SDR appliance: JN1SDD’s NCDXF / IARU Beacon Monitor
On my ongoing search for SDR appliances, I discovered a couple of weeks ago an SDR (Softrock & Linux) based Beacon Monitoring System. The system is making use of the NCDXF Internation Beacon Project (IBP) which consists of 18 timely synchronized automated transmitters, located around the world. It monitors the signals on the various bands and generates in real-time a graphical chart showing the signal’s strength. The chart is uploaded to a webserver and accessible for everyone through the Internet. Lately I had the possibility to interview the author of the system, Atsushi (JN1SDD). In this interview he revealed with great deepness how the system is build up. I hope you will enjoy this interview as much as I did!
JN1SDD: My father was running a small electric factory when I was little, and there were so many electric parts and related books around me. I naturally got interested in that area. Especially in microcomputers.
Regarding amateur radio, I don’t remember very much, but one day I found related articles in some specialized magazines. Honestly speaking, amateur radio was a secondary interest for me. However, I also remember that I found a nice book, when I was an elementary school kid, which taught me that amateur radio was what an attractive hobby. I believe, I still might not have a license today if I haven’t got this book into my finger.
I needed to study hard for university entrance exam, so I had to postpone the amateur radio license exam. but finally after entering the university, I obtained a license. At that time it was a 4th class license. (Currently I have much higher grade license though)
DH1TW: For how many years are you holding now your Amateur radio license?
JN1SDD: From license point of view, I’ve been licensed now for 21 years. But mainly I was a “listener” instead of an operator. I like to receive any radio but not good at operation, honestly speaking.
Real-Time Propagation Chart, generated by JN1SDD’s Beacon Monitoring System
DH1TW: Knowing about Faros, what was your motivation to create a beacon monitoring system by your own? Why did you choose to develop your own application instead of using an already existing one?
Anyway, I decided to build the beacon monitor by myself. I had two goals:
DH1TW: When you started the development, did you had a clear idea from the first day on or did you elaborate the design over time?
JN1SDD: I did not have a clear idea at the beginning, I tried to “progressively elaborate” the system. For instance, my original plan was to to use C language to implement the heart of system. But later, I changed to Octave. After designed a prototype, I also noticed that Bayesian statistic could be used to detect the beacon signals, so I implemented that.
DH1TW: How long did the development of the overall system take?
JN1SDD: The total time was about 2 or 3 months. I worked for the project in lunch-breaks in the office and also in my free time the evenings.
DH1TW: Could you describe briefly the functionality of each software module (Signal Recorder, Signal Archiver, Parameters Extractor, Bayes Classifier, Chart Drawer) and why you have chosen the corresponding programming language?