Intro:

• ADC overflows: when an adc sample is at the limit of the adc range (-2048 or +2047). 
  
• PFB overflows: When there is a register overflow in the butterflies used to compute the fft.
• This normally occurs when a strong tone occurs (eg a radar).

• 0  - 0 errors
• 1 - 1 error
• 2 - 2 to 3 errors
• 3 - 4 to 7 errors
• ..
• 12 2048-4096 errors
• For this processing i used the max value: 2^n
  

• for each day, read the compressed data files recording the number of overflows and the time and za where the overflows occurred.
• For the daily  run, bin the overflow counts to .5 deg za steps and then plot vs za. Do this separately for the adc and pfb errors.
• The amount of radar that gets into alfa depends on:
• the phase of the radar rotation period.
  
• When the radar points at AO once every 12 seconds,the signal get much stronger.
• the telescope az,za, and alfa's rotation angle.

• this data was taken with the azimuth at 0 deg.
• top plot: pfb overflow errors vs za
• bottom: adc overflow errors vs za.
• Each beam is a different color.
  
• Each page is data from a separate day (the date is the start of the daily run).
• the vertical scale is constant for the N days.
• Vertical dotted lines are are drawn for the adc error peaks of 06jun11.
• These peaks are constant for each day.
  
• Page 1: 06jun11:
• lots of pfb errors at za=10.5 to 11
  
• Page 2-6 data for 21,22,23,24,25jun11
• pfb much less for these days. No peak at za=11
• adc errors are similar to 06jun11

• page 1: 01 - 08jun11
• page 2: 09 - 16jun11
• page 3: 17 - 24jun11
• page 4: 25 - 26jun11
• The thick lines 1240,1260 are the aerostat radar.
• 06jun11 doesn't have the aerostat on  while 21-25jun11 does have it present.
  

SUMMARY:

• The pfb errors of 06jun11 did not repeat on 21-25jun11.
• The aerostat was absent from 06-07jun11 while it was present for parts of 21-25jun11
  
• the adc errors have similar counts and peaks for all the days:
• za peaks at za = [2.5,5.5,6.5,14,17] degrees.
• So i'm not sure why the pfb errors were so high for 06jun11..
• I doubt that it was the phase of the radar always lining up with za=11 since i don't think the galfacts updown period is a fixed multiple of 12 seconds.