TGBT15A_915_137 - VPM Scale and Filter Tests

Goals

• Test smaller fftshift values with 950 MHz IF module filter
• Find better vegas.scale value for c0800x0512 coherent search
  • Incoherent modes: 0x555557ff, 0xaaaaabff, 0x555555ff, 0xaaaaaabf, 0x5555555f
  • Coherent modes: 0x55555fff, 0xaaaaafff
• Verify Ray's patch for frequency precision in shared memory
• Test Luke's new BOF file i0800x2048 mode

Details

• Session begins at 13:30
• Editing vegas.conf with new i0800x2048 bof file
• Submitted IncoherentModeTestsCal SB at 13:40 running i0800x2048 to test new BOF file
  • Didn't pick up new BOF file. Restarting VEGAS
  • Resubmitting at 13:47
  • Scan is #1
  • Scan successful, no obvious issues with BOF file.
• Will move on to testing fftshift values. Going to stick with this mode. First will try 0x555557ff
  • Submitted SB at 13:58
  • Scan is #1
    • Levels are too low. Maybe I went in the wrong direction with the fftshift value?
• Will try 0x55555555
  • Submitted at 14:02, scan #3
    • Data are maxing out as expected. Will lower vegas.scale to 5000 (50% reduction)
  • Submitted at 14:04, scan #4
    • No obvious effect. Lowering by 50% again to 2500
  • Submitted at 14:08, scan #5
    • Still too high, but not maxing out now. No sign of overflow artifacts. Will decrease scale by 50% again to 1250
  • Submitted at 14:13, scan #6
    • Data seem mostly OK, but will decrease scale by 70% to 875 to see how that looks.
  • Submitted at 14:18, scan #7
    • Looks encouraging
• This looks pretty reasonable, but I'm curious to see what it looks like with an fftshift of 0xaaaaaaaa
  • Changed vegas.conf and dropping vegas.scale to 10
  • Submitted SB at 14:30, scan #8
    • Not enough power. Will increase vegas.scale to 100
  • Submitted SB at 14:32, scan #9
    • Still too low. Increasing back to 875, scan #10
  • Submitted SB at 14:34
    • Levels were OK but I think we are seeing the overflow artifacts again. Going back to 0x55555555
  • Will try some other incoherent 800 MHz modes.
    • Scans #11--16 will be i0800x0128 -- i0800x4096, with vegas.scale values of 875 or 437.5
    • Submitted SB at 14:43
    • Levels look OK on scans #11, 13, 15, with no obvious overflow artifacts
    • Levels too low on scans #12 (i0800x0256), 14 (i0800x1024), 16 (i0800x4096)
    • Obvious overflow in i0800x1024
• Need to look at these data more carefully, but want to move on to the scale setting for the c0800x0512 mode.
• Submitting CoherentModeTestsSearch SB for a c0800x0512 scan with vegas.scale = 400. No change to fftshift at this time.
  • SB submitted at 14:58, scan #18
    • Levels were still a bit low. Increase scale factor to 800
  • SB submitted at 15:14, scan #18
    • Levels look OK, but will compare with GUPPI
    • Still a bit low compared to GUPPI. Will increase scale to 1015
  • SB submitted for scan #19
    • This looks good.
  • Taking cal scan with this vegas.scale setting to see if it is also OK
    • In agreement with GUPPI
• Ended a little early instead of trying to squeeze in the coherent mode fftshift tests. Restored vegas.conf to original settings and asked Ray or Joe to commit it.
• Session ended at 15:50

Conclusions

• The i0800x2048 BOF file seemed to be OK
• The lower incoherent mode fftshift values seem usable, but more work is needed to understand why some modes show lots of overflow artifacts while others seem to show none.
• The search-mode coherent mode scale for c0800x0512 now looks good. I need to do this exercise for other modes but should be able to use past tests as a guide.
• Didn't get to test the coherent mode fftshift values.