Whistler waves launched from an antenna damp away for small incident power. With increasing power, undamped nondiverging waves (the ducted waves) are observed, together with a field‐aligned density trough and electron heating. However, the density trough is found not only in the wave propagation regime (&ohgr;/&ohgr;c<1), but also in the wave evanescence regime (&ohgr;/&ohgr;c≳1). This implies that the density depression is mainly created by the effect of the antenna near‐zone field rather than by the wave radiation pressure. The intense localized field near the antenna gives rise to electron heating which leads to the density trough. The ducting of antenna‐launched whistler waves has been explained as a filamentation instability in terms of nonlinear wave‐plasma interactions.