| 摘要 |
813,612. Aerials. A.NTIFERENCE Ltd., and BEST, N. M. July 27, 1956 [July 28, 1955], No. 21893/55. Class 40 (7). An aerial system for the reception of signals of two differing frequencies comprises dipole means for the reception of both signals in fixed relationship with parasitic elements for the higher-frequency signal and a parasitic element for the lower frequency mounted so as to be adjustable directionally with respect to rest of the system. In one embodiment a main boom 14 carries a dipole arrangement 11 and higher-frequency parasitic elements 12 and 13. The arrangement 11 consists of a straight dipole 11 connected to a feeder in a central junction box and dimensioned for the lower frequency together with attached stubs for the higher frequency. The boom 14 is supported towards one end by a mast 15 and the short part 14a beyond the mast has a second boom 17 pivotally attached to it at its end 16. The boom 17 carries a parasitic element 18 for the lower frequency. In another embodiment (Fig. 3) the dipole arrangement 11 consists of separate dipoles 11a and 11b for the higher and lower frequency signals respectively coupled by straps 20 and having a common feeder connected to one of the dipoles. In this case the booms 14 and 17 are attached to the support mast 15 by separate clamps 16a and 16b which may be tightened to secure them in any desired angular relationship. In a modification of this embodiment (Fig. 5, not shown) the dipole arrangement 11 is of the type described in Specification 813,613. |
