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TGBT18B_502_14 - Timing Offset Tests with AP
Take coherent mode data with the artificial pulsar hooked directly into the GUPPI and VEGAS ADCs to better characterize timing offsets
AP will be set to 714 Hz. All scans will be in coherent search mode and will be 150 seconds long. We will take 4 consecutive scans in each mode.
Jason hooked things up starting at around 12:30. Had to adjust AP power to hit good input levels for VEGAS and GUPPI.
GUPPI is about 4 dB high in one channel, 1 dB high in another. VEGAS inputs are at -23 and -21 dB. This should be OK.
First short scan was to check bandpass levels in incoherent mode, which look good in both GUPPI and VEGAS
Started timing scan sequence. First scan is #2
Spot check of data makes it look like VEGAS scales might be low, though the AP signal is visible.
For some reason GUPPI is dropping a bunch of packets on GPUs 5, 6, 8, and 9 in c0800x0064 mode. There isn't any useful signal on those banks so I don't think it's an issue, but it is odd.
Levels definitely seem low on VEGAS. Will try again with vegas.scale increased.
Had to play around a bunch with VEGAS levels and fftshift. Still not sure it's optimal but it should be OK for our purposes.
Decreasing scan length to 120 seconds. First good scan is going to be #12.
Now we aren't getting any signal in c0800x0064 on VEGAS.
Same is true for c0800x0128
Going back to original settings and just going to use what we can get. First good scan will be #17.
Scan #29 tried to abort but I continued on.
c0800x4096 was failing for some reason. CLEO message reports that VEGAS has an invalid start time? Tried doing a full system stop/start. Moving on to c1500x0064.
c1500x0064 also aborted.
Cycling VEGAS off/on. First good scan is #47.
Last scan will be c1500x0064, scan #61.
Jason began connecting VEGAS back up at 15:43
Did a quick checkout of GUPPI and VEGAS, and balancing and bandpasses looked normal.
Session ended at 15:49
Will analyze data.
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Topic revision: r2 - 2019-03-12,
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