Amateur radio, space, technology and other geeky stuff by Alexandru Csete
Articles and blogs about the GNU Radio, written by Alexandru Csete OZ9AEC.
Last weekend I wrote about my spontaneous experiments with receiving and decoding APT transmissions from NOAA polar orbiting weather satellites. This weekend I decided to extend the experiments by trying to receive at very low elevations and get images from far away.
Continue reading “More NOAA APT Images with GNU Radio, URSP and WBX”
Just a quick note about some exciting news I have heard. Thanks to Google Alerts I learned about this interesting press release from Gumstix, announcing the Stagecoach expansion board, which creates an OMAP computing cluster of Gumstix Overo COMs.
Continue reading “Embedded USRP and Gumstix Overo COM Clusters?”
This weekend I ended up receiving APT signals from NOAA polar orbiting weather satellites. I only wanted to explore IQ data recording and playback with GNU Radio but when I first used NOAA 15 as test signal and saw what I could receive I got slightly distracted from my original plan.
Continue reading “NOAA Weather Satellite Reception with GNU Radio and USRP”
Yesterday I described how to record the IQ data from the USRP focusing on generating unique file names every time the GNU Radio / GRC script is executed. Playing the recorded IQ data is really simple: We take the corresponding receiver application and replace the USRP source with a file source and a throttle block. Continue reading “Playback of the Recorded IQ Data”
I needed a quick USRP IQ data recorder today to record the APT downlink from NOAA satellites. This is really trivial to implement using the GNU Radio Companion, but I had to figure out how to use dynamic filenames to avoid overwriting previously recorded data. Of course, I could just rename each file when recording has finished but I am too lazy to do things like that. Using the current date and time in the file name seemed to be a good solution.
This quick how-to explains how to use the Python datetime module to generate a unique filename in GRC.
Continue reading “Dynamic File Names in GNU Radio Companion”
This weekend was dedicated to learning and experimenting with Gstreamer – an open source library and framework for constructing audio and video processing pipelines. Despite the weekend being spoiled by lots of bad luck (power outages, Internet down, etc.) I managed to beat the hell out of Murphy and get some work done!
My hidden agenda is of course finding a good audio/video library to accompany a software defined radio created using GNU Radio and the Universal Software Radio Peripheral (USRP), and to eventually be able to transmit real time high definition video over the air. While GNU Radio and the USRP can take care of everything related to software radio and RF, I am still looking for a good framework for flexible audio/video processing.
I’m sorry to report that despite coordinated efforts between Japanese and European teams we have not been able to receive any signal from UNITEC-1 over Europe. Japanese ground stations were able to receive both the orbit determination downlink and the major/minor data downlink during the first pass after launch; however, the signal has been lost during the first mission day sometime between LOS over Japan and AOS over Europe.
The launch of H-IIA F17 carrying AKATSUKI, IKAROS, UNITEC-1 and three cubesats was successful! So was the separation of UNITEC-1 which was confirmed at 22:48 UTC (Epoch time 22:46:20 UTC).
We meet tomorrow afternoon at OZ7SAT for the first communication window predicted to begin around 17:21 UTC. At that time UNITEC-1 will already be at lunar distance! Until then, good luck to the Japanese ground stations with acquiring the first signals.
Demonstration of a the persistence function of the FFT plot in GNU Radio. Persistence emulates the look of very old CRT monitors where the cursor leaves a trace of shadow. This is a new eye candy in the GNU Radio and will be available in version 3.3.0
Yesterday was day 2 where we were repairing the broken Azimuth rotator and making a small 90cm dish ready to track UNITEC-1 on 5.84 GHz. Actually, we already fixed the rotator on Monday but we ended up mounting it 180° off and we decided to fix it properly instead of just correcting it in software.
Fixing the orientation of the Azimuth rotoator was very quick – it took only 17 minutes to get up to the mast, lift the antenna construction, change the orientation of the rotator and fasten the nuts and bolts again. We had the practice from yesterday.
Next item on the agenda was to make a small helix with two turns to feed the 90cm dish so that we can use this smaller dish for tracking UNITEC-1 in the beginning of the interplanetary cruise. We found some online helical antenna calculator to generate the design but that was more than 1 GHz off and it took a lot of tweaking and tuning to get it close to 5.8 GHz. Here are the results, photos and videos.