Tagged: limesdr

Receiving X-Band Images from the Arktika-M1 Arctic Monitoring Satellite

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.

 

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.

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)

A SDR Digital Voice Hotspot with GNU Radio, MMDVM and QRadioLink

Thank you to Adrian (YO8RZZ) for writing in and sharing with us his article explaining how to use an SDR to set up a digital voice hotspot for digital voice modes supported by MMDVM such as D-Star, DMR, System Fusion, P25 and NXDN. Adrian notes that this is possible with any full duplex SDR such as the LimeSDR or PlutoSDR, or with a combination of simplex devices, such as a HackRF for transmitting combined with an RTL-SDR for receiving.

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.

QRadioLink used as the UI for MMDVM-SDR and GNU Radio

LibreCellular: Easy 4G Cellular Network with LimeSDR and Intel NUC

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.

The reference hardware that they are recommending consists of an Intel NUC single board computer ($699), LimeSDR ($315), LimeRFE front end filtered power amplifier ($699), and Leo Bodnar Mini Precision GPS Reference Clock ($140). All together you can create a 4G basestation for around $1850.

LibreCellular Components for a 4G Basestation: LimeRFE, Leo Bodnar GPS Clock, LimeSDR, Intel NUC.

TechMinds: Extending the Range of Transmit Capable SDRs with Amplifier

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.

Extend SDR Transmit Range - LimeSDR - HackRF - Adalm Pluto Amplifier

RadioSlate: A Tablet with Built in LimeSDR or HackRF

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.

The project is due to be crowdfunded on CrowdSupply in the near future, and you can currently sign up to receive updates and be notified when the project launches. They write:

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.

The RadioSlate: An SDR-enabled Tablet
The RadioSlate: An SDR-enabled Tablet

PiSDR Ready to use SDR Raspbian Image Updated to V4.0

It's been a good time for ready to use SDR Linux OS images recently, as we've seen the release of two new images, DragonOS and gorizont-rtlsdr over this lock down period. And now the already popular and mature PiSDR image has also been updated. 

PiSDR is a ready to use Raspbian based operating system for Raspberry Pi's which comes pre-loaded with many programs for software defined radios. It currently supports the RTL-SDR, LimeSDR, PlutoSDR, Airspy, and Airspy HF+ and has preinstalled software such as SDR Angel, Soapy Remote, GQRX, GNURadio, LimeUtil, and LimeVNA.

The latest update includes various bug fixes as well the following new features:

  • Three times smaller.
  • HackRF Support.
  • Verified Compilation on GitHub Actions.
  • New Software: Quisk, CygnusRFI, rpitx, rtl_433, acarsdec, gpredict, multimon-ng, and leansdr
PiSDR Running a SDRAngel with a LimeSDR
PiSDR Running a SDRAngel with a LimeSDR

A Comprehensive Lab Comparison between Multiple Software Defined Radios

Librespace, who are the people behind the open hardware/source SatNOGS satellite ground station project have recently released a comprehensive paper (pdf) that compares multiple software defined radios available on the market in a realistic laboratory based signal environment. The testing was performed by Alexandru Csete (@csete) who is the programmer behind GQRX and Gpredict and Sheila Christiansen (@astro_sheila) who is a Space Systems Engineer at Alexandru's company AC Satcom. Their goal was to evaluate multiple SDRs for use in SatNOGS ground stations and other satellite receiving applications. 

The SDRs tested include the RTL-SDR Blog V3, Airspy Mini, SDRplay RSPduo, LimeSDR Mini, BladeRF 2.0 Micro, Ettus USRP B210 and the PlutoSDR. In their tests they measure the noise figure, dynamic range, RX/TX spectral purity, TX power output and transmitter modulation error ratio of each SDR in various satellite bands from VHF to C-band.

The paper is an excellent read, however the results are summarized below. In terms of noise figure, the SDRplay RSPduo with it's built in LNA performed the best, with all other SDRs apart from the LimeSDR being similar. The LimeSDR had the worst noise figure by a large margin.

In terms of dynamic range, the graphs below show the maximum input power of a blocking signal that the receivers can tolerate vs. different noise figures at 437 MHz. They write that this gives a good indication of which devices have the highest dynamic range at any given noise figure. The results show that when the blocking signal is at the smallest 5 kHz spacing the RSPduo has poorest dynamic range by a significant margin, but improves significantly at the 100 kHz and 1 MHz spacings. The other SDRs all varied in performance between the different blocking signal separation spacings.

Overall the PlutoSDR seems to perform quite well, with the LimeSDR performing rather poorly in most tests among other problems like the NF being sensitive to touching the enclosure, and the matching network suspected as being broken on both their test units. The owner of Airspy noted that performance may look poor in these tests as the testers used non-optimized Linux drivers, instead of the optimized Windows drivers and software, so there is no oversampling, HDR or IF Filtering enabled. The RSPduo performs very well in most tests, but very poorly in the 5 kHz spacing test.

The rest of the paper covers the TX parameters, and we highly recommend going through and comparing the individual result graphs from each SDR test if you want more information and results from tests at different frequencies. The code and recorded data can also be found on the projects Gitlab page at https://gitlab.com/librespacefoundation/sdrmakerspace/sdreval.

DragonOS: Debian Linux with Preinstalled Open Source SDR Software

Thank you to Aaron for submitting news about his latest project called "DragonOS" which he's been working on while in COVID-19 lock down. DragonOS is a Debian Linux based operating system which comes with many open source software defined radio programs pre-installed. It supports SDRs like the RTL-SDR, HackRF and LimeSDR.

Aaron's video below shows how to set up DragonOS in a VirtualBox, and he has two other videos on his channel showing how to set up ADS-B reception with Kismet, and how to run GR-RDS in GNURadio. He aims to continue with more tutorial videos that make use of the software installed on DragonOS in the near future.

DragonOS 10 Installer (download in description)

Screenshot of the GR-RDS Tutorial