The slides from my presentation about GNU Radio and the Universal Software Radio Peripheral given at the AMSAT UK colloquium on August 1, 2010. A video recording is also available at http://www.batc.tv/ under archived videos.
gnuradio
Simple DVB with Gstreamer and GNU Radio
I have had this idea of using my webcam for digital video transmission for quite some time now. Capturing and processing video from UVC webcams has been a routine for a long time and I have had great success with Logitech webcams (the 9000 series) that have great UVC support. I still had a problem though with finding a good way to interface the GNU Radio transmitter and receiver to the video processing pipeline implemented in Gstreamer.
In my experiment with receiving packet radio from the ISS I used a named pipe to create a real time interface between the GNU Radio receiver and the packet decoder multimon. I decided to try this trick for sending video in to and out of GNU Radio and it works! The following experiments were implemented and executed on the 27th and 28th of July with some minimal preparation on the 26th.
VO-52 satellite with GNU Radio, USRP and WBX
On Saturday 10 July 2010, I have recorded this pass of VO-52. It is the linear transponder downlink between 145.875 and 145.925 MHz. I really don’t understand why people get so crowded in the middle of the passband when there is 50 kHz to play with.
Packet radio from the ISS with GNU Radio and USRP
On July 10, 2010, I was listening to the linear transponder downlink of VO-52 when I suddenly noticed a very strong peak about 50 kHz below. I checked Gpredict and found out that it was the APRS downlink from the International Space Station RS0ISS on 145.825 MHz. Thanks to the flexible GNU Radio framework and the USRP, I could easily receive both satellites at the same time as shown on the video below.
Patched AGC2 block and updated SSB/CW receiver
You may have noticed the weird construction I used in the SSB/CW receiver V0.7 implemented in the GNU Radio companion. It was using three AGC2 blocks with different decay rates, running in parallel and selecting one of them using a selector. The reason why I didn’t just use one block and set the decay rate of the block using an option menu or a slider was that this method didn’t work! Today I decided to dig deeper into the code and see how to fix this.
More NOAA APT Images with GNU Radio, URSP and WBX
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.
Embedded USRP and Gumstix Overo COM Clusters?
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.
NOAA Weather Satellite Reception with GNU Radio and USRP
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.
Playback of the Recorded IQ Data
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.