In this note the effect of heating by a powerful radio wave reflected from the F region of the ionosphere is considered. The calculations are made as simple as possible so that the variation of one quantity as a function of another is clear. The numerical values should not be taken too seriously, although they should be correct to within a factor of 2. If the heating is performed by a radio wave reflected by the ionosphere, the heat is injected into a thin slab near the reflection height (we ignore here D- and E-region nondeviative absorption). The thickness [Whitehead, 1956] is about (1) for the ordinary ray and (2) for the extraordinary ray. In these equations N is the electron density and h is the height. The same total amount of heat introduced by the ordinary wave will cause a larger increase in electron temperature, as it is more concentrated; therefore only heating using the ordinary wave is considered.