A systematic study of 7 MHz greyline propagation using amateur radio beacon signals

Sam Lo, Nikola Rankov, Cathryn Mitchell, Benjamin Axel Witvliet, Talini Pinto Jayawardena, Gary S. Bust, William Liles, Gwyn Griffiths

Research output: Contribution to journalArticlepeer-review

2 Citations (SciVal)


This paper investigates 7 MHz ionospheric radio wave propagation between pairs of distant countries that simultaneously lie on the terminator. This is known as greyline propagation. Observations of amateur radio beacon transmitters recorded in the Weak Signal Propagation Reporter (WSPR) database are used to investigate the times of day that beacon signals were observed during the year 2017. The WSPR beacon network consists of thousands of automated beacon transmitters and observers distributed over the globe. The WSPR database is a very useful resource for radio science as it offers the date and time at which a propagation path was available between two radio stations, as well as their precise locations. This paper provides the first systematic study of grey-line propagation between New Zealand/Eastern Australia and UK/Europe. The study shows that communications were predominantly made from the United Kingdom (UK) to New Zealand at around both sunset and sunrise times, whereas from New Zealand to the UK, communication links occurred mainly during UK sunrise hours. The lack of observations at the UK sunset time was particularly evident during the UK summer. The same pattern was found in the observations of propagation from Eastern Australia to UK, and from New Zealand and Eastern Australia to Italy and the surrounding regions in Europe. The observed asymmetry in reception pattern could possibly be due to the increase in electromagnetic noise across Europe in the summer afternoon/evening from thunderstorms.
Original languageEnglish
Article number1340
Issue number8
Early online date22 Aug 2022
Publication statusPublished - 31 Aug 2022

Bibliographical note

Funding Information:
The results from UK to New Zealand showed links in both the sunrise and sunset, whereas the New Zealand to UK direction showed a preference for sunrise. This finding is supported by the Eastern Australia to UK result, but only during the UK summer sunset period.

Funding Information:
This research was funded by research councils NERC and EPSRC grant numbers: NE/P006450/1 and EP/P007678/1.


  • HF communications
  • ionosphere
  • radio propagation

ASJC Scopus subject areas

  • Environmental Science (miscellaneous)
  • Atmospheric Science


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