Wednesday, January 30, 2013

Announcement: KDE 4.10 Release Party in Karlsruhe, Fr 8th February 2013

Important: The location of the event has changed! See below for details. I'm really sorry, I hope this change reaches everybody in time!
The KDE 4.10 release is near, and since Lydia Pintscher moved to Berlin :( there have not been any more release parties! This state is unacceptable and needs to be changed. Thus:

There will be a KDE 4.10 release party in Karlsruhe, Germany, on Friday, the 8th February 2013. Start of the event is 20:00 at "Der Vogelbräu" at Badisch' Brauhaus. Please add yourself to the wiki page if you already know you'll come!
Those events have proven to be a very nice opportunity to meet other KDE enthusiasts and developers from nearby in the past (also there's beer!) -- so if you live near Karlsruhe and you like KDE, there's no reason not to drop by!

Please observe the wiki page for eventual updates.

Saturday, January 19, 2013

RF microstrip breadboard

Have you ever seen such weird structures in a device you disassembled (or on images of such a device)? Well, I have, and I always wanted to know what they do and how they work. There's simulation tools, even free (as in beer) ones, but I usually do not trust simulation tools unless I have verified a few of their results in reality (not because I think the guys who wrote them are stupid, but because I might just be doing something totally wrong, thus generating totally impossible results). However I did not want to design and etch a load of huge boards just for checking out those filters... so I built...

The Microstrip Breadboard ™
The Microstrip Breadboard! In the following, I'll describe what it does and why it is totally awesome.

Saturday, January 12, 2013

Directional Coupler tests

A directional coupler is a device used in radio frequency (RF) circuits and measurement devices. Its effect is quite simple: you can picture an (ideal, 3-port, 20dB) directional coupler as a little grey box with three plugs labeled "IN", "OUT", and "COUPLED". If you feed a RF signal (imagine a 200MHz sine wave) into the IN port, then 99% of that signal will be available at OUT, and 1% be coupled to the COUPLED port. If you switch the OUT and IN ports, i.e. feed the RF signal into the OUT port, then 100% will be available at IN, and nothing will reach the COUPLED port. So, basically, on the COUPLED port, you get 1% of what flows from IN to OUT, ignoring signals going the other way round.

Insertion loss of three pieces of wire, indicating their resonant frequencies, measured with a spectrum analyzer and a directional coupler.
Keep in mind that, for electromagnetic waves, it's not at all a problem to have two waves in the same cable spreading in two different directions. And this is exactly where the coupler comes into play: If there's two signals in a cable spreading in opposite directions, it allows you to measure only one or the other (a 4-port coupler would allow to measure both seperately and simultaneously).

This sounds cool, so I bought one at ebay (24 Euros). So, let's see if it works and what can be done with it!