Helicon waves were excited by a Nagoya type 111 antenna in a steady state argon magnetized plasma column with DC magnetic field 6 = 400-500 G. electron density 10'2-10'3 ~m -~ and neutral species pressure about 20 mTorr. Wavelength measurements made with 6-dot probes at the edge of the plasma COIumn show the presence of multimode standing helicon waves. Azimuthal mode numbers m = +1, 0 and -1 were detected with m = +1 dominant. Radial density profiles were measured with Langmuir probes. The wavelength measurements are shown to agree with theoretical calculations of helicon waves in radially non-uniform plasma.