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Title: 船舶用テレビアンテナの試作について
Other Titles: Studies no Experimentally Manufactured Television Antenna for Ships
Authors: 梅園, 茂
Authors (alternative): Umezono, Shigeru
Issue Date: Nov-1966
Publisher: 長崎大学水産学部
Citation: 長崎大学水産学部研究報告, v.21, pp.265-272; 1966
Abstract: In use of a stationary television set in a ship which changes the direction of its bow continually by the direction of wind or the effect of tide while anchored, or according to its movement in operation, it is a problem how to control the directivity of the antenna to the maximum direction of the coming wave which undergoes continual changes as the ship moves. The purpose can be attained by utilizing the meridianseeking moment of the gyrocompass or the magnetic compass, or by setting the detection current of the television set at a certain value so that theservo-motor may be operated by the alteration of the electric current according to the directional change, or by employing the diversity method. In practice, however, these methods require much expenses and in addition they are attended with much difficulty. Therefore, the three-element Yagi antenna with a common reflector, a cheaper and simpler apparatus, was manufactured for experiment and used in practice. Some results obtained in the experimental use are as follows: 1. As one set of the three-element Yagi antenna which was formerly used could not catch the direct wave and the echo at the same time because its directive angle was about 70°, the ship was often brought out of the visual angle owing to the change of the ship's direction, and a great trouble to control the directivity of the antenna was experienced every time. But this experimental antenna can cover all the directions and catch the coming wave at any time, and the picture can be controlled to obtain the best condition by only turning the antenna switch. 2. The experimental antenna can bring about a condition free from the disorder by the sea-surface echoes and the effect of the multiplied echoes by the antenna handling. 3. With very solid construction having decreased in number of elements by the use of a common reflector, and designing the length of the elements so as to resonate with the short wave channel it is durable for all the wind pressures in the sea. 4. In case of applying the experimental antenna to more than one television set, each set is to be fixed with an antenna switch. The reason is that each set needs to select its own condition of antenna because the incoming angle of the echo varies except when both sets receive the direct wave. 5. Although the standing wave ratio and the current transmission rate had low values in calculation because a coaxial feeder with low inpedance was used for the purpose of noise suppression and prevention of salt erosion, the quality of picture was not so bad in practice because the test was carried out in a strong field intensity. / 1. 従来使用していた3素子八木アンテナ1組では指向角度が約70度であったから,直接波と反射波を同時に捕捉出来ないため船体の方向によってはしばしば難視角内に入り,その都度アンテナの指向を修正せねばならない不便があったが,試作アンテナ使用後は全方向をカバーするので常に到来波があり,アンテナ切換器を操作するだけで画面を最良態に調整出来る. 2. 試作アンテナでは海面反射波による擾乱や多重反射波の影響をアンテナ切換器の操作により除去し得る. 3. 反射器を共用にして素子の数を減らし,短い波長のチャンネルに共振するように各素子の長さを設計したので構造も堅牢に出来て海上での風圧にも充分耐える事が出来る. 4. 試作アンテナを2台以上のテレビに使用する際は,各テレビにアンテナ切換器の取付けが必要である.理由としてはともに直接波を受像する場合を除いて反射波の到来角が異るので各個にアンテナの選択が必要となるからである. 5. 雑音防止と塩害を考慮してインピーダンスの低い同軸型き電線を使用したので,定在波比や電流透過率は計算上悪い結果となったが,強電界中で試験したため画面の品位は余り下がらなかった.
URI: http://hdl.handle.net/10069/31503
ISSN: 05471427
Type: Departmental Bulletin Paper
Text Version: publisher
Appears in Collections:第21号

Citable URI : http://hdl.handle.net/10069/31503

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