06jun11: on telescope testing of CMS. (top)

• 327 receiver, center freq 327 Mhz, 302=352 filter installed
• mock spectrometer: 43 Mhz bandwidth, 8192 channels (5Khz resolution), cfr 327 Mhz, 1 second dumps.
• Since the compressor monitor is on the dome, the az,za position should not make much difference.
• Data was taken for about 750 seconds.
• Around second 400 to 500 seconds, willie iguina openned the huffman box of the compressor monitor to get access to turn off the device.
• At 542 seconds the compressor monitor system was turned off.

• a bandpass to flatten the spectrum was computed by:
• average the 750 seconds of data
• do a robust fit (throwing out outliers) using a first order polynomial and a 43 order harmonic function.
• divide each of the 1 second integrations by the bandpass generated by the fitting (then remove 1.)
• For each 1 second record remove the median value (to get rid of continuum source drifting through the beam).
• I used a fit for the bandpass correction instead of a median bandpass so that contstant rfi would not get removed.

• the image was made using polB.
  
• the horizontal dashed line at 542 seconds is where the compressor monitor system was turned off.
• The image has been smoothed and decimated by 6 so that the image will fit on the computer screen. This changes the resolution bandwidth from 5 khz to 30khz.
  
• There are no obvious lines that stop at this point.

• Top frame: polA, bottom frame polB.
• The black line is the average (500 seconds) with the compressor monitor on.
• The red line is the average (250 seconds) with the compressor monitor off.
• A birdie from the compressor monitor would have a black spike with no corresponding red spike. I don't see any of these.

Summary:

• No birdies were seen from the compressor monitor dynamic spectra using 1 second and 30 Khz resolution.
• An average spectra of 250 seconds and 5 Khz resolution also showed no birdies from the compressor monitor.
  

14/15apr11:Compressor monitoring system in the lab (top)

• Compressor monitor system inside huffman box.
• agilent E4445A spectrum analyzer, 601 channels, and preamp on.
• 1 MHz to 10 Ghz. I've included the data from DC to 6gHz.
  
• Probes used:
• ETS model 7405 902 probe: magnetic field. upper resonance > 1.5 Ghz
• ETS model 7405 904 probe:  E-field probe  upper resonance > 1Ghz
• A separate set of plots was made for each of the 2 probles used.
  
• Move the probe around the device looking for maximum value (spectrum analzyer set to max hold).
  
• Do the tests with the huffman box open and repeat it with the huffman box closed.
  

• Page 1-2: scan 0 to 1500 MHz H,E probes
  
• Page 3-4: scan 1500 to 6000MHz H,Eprobes
  
• Page 5-6:higher resolution scans for 327,430,750, and sband narrow receivers. H,Eprobes
  
• 
  
• 14apr11: rfi with huffman box open (.ps) (.pdf)
• the 902 probes measures the H field, the 904 probe measures the Efield
  
• lots of rfi 0 to 500 MHz..
• 62.4964 MHz comb  continues to 3 Ghz.
  
• Wide bump around 1070.
• Some of the wider rfi in the hi-res spectra move in freq between the 902 and 904 measurements. The might not be associated with the device.
  
• 14apr11: rfi with huffman box closed (.ps) (.pdf)
• Below 100 MHz lots of rfi.
• Luis mentioned that the below 400 MHz the problem is the switching power supply.
  
• Comb not visible.
• 15apr11:rfi with huffman box closed after luis did some shielding (.ps) (.pdf):
• luis added some shielding to the devices in the huffman box (.pdf) and then remeasured the rfi on 15apr11.
  
• data was only measured up to 2500 MHz on this data with the huffman box closed.
  
• 902 probe: rfi below 100 MHz way down
• 904 probe: rif below 100 MHz actually got stronger.
• either the probes looked at different spots between 14,15 closed or ??
• 
  

Summary:

• The  Compressor monitor has a 62.4964 MHz comb
• With the box open this extends up to 3GhZ.
  
• With the box closed it is not seen.
• With the box closed there is strong rfi 0 to 125 MHz probably coming from the switching power supply.
• After some additional shielding of the device, the H field rfi belwo 125 MHz went way down while the E field measurement went up.