GB497035A - Improvements in or relating to protective systems for radio transmitters - Google Patents

Abstract

497,035. Protective cut-out arrangements. STANDARD TELEPHONES & CABLES, Ltd. (Piece, R.) June 11, 1937, No. 16277. [Class 38 (v)] [Also in Groups XL and XXXV] A radio transmitter has a safety air gap associated with the aerial for protection against lightning discharges, and a switch is provided which in response to an increase in radio-frequency current in the earth lead when the spark gap flashes over, causes the discontinuance of the radio frequency feed to the aerial, and removes the high-tension supply from the transmitter valves. The aerial feed coil T R and the series condenser C are shunted by a gap S G which discharges a lightning flash direct to the earth lead L. When this occurs, the aerial and the earth lead L may carry excessive radio-frequency current which tends to maintain the spark-gap SG conductive. A coil coupled to the earth lead L and forming the secondary coil of a radio-frequency current transformer CT, is connected as one diagonal of a rectifier bridge R, the other diagonal being connected to a relay A, which is rendered operative by the rectified radio-frequency current. A further relay B is thus operated to disconnect the feed from the aerial, and to operate a counter G. A further contact may control a no-volt coil BBC on all oil switch. The relays restore to normal position when the are across the gap SG is extinguished. The screen. S of the transformer TR may be connected to the earth lead L.