Intro

    On 15jun23 a pulsar observation was done on B0320+54 using the 3GHz filter (wb3) of the cooled wide band receiver. The observations
showed lots of rfi/problems in polB.

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Setup:

• The 12meter receiver used the wb3 filter
• there were 5 1" shims installed when this  data was taken.
  
• 5 mock spectrometer were used:
  
• 172.032 MHz bw polA,B recorded
• cfr:  2846 2988 3130 3272 3414
• 256 freq chan/band 
  
• .5 millisecond  integration
• 1800 secs of data
• a 90 sec winking cal on,off take at the beginning.
  

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Processing the data

• Ben used the standard psr processing routines to look at the data.
• I later looked at the data with idl

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Looking at the data:

Ben's pulsar processing:

 The first plots show ben's standard pulsar processing (.pdf)

•  The red lines in the upper left dynamic spectra are where data was excluded by the rfi processing.
• PolB has lots of rfi between 3000 and 3100 MHz
• The bottom left plot shows the folded pulsar period vs time (it is probably folding 10sec at a time)
• You can see an black stripe moving across the band in a little less than 4 minutes.
• Dips like this can occur if the system has gone into compression.
• Since the data has been folded at the pulsar period (.7145..secs) this drift is the difference between the actual signal and the folding period.

The 1st 401 secs of data with idl

• I used the first file of 401 secs of data
• spectra were integrated to 500 Usecs, 256 channels
• each band was 172MHz wide.
• I first computed the rms/mean by freq channel for each 1 sec of data (giving 401 rms vs freq)
• I then computed the 1 second averge of the spectra  (giving 401 spectra)
• I combined all of the freq bands (excluding the overlap region)
  

The first image shows the dynamic spectra   for the 1 second averaged data (.jpg)

• the top frame is pola, the bottom frame is polB
• the images have been flattened by the median spectrum.
• polB has a lot more periodic rfi around 3300 MHz than polA

The rms/mean by freq channel for each 1 second . (.jpg)

• The rms/mean by freq channel was done for each 1 sec of data (2000 spectra)  and then a "dynamic spectra" was made of this data.
• The extra rfi in polB   stands out.

The amplitude of the rms/mean by freq channel is seen in the next 2 plots

• the 401 rms/mean be freq channel are overplotted.
  
• The top frame is polA, the bottom frame is polB
  
• The rms/mean was computed for each second and then over plotted (.pdf)
• Blowup in amplitude of rms/mean by freq channel  (.pdf)
• The expected rms/mean of .086 is close to the measured value.
• A few seconds have elevated values between 2850 and 2980 MHz

The following images over plot the 2000 spectra in each second for seconds 297-299 :

• The top frame is pola, the bottom frame is polB
• each color is a different 400 MHz spectra
• The vertical scale is mock spectrometer counts.
• 16 bit data is recorded, so the largest value would be 32767.
• The red horizontal line at the top  shows the maximum possible value.
  
• sec 297 (.jpeg)
• Peak rfi at 3041.55.
  
• PolB has an occasional strong peak at 3043.8 MHz
• sec 298 (.jpeg)
  
• the 3041.55 peak is still present
• a much large peak appears at 3060 MHz
• the values in now hitting the 16 bit maxium value
  
• 20 MHz sidebands are also present around this value
• These may be  created when the 16bit  max level is hit
• There is also a periodic (in freq) set of rfi at a much lower value in polB
• These have a more constant value of 4096 counts spaced by about 10 MHz
• This could be from the 16 bit saturation.
• I've also seen this we the fpga can't process fast enough  when used hires mode. It an drop/add a bit in the accumulation.
• since this was not hires mode, i'm not sure this is occuring.
• sec 299 (.jpeg)
• the 3041 rfi is stronger.
• polA is not quite hitting the 16 bit max value
  
• PolB is hitting  the 16bit max
• the 3060 MHz birdie is present but a lot weaker.
• the periodic in freq birdies are no longer present.
  
  
  

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Summary

• pulsar data was taken on B0329+54 at 3GHz
• the pulsar was detected in 1800 sec with a s/n of about 15
• In the following days this value got up to 200 (we've seen ampl of this pulsar vary a lot with the old receiver)
• Lots of "extra" rfi was seen in polB
• this was probably coming from the 500 Usec sec spectra saturating in the 16 bit accumulator.
• The periodicity of some of the 3Ghz rfi is probably coming from the 2900-3100 Mhz radar
• I'll use the vela pulsar data (sampled at 32Usec) to check the periodicity.
  

processing: x101/230615/psrchk/psrchk.pro