TGBT14A_912_86 - VEGAS Bank Discrepancy Problems

Goals

  • Perform the definitive "with DCR" tests

Setup

Noise source inputs

  • Inputs to either ADCs directly, or VEGAS Analog IF module inputs
  • connect power meter to E1 splitter cable (ADC inputs) or Analog IF monitor output for EI
  • terminate E1 ADC when there is no input

Receiver IF inputs

  • Configure the system as follows:
    • Configure the IF Rack so that the two polarizations of the X-band receiver are connected to two low DCR ports (I don't know what numbers they will be now, but should be in range 1-8)
    • Connect seven of the VEGAS Analog IF module monitor points for banks E through H to DCR ports 9-15
    • Connect E0 (i.e. first pol) one of the VEGAS Analog IF module monitor points to the power meter. .
    • Configure VEGAS for alternately Mode 1 and 4.
    • Take a series of Off/On Low/On High/Off/On Low/On High/Off total power no cal data (so single phase), switching noise source on and off manually between scans.
  • Recorded data will be:
    • Receiver RF power straight into DCR (first two ports)
    • VEGAS Analog IF monitor outputs into DCR (next eight ports)
    • VEGAS ADC measpwrs
    • VEGAS filtersnap_nogain measpwrs (from filtersnap_nopgain sampler)
    • VEGAS filtersnap measpwrs (from filtersnap samplers)
    • VEGAS spectra. Convert VEGAS spectra into total power by summing over channels, and normalizing by some useful number.
  • For each automated data source, for each scan, form mean and std deviation for the ~ 60 good 1sec samples (ignoring obviously discrepant values).
    • power meter reading, plus error in reading, will have to be entered by hand in some convenient way (maybe CSV file with scan, power, error).
  • For a given pair of input scans, for the RF power into the DCR (two values), and all other quantities (eight values; can just be labelled 1 through 8 on X-axis) plot:
    • "On" value with errors
    • "Off value with errors
    • "On-Off" with propagated errors
    • "Off/(On-off)" with propagated errors

  • Repeat for Mode 1 and Mode 4

Details

X-band RF / IF tests

  • VEGAS J16 (H2) has a dodgy cable for these tests.
  • 10:30am. Galen connects up IF monitor outputs. Module E1 is connected to power meter.
  • run bank_gain_mode4_xband_nocal
  • run balance. Three inputs won't balance - why not?
  • have an LO power level error from X-band receiver. Manually increase LO power level.
  • System still won't balance. Problem seems to be in Converter Rack (attenuators are at zero). Why is this?
  • Try swapping around between modes and balancing; things seem to improve a bit, not sure why (I think I changed receivers...) *
  • Setup
    • Archivist
    • bank_gain_mode4_xband_dcrIF - sets up DCR channels 2 and 4 to connect straight to Rx, 1280MHz filter in IF rack. DCR power is 5.75V for channel 2. Hope this stays this way.
    • bank_gain_mode4_xband_vegas_dcr_config check what receiver is selected
    • DCR banks 2 and 4 seem the same - need to turn them back on manually.
    • DCR channel 9 has no input (as expected); remainder are around 10v.
    • Power meet reads -2.23926857E+001 dBm).
    • Manually tweak converter rack attenuators to:
9    3.25
10 2.125
11  0.0   - VEGAS at -22.2dBFS
12  4.0
13  6.25
14  10.0
15  4.75
16  0 - - VEGAS read -25dBFS

  • Try toggling noise source. Do all values change as expected?
  • All values change. Pol 1 change seems much stronger than Pol 2 (1.5dB c.f. 0.5dB). Power meter changes from -22.36 to -20.90
  • DCR port 2 changes from ~5 to ~ 8
  • Toggle back and run a scan
  • scan 1 60 sec scan, no noise - Aborts, Antenna in scan coordinator
  • scan 2. Power meter -22.345, -22.320, -22.3245, -22.338. Seems stable to around 0.01dB. All data looks good. Go to lunch at this point.
  • Back from lunch - everything still looks good. Run a series of of/lo/hi scans
scan noise power meter ( /10)
3        off      -2.2430
4        lo       -2.2232
5        hi       -2.1001
6        off      -2.2425
7        lo       -2.2219
8        hi       -2.0945
9        off      -2.2379
10      lo       -2.2219
11      hi       -2.0962
12      off      -2.2382

  • Manually set Converter Rack attenuators, so VEGAS power levels are as close as possible to -17dBFS (can't reach any higher).
  • Remove 3dB of attenuation from Converter rack - doesn't appear exactly right...
scan noise power meter ( /10)
13      off      -1.9472
14      lo       -1.9198
15      hi       -1.7784
16      off      -1.9181
17      lo       -1.8959
18      hi       -1.7673
19      off      -1.8938
20      lo       -1.8211
21      hi       -1.7575
22      off      -1.8759
  • Set converter racks to -23dBFS (all but H2 make it)
scan noise power meter ( /10)
23      off      -2.5360
24      lo       -2.5323
25      hi       -2.4028
26      off      -2.5579
27      lo        -2.5426
28      hi       -2.4238
29      off      -2.5646
30      lo       -2.5458
31      hi       -2.4214
32      off      -2.5502
  • Reconfigure as close as possible to -20dBFS
  • Manually set up both VEGAS and DCR for switching (1 sec swper), and run scans with low and high cal diodes.
  • Scan 33 - low power
  • Scan 34 - high power
  • scan 35 - low power
  • scan 36 - high power
  • Scan 37 - low power
  • Scan 38 - high power

Noise source Into VEGAS IF tests

  • CLEO hangs up on me, Bank A Accessor seems to have died, then comes back...
  • Connect E0 line of splitter to noise source, to monitor the attenuator levels
  • VEGAS H2 (J16) is discrepant from all the rest...
  • Configure VEGAS J9 to be connected to no input if possible.... turn off power to laser, and sett attenuator to 31dB. Reads -43dB
  • Galen fiddles with J16 VEGAS Analog output to ADC, and manages to get it back - had to replace the cables
  • Power meter readings seem slightly out of whack with VEGAS, but continue regardless
  • No amplifier on the noise source for this test.
  • attenuator setting of 17dB corresponds to VEGAS level of -20dBFS. Run from 0 to 31db in 1 dB steps
  • When I change the power level into E2, the power measured by VEGAS in E1 changes!!
  • Galen says there is not infinite attenuation between the two channels
Power meter can jump around by ~ 0.1dB, but sometimes 1dB (e.g.
Scan   Att Power Meter
39        0   -2.5558
40        1   -2.6564
41        2    -2.7627
42        3    -2.8403
43        4    -2.9447
44        5    -3.0330
45        6    -3.1388
46        7    -3.2448
47        8    -3.3486
48        9    -3.4453
49      10    -3.5519
50      11    -3.6833
51      12    -3.8306
52      13    -3.9781
53      14    -4.0421 -noisy
54      15    -4.2950 - noisy
55      16    varying by 3dB....
56      17 
57      18
58      19
59      21  <- Ray called me!
60      20
61      22
62      23
63      24
64      25
65      26
66      27
67      28
68      29
69      30

  • Swap noise source to input of ADCs
  • amplifier back in
  • attenuator of 4 is approx -20dBFS
  • Seems like H2 is not connected now.
Scan   Att Power Meter
70    0  -5.0910
71    1  -6.0818
72    2  -7.0967
73    3  -7.8520
74    4  -8.8359
75    5  -9.6529
76    6  -1.0634 * 10
77    7   -1.1648
78    8   -1.2629
79    9   -1.3411
80   10  -1.4391
81   11  -1.5411
82   12  -1.6391
83   13  -1.7453
84   14  -1.8438
85   15  -1.9451
86   16   -2.0446
87   17   -2.1529
88   18   -2.2528
89   19   -2.3580
90   20   -2.4579
91   21   -2.5436
92   22   -2.6452
93   23   -2.7562
94   24   -2.8865
95   25   -2.9643  -40dBFS
96   26   -3.0916
97   27   -3.2098 - Jason starts disconnecting here...
  • 4:15pm Done

Analysis

See: CICADAGreenBankSpectrometer2015Apr02Analysis

-- RichardPrestage - 2015-03-30
Topic revision: r6 - 2015-04-08, RichardPrestage
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