After my initial attempt at Covid 19 data I created another set of plots, which show the development per country. They are based on the data from ourworldindata.org, which include testing data from most countries.

There are plenty of plots out there to show the coronavirus pandemic already, but to really see the changes in exponential growth one needs logarithmic scale, relative to population size.

Ludzie gadają i marzą tyle

O przyszłych lepszych dniach.

Do szczęśliwego złotego celu

Wciąż biegną i nań polują

Świat się starzeje i rodzi na nowo

A człowiek ma nadzieję, że się poprawi

Digital sampling of analog signals can produce surprising effects. It is tricky to explain and understand the frequency aliasing, which happens when undersampling. What is the aliased frequency? Why are there positive and negative frequencies in FFT, but only one Nyquist frequency?

In electronics there is hardly anything simpler than a voltage divider circuit. Most people know that `Vo = R2 / (R1 + R2) * Vi`

, where `R2 / (R1 + R2) = f`

is the divider fraction. But it is not obvious how to choose the resistor values. You can start with one value, calculate the other one, get...