Recently on Twitter @arvedviehweger (Arved) has tweeted that he has successfully received images from the Russian Arctic monitoring satellite known as ARKTIKA-M1, via it's X-band downlink at 7865 MHz. We've reached out to Arved and he's provided the following information on his setup and how he's receiving and decoding the images.
My first good picture from the ARKTIKA-M1 satellite on 7865 MHz!
It appears that the satellite downlink is a lot stronger now which allows me to finally get a clean decode. I really hope it will stay that way! pic.twitter.com/qy7HDA2uAP
The Arktika-M1 satellite is a Russian weather satellite which operates in a HEO orbit. It was launched in February 2021 and has downlinks on multiple bands. The main payload downlink for the imagery is on 7865 MHz (which is also known as the lower X-Band). The satellite only transmits imagery on the X-Band at the moment, it is currently unknown whether it will ever transmit any image data on L-Band.
For Amateur reception that means having access to X-Band RF gear. It usually consists of a low noise pre-amplifier and a downconverter to convert 7865 MHz down to a lower frequency for easier reception with a high bandwidth SDR such as the LimeSDR, a USRP etc.
In my personal setup I use a surplus pre-amplifier made by MITEQ (around 36dB of gain, 1dB NF), my own self-made DK5AV compact X-Band downconverter and a LimeSDR-USB.
My L-Band gear is now mounted on top of my X-Band gear which allows me to do both at the same time 🙂 I will probably try that on FY3B in the future. pic.twitter.com/SFdy04EwuT
The L-Band gear is mounted on top (helix and the pre-amp behind it) and the X-Band gear is right below. From left to right you can see the feed, the downconverter (silver box) and the LNA (mounted to a heatsink and a fan). Recording is done with a LimeSDR-USB running at a sample rate of 50 MSPS. The satellite transmits every 15 minutes once it reaches its apogee, each transmission including the idle period lasts for about 10 minutes. Some pictures of the idle transmission and the actual data transmission can be found in this Tweet, [noting that Idle = more spikes, actual data looks weaker]:
Depending on the geographical location a rather large satellite dish is also required for Arktika-M1. Reception reports all over Europe clearly show that the satellite has a beamed antenna (similar to ELEKTRO-L2).
In my setup I can get away with a 2.4m prime focus dish (made by Channel Master) in North Eastern Germany. It produces around 9 - 10 dB of SNR in the demod of @aang254’s excellent SatDump software. Anything above 5dB will usually result in a decode but since the satellite does not have any FEC you will need more than that for a clean picture. (Image of SNR in Satdump)
SDRAngel is a general purpose software defined radio program that is compatible with most SDRs including the RTL-SDR. We've posted about it several times before on the blog, however we did not realize how much progress has occurred with developing various built in plugins and decoders for it.
Thanks to Jon for writing in and sharing with us a demonstration video that the SDRAngel team have released on their YouTube channel. From the video we can see that SDRAngel now comes stock with a whole host of built in decoders and apps for various radio applications making it close to an all-in-one SDR platform. The built in applications include:
ADS-B Decoder: Decodes aircraft ADS-B data and plots aircraft positions on a map
NOAA APT Decoder: Decodes NOAA weather satellite images (in black and white only)
DVB-S: Decodes and plays Digital TV DVB-S and DVB-S2 video
AIS: Decodes marine AIS data and plots vessel positions on a map
VOR: Decodes VOR aircraft navigational beacons, and plots bearing lines on a map, allowing you to determine your receivers position.
DAB+: Decodes and plays DAB digital audio signals
Radio Astronomy Hydrogen Line: With an appropriate radio telescope connected to the SDR, integrates and displays the Hydrogen Line FFT with various settings, and a map of the galaxy showing where your dish is pointing. Can also control a dish rotator.
Radio Astronomy Solar Observations: Similar to the Hydrogen line app, allows you to make solar measurements.
Broadcast FM: Decoding and playback. Includes RDS decoding.
Noise Figure Measurements: Together with a noise source you can measure the noise figure of a SDR.
MMDVM is firmware that normally runs on an ARM microcontroller board such as the Arduino Due, and is designed to be interfaced with hardware radios via the microcontrollers built in ADC and DAC hardware.
In order to use an SDR instead of physical hardware radios, Adrian's article describes how a fork of MMDVM called MMDVM-SDR is used in his system as this allows the code to run on a normal Linux computer with an SDR. GNU Radio running on Adrian's own QRadioLink software is then used to create software ADC/DAC interfaces for the SDR and MMDVM-SDR to interface with, as well as providing a user interface.
The software is compatible with RTL-SDR, Airspy, BladeRF, HackRF and LimeSDR radios. It has features including demodulation, base band and pass band recording, playback, and spectrum and waterfall visualizations.
We recently came across the LibreCellular project which is aiming to make it easy to implement 4G cellular networks with open source software and low cost SDRs. The project appears to be in the early stages, and seems to be focusing on deploying and modifying existing open source 4G basestation software known as srsRAN which will be used with a particular combination of hardware in order to create a reliable and easy to set up 4G basestation solution.
Cheaper RTL-SDR and SDRs use a low quality crystal oscillator which usually has a large offset from the ideal frequency. Furthermore, that frequency offset will change as the dongle warms up or as the ambient temperature changes. The end result is that any signals received will not be at the correct frequency, and they will drift as the temperature changes. Higher end SDRs and improved RTL-SDRs like our RTL-SDR Blog V3 use a temperature compensated oscillator (TCXO) which has a very small frequency offset and very little temperature drift.
CalibrateSDR can be used with almost any SDR to determine the frequency offset. Andreas notes that CalibrateSDR uses the synchronization channel symbols from DAB+ digital audio stations to determine the offset. His post contains a great explanation of how this works. If you don't have DAB+ in your area, an alternative is Kalibrate-RTL which uses GSM cellphone signals to calibrate.
His results were as expected, showing that the generic RTL-SDRs have large frequency offsets, and his RTL-SDR Blog V3 and LimeSDR have much better precision.
Over on his YouTube channel TechMinds has uploaded a new video showing how to use RF amplifiers to extend the transmit range of transmit capable SDRs like the LimeSDR, HackRF and PlutoSDR. Whilst they are transmit capable, most low cost SDRs like those mentioned above can only transmit at very low power levels typically much less than 30 mW. In the video TechMinds tests a wideband SPF5189Z and filtered 2.4 - 2.5 GHZ CN0417 based amplifier, and shows the output power obtained using an inline power meter.
He also notes that these wideband amplifier will also amplify harmonics so filtering is recommended. At the same time we note that you should only transmit if you are licenced to do so (for example with a ham radio licence), especially if you are amplifying the output.
A new project called "RadioSlate" has recently been announced by Yian IT, a Chinese IoT company. RadioSlate will be an SDR-enabled tablet designed to be used with a HackRF or LimeSDR software defined radio that will be mounted internally behind the screen under some metal shielding. The tablet uses a 1024 x 600 touchscreen and runs an Intel M3 8100Y 1.1 to 3.4 GHz dual core CPU with 8GB of RAM, 64GB of storage and it supports both Linux and Windows. Batteries will not be included, but it supports batteries in the standard 18650 form factor which can be purchased anywhere.
RadioSlate is a sturdy aluminum tablet with an industry-favorite software-defined radio (SDR) board—your choice of HackRF or LimeSDR—tucked away behind its touchscreen. Whether you’re a Ham radio operator, a network engineer, a mobile base station designer, a security auditor, or some other variety of SDR enthusiast, RadioSlate lets you do your thing, even if that thing requires you to go outside and walk around, get unusually close to transmitters and receivers, keep one hand free for other tasks, or manage all of the above without drawing undue attention to yourself.
Explore the spectrum, while on the go, without having to drag along your laptop, an SDR board, and cables.