High frequency spectrum: propagation, characterization, data communication and spectrum monitoring

Recent natural disasters such as the Asian tsunami in 2004 and Jogjakarta earthquake in 2005 have proven the usefulness of HF communications in relief operations. With the destruction of existing communication infrastructure, HF communications systems and infrastructure can be set be set-up and operational with minimum time and cost. Long range communications is possible by the refraction of radio waves in the ionosphere. Despite the presence of satellite and optical communications, HF communications is still important to the military, law enforcement, search and rescue, relief organizations, amateur radio, shipping and diplomatic services. Besides voice and telegraphy, data communication services available include short messaging, email and telemetry. This paper provides an overview on HF propagation, channel characterization, adaptive data communications and spectrum monitoring. Preliminary results will be presented with the direction of research that will be pursued. The research outcomes will provide a better understanding on characteristics of the HF communications channel, and solutions for effective data communications and spectrum monitoring

Development of radio direction finder using 6 log Periodic dipole array antennas

Radio Direction Finder (RDF) system can be used in search and rescue operations. However the existing RDF system is complex, expensive and not suitable for mobile operation such as search and rescue operations. This paper presents the development of a unique low cost Radio Direction Finder (RDF) using 6 Log Periodic Dipole Array (LPDA) antenna. Six unit of log periodic printed circuit board antenna from WA5VJB is used in this project since it is commonly used in UHF licence-free band. A modified amplitude comparison method has been made in order to match the antenna character. The unique physical design, electronics design and software design implemented in the RDF system are described in this paper. Also a test has been conducted and the system performance shows the RSM error of 14°

Public Awareness and Practices Towards Self-Medication with Antibiotics Among Malaysian Population: Questionnaire Development and Pilot Testing

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