Yesterday, there was a big hailstorm in my town. During the storm, I rushed to the radio shack to see if this produced any effects in my Ku-band satellite receiver. This is a 95cm dish pointing to the 26ºE geostationary orbital position, and it will be used to receive Es’hail-2 in the future. In the image below, you can see that the difference is huge.
In the waterfall, you can see several beacons from broadcast satellites. It is clear that during the hailstorm the noise floor was much higher. In fact, 2.5dB higher. This is probably caused by scattering of DVB-S signals from satellites in other orbital positions, scattering of thermal ground noise, or a combination of both. Also, although it is not easy to see in the waterfall, the beacons of the satellites where weaker during the hailstorm. For instance, the beacon of BADR-5 was 0.9dB weaker, due to the increased attenuation caused by hail.
These differences may not seem large, but in fact they are. I have a cheap DVB-S2 decoder connected to the system. It usually receives fine several channels from the BADR satellites (on some other channels, the signal is not good enough, apparently). However, during the hailstorm, this receiver couldn’t even get a lock on the DVB signal.
Recently, Mike DK3WN pointed me to some decoder software for the satellite GOMX-3. This satellite is a 3U cubesat from GomSpace and transmits in the 70cm Amateur band. It has an ADS-B receiver on board, as well as an L-band SDR. As far as I know, no Amateur has decoded packets from this satellite previously, and Mike had some problems running the decoder software. I have taken a look at the software and tried my best to decode some packets from GOMX-3. So far, I have been able to do Reed-Solomon decoding and get CSP packets. However, I don’t have the precise details for the beacon format yet. Here, I describe all of my findings.
After sorting out some problems with several connectors which caused huge phase noise in the external 27MHz reference, I have my 10GHz receiver up and running as it should. This station will be used to receive Es’hail-2 in the future. The station is composed of a 95cm offset dish, an Avenger PLL321S-2 Ku-band LNBF modified to use an external 27MHz reference, an OCXO/Si5351A kit used as the 27MHz reference, an RTL-SDR, and a cheap DVB-S2 receiver as a power supply (this allows me to change polarizations and LO frequency easily).
The dish is pointing to the 26ºE or 25.5ºE orbital position, where Es’hail-2 will be. Actually, I have pointed the dish to peak the beacon from BADR-5 the best I can. To test the performance of the station, I have tried to receive the beacons from several Ku-band satellites. Here are the results.
Today I woke up early to receive the signals from AAUSAT-4 as it passed over Spain for the first time. This satellite was launched from Kourou yesterday at 21:02UTC into a Sun-synchronous orbit. The main payload for the launch was Sentinel-1B, a 5GHz Synthetic Aperture Radar satellite from the Copernicus project of the ESA. The remaining satellites that were launched by the Soyuz rocket were Microscope, from the French CNES, designed to test Einstein’s equivalence principle and the three cubesats in the Fly You Satellite! program: OUFTI-1, from the University of Liège, which carries a D-STAR amateur radio transponder, e-st@r-II, from the University of Torino, and AAUSAT-4, from the University of Aalborg, which carries an AIS receiver. Since the launch was into a polar orbit, the first pass of the Fly Your Satellite! cubesats over Spain was at 05:42UTC today.
I’ve recently installed my satellite dish and modified LNBF in my garden. This equipment will be used to receive Es’hail 2, the first geostationary satellite carrying an amateur radio transponder. Here I’ll look at the hardware I’m using, how I did the alignment to the 25.5ºE geostationary orbital position where Es’hail 2 will be located, and how to have some fun scanning the direct broadcast satellites in the Ku band with a FUNCube Dongle Pro+.
In a previous post, I recorded and decoded LilacSat-2 telemetry. This satellite transmits telemetry on 437.200MHz and 437.225MHz using two different radios and antennas, as can be seen in the radio info page. The transmission on 437.200MHz is usually 9k6 BPSK telemetry, but this is the same frequency, radio and antenna that is used for the amateur FM transponder when it is active. Looking at the waterfall as I recorded the IQ, I had the impression that the signal on 437.200MHz was much weaker than the signal on 437.225MHz. Using my LilacSat-2 receiver and the IQ recording I did, I have plotted the signal strength on both frequencies to compare.