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Intro

   Calon,offs were done while tracking the sun and then moving  2 deg in azimuth off the sun. The setup was:

• A jpl horizons ephemeris was used to track on and then off the sun
• 10 second cal on followed by 10 second cal off was performed on and then off the sun.
  
• The sequence was; off sun calon/off, on sun calonoff, off sun calonoff, on sun calonoff.
• The cal diode is probably around 45K (need to measure in more accurately).
• When on the sun
• The telescope tracked + 8.4 arcmin in el  from the center of the sun.
• The signal was many times stronger at this offset. Later mano looked that the sun output, and this was close to an active region
• When off the sun.
  
• 2 deg (great circle ) offset in azimuth was used to get off the sun.
• xband receiver using 8050 to 9200 MHz
• Mock spectrometer used to record the data.
• 7 172 MHz bands centered at:
  
• 8132,8296,8460,8624,8788,8952,9116
• Each band spaced by 164 MHz
• 2 pols, 4096 channels/pol, 42 KHz channel width
• spectra dumped once a second

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Processing the data

• The total power was computed for each 1 second sample of each 172 Mhz band. no rfi excision was attempted.
• For each frequency band, the total power was normalized to the average of the calOff data when off the sun.
  

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Plotting the results:

    The plots show the results of the calon,offs (.ps) (.pdf):

• Page 1: calOn,offs all freq bands
• The x axis is the total power samples (1 per second). 10 calon, 10 caloff,, repeated for the 2 sets
• the y axis units are Tsys (caloff, offsun avg).
  
• 1st,2nd frames: polA
• 1st : on Sun: calOn,off on sun
  
• On the sun the signal increased by 2.8 Tsys
• the cal off is a bit stronger than the cal on.. so the system is saturated
• 2nd: Off sun, calonoff
  
• calOff has be defined to be 1. the cal is .4 to .6 Tsys. We don't (yet) know how the cal value changes with frequency;
• 3rd,4th frames: PolB
• 3rd: on sun
• the system level (calon,or off) is less than when we are off the sun. So we've hit a voltage rail in an amp.
• this  is  probably happening in the 4.2 - 8 GHz part of the band that has so much  power.
• The caloff is stronger than the calOn
• 4th: off the sun. we see a cal deflection of about  .3 Tsys.
• Page 2: same plots blownup showing a single freq band: 8624 Mhz
• 1,2 polA
• 1 - on sun. little difference between calon and caloff
• the level has increased from 1 to 3.75 units. So the sun was at least 2.75 Tsys units (since we went into saturation it must be more that this).
• 2 - off sun. cal is about .5 Tsys.
• 3,4 polB
• 3 - on sun.
  
• cal off is stronger than cal on
• the level went down from the off sun level
• 4 off sun. cal is about .3 Tsys

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Summary:

• Both polA and polB saturated when we were on the sun.
• PolA level went from 1 to 3.8 Tsys. so the sun is at least 2.8 tsys units (more since it was saturated).
• PolB level decreased at all freqbands when we went on the sun.
• A portion of the band outside the 8-9GHz range is probably causing the saturation.
• When it hits an amplifier voltage rail, portions of the spectrum outside the region will decrease.
• this is probably the 4.2 to 8 GHz increase in power we've seen in the frontend.
  

processing: x101/210617/onoffsun.pro