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, a super low noise preamplifier from Kuhne and GNU Radio software.
The MP-1 is a small, light-weight vertical antenna intended for portable use. The antenna consists of a base rod, a tuning coil and a telescopic whip. The coil is used for band change, while the telescopic whip can be used to fine tune the SWR on the desired frequency.
I took a long weekend from 28. Oct to 1. Nov. The plan was to drive from Paris to Denmark by car and take some of my stuff home as part of my moving back to DK. I left Les Mureaux on the 28. around 1000 local time and I actually arrived in JO45 after 14 hours. Not bad on a friday.
The ATX-1080 is a small multi band vertical antenna covering 80 – 6 meters, including the WARC bands. It is very similar to the MP-1, a major difference being that the coil is placed at the bottom. Also, the MP-1 has a continuous tuning on the coil while the ATX-1080 has fixed taps for the connections. I bought the antenna at the German Wimo who even supplies some extra documentation along with the original paper.