Sunday, January 22, 2023

Identify chemicals with radio frequencies - Nuclear Quadrupole Resonance (MRI without magnets)


How to build and test an NQR spectrometer, which is similar to MRI, but uses no magnets.  NQR frequencies are unique among all tested compounds, so detecting a resonance indicates a near certainty that a specific chemical is present.

Tektronix 2-series oscilloscope: Video capture was done via VNC client

Zeeman effect shifting optical spectral lines:

Atomic clock calibration using Zeeman effect:

W2AEW's RF tutorial on quarter wave transmission lines:

Water deflected by electric field:

Litz wire only helpful between 50KHz and 1.5MHz -

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Why use vacuum variable capacitors? The parallel LC circuit develops well over 1000 volts during transmit, and they are much easier to finely adjust over a large range.

I've spent quite a few hours making this work since late last year.  I failed to detect a signal from urea, which burned dozens of hours.  Switching to NaNO2 suddenly produced a huge signal.

NQR calculations spreadsheet -

NQR references (many!) :