Category: PlutoSDR

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.

SATSAGEN: Software to use a PlutoSDR as a Tracking Spectrum Analyzer

Thank you to Frank, HB9FXQ for submitting news about a new Windows program called SATSAGEN which allows you to use a PlutoSDR as a wideband spectrum analyzer. SATSAGEN was created by Alberto IU1KVL and is entirely free to use. This makes it possible to get wideband scans of RF components like filters and attenuators. Together with a directional coupler it could also be used to measure the SWR of antennas as HB9FXQ demonstrates in his Twitter post.

The PlutoSDR is a low cost RX/TX capable SDR with up to 56 MHz of bandwidth and 70 MHz to 6 GHz frequency range. It is typically priced anywhere between US$99 - US$149 depending on sales.

In the video below Alberto demonstrates SATSAGEN performing some wideband scans, and he shows the various features of the software. He writes that the system has a scan range from 70 MHz to 6 GHz and can show results in dBm. The spectrum analyzer works with the TX part of the PlutoSDR to provide a tracking generator with resolution of up to 1024 points. The software can also use the PlutoSDR as a frequency generator with 1 kHz of resolution.

There is also a support group available at groups.io/g/satsagen.

SATSAGEN Screenshot
SATSAGEN Screenshot

SATSAGEN BASICS

PiSDR Updated to Version 3.0: Now Supports the Airspy HF+

PiSDR is a Raspberry Pi distribution that is pre-loaded with multiple programs for various software defined radios. It currently supports RTL-SDR, LimeSDR, PlutoSDR, Airspy, and as of the most recent update the Airspy HF+. The currently pre-installed software packages include SDR Angel, Soapy Remote, GQRX, GNURadio, LimeUtil, and LimeVNA.

Recently version 3.0 was released, and this new version adds a few new features like Desktop shortcuts, Raspberry Pi 4 support, Airspy HF+ support and documentation.

The latest image can be downloaded from the PiSDR website at https://pisdr.luigifreitas.me. It can be burned to an SD card in the same way that you would with a standard Raspbian installation. This is a great image to start from if you're experimenting with RTL-SDRs on a Raspberry Pi, as it means that you don't need to go through all the steps of installing the drivers and software like GQRX and GNU Radio which can take a long time to install.

PiSDR Running a SDRAngel with a LimeSDR
PiSDR Running a SDRAngel with a LimeSDR

Using a PlutoSDR to compare FreeDV Digital Voice with other Modes

Over on YouTube user Adrian M has uploaded a video where he compares the HF amateur radio digital voice mode known as FreeDV against other common voice modes such as USB, AM, FM and QPSK. To perform the test he uses a PlutoSDR, a GNU Radio program and a GUI called qradiolink.

FreeDV is an open source amateur radio digital voice mode that uses Codec2 compression. It's designed to compress human voice and works with narrow bandwidths and with weak signal power.

In the demonstration Adrian reduces the TX power slowly for each mode, so you can see what the voice sounds like at high and low signal power. The FreeDV mode is not high fidelity in terms of audio quality, but the voice remains able to be copied at low power when the other modes could not.

Transmit and receive FreeDV 1600 and 700C with SDR hardware

Talks from GNU Radio Days 2019

GNU Radio Days 2019 was a workshop held back in June. Within the last week recordings of the talks have been uploaded to YouTube by the Software Defined Radio Academy channel. The talks cover a wide range of cutting edge SDR research topics and projects. Many of the presenters have also made use of RTL-SDR dongles, as well as other higher end SDRs in their research.

All the talks are combined into two 3 hour long videos from the morning and day sessions from day one. Day two also has two videos that consist of recordings from the tutorial sessions which make use of the PlutoSDR. Finally there is also the keynote speech from Marcus Müller where he dives into the internal workings of GNU Radio.

Below we list the talks with timestamps for the YouTube video. Short text abstracts for each of the talks can also be found in the conference book. We note that not all the abstracts appear to have been presented in the videos, so it may be worth checking out the book for missed talks about passive radar, a 60 GHz link, embedded GNU Radio on a PlutoSDR, an SDR 802.11 infrared transmission system, PHY-MAC layer prototyping in dense IoT networks and hacking the DSMx Drone RC protocol.

Continue reading

Using SDR For QO-100 Satellite Operation

Es’hailsat, otherwise known as QO-100 is the first geostationary satellite with an amateur radio payload on-board. The satellite contains both a Wide Band transponder for experimental modes and DVB-S Digital Television and a Narrow Band transponder used mostly for SSB voice and some digital mode contacts with other amateur operators. If you’re unfamiliar with this satellite we’ve covered it in previous articles, like in [Es’hail Transponder Now Active]

While many choose to use a transverter connected to a traditional amateur transceiver, others have turned to use Software Defined Radios to complete their satellite ground stations.

[Radio Innovation] posted a video back in March showing his contact on QO-100 using a LimeSDR Mini as the 2.4 GHz transmitter and a 10 GHz LNB for the downlink.

Calling cq on QO-100 with LIMESDR

The PlutoSDR has been frequently seen used for QO-100 satellite operation on the Wide Band transponder due to its ease of DVB-S transmission utilizing software such as [DATV Express] but more recently there have been more and more operators turning to SDR for their day to day satellite operation.

It will be interesting to see how these stations evolve, perhaps by the time North America has access to a similar satellite, we’ll be prepared to operate it.

PiSDR Image Gains PlutoSDR Support

[@Lugigi Cruz] has announced on twitter that his latest PiSDR image now includes full PlutoSDR support. PiSDR is a pre-built Raspberry Pi distribution that supports several SDRs including the RTL-SDR. It comes with many applications and libraries ready for you to use some of which include GQRX and GNURadio Companion. PiSDR is available on [GitHub] and just needs to be burned to an SD card to be used. The PlutoSDR is a low cost (typically priced anywhere between $99 – $149 depending on sales) RX/TX capable SDR with up to 56 MHz of bandwidth and a 70 MHz to 6 GHz frequency range.

With this update support for the PlutoSDR has been added. This should allow for a host of new interesting uses for the image as it includes SDRAngel, an SDR application that works with transmit capable SDRs. While I’ve not yet tested the image myself, this should in theory mean that the PiSDR image could be used with a transmit capable SDR like a PlutoSDR or Lime/Mini SDR to both transmit and receive anything from DATV to voice and more.

Below you can see the image running the Raspbian desktop with the SDRAngel software connected to the PlutoSDR. Those with a keen eye may also see the LimeSDR mini laying on the desk s well. The concept of SDR on a small microcomputer such as the Raspberry Pi isn’t a new one, but the existence of this distribution makes it much easier for people to jump in and start using it without having to configure and install software from scratch which can sometimes be a daunting task.

Running a Tesla Model 3 on Autopilot off the Road with GPS Spoofing

Regulus is a company that deals with sensor security issues. In one of their latest experiments they've performed GPS spoofing with several SDRs to show how easy it is to divert a Tesla Model 3 driving on autopilot away from it's intended path. Autopilot is Tesla's semi-autonomous driving feature, which allows the car to decide it's own turns and lane changes using information from the car's cameras, Google Maps and it's Global Navigation Satellite System (GNSS) sensors. Previously drivers had to confirm upcoming lane changes manually, but a recent update allows this confirmation to be waived.

The Regulus researchers noted that the Tesla is highly dependent on GNSS reliability, and thus were able to use an SDR to spoof GNSS signals causing the Model 3 to perform dangerous maneuvers like "extreme deceleration and acceleration, rapid lane changing suggestions, unnecessary signaling, multiple attempts to exit the highway at incorrect locations and extreme driving instability". Regarding exiting at the wrong location they write:

Although the car was a few miles away from the planned exit when the spoofing attack began, the car reacted as if the exit was just 500 feet away— slowing down from 60 MPH to 24 KPH, activating the right turn signal, and making a right turn off the main road into the emergency pit stop. During the sudden turn the driver was with his hands on his lap since he was not prepared for this turn to happen so fast and by the time he grabbed the wheel and regained manual control, it was too late to attempt to maneuver back to the highway safely.

In addition, they also tested spoofing on a Model S and found there to be a link between the car's navigation system and the automatically adjustable air suspension system. It appears that the Tesla adjusts it's suspension depending on the type of road it's on which is recorded in it's map database.

In their work they used a ADALM PLUTO SDR ($150) for their jamming tests, and a bladeRF SDR ($400) for their spoofing tests. Their photos also show a HackRF.

Regulus are also advertising that they are hosting a Webinar on July 11, 2019 at 09:00PM Jerusalen time. During the webinar they plan to talk about their Tesla 3 spoofing work and release previously unseen footage.

GPS/GNSS spoofing is not a new technique. In the past we've posted several times about it, including stories about using GPS spoofing to cheat at Pokémon Go, misdirect drivers using Google Maps for navigation, and even a story about how the Russian government uses GPS spoofing extensively.

Some SDR tools used to spoof the Tesla Model 3.
Some SDR tools used to spoof the Tesla Model 3.