• if2 noise source was selected.
• group 0 and group 1 pdev boxes were used: BnSmG0 and BnSmG1  (n=0..6),m=0,1
• the lo band (175 MHz lo) and the high band (325 MHz lo) were both used.
• The spectrometers were setup for:
• 172.032 MHz clock
• decimation =512 (gives bw=172.032/512= .336 MHz)
• 8192 channels (-->41 hz resolution)
• 30 second integration.

• Each color is a different beam or box.
• The top plots are polA, the bottom plots are polB.
• For a given beam/box, groupN band0 and groupN band 1 come from the same box (but different fpga's inside the box).
  
• Page 1: group 0 band 0. (this is the 175 MHz lo)
• there is a comb with about 3 khz spacing in both polA and polB
• This comb is not very strong in group 1 band 0.
• It is not seen in group 0 band1.
  
• Page 2: group 1 band 0. (same data as page 1)
• Page 3: group 0 band 1. This is the 325 MHz lo)
• Page 4: group 1 band 1. Same data as page 3.

• A 3 KHz comb is seen in group 0 band 0
• It is not seen in group 1 band 0 ( the same data split after the mixer).
  
• so it must come after the group 0,group 1 split in the mixer chassis.
  
• It is not seen in group 0 band 1.
• these are in the same box but  different fpgas.
• There may be some geometry causing this:
• group 0 boxes are above mixer chassis, below pserv cpu
• group 1 boxes are below mixer chassis, above pserv cpu.
• birdies at 75-80KHz.
• some boxes have them at a common freq.
• When a box doesn't have this birdie, it doesn't have it in both high and low bands
• see bm 1, band 0 group 0 and bm1, band 1, group 0.
• Probably means the birdie is coming from the box
• I think this was around a freq of the power supply
• 1/2 and multiples of this frequency are also seen.
  

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