The ionospheric propagation of radio waves of frequency 30¿65 kc/s over short distances

The paper describes experiments carried out at Cambridge on waves of frequency 30¿65 kc/s reflected from the ionosphere at steep incidence. The phases and amplitudes of two linearly polarized components of the downcoming wave were measured with reference to the ground wave. The results for frequencies of 30, 43 and 65 kc/s are considered in turn, and compared with the results for 16 kc/s. The main conclusions were as follows: (a) The day-to-day variations of the downcoming wave were greater at the higher frequencies. (b) The change of height of reflection in passing from day to night was about the same for all the frequencies. (c) In summer, the amplitudes by day and by night were very different, except at 16 kc/s. (d) The polarization at all the frequencies was approximately circular, left-handed and constant. The height of reflection of waves of frequency 30 kc/s was determined by using the frequency-change method of Appleton and Barnett.