24may12 p2030 data

• alfa receiver.tracking each pulsar for about 300 seconds
• The cal was turned on for about 6 seconds at the start of each 300 second integration.
  
• mock spectrometer:
• 2 172 MHz bands center at sky frequencies of 1300 and 1450 MHz
• 512 channels
  
• 65.47619usec integration of each spectra
• 16 bit Stokes I data recorded.
• Offline the data was packed to 4 bits

• Time Domain Plots:
• total power vs time 1450 MHz band (.ps) (.pdf)
• total power v s time 1300 MHz band (.ps) (.pdf)
• The vertical scale is Tsys. I've offset the plots for displ
• The data was smoothed and decimated to .65 millisecond resolution.
  
• The jump at the start is the cal on for 6 seconds.
• The block of rfi every 5 seconds is the dewar monitoring glitching the  bias lines.
• The 1300 MHz band has two radars (with 12 second periods)
• at 12.5 seconds and 17.5 seconds.
• Spectral plots:
• A 4  million point fft was done on the total power data (i used data after the cal deflection).
• The magnitude of the spectra was then plotted. The scaling turns out so that a sine wave in the voltage equal to tsys would be 1 unit in the plots.
• 0-100 Hz spectral plots (.ps) (.pdf):
• I plotted the first 100 Hz of the spectra.
  
• Top 1450 band.
• Bottom: 1300 band
• The large interference at multiples of 20 Hz is from the dewar monitoring.
  
• spectral Blowup showing 0 to 5 Hz  (.ps) (.pdf)
  
• Top: 1450 band
• Bottom: 1300 band
• There is a spike at .838  Hz (1.194 seconds). It is strongest in beamm4 (about .0007 Tsys(voltage)).
• there is another spike at 2.516 Hz (.397 secs). 
• This looks like the 3rd harmonic of the .838 hz spike. Its strength by beam varies the same as the .838 hz birdie.
  
• The 1300 MHz band also has spikes below one Hz from the rotation rates of the radars.
• There is no 1.5 Hz interference.
  

Summary

• The alfa dewar monitoring is creating  periodic power at 20.827 Hz and harmonics of this.
• It occurs in all beams and both pols.
• This can now be turned off during pulsar experiments
• There is a .838 hz period showing up in the pulsar search data. The magnitude (abs(fft)) is about  .0007 Tsys.
• A 2.516 hz birdie is probably the 3rd harmonic of the .838 hz birdie.
  
• There is no 1.5 Hz signal as reported by the pulsar observers.