Decoding satellites from the PSLV 2018-004 launch

On Friday 12 at 03:59 UTC, a PSLV-CA launched from Satish Dawan Space Centre, India, to deliver Cartosat-2F, as well as some smaller satellites, into a Sun-synchronous polar orbit. Cartosat-2F is an Earth observation satellite for cartographic applications. The ride was shared by several Amateur satellites: FOX-1D, which is AMSAT-NA's third 1U FM cubesat, and the first one supporting the L/V mode (as well as the usual U/V mode); PicSat, a 3U cubesat from the Observatoire de Paris designed to observe the Beta Pictoris star system, which also carries a V/U FM transponder for Amateur use; CNUSail-1, a solar sail demonstrator 3U cubesat from Chungham National University, South Korea; CANYVAL-X 1 & 2, a system from Yonsei University, South Korea, consisting of a 1U and a 2U cubesat in formation flight which form a virtual telescope (with the light focusing unit in one cubesat and the detector in the other); KAUSAT-5, a 3U infrared Earth observation cubesat from Korea Aerospace University; and STEP Cube Lab, a 1U cubesat from Chosun University, Korea. There were also several non-Amateur small satellites in the launch.

On Saturday 13 morning, at 09:54:46 UTC, I did a recording of the 70cm Amateur satellite band to try to receive and decode all these satellites. I used a 7 element handheld yagi from Arrow and a LimeSDR directly connected to the antenna with a short coaxial cable. My location was approximately 40.5961º N, 3.6963º W, 700m ASL (locator IN80do). The recording is IQ at 4Msps, centred at 436.5MHz, and lasts 8 minutes and 4 seconds. Here I detail my analysis of the recording.

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Saving and plotting bandscope data with the Hermes-Lite 2

The Hermes-Lite 2 and other SDR transceivers based on the openHPSDR protocol support sending bandscope data from the SDR to the PC. The bandscope data consists in fixed-length chunks of samples taken directly from the ADC. Since the ADC in a DDC receiver runs at a high sampling rate, by taking the Fourier transform of these chunks, the bandscope data can be used to display a spectrum or waterfall of a huge frequency range, covering all the HF bands. In the case of the Hermes-Lite 2, the ADC samples at 76.8MHz, so the bandscope data gives us a spectrum from 0 to 38.4MHz.

Note that the the chunks of the bandscope data are not contiguous. Streaming samples at 76.8MHz from the ADC into the PC continuously would be a lot of data. Thus, a chunk is taken and stored in the FPGA and then sent to the PC slowly. Therefore, bandscope data is only intended for wideband spectral analysis and probably has very little use outside of that.

By recording and processing the bandscope data, one can produce plots similar to the full day waterfall from the University of Twente WebSDR. Here I describe my first tests using Python.

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Interfacing the Hardrock-50 HF amplifier to the Hermes-Lite 2

Since several months ago, I'm operating my HF station "remotely" from another room in the house. The station consists of a Hermes-Lite 2.0 beta2, a Hardrock-50 HF amplifier, and an outdoor MFJ-993BRT antenna tuner. My plan is to operate all of this from a laptop with ethernet connection from anywhere in the house.

The Hermes-Lite poses no problem, since it is always controlled by ethernet only. However, I need to be able to operate the Hardrock amplifier remotely: I need to change the bands, which is usually done via buttons on its front panel, and to check the output power and SWR, if only to be sure that the antenna tuner has found a tuning solution. This is usually done by looking at the Hardrock front panel display or by looking at a Diamond SX20C power/SWR meter that I also have installed in the shack.

I have taken advantage of the holidays to finish making all of this controllable by ethernet. Here I describe my solution.

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