The paper studies integral characteristics and one-dimensional distribution of RF power absorption in a helicon plasma with external magnetic field directed at an angle to a plasma plane. Two kinds of working gas heli and hydrogen are considered. A simplified model of a helicon plasma plane layer is used here. Calculation results are used to explain power absorption in a compact helicon ion source with nonuniform external magnet field. An ion source is a part of a nuclear scanning microprobe (NSMP) injector at the Institute of Applied Physics NAS of Ukraine. Calculations for ion source parameters of the NSMP injector show a resonant behaviour of integral RF power absorption as a function of a magnet field inclination angle. A model (planar) geometry is verified here for solution of this problem.