I went to OZ7SAT today to do some measurements on the receiver boards. I wanted to see how the sensitivities compare to that of the WBX receiver that I have measured earlier using a CW signal and SSB receiver. The criteria was again to find the weakest signal that I could both hear and see on the spectrum scope and that I would be able to decode if it was a Morse code transmission. The limiting parameter is actually the spectrum scope, because I can hear tones much weaker than what is visible on the 512 channel FFT scope.
Yesterday I have received the C-band down-converter that I have ordered last week for the UNITEC-1 receiver station. Watch video on YouTube. I have also uploaded a few high resolution photos to my Picasa Albums: If you can’t read the specs, you can see them on my work-in-progress wiki page about the C-band Receiver Station. … Read more
If everything goes according to current plans, JAXA will launch their PLANET-C spacecraft towards Venus on May 18, 2010. To fill out the empty space and available payload mass on the H-IIA rocket, they will also bring four university built cubesats into orbit. One of these cubesats, UNITEC-1, is very special in that it will … Read more
I had a few hours to spare tonight and I decided to do a quick check of the WBX receiver. Didn’t have time for much so I just compared it to the TVRX tuner using a strong FM broadcast station. The software was a simple WFM receiver constructed in the GNU Radio Companion graphical editor. … Read more
I made good progress with the portable S-band ground station this week.
I took the receiver to the OZ7SAT lab to measure its performance. Using the USRP+DBSRX and no LNA we could easily detect a -132 dBm CW signal with modest FFT integration (fraction of a second) in a GNU Radio spectrum scope. Using the LNA we could go down to about -138 dBm, i.e. an improvement in SNR of 6 dB. These figures were measured at an SNR ~5 dB. This is excellent, but please note that this is not real “sensitivity” in the traditional sense because we were not demodulating or decoding the signal. We were simply integrating the spectrum for a fraction of a second to detect the presence of the signal. The measurements were done by sampling a 250 kHz wide spectrum.
In this new video blog I am introducing a new project that has kept me occupied for a few weeks now: A low cost S-band ground station for receiving signals from NASA’s lunar spacecrafts LRO and LCROSS. More info at Receiving LRO and LCROSS. Based on the Universal Software Radio Peripheral (USRP) with DBSRX daughterboard, … Read more