Patent GB-614409-A (GB)
Title: Radio direction finder systems
IPC: G01S1/02
Filed: 1945-10-25
Abstract: 614,409. Radio direction-finding. STANDARD TELEPHONES & CABLES, Ltd. Oct. 25, 1945, No. 28251. Convention date, April 6, 1942. [Class 40 (vii)] In a radio direction-finder, the indication shown on the screen of a cathoderay tube near the aerial system is repeated on a further cathode-ray tube at a distant station. The directivity of the aerial system is rotated continuously and a synchronizing signal is produced and is transmitted by a transmission line to the distant station to cause the beam of the cathode-ray tube to rotate synchronously with that at the local station. The received signals are amplified and detected and are transmitted over the same or a further transmission line to the distant station, where they are applied to the cathode-ray tube to give an indication similar to that at the local station. The search coil 15 of a radiogoniometer of an Adcock aerial system is rotated continuously by the motor 19 which also rotates the deflection coils of cathode-ray tube 18. The search coil output is applied to a receiver and full wave rectifier 16 and thence to one pair of deflection coils of the tube 18. A pattern is produced on the tube indicating the direction from which a signal is received. To obtain sense the central aerial 21 is switched in parallel with the search coil by means of switch 22. Switch 23 also operates to change the deflection coils that are used, so that the new pattern will still indicate the true, and not a perpendicular, direction. Signals are transmitted to the remote apparatus by transmission lines 27 and 28, the output of receiver 16 being sent by line 27 and a synchronizing signal from the alternating current source 20, which drives the motor 19, being sent by line 28. A 90 degrees delay network 24 is introduced by switch 23<1> when sense determinations are being made in order to ensure the correct phase relationships at the distant station. At the far end of each line are placed an amplifier and a phase control circuit. The output from line 28 is used to drive motor 34 which drives a distributer arrangement 36, such as that described in Specification 596,691, which applies the signals from line 27 in such a manner to cathode-ray tube 35 that the figure obtained on the screen is the same as that on the screen of tube 18. Alternatively, the presentation unit may be similar to that at the local end of the apparatus or it may be of the type described in Specification 581,808. In another embodiment of the invention, Fig. 2 (not shown), both sets of signals are transmitted over the same transmission line, the synchronizing signals being modulated upon a 5000 c/s. carrier and the two signals being separated by filters at the remote station. In the embodiment of Fig. 3 (not shown), the frequency spectrum of the received output signals is inverted so that the more important low-frequency components may be transmitted more easily. In a further embodiment, Fig. 4 (not shown), telephony signals are transmitted together with synchronizing signals modulated on to a 5000 c/s. carrier over one transmission line and the receiver output signals are transmitted over another.