For good reason, many NMR users find the electronics in an NMR probe daunting as they can be quite complicated, depending on the configuration of the probe (double resonance, triple resonance etc ...). The electronics in a simple single frequency NMR probe, on the other hand, are very simple and can be built on the bench in a matter of minutes. A single frequency probe can have the following tank circuit with only two capacitors and a coil. Of course, all of the components must be nonmagnetic.
CT is the tuning capacitor. It is used to tune the circuit to a specific frequency (i.e. from one nucleus to another). CM is the matching capacitor. It is used to alter the quality factor of the circuit. L is the coil in which the sample is placed. It may be a solenoid or Helmholtz coil. The inductance of the coil is an important property to consider in achieving the desired tuning range of the probe . The coil must be effective at both transmitting rf to the sample as well as detecting the small NMR signal from the sample.