Tuning and matching is the process of optimising the frequency and resistance of the circuit that includes the detection coil. Every sample has a slightly different ionic content and so the probe should be tuned and matched for each sample. Modern NMR probes have automatic tuning and matching devices, but the Skaggs NMR Facility probes do not. Here, I look at the impact of poor tuning and matching on a 1D 1H spectrum.