It has been demonstrated in the Phaedrus‐B tandem mirror [Phys. Fluids31, 714 (1988)] that radio‐frequency (rf) waves applied below the ion cyclotron frequency (&ohgr;/&OHgr;i≊0.75) can stabilize a mirror plasma against the interchange instability. Results presented here demonstrate stabilization over a range of frequencies (0.65≤&ohgr;/&OHgr;i≤0.8) with themMHD=−1 instability stabilized and higher‐order (‖mMHD‖≥2) low‐amplitude modes present. Radial profiles of the rf magnetic fields at a number of axial locations as well as parallel wavenumber measurements indicatemrf=−1 slow shear Alfve´n wave excitation over this frequency range. Measurements at frequencies below 0.75&OHgr;iindicate attenuation of rf waves by gas baffles and a gas box.