11may20: ips data and lna stage 2 currents (top)

    IPS (InterPlanetaryScintillation) is taking data with the 327 receiver and the mock spectrometer. The processing is:

• Dump 50 MHz spectra every 2 milliseconds. Do this for 180 seconds
• Split the spectra into 5 10MHz bands.
• remove the rfi and the compute the total power for each 2 ms
  
• Compute the spectra of the total power time series taking 10 seconds of data at a time (.1 Hz resolution)
• We end up with 18 10 second spectra  for each of the 5  10mhz bands
• Then take the average and the median spectra over the 18 spectra and then over the 5 10mhz bands.

A movie was made showing the spectra of the total power for the  327 receiver data on 11may20 (.avi)

• the best way to view the move is with mpv.. mpv --loop inf  200511_ips.avi
• mpv keys:
•  period steps you forward,
  
• comma steps you backwards
• If the movie is hard to look at , the individual frames of the move are here
• the files are in increasing time order in the directory.
  
• each frame contains:
  
• left column : polA
• middle column: polB
• top row (col 1,2): average the 18 spectra
• bottom row(col 1,1): median of the 18 spectra
• right col, top:  average and median of all bands, all pols.
• This also includes the time (ast) for the start of the 3 minute scan
• bad frames:
• 3 : 15:09
• 5:  15:27
• 7: 15:51 .. the worst
• 8: 16:02 .. the 2nd worst
• You can see the large powers at the right of the band for polA.. polb is also affected a little

The plot shows the bias currents for 327 stage 1 and 2 for 11may20 afternoon (.ps) (.pdf)

• The top two frames are stage 1  polA and polB
• The bottom two frames are  stage2 polA and polB
• The vertical lines show the start of each 3 minute observation from the movie
• the solid line is the start
• the dashed line is the end of the 3 minute scan
• Green lines are frames(scans) in the movie that did not have the high freq power
• the red lines have the high frequency power
• the purple line is intermediate.. it had a few small bumps
• The worst 2 red scans around 16:00  are when polA stage 2 current was jumping around the most.
• Note that the current is only moving by .01 or .02 milliamps..
  

Summary:

• polA stage 2 bias current is jumping around causing 30-120+ Hz power variations in the sampled data.
• this is affecting the ips measurements being taken during the covid19 down time.
• It will also cause problems with the p1693 pulsar search.
• There has been a recurring set of intermittent  glitches in the 327 receiver (for over a year). it would come for a few minutes and then go away.
• I wonder if the could be causing it?
  

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