We present the design of a versatile rf heterodyne spectrometer covering a 100 kHz to 190 MHz frequency range, which has been useful in nuclear magnetic resonance and acoustic experiments over its whole range. Commercial instruments were used wherever possible: two units, an rf pulse generator, and a 30‐MHz IF amplifier/detector were constructed and are described in detail. Also, we briefly outline application to ultrasound and NMR measurements and interfacing to a minicomputer‐based data processing system.