| 摘要 |
890,786. Aerials. HARLOCK, F. H. March 12, 1958 [July 19, 1957], No. 7886/58. Class 40(7). A directional aerial assembly capable of operation at a number of frequencies comprises a primary element pair D, E, director elements A, B and also C, and reflector element F, G. The director C is made of such a length as to be substantially effective only at the highest operating frequency it is proposed to use and the elements A, B and F, G have centrally arranged circuits Tl and T2 rendering them effective at all the design operating frequencies. Fig. 2 shows the arrangement of such a circuit for three operating frequencies. The values of the circuit components L1, C1, L2, and C2, are so chosen that at the highest of the design frequencies the two halves of the elements are electrically isolated, at another they are electrically connected and at the lowest they are connected by the circuit acting as a loading means to increase the effective length of the elements. It is stated that adding further circuit elements makes it possible to increase the number of frequencies at which the aerial will operate. The feed to the element DE may be a 300 ohm balanced open line. The element does not resonate at any of the design frequencies and is only resonant using a portion of the feed line. Dimensions are given for an aerial effective at frequencies in the 10, 15, and 20 metre bands. |
