Ansel, Georgia

While noise hunting at EX we noticed that there are sidebands around the 100Hz line visible in the SUSRACK magnetometer at EY. Ansel and I went to EY to look at the ESD electronics, and tried powering off the Beckhoff chassis.

• We found that there are ESD power supply monitors at End Y as well. The channels are:
  • +18V monitor -> test 8 -> ADC???
  • -48V monitor -> test 9 -> ADC 17
  • +18V monitor -> test10 -> ADC 16
• Looking at the magnetometer spectrum it is quite different to EX - there's the 100Hz Beckhoff communication line, and then sideband with spacing at 2.5 Hz and 5.05Hz. The sidebands are narrow (fig 1) compared to EX's broad lump of noise.
• We tried powering off the Beckhoff chassis in the ebay
  • We powered off ISC common, this eliminated the 100Hz line and sidebands (fig2, blue)
  • We then powered ISC common back on and powered off End station 2. This changed the frequency of the sidebands to ~3.75 (fig 2 green)
  • We then powered End station 2 back on and powered off End station 3. This shifted trhe frequency of the sidebands again (fig 2 dark purple/brown)

We also noticed it was quite warm in the EY ebay.