[1] We experimentally observe the location and angular size of the high-frequency (HF) radio window in the bottomside ionosphere, which permits radio wave propagation to the topside ionosphere, with high angular resolution at the European Incoherent Scatter (EISCAT) facility. HF pump-induced ion line enhancements were observed by the EISCAT UHF incoherent scatter radar on the ionospheric bottomside and topside. The radar zenith angle was scanned in small steps in the magnetic meridian. The HF pump duty cycle was deliberately kept low enough to minimize the growth of artificial field-aligned irregularities. The locations of the bottomside radio window and topside enhanced radar echoes are consistent with the expected position determined by ray tracing performed using the observed plasma densities.