GB601055A - Indicators suitable for use with radio-direction finders and the like - Google Patents

Abstract

601,055. Radio direction-finding. SMITH, S. B. Nov. 20, 1944, No. 23084. [Class 40 (vii)] [Also in Group XIX] In an indicator the scale is normally invisible, and after a cursor or marker has been adjusted to the position of the indication the scale is rendered visible so that the reading may be determined by comparison of the cursor or marker and the scale. This enables a succession of readings to be taken, for the purpose of determining a mean, without bias due to the presence of the scale. In the application of the invention to a radio direction-finder of the type employing a continuously rotated goniometer, the indicator comprises a cathode-ray tube CRO with a sliding cursor Cu in front of the screen Sc. A hood H excludes external light and the scale S on the tube screen is normally invisible. The cursor Cu is adjusted by the handle CH in its normally OUT position, to the indicating point D of the trace on the screen and the handle CH is then depressed to the IN position, closing contacts S1 and S2 and the circuit for lamps L which thus floodlight'the screen and scale so that the position of the cursor may be read from the scale as in Fig. 1c. Depression of handle CH disengages the cursor driving mechanism and contacts S1, S2 may also be arranged to extinguish or dim the trace on the cathode-ray tube screen. Handle CH. when released may also be arranged to displace the cursor so that the previous setting is completely removed. If the direction finding system is of the type in which the position of a pattern or line on a cathode-ray tube is compared with a circular scale, the light-excluding hood may be arranged for rotation axially with respect to the tube to control the cursor and may be depressed bodily to disengage the cursor and operate the switch contacts, Fig. 2 (not shown).