Measurement of HF radio wave environment utilizing ionospheric routine observation

The HF radio wave environment is influenced by natural and artificial electromagnetic activities and the monitoring of HF radio wave environment is important for an efficient use of the HF radio wave telecommunication circuits. An equipment adaptive to the usual ionosonde which is routinely operated every 15 minutes has been developed so as to make it possible to measure the intensity of interfering radio waves separately from the sounding signals. By means of the equipment, successive variations in the interfering waves and radio noises, in other words, the HF radio wave environment at Kokubunji, Tokyo ionospheric station was observed. The descriptions of the adaptive equipment and the modified ionosonde are presented together with some interpretations of observational results.