GQRX receiving the HO-68 satellite

The gqrx software receiver implemented with GNU Radio and Qt GUI is now taking shape and becoming useful. Yesterday evening I went to OZ7SAT and had the USRP+WBX connected to a real antenna tracking amateur radio satellites. The video below shows reception of the evening pass of HO-68, aka. XW-1.

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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. Continue reading “VO-52 satellite with GNU Radio, USRP and WBX”

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.

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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.

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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.

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5.8 GHz Helical Feed for the 90cm dish

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.

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SSTV Robot OZ9STV with USRP and WBX

I was fooling around with the USRP / WBX on the 2 meter band tonight when I suddenly stumbled upon some very strong SSTV transmission. It turned out to be the OZ9STV robot located only a few kilometers from me. That explained why I had more than 40 dB SNR even though I was only using a bad whip antenna indoors.

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UNITEC-1 5.8 GHz Receiver Test Using OZ7IGY

USRP with WBX and TVRX

Tuesday, April 13, 2010 we finally got a chance to test the 5.8 GHz receiver for the UNITEC-1 ground station on the air. The weather was nice and the weak wind allowed us to be on the roof and listen for the OZ7IGY beacon 40 km away.

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GNU Radio SSB/CW/AM/FM Receiver v0.6

New update of the simple receiver – version 0.6 – with the following changes:

  • Added frequency entry widget to change USRP frequency
  • Also created AM and narrow FM versions

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Improved AGC for the simple SSB receiver

Few days ago I wrote about how I upgraded the simple double side band receiver implemented in the GNU Radio Companion to a simple single side band receiver. This initial implementation used some default values for the AGC attack and decay rates. These values were acceptable; however, I wanted to spend some time trying to find better values that would correspond to Fast, Medium and Slow AGC – just as we are used to in commercial radios.

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