Heinrich Hertz had discovered that electromagnetic waves
bounced off metallic objects.
Christian Hülsmeyer used that idea
to invent the telemobiloscope.
A spark-gap transmitter and a rotating parabolic antenna
detected the presence and the direction of a ship in the fog.
Additional measurements and basic trigonometry
determined an object’s distance.
However, lacking tuning circuits, the telemobiloscope
was confused by wireless devices on other ships.
Radar
Add control for the signal frequency.
Add tuning for the receiver.
Add amplification.
Add slotted waveguide.
Add parabolic dish for broadcasting and receiving.
Add control of the signal polarization.
Add Doppler analysis to detect movement.
Add digital signal processing.
Add chain of coastal stations.
Add phased array radars.
Signals
I send out signals all the time,
see if any bounce back,
tell me what’s out there
and how far away,
whether it’s moving in my direction
or farther away,
whether to dodge or chase it.
I send signals out in all directions,
see if anyone responds.
I gradually improve the signal
and the signal processing.
Yes, this has been a metaphor
from the beginning.
I’m just trying to see
if you’re paying attention.
The telemobiloscope was a precursor to the first radar systems,
which required further technical advances
and were developed in secret by several nations
before and during the Second World War.
The telemobiloscope was a precursor to the first radar systems, which required further technical advances and were developed in secret by several nations before and during the Second World War.
See also in The book of science:
Readings on wikipedia: