Rasmussen et al. (1980) described low-altitude reflections observed with a VLF/LF ionospheric sounder, apparently from a C layer, which could be interpreted as having come from ionospheric layers of constant conductivity. In the example given in their paper, they found a layer that extended from 63 to 69 km in height. This brief paper presents an improved method for calculating such layers which shows that, in fact, the best fitting layer for their example extends from 60 to 66 km. ¿ American Geophysical Union 1987