of ENGINEERING-HUNEDOARA, ROMANIA 227 1. DEVELOPMENT OF 20dB HELICAL ANTENNA OPERATING IN AXIAL MODE FOR EFFECTIVE COMMUNICATION

G Adedokun, J A Oladosu, I B Olusola
unpublished
Rapid advance in information giving out through communication network brought about information network system, which helps telecommunicating stations whereby any transmission from inaccessible area, can be relayed through antenna to any part of the world. Some stations operate effectively and have wide coverage area but some can hardly be received even within the state not talk about outside the state. One of the problems associated with television transmission is the attenuation of signal
more » ... distance and to reduce this effect a very sensitive and high gain antenna have to be installed with receiver to improve signal strength in fringe area where the signal is too weak to give clear reception. Hence, this brought about development of a 20dB Helical antenna to strengthen the transmitted signal at fringe locations without necessarily using electronic amplifier. INTRODUCTION Communication and information dissemination plays a vital role in human life. Speech and music are transmitted directly from their sources to listeners across short distances by means of acoustic wave. Similarly, a picture is transmitted directly by optical waves across short distances. However, to transmit signals for over long distances, wire and radio communication are used and it is a special circuit component called "antenna" which has made the radio communication possible in practice (Collin, 1985). An antenna is a metallic structure used to convert high frequency current to electromagnetic waves, and vice versa. This wave is the energy sustained in space by electricity and magnetism, which propagate according to light laws (Ballanis, 1982). If the antenna is not precisely the right length for the frequency used, the radio waves cannot be emitted or captured efficiently; hence it should neither be too long nor too short (Chatterjeer, 1989). However, one of the problems attributed to signal transmission is the attenuation of the signal with distance from the radiating source (William, 1987). To reduce this effect there is need to install an antenna of a very high gain and sensitivity with low cost of construction, accessible and obtainable by the common man to give a clear reception. PROBLEM DEFINITION Many broadcasting stations operate effectively and they have wide coverage area but it has been observed that T.V signal viewers living in remote areas do not receive faithful signal transmitted into the troposphere from transmitting stations because of the distance and physical conditions. It has been realized that there is need to improve the gain and reduce the noise level of the signal in order to annul the adverse consequence of fading while programme is being relayed to space. To achieve this, a very sensitive and powerful high gain antenna has to be installed with T.V receiver to improve reception at fringe locations. Many antennas, especially, Yagi antennas are common everywhere both in rural and urban area but these types of antennas are able to achieve their goal only with the aid of electronic amplifier (booster) coupled with them. Hence, there is a need to develop a cost-effective method of improving signal level which will not rely on electronic amplifier. One of the antennas that possess this characteristic is the Helical antenna. Consequently, this brought about design and construction of a 20dB Helical antenna to strengthen received signals. This antenna is applicable at higher frequencies, particularly as a U.H.F and V.H.F transmitting-receiving antenna (Kraus, 1998). RELEVANCE OF THE STUDY & OBJECTIVE The purpose and significance of this research work is twofold, namely; To effectively couple to space the output of a transmitter or the input of a receiver. To improve the electromagnetic wave level at a particular location. The main focus of the study is to reduce the noise level and improve the gain of the antenna in a fringe area to produce faithfully,
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