From Applied Science.

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: https://www.tek.com/en/products/oscilloscopes/2-series-mso Video capture was done via VNC client

Zeeman effect shifting optical spectral lines: https://youtu.be/JV4Fk3VNZqs?t=74

Atomic clock calibration using Zeeman effect: https://www.youtube.com/watch?v=xTy1kY_wtsY

W2AEW’s RF tutorial on quarter wave transmission lines: https://www.youtube.com/watch?v=A1BAq0KxIdc

Water deflected by electric field: https://youtu.be/NjLJ77IuBdM?t=468

Litz wire only helpful between 50KHz and 1.5MHz – https://youtu.be/FUCRB9UdfUg?t=2010

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Q/A
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 – https://docs.google.com/spreadsheets/d/1pkWlgvEXlANemZt3DR1J5g59S7hsejbvs995Y4FRsl0/edit?usp=sharing

NQR references (many!) : https://docs.google.com/document/d/1XoNUhFceH38nSjAFZoxglNiZlUzn6QMxa6CYTyAM92c/edit?usp=sharing