Wyniki wyszukiwania - Biblioteka Nauki

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Nonlinear Behavior of the Radio Frequency Interference (RFI) Sources at Faculty of Applied Sciences, MARA University of Technology

100%

Hamidi Z. S. , Shariff N. N. M.

International Letters of Chemistry, Physics and Astronomy

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2014

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tom Vol. 15

39--47

EN

In this article, we describe and compare several sources of the nonlinear of Radio Frequency Interference (RFI) based on classification methods. It is very important to characterize and understand the nature of interference in as much of the candidate spectrum as possible. Preliminary analysis has been done in 2011. As data sizes of observations grow with new and improved solar monitoring system, the need for completely automated, robust methods for RFI mitigation is highlighted. The current status of RFI noise level is being compared at two different sites (i) indoor and (ii) outdoor. The main objective is to evaluate and find the best range of low frequency in MHz for the solar monitoring purpose. Our findings are consistent with those of previous studies. There is not much different in terms of the sources of RFI. However, the level of RFI is become increase. Based on the results, it was found that the distribution of RFI sources in indoor site is in the range from -(80-105) dBm. A strong and moderate RFI can be identified in the range of -100 dBm. The dominant sources in this region are due to the fixed mobile signal with 10 points of this signal from 1-2000 MHz. If we compare with outdoor site, the distribution of RFI sources in indoor site is in the range from -(75-105) dBm. It means that the signal of noise is larger compared with indoor site. While new sources strive to remain the increasing of RFI signal levels, numerous factors interact to influence the pattern of this noise. Reporting to the authoritative body should be made to make sure the allocation of the solar monitoring frequency region was not used by other applications. This work is a current scenario of the nonlinear RFI level at our site.

2

Evaluation of Spectral Overview and Radio Frequency Interference (RFI) Sources at Four Different Sites in CALLISTO Network at the Narrow Band Solar Monitoring Region

100%

Hamidi Z. S. , Shariff N. N. M. , Monstein C.

International Letters of Chemistry, Physics and Astronomy

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2014

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tom Vol. 11, iss. 2

135-145

EN

Continuous observation of solar radio burst in CALLISTO network was started since 2002 with Blein Switzerland is the first site that launched the system. Since then, there are more than 35 sites around the world that monitor the Sun activity within 24 hours until 2014. However, there is an issue of Radio Frequency Interference (RFI) that need to be considered. This noise is a major obstacle when performing observation with CALLISTO system. We selected 4 sites as preliminary analysis to analyze in detailed at a specific frequency which is very important in solar burst monitoring. The selected sites are (i) Blein, Switzerland (ii) Mauritius (iii) KASI Korea and (iv) ANGKASA, Malaysia. The regime narrow band that we focused are from (i) 72 – 75 MHz (ii) band 145 – 153 MHz (iii) 240 – 250 MHz (iv) 320 – 330 MHz (v) 406 – 410 MHz. The results of the sources of the RFI also will be highlighted. This work is was part of a larger study which focuses on a specific region that can be used for detailed investigation of solar burst. This issue of Radio Frequency Interference (RFI) needs a dialogue and interactions between different actors and networks.It is hoped that the analysis will help the solar physicist to choose a better data.

3

Investigation of Radio Frequency Interference (RFI) Profile and Determination of Potential Astronomical Radio Sources

100%

Hamidi Z. S. , Shariff N. N. M.

International Letters of Chemistry, Physics and Astronomy

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2014

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tom Vol. 5

43--49

EN

In this article, we have recognized a Radio Frequency Interference (RFI) sources that can potentially affect for radio astronomical observation. The main objective of this surveying is to test and qualify the potential of radio astronomical sources that can be observed in Malaysia generally. Analysis process focuses on the high sources that contribute the pollution and the significant region that can be considered for astronomical purpose beginning 1-2000 MHz. It was found that 13 individual sources contribute as a noise and mostly are telecommunication and radio navigation applications. We then compared of the RFI profiles based on three different periods in order to observe the variety of the signals. The main regions that still excellent to do an observation are: 13.36 -13.41 MHz (solar), (25.55-25.67) MHz (Jupiter) and (37.50-38.25) MHz (Continuum) respectively. This work is also an initiative of the International Space Weather Initiative (ISWI) project where Malaysia is one of the countries that involve in e-CALLISTO (Compound Astronomical Low Cost Low Frequency Transportable Observatory) network project. Some suggestions are recommended in order to improve the quality of the radio frequency profile.

4

An Observation of an Inverted Type U Solar Burst Due to AR1429 Active Region

88%

Hamidi Z. S. , Shariff N. N. M. , Monstein C.

International Letters of Chemistry, Physics and Astronomy

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2014

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tom Vol. 10

81--90

EN

A detailed investigation of an inverted type U solar burst in meter region and their associated the solar flare and Coronal Mass Ejections (CMEs) has been reported. Solar type U burst has been observed at the National Space Centre, Banting, Selangor detected by the Compound Low Cost Low Frequency Transportable Observatories (CALLISTO) system in the 150 MHz till 400 MHz at the low frequency band. An inverted U type is occurring on 9th March 2012 between 4:00 UT to 4:15 UT within 1 minute (4:12 − 4:13) UT. From the dynamic spectra of CALLISTO, we have identified metric type U burst with maximum emission near the frequency 385MHz. In specific, the continuum type III burst will soon structure this burst due to our observations. Other types such as type II and IV are only appearing only after type U burst is ejected and appear at the same point of the solar flare event. Since the U burst activity coincides with the peak of the hard X-ray flare at 4:12UT in AR1429, we classified that the event is associated with the injection of the high energetic particles. In conclusion, it is confirmed that an inverted type U burst is initiated after a complex and a group solar radio burst type III.

5

Aktualna procedura badań układów izolacyjnych linii napowietrznych 400 kV

75%

Mikulski J. L.

Przegląd Elektrotechniczny

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2016

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tom R. 92, nr 10

138--141

PL

W artykule przedstawiono pełną procedurę postępowania w badaniach układów izolacyjnych konkretnej linii napowietrznej 400 kV wraz z analizą i oceną uzyskanych wyników tych badań.

EN

The article contains the full procedure to be followed when testing the insulation system of a particular 400 kV overhead line along with the analysis and evaluation of the obtained test results.