| 摘要 |
863,656. Aerials; R.F. couplings. WOLSEY ELECTRONICS Ltd. July 31, 1959 [Aug. 5, 1958], No. 25027/58. Class 40(7) [Also in Group XL(b)] An aerial system which is resonant at two spaced frequencies consists of two conductive elements connected by parallel-connected inductance and capacitance. For example the folded dipole 1 may have its two elements centrally connected by inductor L in parallel with capacitor C. The aerial feeder is connected at the terminals 2, 3. The capacitor serves to by-pass the inductor to give resonance at a higher frequency whilst the inductor tunes the system to resonance at a relatively low frequency. At this low frequency the impedance of the capacitor will be high. In another arrangement straight elements in V formation interconnected centrally by the parallel inductance and capacitance units are used. In this embodiment the feeder is connected to the opposite ends of the parallel circuit. The folded dipole elements may also be arranged in V formation and may be mounted on a housing containing an amplifier and the inductor and capacitor (Fig. 3, not shown). In one form of amplifier the aerial signals are fed to the grid of valve 4 having two series connected inductors L2 and L1 in its anode lead. The junction of the two inductors is connected to earth through Cl and they are respectively inductively linked with windings 6 and 7 series connected in the output circuit. At the higher frequency Cl presents a relatively low impedance and the load impedance of the valve is L2 in parallel with the valve internal capacitance (C2). At the lower frequency L2 and C2 are not important and the load is formed by L1 and Cl. |
