Proximity detector - primitive radar

Created: Apr. 2000. Edited: Mar. 2023

Fig. 1: Side view of reflectometer & horn aerial

Fig. 2: Perspective view of reflectometer & horn aerial

Fig. 3: Reflectometer with target reflector

Fig. 4: Inside of reflectometer assembly

Fig 5: diode detector

The first radar was inadvertently invented in 1922, when the US NAVY Research Lab, on the southern portion of Wash DC, was experimenting with a VHF aerial array pointing across the Potomac River and running at 60 MHz. While measuring the VHF array's return loss, they saw a periodic change. Eventually they figured out it was caused by ships in the river, moving across the array's beam. This "remote reflectometer" was way ahead of formal RADAR development, but the first reported use of radio waves to detect objects [1].

More details of the horn aerial can be found under this site's "Aerials" section. [3.5 GHz coffee-can horn ]

article_MotionDtr@3g5_00.pdf

References

[1] T. Williams, "Sheets of Italian microwave absorber foam", The Microwave Archive, 28 Mar 2014 .