OZ9AEC

I have previously written about interference from FM stations on the HO-68 linear transponder. Now it appears the other satellites with linear transponders also suffer from local FM traffic by people who haven't got a clue that they are transmitting in the satellite uplink segment of the 2 meter band.

Wednesday, November 10, Pete MI3EPN reported that he heard what sounded like FM transmissions on the lower end of the HO-68 / XW-1 linear transponder and it didn't sound like ham radio operators making contact over a satellite. It was an interesting coincidence because I could remember that I have seen some FM-like signals while I was recording HO-68 on Tuesday evening but I thought it was some local interference.

Here is a recording of mounting the KU LNC 5659 C PRO downconverter on the 7 meter dish. It took about 20 minutes.

Today, there were two good passes of SO-67 over Europe with the amateur radio transponder activated.

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.