Measurements were made of the phase, attenuation, and coupling constants of circularly polarizedm=±1 traveling helicons inn‐type InSb cylinders at 54.2 MHz. Values ofkHabetween 0.25 and 3.0 were achieved by varying the temperature from 81° to 373°K and the magnetic field from 0 to 11 kG. The quantitykHis the infinite‐medium phase constant andais the cylinder radius. Theoretical calculations were made extending earlier work to the values ofkHaand &ohgr;c&tgr; covered experimentally, where &ohgr;cis the cyclotron frequency and &tgr; is the collision time. The results differ from the earlier work, and in particular, it is found that them=×1 modes do not have the same polarization near the cylinder axis. Transverse magnetoresistance and Hall measurements were made to determinekHaand &ohgr;c&tgr;. The agreement between experiment and guided theory was found to be relatively good. Both of the guided helicon modes excited had higher phase velocities and much larger attenuation constants than the values calculated from infinite‐medium theory. These results indicate difficulty in achieving the conditions necessary for predicted two‐stream helicon instabilities.