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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Main Authors: Sanjin Valčić, David Brčić
Format: Article
Language:English
Published: MDPI AG 2023-06-01
Series:Journal of Marine Science and Engineering
Subjects:
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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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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