Modulation, Frequency Spectra, and Receiving System Performance

Watt, A. D.

doi:10.1016/b978-0-08-012313-4.50010-4

Cited by 2 publications

(3 citation statements)

References 31 publications

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“…Antenna sag is considered in the modeling process, and the wire is pulled. The wire conductivity is not considered [1,2], as the actual projected data from the past suggest that the wire loss resistance is essentially negligible compared to the total resistance. The support and radiation structure of the umbrella antenna are made of PEC.…”

Section: Umbrella-type Antenna Vs Ground Grid Systemmentioning

confidence: 99%

“…Very-low-frequency (VLF) communications use long wavelengths and a frequency range of 3-30 kHz for transmissions. The transmitting antenna is usually electrically small, with a low radiation resistance and a large ground loss resistance, resulting in inefficient radiation [1,2]. A large-scale ground network system is laid out in order to reduce the ground loss resistance and improve the radiation efficiency of the VLF shorebased transmitting antenna.…”

Section: Introductionmentioning

confidence: 99%

“…The confluence ring is a safety mechanism which acts as a bridge, electrically reconnecting the functional parts of a grid when a part of it breaks or corrodes, so as to avoid a sharp loss of resistance. Arthur Watt (1973) first elaborated on the calculation method for the ground loss resistance in the ground grid system [1]. Liu Chao et al (2008) further expounded on the calculation of ground loss resistance for the umbrella-type antenna [2].…”

Section: Introductionmentioning

confidence: 99%

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Effects of Introducing Confluence Rings on Ground Loss Resistance of VLF Umbrella-Type Antenna

et al. 2022

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In this work, we analyze the influence of introducing confluence rings on the ground loss resistance in the ground grid system of the VLF umbrella-type transmitting antenna. The geometric deconstruction model of the confluence ring, the model of the VLF umbrella-type transmitting antenna, the models of the umbrella-type antenna ground grid system, and the formulae for the average conductivity are established. The working principle of the confluence ring was analyzed, and the ground loss resistance of the confluence ring structure with different numbers of layers and varying degrees of wire damage was simulated using Feko. The simulation results demonstrated the effect of increasing the number of confluence ring layers on the ground loss resistance of a fully functional grid to be relatively weak. However, when the ground grid wire is broken, the confluence ring structure can effectively reduce the ground loss resistance, thereby improving the radiation efficiency of the antenna.

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Section: Umbrella-type Antenna Vs Ground Grid Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of Introducing Confluence Rings on Ground Loss Resistance of VLF Umbrella-Type Antenna

et al. 2022

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Evaluation of Detection Efficiency of World Wide Lightning Location Network in Southeast Asian Region

Rafi,

Holzworth,

Mostafa

2024

JGR Atmospheres

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The detection efficiency (DE) of the World Wide Lightning Location Network (WWLLN) is evaluated in Southeast Asia by comparing WWLLN data with the Earth Network Total Lightning Network (ENTLN) data taking into account time, distance, and peak‐current parameters. The performance of WWLLN is evaluated in the months of November and December in two different years (2020–2021). These periods are selected to assess the change (if any) in DE overtime and the inclusion of new stations. The strokes between the two networks were considered matched if they fell within a time criterion of 100 µs and a location difference of 25 km. Using this criterion, 5.2 × 106 WWLLN strokes were matched with ENTLN cloud‐to‐ground (CG) lightning strokes in November‐December 2020, resulting in a DE of 32.9%. Similarly, 4.6 × 106 WWLLN strokes were found to match in November‐December 2021, yielding a DE of 36.5%. Analysis of the peak‐currents reveals that DE is lowest (<10%) for a peak‐current below ±10 kA. However, for peak‐current exceeding ±50 kA, the DE increases to ∼60%. During November‐December 2021, WWLLN reported 38.95 × 106 lightning strokes globally; amongst them, Dhaka station detected 0.5 × 106 strokes, contributing to a 1.3% increase in the global DE. Dhaka station detects most lightning strokes within 8 × 103 km, which diminishes to zero after 10 × 103 km. The Dhaka station recorded a larger number of strokes at longer detection distances during midnight (22:00–02:00) than during noon (10:00–14:00). The results signify a positive impact of the Dhaka station on WWLLN's DE during the mentioned period.

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Modulation, Frequency Spectra, and Receiving System Performance

Cited by 2 publications

References 31 publications

Effects of Introducing Confluence Rings on Ground Loss Resistance of VLF Umbrella-Type Antenna

Effects of Introducing Confluence Rings on Ground Loss Resistance of VLF Umbrella-Type Antenna

Evaluation of Detection Efficiency of World Wide Lightning Location Network in Southeast Asian Region

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