field notes troubleshooting

Bruker NMR interference?

I was called to discuss the installation of an access point in a chemistry research facility where a Nuclear Magnetic Resonance (NMR) spectrometer by Bruker is operating. It’s a model slightly smaller than the one pictured below.

Credits: Mike25. Source: Wikipedia

Researchers operating the laboratory were concerned about the signal from a wi-fi access point in the same room possibly interfering with the instrument. My concern was in turn that the NMR would interfere with the wi-fi operations, given the much higher energy in play in an NMR spectrometer.

Upon discussion with the lead researcher, it was ascertained that the spectrometer works with RF below 1 Ghz, mainly in the 400 Mhz range. According to Wikipedia, it operates in the 60-1000 Mhz range.

Interestingly, a spectrum analysis with Metageek Chanalizer in the lab showed a distinctive interference on 2.4 Ghz centered on channel 2 and a lesser signal on channel 1. The measure was taken from a fixed position at 3m from the spectrometer, while it was operating.

The signal on channel 2 has a high duty cycle with 95% at -50dBm in a 20 minute interval.

At -70 dBm the duty cycle on channel 1 was above 80%.

Moving away from the NMR into adjacent rooms, the interference weakened and wasno longer detectable. I was not able to identify the exact source of the interference, besides it being related to the Bruker device operations. The access point was moved out of the room into the corridor.