Patent GB-852694-A (GB)
Title: Improvements in or relating to radio position indicating systems
Inventor: JOLLIFFE SIDNEY ARTHUR WALTER
IPC: G01S13/46
Filed: 1958-01-20
Abstract: 852,694. Radio-navigation. MARCONI'S WIRELESS TELEGRAPH CO. Ltd. Oct. 14, 1958 [Jan. 20, 1958], No. 1850/58. Class 40(7). The position of a radio transmitter is determined by the point of intersection of a plurality of trace lines produced on a single cathode-ray display tube from bearing signals derived from a like plurality of spaced radio direction finders in known positions. One of the latter (of which four are employed) is shown in the drawing and comprises an Adcock aerial DFAI the associated goniometer G1 of which is driven by a motor M1 to impart a 25 c.p.s. modulation to the received signals, the motor also driving a 25 c.p.s. reference frequency generator R1 The output of the latter is supplied to a phase splitter P1 from which two outputs in phase quadrature are fed to a phase discriminator PD which also receives the output of the goniometer G1 The phase discriminator then produces, in known .manner, outputs consisting of D.C. voltages at the terminals N, S, E and W these voltages being respectively representative of the bearing components of the transmitter in the north, south, east and west directions. From such D.C. voltages sawtooth waves are produced by feeding the voltages through individual resistances to charge respective condensers NC, SC, EC and WC which are periodically discharged by shortcircuiting under the control of switches DS1- DS4 operated by a drive unit DU. The sawtooth waves so produced are then fed via the first contacts of switches S1, S2, S5 and S6 to the control grids of two pairs of valves, only one such pair WP and EP being shown, the anode circuits of which contain the deflection coils WD ED and SD, ND for the display tube CRT. Each valve of the pairs of valves is shunted by a second valve of which only two WT and ET are shown and to the control grids of these latter valves a D.C. potential is supplied via the first contacts of switches S3, S4 S7 and S8 such D.C. potentials being derived from potentiometers NL, SL, EL and WL and having a valve representative of the bearing components of the receiver DFAI with respect to a fixed reference position. In this manner the scanning beam of the tube CRT is deflected to the position 1 under the control of the D.C. potentials and deflected under the control of the sawtooth waves to produce a trace corresponding to the bearing of the transmitter. In a similar manner sawtooth waves the amplitudes of which are representative of the bearing of the transmitter and D.C. potentials representative of the bearing of the direction finder receiver with respect to the first reference position are produced at other spaced positions 2, 3 and 4, and fed to the second, third and fourth contacts of appropriate one of the switches S1-S8. These switches are then operated to cyclically connect the four contacts to the CRT deflection circuits the speed of switching being such in relation to the "after-glow" period of the screen of the CRT that four bearing traces are substantially continuously reproduced. The point at which these traces intersect is then the position of the transmitter.