Interfering VLF Radio Signals observed on GBR-16.0 Kc/s Transmissions during November and December 1965

Abstract

IN May and June 1962, Rohan et al. observed unexplained sudden amplitude and phase changes on GBR signals at Salisbury, South Australia¹. Allan reported similar observations made simultaneously at Lower Hutt, New Zealand². He suspected interfering signals from a powerful transmitter in the vicinity of Australia and operating near 16.0 Kc/s^*. In April 1963, Allan recorded anomalies on the 18.0 Kc/s very low frequency transmissions emitted by NBA³ and in 1964 Isted proposed an explanation of these “peculiar phenomena” in terms of antipodal signal interference and changes in propagation conditions over one or both great circle routes⁴.