Wave propagation and rf power absorption are considered in a large helicon plasma source excited by a flat antenna along the magnetic field. Various single-, four- and six-turn antennas of different dimensions are examined comparatively. The simple physical model and computation code accounting for the most important features of the system are introduced. Profiles of the rf magnetic field and absorbed power and the antenna loading resistance are computed over a broad range of parameters. Computation results are interpreted considering propagation characteristics of the waves, such as the group velocity and characteristic angle, and are compared with measured data. (c) 2005 Elsevier B.V. All rights reserved.