Reversal of the diurnal phase variations of GBR (16 kilocycles per second) observed over a path of 720 kilometers

The diurnal phase and amplitude variations of the 16-kc/s radio signals from GBR, Rugby, have been observed in Frankfurt, Germany, for almost two years. It is found that there is a tendency for the diurnal phase variations to be reversed at sunrise and/or sunset. This tendency is especially strong during the equinoxes. It is suggested that the occurrence of a normal or reversed diurnal change depends on whether the skywave amplitude is greater or less than the groundwave amplitude.