A pair of geeky Advent calendars…

December 9, 2014 | Amateur Science, Computer Science | By: Mark VandeWettering

Advent is the season observed in many Christian traditions that is a time of expectant waiting and preparation for Christmas. When I was young, we’d have an Advent calendar, which counted down the days to Christmas, and would gift us with a little chocolate or candy each day.

While I am no longer religious, the idea is kind of cool: to take a little time out of each day and enjoy a tasty treat of some sort, and think of the upcoming holiday. A couple of cool examples have crossed my desk…

I like to experiment with embedded controllers, machine emulation and operating systems, so I am of course familiar with QEMU, but in case you are not: QEMU is a generic and open source machine emulator and virtualizer. It allows you simulate machines and run code written for one machine (say, an ARM board) on your PC using virtual hardware peripherals. It also serve as a “virtualizer”, which basically means that if you have an x86 Linux box, you can run a different x86 operating system on the same hardware, at very nearly native performance. In short, it’s pretty awesome.

If you like this kind of thing, you should check o ut The QEMU Advent Calendar 2014. It presents a new QEMU disk image each day until Christmas, enabling you to play with new operating systems, programming languages and graphical goodies. For instance, Day 6 is a tiny image that generates Julia sets.


Other days allow you to boot ancient versions of Slackware Linux, run an Atari ST emulator inside QEMU, and even play Zork. Awesome.

But even greater than that is the offering by Alan, VK2ZA7. Back in 2011, he did a series of 24 Youtube videos that each described a small electronic circuit that he tinkered together during the Christmas season. Many of them had to do with generating small bits of test equipment or illustrate some cool little circuits. Ones that I liked were his LED based transmitter/receiver:

and this nice little crystal radio, very traditional, with a cobweb style coil wound with Litz wire, but with a polyvaricon variable capacitor instead of the traditional 365pf variable cap.

What’s awesome is that after a hiatus of a couple years, Alan is back in 2014 with new projects. Very, very cool.

I particularly liked this one on building variable capacitors (a laser cutter would be helpful). I hadn’t seen this kind of geometry in one before, and Alan’s patter is very interesting.

A particularly useful little bit of tech for us radio tinkerers:

I’ll be checking back each day until Christmas. Thanks Alan!