How does RADAR work, and is it limited by the curvature of the earth?



How does RADAR work, and is it limited by the curvature of the earth?

In: Engineering

As I’m sure you know, (since you put the name in all caps) RADAR is an acronym for RAdio Detection And Ranging. The first clue of how it works is right there. A big antenna sends out a dome of radio waves. It’s a lot like the AM radios in a car but on a different frequency. When those radio waves come in contact with a solid object, they are absorbed and reflected.

The reflected radio waves will change in frequency slightly due to the Doppler effect. A separate dish near the transmitting antenna will pick up these reflected radio waves and use some computerized math to determine the direction (from the direction of reflection) and the range (by the change in frequency from the Doppler effect). Since radio waves travel super fast, it’s all essentially a live picture.

And yes radar can only stretch from horizon to horizon. Which is why they are place at high elevations and on antennas. To get the most coverage from a single antenna.

Edited note: in order to limit radio waves from interfering with each other, the “bubble” from the signal usually stops a few degrees above the horizon. The reflected radio waves would muddy the picture if they bounced off the ground. Which is why you can “fly under the radar”

Its basically echolocation, like with bats, but with radio waves. You have a big transmitter spit out a bunch of radio waves, you attach a receiver to it to catch the waves that bounce back. Attach a computer to compare the radio waves that bounce back vs the ones sent out to figure out things like, distance, size, speed, etc.

>Is it Limited by curvature of the earth?

Yes, Depending on how high up you place the radar disk there will be a blind spot caused by the curvature of the earth. Hence the term “flying under the radar”. Before other more practical options came about planes used to just fly real low to the ground in order to avoid radar for as long as possible.