Measurement and Evaluation of Electromagnetic VHF and UHF Television Signal Field Strength Distributions in Urban Environments

2014 ◽

Vol 716-717 ◽

pp. 1139-1143

Author(s):

Hui Chun Xie ◽

Jian Gong Zhang ◽

Zhuo Yi Zhou

Keyword(s):

Field Strength ◽

Transmission Line ◽

Test Method ◽

High Voltage Transmission Line ◽

Fine Weather ◽

Television Signal ◽

Before And After ◽

Ac Transmission ◽

Signal Field ◽

Peak Value

High-voltage transmission line corona and sparking will bring television interference (TVI). Study has been seldom executed about active TVI from HV transmission line, and much less research on UHV AC lines. Based on present literatures, this paper brings forward test method of TVI from HV transmission line. Near straight span and tension tower of Chinese UHV AC Pilot Demonstration Project, several tests about TV picture, TVI field strength, the television signal field strength before and after lines energized, has been carried out in good weather. According to observation, interference characteristics to TV picture has been analyzed. Results indicate that, with increasing distance from the outer phase, UHV single circuit TVI field strength in fine weather attenuates negative exponentially. This paper illustrates it is questionable to use CISPR quasi-peak value for assessment of interference on TV picture caused by UHV transmission line corona and sparking noise.

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Variation of Low-Frequency Time-Code Signal Field Strength during the Annular Solar Eclipse on 21 June 2020: Observation and Analysis

Sensors ◽

10.3390/s21041216 ◽

2021 ◽

Vol 21 (4) ◽

pp. 1216

Author(s):

Xin Wang ◽

Bo Li ◽

Fan Zhao ◽

Xinyu Luo ◽

Luxi Huang ◽

...

Keyword(s):

Field Strength ◽

Solar Eclipse ◽

Low Frequency ◽

Signal Propagation ◽

Normal Operation ◽

Time Code ◽

Long Distance ◽

Time Service ◽

Annular Solar Eclipse ◽

Signal Field

Due to the occlusion of the moon, an annular solar eclipse will have an effect on the ionosphere above the earth. The change of the ionosphere, for the low-frequency time-code signal that relies on it as a reflection medium for long-distance propagation, the signal field strength, and other parameters will also produce corresponding changes, which will affect the normal operation of the low-frequency time-code time service system. This paper selects the solar eclipse that occurred in China on 21 June 2020, and uses the existing measurement equipment to carry out experimental research on the low-frequency time-code signal. We measured and analyzed the signal field strength from 20 June 2020 to 23 June 2020, and combined solar activity data, ionospheric data, and geomagnetic data, and attempted to explore the reasons and rules of the change of signal parameters. The results showed that the field strength of the low-frequency time-code signal changed dramatically within a short time period, the max growth value can reach up to 17 dBμV/m and the variation trend yielded ‘three mutations’. This change in signal field strength is probably due to the occurrence of a solar eclipse that has an effect on the ionosphere. When the signal propagation conditions change, the signal strength will also change accordingly.

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