GB491220A - Improvements in or relating to antenna systems for radio receiving systems - Google Patents

Abstract

491,220. Wireless receiving systems. AMY, E. V., and ACEVES, J. G. Feb. 26,1937, No. 5857. [Class 40 (v)] An antenna comprising a doublet is capable of acting as a dipole for short wave reception and as a T-aerial for long wave reception. Interference may further be neutralized by the combination of the two systems. The Figure shows the two halves 1, 2 of a doublet, which may not be equal, and are connected to a twisted symmetrical lead-in 5, 6, connected to the closely coupled coils 7, 8, forming the primary of a transformer. The secondary winding 9 is connected at one end to point 0 and to the earth terminal 15 of the receiver bv way of inductance, resistance and capacity 11, 12, 13. The other end of 9 is connected to the aerial terminal 14 and by way of condenser 10 to coil 8. Due to the dipole action or the use of asymmetrical branches circulating currents are produced in 7 and 8 and induce voltages in 9 which are supplied to the set. Due to the action of the aerial and leads as a T antenna, currents flow in the same direction in 7, 8 and produce no voltage in 9 ; if resistance 12 is not zero however, a voltage will be supplied to the receiver. Local interference may be neutralized by suitable adjustment of the inductance, resistance, condenser combinations 11, 12, 13, interference voltages picked up on the down lead concelling those picked up by the doublet, with only a small reduction in signal strength. Figs. 2, 3, 4 (not shown) illustrate modications in which the interference neutralization is controlled by varying the effective length of the leads by means of tappings. The series impedance in the connection to the earth terminal of the receiver mav under suitable conditions comprise only pure resistance, capacity or inductance. Specification 424,239 is referred to.