How was the first radar made into a screen that produced a dot?


I understand they managed to emit a sound wave that came back, but how in the world did they digitize that?

In: 4

First a radar doesn’t use sound waves, and their output was not digitized at the start either. **Rad**ar uses **rad**io waves to detect objects, not sound. To digitize something means to convert into a digital form such as for processing by computers, and radar didn’t do that originally.

Instead the first radar displays were basically oscilloscopes. A beam of electrons was shot at a screen with phosphorous which would glow when excited by the beam, and the beam could be deflected in various directions with the use of magnetic fields. The beam would be swept across the screen at a known, steady speed and the input signal would affect the vertical movement. What would result is a viewable graph of the oscillation of the signal across the screen. To produce only a dot for a specific return could be done by placing a limit on how strong a signal needed to be in order to register on the display.

Believe it or not, it wasn’t digitized. That dot on the screen is every bit as analog as an old television signal on a cathode ray tube. You’re essentially looking at an oscilloscope that traces out a line from the center to a point on the circumference of a circle in sync with the radar antenna’s rotation. There’s still a lot of electronics magic happening here, but it’s fundamentally an analog process.

Radar is not sound it is radiowaves, sonar is sound.

The displays were []( the same technology that was used in TV until the last 20 years.

It is a tube with a vacuum in it where electrons are accelerated to the front of the screen where there is a phosphorescent screen that glows where the electron beam hits it. The phosphorescent was just a single color usually green because phosphor was used. TV used a material that emitted white light for black and white TV and red, green, and blue for color TV.

The electron beam is controlled by a magnetic field or electrostatic deflection. In both cases, you can use electrical signals to control the deflection. The brightness of a pixel depends on the input current to the election cannon.

Radar and sonar work by you sending out a pulse of radio waves or sound and then listening to what is reflected back. Because both sound and light travel at finite speed the distance to an object depends on the time it takes for the reflection to return to you

So for a radar or sonar, you create a single that moves the electron beam out at a constant rate when a signal is sent. The direction it moves it depends on the direction of the radar dish. The signal you receive back then controls the intensity of the election cannon, after some amplification stage.

The earlier system did not use a circle. You have contact brightness and you let time be the X-axis. You control the Y.axis with the return signal strength. This is how an oscilloscope works, one in one direction and signal strength in the other. The first rada display was simply oscilloscopes. When radar was invented they were established technology, the first with a CRT display was made in 1897, the first radars are from the 1930s

Broadcast TV with CRT display was introduced in the 1930s.

Sonar existed in WWI with prototypes. I am not sure if displays or just earphones were used. There was usage with displays in WWII

The first operational radar screens didn’t produce a dot, but instead a graph showing the strength of return signals against distance. [Here’s an example display image]( where strong returns cause downward spikes. The operator had to manually vary the radar antenna configuration (there were multiple huge, fixed antennas) to make the spike of interest as large as possible and that would give the direction.

The display was essentially an oscilloscope where an electron beam could be steered across the phosphor coated vacuum tube, exactly like an old TV but much simpler. In this case the beam was repeatedly swept left to right at a fixed rate, synchronised with the outgoing radar pulses, so that the horizontal line matched the scale of miles needed. The strength of return radar signals was used to drive the beam downwards to form the spikes you can see. This was all analogue, vacuum-tube electronics developed in the 1930s, long before the invention of the transistor. If you wanted a record, you photographed the screen.