Use of Novel Distributed Instrumentation in Ionospheric Research

Abstract

In recent years, a new globally distributed data source has become available using software radio. These new, configurable devices have been adopted by many radio amateurs across the world and provide a rich source of radio propagation information that can be used in scientific research.

Long-distance HF radio communication links can show clustering around the terminator times from a phenomenon known as greyline propagation. The reason for this sunrise/sunset propagation poses a long-standing research question. Interest in greyline propagation has lasted for over a century but it has mainly been reported on in recent years by the amateur radio community. These reports have included records of long-distance communications between, for example, the UK and New Zealand, often being made in the UK early morning close to sunrise. Such reports provided a motivation to look to see whether the statistical evidence from the Weak Signal Propagation Reporter (WSPR) network supported these reports.

The WSPR network data contains a range of discrete radio frequencies. For this research 7 MHz was chosen because it propagates well during the lower periods of the sunspot cycle and is also a popular choice for WSPR equipment across the world. The year 2017 was chosen which was the most recent full year of data at the start of the research.

The results show that HF communication links at 7 MHz show clustering around the terminator times throughout most of the year for communication between Europe and Australia/New Zealand. They also show that between the regions of Europe and the USA there is a preference for night-time propagation when the absorption of the signals is lower. This is also shown for the links between the USA and Australia/New Zealand regions. A surprising additional result emerged from the study where directional asymmetry was found during the European summer sunset time for radio links between Europe and Australia/New Zealand.

Possible explanations for the results were explored using the simulation tool PHaRLAP (Provision of High-Frequency Raytracing Laboratory for Propagation) with the IRI2016 (International Referenced Ionosphere 2016) model. Some of the temporal propagation patterns were explained by night-time propagation paths, but the directional asymmetry during the European summer sunset time was not explained. Further investigation of the directional asymmetry can be supported in the future through enhancements to the observational capabilities of the WSPR network and other additional instrumentation. These enhancements include HF noise observations and angle-of-arrival and polarisation discrimination capabilities.

Amateur radio instrumentation can provide useful information about HF radio propagation. This research project should encourage further use of amateur radio observations for ionospheric radio research.

Date of Award	27 Apr 2022
Original language	English
Awarding Institution	University of Bath
Supervisor	Cathryn Mitchell (Supervisor) & Peter Wilson (Supervisor)