In commemoration of the 20th Anniversary of ARISS, the International Space Station is transmitting Slow Scan Television on 145.800. The SSTV event started on the 20th July and will continue until the 24th.
Two months ago I hooked up my VHF satellite receiver to the SatNOGS network. Since then, the receiver has been receiving many different satellites, including APT images from NOAA 15, 18 and 19.
Back in December 2016, Shaun Whitehead of ThumbNet sent me of their new rtlsdr-based N3 Nongles but I was too busy to do anything serious with SDR. Now that I got a 137 MHz turnstile antenna up for testing I had an obvious opportunity to try it with the weather satellites.
Some time ago I got a 137 MHz turnstile antenna from Jørn OZ6TA. We decided to build an automated NOAA weather satellite image receiver using a modern SDR device. He also had an Airspy he wasn’t using and so it became the SDR radio we were going to use for this.
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. Continue reading “Switching from the 90 cm to 7 meter dish”
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.