On Detection of Anomalous VHF Propagation over the Adriatic Sea Utilising a Software-Defined Automatic Identification System Receiver
This paper represents observations on detection of Very High Frequency (VHF) anomalous propagation over the area of the Adriatic Sea. During the research campaign, a Software Defined Radio (SDR) Automatic Identification System (AIS) receiver was employed for collection of AIS data packets at a fixed...
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MDPI AG
2023-06-01
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Series: | Journal of Marine Science and Engineering |
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Online Access: | https://www.mdpi.com/2077-1312/11/6/1170 |
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author | Sanjin Valčić David Brčić |
author_facet | Sanjin Valčić David Brčić |
author_sort | Sanjin Valčić |
collection | DOAJ |
description | This paper represents observations on detection of Very High Frequency (VHF) anomalous propagation over the area of the Adriatic Sea. During the research campaign, a Software Defined Radio (SDR) Automatic Identification System (AIS) receiver was employed for collection of AIS data packets at a fixed location in the Northern Adriatic. Data were collected during the 24-h period (25 February 2023 15:32 LT to 26 February 2023 15:32 LT), providing information from 115 AIS targets, or 159 965 AIS packets with 54.3% Packet Error Rate (PER), respectively. Subsequent analysis and post-processing of successfully demodulated signals and decoded packets was presented further. In certain instances, the SDR AIS receiver detected, received and decoded data packets from AIS targets distant several orders of magnitude larger than the VHF nominal ranges. To determine the magnitude of line-of-sight and over-the-horizon radio waves propagation, the great circle distances between the SDR AIS receiver antenna and AIS packets’ decoded positions were calculated, revealing hundreds of Nautical Miles (NM). Possible reasons for these occurrences, including tropospheric scattering, diffraction, ionospheric sporadic E layer and refraction were discussed and evaluated, in accordance, among others, with the previous research. By exclusion criteria and neglection of possible causes, it was concluded that the enhanced, over-the-horizon propagation of AIS signals occurred as a result of refraction effects, namely trapping/ducting, subrefraction and superrefraction. Data from nine World Meteorological Organization (WMO) radiosondes surrounding the greater reception area were collected for the same observation periods. Atmospheric profiles were created using Advanced Refractive Effects Prediction System (AREPS) program, and analysed for each individual station measurement. The results confirmed anomalous, over-the-horizon enhanced propagation and their probable origins, i.e., the occurrence of refractive conditions in the atmosphere over the Adriatic Sea area. These findings provide a solid foundation for further research in the area of propagation of VHF signals and their anomalous features caused by the atmospheric phenomenon effects. |
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language | English |
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publishDate | 2023-06-01 |
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series | Journal of Marine Science and Engineering |
spelling | doaj.art-34715b24d14a4354adbaa3baf5da58ff2023-11-18T11:06:50ZengMDPI AGJournal of Marine Science and Engineering2077-13122023-06-01116117010.3390/jmse11061170On Detection of Anomalous VHF Propagation over the Adriatic Sea Utilising a Software-Defined Automatic Identification System ReceiverSanjin Valčić0David Brčić1Faculty of Maritime Studies, University of Rijeka, 51000 Rijeka, CroatiaFaculty of Maritime Studies, University of Rijeka, 51000 Rijeka, CroatiaThis paper represents observations on detection of Very High Frequency (VHF) anomalous propagation over the area of the Adriatic Sea. During the research campaign, a Software Defined Radio (SDR) Automatic Identification System (AIS) receiver was employed for collection of AIS data packets at a fixed location in the Northern Adriatic. Data were collected during the 24-h period (25 February 2023 15:32 LT to 26 February 2023 15:32 LT), providing information from 115 AIS targets, or 159 965 AIS packets with 54.3% Packet Error Rate (PER), respectively. Subsequent analysis and post-processing of successfully demodulated signals and decoded packets was presented further. In certain instances, the SDR AIS receiver detected, received and decoded data packets from AIS targets distant several orders of magnitude larger than the VHF nominal ranges. To determine the magnitude of line-of-sight and over-the-horizon radio waves propagation, the great circle distances between the SDR AIS receiver antenna and AIS packets’ decoded positions were calculated, revealing hundreds of Nautical Miles (NM). Possible reasons for these occurrences, including tropospheric scattering, diffraction, ionospheric sporadic E layer and refraction were discussed and evaluated, in accordance, among others, with the previous research. By exclusion criteria and neglection of possible causes, it was concluded that the enhanced, over-the-horizon propagation of AIS signals occurred as a result of refraction effects, namely trapping/ducting, subrefraction and superrefraction. Data from nine World Meteorological Organization (WMO) radiosondes surrounding the greater reception area were collected for the same observation periods. Atmospheric profiles were created using Advanced Refractive Effects Prediction System (AREPS) program, and analysed for each individual station measurement. The results confirmed anomalous, over-the-horizon enhanced propagation and their probable origins, i.e., the occurrence of refractive conditions in the atmosphere over the Adriatic Sea area. These findings provide a solid foundation for further research in the area of propagation of VHF signals and their anomalous features caused by the atmospheric phenomenon effects.https://www.mdpi.com/2077-1312/11/6/1170very high frequencyautomatic identification systemsoftware defined radioanomalous propagationover-the-horizon propagation |
spellingShingle | Sanjin Valčić David Brčić On Detection of Anomalous VHF Propagation over the Adriatic Sea Utilising a Software-Defined Automatic Identification System Receiver Journal of Marine Science and Engineering very high frequency automatic identification system software defined radio anomalous propagation over-the-horizon propagation |
title | On Detection of Anomalous VHF Propagation over the Adriatic Sea Utilising a Software-Defined Automatic Identification System Receiver |
title_full | On Detection of Anomalous VHF Propagation over the Adriatic Sea Utilising a Software-Defined Automatic Identification System Receiver |
title_fullStr | On Detection of Anomalous VHF Propagation over the Adriatic Sea Utilising a Software-Defined Automatic Identification System Receiver |
title_full_unstemmed | On Detection of Anomalous VHF Propagation over the Adriatic Sea Utilising a Software-Defined Automatic Identification System Receiver |
title_short | On Detection of Anomalous VHF Propagation over the Adriatic Sea Utilising a Software-Defined Automatic Identification System Receiver |
title_sort | on detection of anomalous vhf propagation over the adriatic sea utilising a software defined automatic identification system receiver |
topic | very high frequency automatic identification system software defined radio anomalous propagation over-the-horizon propagation |
url | https://www.mdpi.com/2077-1312/11/6/1170 |
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