| 摘要 |
1,267,089. Aerials; radio direction-finders. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. 18 Aug., 1969 [17 Aug., 1968], No. 41118/69. Headings H4A and H4D. A direction-finder aerial is arranged so that it can be used both as a frame aerial and an Adcock aerial. As described, two pairs of parallel vertical dipoles 1-1, 2-2 and 3-3, 4-4, Fig. 1, are provided with respective horizontal interconnections 5 at their upper and lower ends and with switching devices 6, from which they are fed. The two devices 6 are interconnected, and frame aerial voltages are developed at upper terminals 7 and Adcock aerial voltages at lower terminals 8. In the Adcock aerial mode the two dipoles of each pair are effectively in parallel (Fig. 2a, not shown) and the two pairs provide an H-type aerial. In the frame aerial mode the upper and lower arms of the dipoles of each pair provide with their interconnections, two loops in parallel (Fig. 2b, not shown). The switching devices 6 each comprise a transformer 19, Fig. 3, the windings of which are cross-connected between pairs of terminals 11-13, 12-14 associated with the respective dipoles of a pair. The transformer windings present a very high impedance to the currents due to the aerial elements acting as dipoles, but pass the currents due to the aerial elements acting as loops. Hence, a voltage may be picked up at terminals 15, 16 which is substantially due only to frame aerial action. Pairs of capacitors 24-24 are connected between terminals 11, 12 and 13, 14 and, by using a frequency for Adcock aerial operation which is considerably higher than that used for frame aerial operation, they may be arranged to pass the Adcock aerial signals and to block the frame aerial signals. Suitable frequencies are 20-80 MHz (Adcock) and 5 MHz (frame). The voltages due to the Adcock aerial action may be picked up at terminals 20, 21 at the centres of respective windings 22, 23 of an additional transformer connected between each pair of capacitors 24-24. Two of the aerials shown in Fig. 1 may be arranged to form a combined crossed H-type Adcock aerial and crossed-loop aerial. |
