sbc 3,4 high Tsys. halfband fitlers 3,4

• halfband filters hb1->sbc1 ,hb2->sbc2 are in the same chassis and share the same power supplies
• halfband filters hb3->sbc3 ,hb4->sbc4 are in the same chassis and share the same power supplies.
  

• lbw 1405 Mhz sent to all 4 interrim correlator boards with 1024 lags.
  
• cycle through bandwidths 25 down to 195 Khz second
• The bandwidth numbers used for the plots are:
• 2-25Mhz,3-12.5Mhz,4-6.25Mhz .. 9-.195Mhz
  
• For each bandwidth do a 10 second calOn, calOff observation.
• We computed the total power Tsys (using the cal value).
• We also computed the spectra of Tsys (in degK).
  
• Repeat this for 9 level and 3 level sampling.
• Normally PolA is about 2K higher than polB.
  

• Page 1: 9 level, total power Tsys
• The symbols used are: + polA, * polB.
• each sbc (interim cor board) is plotted in a different color.
• black,red (sbc 1,2) is about 3K less than the corresponding sbc (3,4).
• Page 2: 9 level spectra of Tsys
• top polA, bottom polB. black,red = sbc1,2  green,red=sbc3,4
• For each sbc3,4 is higher than sbc1,2
• the noise structure is similar for both
• Page 3: 3 level, total power Tsys
• the symbols, colors are the same as page 1
  
• black,red (sbc 1,2) is about .5K  less than the corresponding sbc (3,4).
• Page 4: 3 level spectra of Tsys
• the colors are the same as page2.
  
• For each sbc3,4 is only slightly  higher than sbc1,2
• the noise structure is similar for both
• Page 5,6: repeated 9 level measurements of page1,2
  
• same results.

• Page 1: 9 level, total power Tsys
• PolA is the same for all 4. sbc1 polB is about .2K less than the other 3.
• Page 2: 9 levele tsys spectra.
• all overlay and the noise is the same
• Page 3: 3 level, total power Tsys
• same values
• Page 4: 3 level tsys spectra.
• same values
  

• We repeated the measurements (with the power supply fixed) and got the same results.
• The polA 9level total power offset was no longer there.

Summary:

• the +5 analog supply for halfband filters 3,4 failed sometime around 21jun11.
• this caused the Tsys for sbc3,4 to increase by about 3 deg K for 9 level sampling.
• 3level sampling has a tsys increase of about .5 K
• The noise seemed to stays the same in the four bands.