fit rms is .47 K/Jy.
• Fig 2 bottom: The fit residuals. The colors are different sources.

28feb05: system performance for gain curve data mar03-feb05 (top)

• 6 < gain < 11.5 K/Jy
• Sefd < 18
• average beam width between 800 and 950 arc seconds.

• Fig 1 top: the az, za coverage for the data
• Fig 1 bottom: the time of day when the data was taken
• Fig 2: gain, tsys, sefd, and average beam width. B0640+233 had a beam width that was larger than normal. It tended to make the gain a little less.
• Fig 3: coma, avg first sidelobe, eta main beam, eta main beam + first sidelobe.
• Fig 4: pointing error: za vs za, za vs az, az vs za, az vs az. The large az error for B0017+154 was after the horn had been moved and before the final turret offset had been computed. This is purely an az offset and did not affect the gain. Some of the other az,za pointing offsets were probably from tilts (rain etc..) that would also affect the gain.

07jan04: 327 receiver moved to new turret position.   (top)

• Fig 1 has the pointing error in great circle arc seconds vs azimuth and za. The black color is before the move with the turret at 21.5 degrees. The green color is after the move with the turret at 340.2 degrees.

The average az error with the turret at 340.2 degrees is (-11.73-(-26.84))=15.1 asecs too small. We need to move the azimuth by +15.1 asecs. The turret coordinate system is opposite to the azimuth and 1 turret degree equals 45 arc seconds on the sky. The turret needs to be moved to 340.2-(15.1/45)=339.9 This will be the new turret position.

08aug02:calOn/off load and sky. Tsys contributions receiver, sky.  (top)

• Top:  Cal on,off using the load.
• Bottom: Cal on,off tracking blank sky.

    On load calOff the average temp was 375K. Using 305K for the ambient load temperature gives a noise contribution from after the load of 375K-305K=70K for a noise contribution after the load switch. This is what is expected for the room temperature amplifier.
    On sky calOff the average temp was 135K. This includes the flange temperature, sky temperature, and any ground/scattered/spillover radiation. Using 40K for the sky contribution and 70K for the flange temperature gives 25K from the spillover/scattered ground radiation. Higher frequency receivers have shown scattered radiation ranging from 10 to 20 K so 25K for the 327 receiver seems reasonable.
     The sky temp was crosschecked with chris salters 408 Mhz survey and it came out to 39.1K.
 

327 Tsys budget

load temp	305K
receiver temp	70K
Tsys on sky	135K
sky temp	40K
spillover,scattered radiation	25K

07aug02: calibration runs 3C138,B0640+233, and B0824+294  (top)

jul02   Room temperature  receiver installed

29sep00: Turret Position:

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