TGBT15A_915_102 - Test 32-channel pulsar modes

Goals

  • The i1500x0032 mode appears to be shifted in frequency from the expected center of the bandpass. The goal is to find the source of the shift.

Details

Session begins at
  • Session began at 15:03
  • Switched to Justin's VPM branch
  • Relevant BOF files are:
    • i1500x0032_x14_7_24t_095binw_2017_Jun_22_0831.bof
    • i1500x0064_x14_7_2016_Apr_19_0813.bof
    • i0800x0032_x14_7_24t_095binw_2017_Jun_13_1343.bof
  • Using IncoherentModeTests SB
    • Scan #1 is i1500x0032
      • Frequency shift is still present
    • Scan #2 is i1500x0064
      • Verified that major bandpass features show up at different reported frequencies. However, IF tuning seems to be the same as in i1500x0032
    • Scan #3 is i1500x0064, this time with test tone at 1400 MHz, -10 dBm
      • Test tone is at expected frequency
    • Scan #4 is i1500x0032, with test tone at 1400 MHz, -10 dBm
      • Test tone shows up at a reported frequency of 1000 MHz, so 400 MHz off.
      • LO1 is tuned correctly (RF = 1500 MHz, LO1 = 4500 MHz, IF = 3000 MHz)
      • LO2 is tuned to 12750 MHz, so IF should be 12750-3000 = 9750 MHz. This is identical to set up for i1500x0064.
      • LO3 is fixed at 10500 MHz, so IF should be 10500-9750 = 750 MHz. This is the correct baseband input for VEGAS with 1500 MHz (i.e. center baseband frequency = 1500/2 = 750 MHz)
    • Scan #5 is same as last
      • vpmMonitor.py shows tone at 1000 MHz in that bandpass as well
    • Scan #6 is i0800x0032 with tone at 1400 MHz, -10 dBm
      • Test tone shows up at 1400 MHz as expected
  • Switching back to release branch at 15:41
  • Submitted CheckMode1 SB
    • Looks good
  • Submitted CheckMode29 SB
    • Looks good
  • Session ended at 15:50

Conclusions

  • Config tool seems to be exonerated. We confirmed that the tone shows up at the right frequency in the i0800x0032 mode and the i1500x0064 mode, but not the i1500x0032 mode. Jason will look at the BOF file for this mode for possible issues.
-- RyanLynch - 2017-07-19

This topic: CICADA > WebHome > GreenBankSpectrometer > CICADAGreenBankSpectrometerCommissioningLogs > CICADAGreenBankSpectrometer2017Jul19
Topic revision: 2017-07-19, RyanLynch
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