Jerk

What is jerk? Jerk is to acceleration as acceleration is to velocity. And, acceleration is to velocity as velocity is to position. So let’s start there. The instantaneous velocity at which you travel tells you…

Submitted on 20 November 2017

Randomness Explains Flat Tire Anecdotes Perfectly Well

Figure 2. First five simulated periods of 30 years.

Flat tires are random events. However, it seems that the human mind expects random events to be more regular than they actually are. This intuition on randomness might lead to the feeling that your own experience is somehow unexpected or strange, with anecdotes such as “my uncle seems to never have any flats, but my sister had three in the last year alone”. This is related…

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Submitted on 22 January 2017

How to Create a Configurable Filter Using a Kaiser Window

Figure 3. Frequency response of a low-pass filter with a Kaiser window; A=60.

This article explains how to create a windowed-sinc filter with a Kaiser (or Kaiser-Bessel) window. The windowed-sinc filters in previous articles typically had two parameters, the cutoff frequency and the transition bandwidth (or rolloff). With a Kaiser window, there is a third input parameter, the ripple. For the specific case of the Kaiser window, the same…

Submitted on 26 December 2016

The Transition Bandwidth of a Filter Depends on the Window Type

Figure 1. Low-pass filter with Blackman window, r=4.0 (filter has 41 taps).

This article contains more detailed information on setting the transition bandwidth (or roll-off) from How to Create a Simple Low-Pass Filter. That article suggest to use, as the filter length N, an odd number close to 4/b, where b is the required transition bandwidth. This is a good basic rule. However, in…

Submitted on 6 December 2016

The Radio Meteor Signal Path from Transmitter to Spectrogram, Part 3

Figure 3. Spectrogram of sampled signal.

This is part three of an article that describes the signal path of a radio meteor. The next step is sampling. At the point of sampling, there is a difference between a real-world BRAMS system and the simulation that produced the illustrations in this series of articles. In the real system…

Submitted on 5 September 2016