Experimental results are reported on a continuously‐variable delay line using acoustic waves to diffract and frequency‐shift a portion of an argon ion laser beam. Data was obtained from 300 to 700 MHz utilizing thin‐film CdS transducers deposited on a single‐crystal Z‐cut quartz rod placed within the laser cavity. The diffracted, frequency‐shifted beam was optically heterodyned on a PIN detector. Variable delays of the order of 10 &mgr;sec were obtained by varying the distance from the CdS transducer to the beams' intercept point. A novel folded‐acoustic path configuration is also described.