| 摘要 |
652,184. Aerials. BELLING & LEE, Ltd. July 2, 1948, No. 17881. Addition to 621,876. [Class 40 (vii)] An aerial system comprises a half-wave V- aerial structurally combined with and electrically connected in parallel with a further half-wave aerial, the resonant frequency of which is either one-half or twice that of the V-aerial. The aerial, which is a modification of the aerial described in the parent Speci. fication, includes a half-wave V-aerial comprised of the elements 13, 14 (Figs. 1 and 2), secured in an insulator 4 by means of screws 15, 16 through which electrical contact is made between the elements 13, 14 and a balanced transmission line 19 via conducting strips 7 and 8. A second insulator 5 arranged co-axially with insulator 4 and supported thereon by means of a screw 6 carries two elements 26, 27 between which and the elements 13, 14 electrical contact is made by means of screws 28, 29 the heads of which are in sliding contact with two arcuate conducting portions 9, 10 (Fig. 3), arranged on the top surface of insulator 4 and in electrical contact with screws 15 and 16 respectively. The elements 26, 27 may be of one-half or of twice the length of the elements 13, 14, and may have an upright V-shape instead of the shape shown. The complete system is supported by means of a tubular mast 20, the top end of which is split so that it can be tightened on to the insulator 4 by means of a clamping ring 21. When operating at the higher of the two frequencies at which the system resonates the effect of the elements associated with the lower frequency resonance is said to be equivalent to a resistance of about 4000 ohms shunted across the transmission whose characteristic impedance is 80 ohms. When operating at the lower resonant frequency the elements associated with the higher frequency resonance act as a capacitative reactance of about 300 shunted across the transmission line. |
