TGBT14A_912_90 - VEGAS bank to bank tests with Spectrometer, etc

Goals

  1. Configure the system as normal for VEGAS and the Spectrometer, and look at the respective backend inputs with a Spectrum Analyzer. Look for anything which looks anomalous between the two.
  2. Take a cable (or cables) which normally connect the AFR to the Spectrometer, and either tee them off or connect them into the inputs of the VEGAS IF modules. Take tp with cal data (i.e. cal diode switching) either simultaneously, or consecutively with the Spectrometer and VEGAS. Compare the results.
  3. Take data with VEGAS with the IF system configured for Mode 1, but trick VEGAS into running with Mode 4 (i.e. same IF configuration all the way to the VEGAS ADCs). Compare Mode 1 and Mode 4 results.
  4. As above, but try different settings for the IF rack bandpass filter, from all-pass down to 20 MHz. Look at the converter rack attenuator settings to confirm Steve's point about bandwidth and variance.
  5. Repeat above looking at the noise source in the IF rack
  6. Physically swap some Converter Modules (not just the cables). See whether the results move around with the converter modules or not.
  7. Repeat the tests were we drive some VEGAS IF modules with identical copies of a single converter module through a splitter, and others with their normal converter rack inputs. Compare the results.
  8. (suggestion from Ray) - use a narrow band mode, and spread it across the wide band IF.

Details

  • Set up at 8:00am
  • Ray needs to swap versions, Galen sets up Spectrum Analyzer
  • Weather is terrible; thick grey cloud, rain...

Spectrum Analyzer Checks

  • Run a tp spectrum to make sure system is configured correctly, and leave exactly this way for visual inspection.
  • VEGAS Mode 1
    • bank_gain_mode1_xband - Accidentally had A, not E - need to redo E.
    • archivist
    • balance - this does not seem to balance the IF rack! - fiddle around manually, with cleo, then run balance again
    • SetValues (5.644)
    • Scan 1: Track - but set up wrong. Decide we want to use the same converter modules for Spectrometer and VEGAS - A,B,C,D
    • bank_gain_mode1_xband_acs - confirms we will be using A,B,C,D
    • bank_gain_mode1_xband - hi cals running! Proceed with this anyway....
    • Scan 2: Track: Tsys [78.53,81.76,81.16,80.71,74.71,75.61,75.47,76.49]
    • Galen is seeing 10dB "spikes" appearing in the spectrum analyzer.
    • Switch inputs in IF Rack to be wideband noise source. Rebalance, but do not otherwise configure
    • Galen deduces the spikes are probably RFI.
  • ACS "Mode 1" (800 MHz)
    • bank_gain_mode1_xband_acs
    • balanceACS
    • Scan 3: Track: into Spectrometer. IF power levels 8,3,1 off by 0.85,0.54,0.51dB
    • Tsys (from Spectrometer): [66,64,67,65,66,64,67,65] - but did this with lo cal diode
    • Spectrometer Samplers 3 and 6 are faulty at the moment. Tee-off samples 1,2,7,8 to VEGAS.

    • Green path, green numbers

    • Connect up Converter Rack A CM1&5 and CM4&8 to Spectrometer J1, J2, J7, J8, Tee off to VEGAS A1,A2,B1,B2 (not convinced which order), straight into ADC
    • Make Spectrometer switching signal master for everything
    • Scan 4: Track. Need to fill spectrometer data manually
    • compare scan 4 to scan 2; scan four Tsys spectrum lines up much more closely than scan 2 between different IFs
    • Scan 5 - Track on IF wideband noise source (need to adjust converter rack attenuators) Nonsense; no noise source.
    • Scan 6 - simulates the "on". Turn switching signals off - still looking at noise source
    • Increase all attenuators by 1dB. After this, values:
      • CM1 1dB
      • CM5 5dB
      • CM4 9dB
      • CM8 6.5dB
    • Scan 7 - simulates the "off"
    • Check Scan 4
    • bank_gain_mode1_xband_acs, tp, low noise.
    • archivist
    • balanceACS - does not correctly balance Spectrometer, do it manually again.
    • CM1,5,4,8: 0,8,9.9.5 - sets levels good for VEGAS, slightly off for Spectrometer (1.24,0.98,0.84,0.77)
    • Scan 8 - Track
    • adjust CM attenuators so that Spectrometer is as close as realistic to 0.848 - this seems to be as close as we can get
    • VEGAS Tsys values 52.30,51.82,52.53,51.18
    • Spectrometer Tsys values 82.37, 85.5, 79.0, 75.1

    • red path, red numbers

    • Take the outputs of the AFR, and feed them into the inputs of the VEGAS IF Module. Need to take pads off input to Spectrometer, and add them to input to VEGAS IF modules
    • CM1,5,4,8 - 13.0,22.5,23,24dB
    • Scan 9 - Scan 9 seems significantly worse than Scan 8; Scan 8 in VEGAS agrees reasonably with Scan 4
    • Need to do this more systematically.

    • A,B, IFR connected to input of VEGAS IF module
    • IF Rack 17,20,16,19
    • CM rack 13.0, 22.5, 23, 24
    • VEGAS: -20.6,-20.6, -19,-19 (slowly varying)
    • Spec Duty cycles 0.83, 0.81,0.79,0.87
    • Scans 10-14 five "identical" scans simply submit Track 5 times
    • balanceACS - just does a "balance"
    • Sets IF rack to 16,20,16,19
    • CM rack 13.875, 22.625, 24.625, 23.875
    • VEGAS ~ -20.5, -20.5, -18. -19
    • Spec Duty cycles 0.84,0.88,0.97,0.82
    • Scans 15-19 five "identical" scans
    • From GBTIDL; Tcal p0 = 2.00, Tcal p1 = 1.88

    • Green path, green numbers again

    • A,B, IFR connected directly to input of ADC (switch pads around again).
    • balanceACS - Converter Rack fails
    • IF rack 14, 17, 14, 17
    • CM Rack 0,9,10,10
    • VEGAS -19,-20,-21,-20
    • Spec duty cycles 1.1,1.1,1.0,0.93
    • Scans 20-24 five "identical" scans

    • Red path, purple numbers

    • revert to path where AFR goes to input of VEGAS IF modules
    • On A, move 15dB pad from before ADC to before VEGAS IF module
    • Removed 15 dB from before Spectrometer
    • Remove 3dB pad from Bank A, 6dB pad from Bank B
    • balanceACS
    • IF rack 13, 16, 13, 16
    • CM 15,24,25,25
    • VEGAS -19.5,-19.5, -21,-20
    • Spec duty cycles 1.3,1.29,1.16,1.04
    • Scan 25-29 five "identical" scans

Put Everything back to normal

  • Configure just for Spectrometer: bank_gain_mode4_xband
  • Scan 30 - pol 1 in all Banks falls off and then starts recovering during the middle of a scan!! Mode 4 by mistake
  • Scan 31 - mode 1 VEGAS
  • Scan 32 - Spectrometer 800 MHz
  • All seems ok
  • 4:30pm

-- RichardPrestage - 2015-04-14
Topic revision: r5 - 2015-04-14, RichardPrestage
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