Radar was first patented and demonstrated in 1904 by the German engineer Christian Hülsmeyer. As is well documented, his telemobilskop used a special spark-gap transmitter operating on a 40-50-cm wavelength and a separate receiver that rang a bell when detecting ships up to 5 km from the receiver. The first fully documented demonstration of the telemobilskop was in Cologne, in May 1904, with both the transmitter and receiver located on a platform under the Rhine Bridge (a chain suspension bridge destroyed during World War II) in a monostatic configuration to detect ships on the Rhine River. Purists might argue that Hülsmeyer's telemobilskop was not a radar because it did not directly measure range, as in 'radio detection and ranging,' and technically they would be correct. However, his invention included the essential elements of a radar, all reduced to practice: antennas, transmitter, receiver (with adequate shielding), and indicator, in this case an audio alarm to signal when a target was sufficiently close in range to require attention. More sophisticated indicators would have to await the development of timing circuits and displays.

Chapter Contents:

• 2.1 Beginnings
• 2.2 First Resurgence
• 2.3 Second Resurgence
• 2.4 Third Resurgence
• References

Inspec keywords: radar transmitters; patents

Other keywords: timing circuit; radar; audio alarm; patent; spark-gap transmitter; chain suspension bridge; wavelength 40 cm to 50 cm; telemobilskop; ship detection; Rhine Bridge

Subjects: Radar equipment, systems and applications