Patent GB-647926-A (GB)
Title: Improvements in or relating to telemetering systems
Inventor: JONES FRANCIS EDGAR
IPC: G01S13/76
Filed: 1948-05-22
Abstract: 647,926. Electric indicating systems. MINISTER OF SUPPLY. May 22, 1948, No. 13908. [Class 40 (i)] [Also in Group XL (c)] In a radar telemetry system a mobile remote transponder is triggered by a train of interrogating RF pulses from a ground radar station, to emit a train of secondary pulses by which its position may be tracked from the ground station. Selected groups of secondary pulses are cylically characteristically modulated to mark the beginning and end of a time interval representative of the reading of a measuring instrument at the remote station and such modulated pulses are separated at the ground station to produce indications of the remote reading on recording apparatus, which is synchronized with the modulating apparatus by other selected groups of modulated pulses. The readings of a plurality of instruments may be sequentially transmitted. A radiosonde assembly is attached to a free balloon and comprises (Fig. 2) a radio receiver and aerial 5, 6, a transmitter and aerial 10, 11, and a modulator 8, constituting a transponder triggered by a known ground radar station which tracks the radiosonde to give wind velocity and direction data. A telemetering unit 9 comprises a barometer 27 (Fig. 3), a thermometer 28, and a hygrometer 29 which axially traverse the contact arms 24, 25, 26 along a drum 21 which carries a helical metal rib 22, engaging the moving contacts and the fixed contact 23. The drum is rotated by an electric or clockwork motor 20 driving the synchronizing contacts 15 which at 1/30 second intervals connect the condenser 17 in the modulator circuit to slightly widen a group of secondary pulses. At 15 second intervals the ribbed drum sequentially engages contacts 23, 24, 25, 26, momentarily closing contacts 16 to connect condenser 18, which considerably widens a further group of secondary pulses. The drum may alternatively mechanically operate detached pairs of contacts. At the ground station the signals are separated by known circuits into the ordinary train of narrow pulses which is tracked, a group of slightly wider pulses every 1/30 second which synchronizes a recorder drum with the telemetering drum, and four successive groups of considerably wider pulses every 15 seconds, which define three time intervals representing respectively the barometer, thermometer and hygrometer readings at the radiosonde. The time intervals are converted by known apparatus into deflections of styli recording the remote readings on the drum. The electrical elements of the radiosonde may be thermally insulated and communicate through ports with the external meterological instruments. In a modification, data is transmissible from the radiosonde by varying the timing between the receipt of a triggering pulse and the emission of a secondary pulse. A ranging pulse may be emitted immediately followed by a signal pulse after a variable time interval dependent on instrument readings. The Provisional Specification refers to a free-running radiosonde transmitter emitting data modulated pulse groups, which cannot be tracked by ground radar, to give wind velocity and direction.