### Learning never stops

#### Eddie sez:

Radar was invented by the militaries of the world leading up to World War II as a method of detecting and determining direction and range to an enemy. The term RADAR was coined by the United States Navy: Radio Detection And Ranging. A scientist at M.I.T., working for the United States Air Force, came up with a way to use radar to detect weather. Interesting? Maybe not, but it is a good introduction to understanding how weather radar works.

Everything here is from the references shown below, with a few comments in an alternate color.

#### Last revision:

20131128

The purpose of the radar is:

• Find the distance to a target
• Find the direction to a target
• Determine the target's reflective characteristics (size, movement, and depth)

#### (1) Distance: Radar Signal Flow

Figure: Radar signal flow diagram, from Honeywell Radar Training Course, Part 1, Slide 12.

A radar signal travels at the speed of light: 186,280 statute miles per second. The radar tracks the time from transmission, reflection, and reception to determine the distance of the target.

#### (2) Direction: Radar Sweep Angle

Figure: Finding the target's direction, from Honeywell Radar Training Course, Part 1, Slide 15.

The radar continuously sweeps from side-to-side, and only receives reflections from targets in the beam width during that instantaneous moment, enabling it to determine direction relative to the aircraft.

#### (3) Reflective Characteristics: Signal Amplitude

Figure: Determining reflection characteristics, from Honeywell Radar Training Course, Part 1, Slide 16.

The radar measures the amplitude of the reflected signal to determine the size of the return, displaying increasing amplitudes in green, yellow, and red (or more variations, depending on radar.)

### How the Radarâ€™s Information is Presented to the Pilot

Figure: Providing radar information to the display, from Honeywell Radar Training Course, Part 1, Slide 17.

A "radial" of information isn't a "degree" of information, rather it is a series of colors for a snapshot in time for that particular direction. A wider beam width will paint all the weather in a particular distance to be the same. The narrower the beam width, the greater the fidelity of the information you are seeing.