Stefan's Radio Blog

Off-Topic: Managed to get my German Hunting License

This month I achieved an important milestone in becoming a Swiss hunter: I passed the German Hunting Exam :-) This may sound a little bit weird: Why do you need to pass a German exam for becoming a Swiss hunter? Actually you don't - but earlier in this year I was told that as a native German you have to pass also a German hunting exam if you want to hunt in Germany. So I decided to do learn only once and try to become not only a Swiss hunter but also a German one.

In April I passed already the Swiss firearm safety and hooting test. Up to October I had to learn a lot  - either at home at my desk, in our hunting class or in the woods. So no time was left for HAM Radio. Hopefully I will now find some time again for my old radio Hobby - until some weeks before my last Swiss hunting exam in June next year.

APRS Windows Phone - Working on version

I finally found again some time to work on next version of the APRS Windows Phone app. Since I got a new notebook I had to prepare the development environment first. That took quite some time today. As a first step I implemented a bug fix for the reported speed and improved some input validations for the settings. Tomorrow I will test the reported speed and begin to work on APRS monitoring.

Frank's Sputnik Replica - The Transmitter

In the Januar edition of the RAZzies magazine Frank Waarsenburg PA3CNO continued to report about building a replica of the original Sputnik 1 transmitter. In his interesting article he writes about the difficulties and obstacles he faced: Missing data for winding the coils, errors in 2p19b datasheets and a critical bug in the schematics. He described his approaches to tackle these problems and I was happy to read that he found my blog providing some useful information for him.

I think for everyone who is interested in understanding the Sputnik 1 transmitter or who wants even to build a replica Frank's article is a must read. Please note that the RAZzies is a Dutch HAM magazine. If you don't understand Dutch simply use the Google translator or similar tools in order to get a translation.

The image above shows Frank's version of the Sputnik 1 transmitter and a switching power supply build on a Veroboard.

Hacker Attack

Yesterday this blog has been attacked by a hacker. He or she succeeded to post an article and to create a new administrator. Today I removed the user and the article again. Please leave me a message if you encounter any weird content.

The software in SDR - how does it work?

Last year I have spent some time trying to understand how the software in SDR works. After reading some books about digital signal processing and also articles about SDR published in the internet I found the project This project offers a really nice book giving a great introduction into SDR with a lot of experiments using Matlab and the RTL-SDR. If you want to understand the software part of SDR I would recommend to start with their book. You can download either the free PDF version from their website or buy the printed version.

Yesterday a small article in German about this topic has been published on