27FEB14: Resolution:

• high freq resolution data taken 27feb14 showed that the receiver is not going into compression. The power dips occur because the rfi is jumping in frequency for a few 100 millisecs. During the jump, the power level of the rfi goes down. (more info).
  

20feb14: total power dropouts  (top)

setup:

• pulsar search data was taken with the 327 receiver and the mock spectrometer. cfr: 327 Mhz.
  
• bandwidth: 57.344 Mhz, 1024 channels, sample time: 125 usecs,16 bit, polA,polB summed in mocks
• The project takes scans that last for 1 hour.
• The data after midnight 20feb14 started at 00:48.
  

Processing:

• The first 2 gbyte file of each scan was processed (129 secs/file). There are 7 files starting at:
• 00:48, 01:48, 02:48, .. 06:48
• For each file
  
• the total power was computed (at 125 usec resolution) and then smoothed to 1.25 millisecs
  
• the spectra were averaged to 1 second resolution.

The plots:

• Total power was computed over the 57 Mhz.
• The data was smoothed to 1.4 milliseconds
• Page 1: file 00000.
  
• 00:48 ast
  
• Top: total power vs time.
• the red vertical lines are my estimates (rough) of the start of each dropout.
• Bottom:
• Time difference between adjacent dropouts (time between red dashed lines in top frame).
• Page 2-4. total power vs time for files 100 -> 700.
• the dropouts became weaker, and then returned in file 500.

Dynamic spectra using the 6 files

    Dynamic spectra were made using the 1 second averaged spectra from files 00000 .. 0600 (7*129 makes an image a little too big for my display).
The processing was:

• Normalize the 129 spectra of each file to the median value (a single value, not a bandpass correction).
• Bandpass correct all 6*129 spectra by computing the median spectra for the combined files

• You can see the steps between each 129 file (they are separated by 1 hour in time).
• the 3rd harmonics of the fm stations are clearly seen: (102.9,104.1,107.3)*3=308.7, 312.3, 321.9
• The rfi at 322.5 is drifting in frequency.
• The 10 sec periodic signal is at 352 and 354 Mhz
• The 3rd group from the bottom has a baseline with lots of ripple in it.
• it had an ra,dec of around 12:35:40, 10:51:13
  

SUMMARY:

• dropouts were seen in the total power.
• The decrease was about 1% of Tsys.
• the spacing between the dropouts alternated between 1.42 and 1.66 seconds
• I looked at the a/d blanking.. there was none during this period..
• the plots show that the dropouts changed over hours. They were strong at 00:48 and 05:48

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