Tagged: rtl-sdr

Hack Chat: Learning SDR and DSP with Marc Lichtman

On Wednesday Nov 11 Noon Pacific time, Hackaday will hold a hack chat (group text chat session) with Marc Lictman, author of the free online book "PySDR: A Guide to SDR and DSP using Python". We posted about the release of this book last month, noting that it is probably one of the best books in terms of explaining DSP fundamental concepts in an easy to understand way. Hackaday write:

Join us on Wednesday, November 11th at noon Pacific for Learning SDR and DSP Hack Chat with Marc Lichtman!

“Revolution” is a term thrown about with a lot less care than it probably should be, especially in fields like electronics. It’s understandable, though — the changes to society that have resulted from the “Transistor Revolution” or the “PC Revolution” or more recently, the “AI Revolution” have been transformative, often for good and sometimes for ill. The common thread, though, is that once these revolutions came about, nothing was ever the same afterward.

Such is the case with software-defined radio (SDR) and digital signal processing (DSP). These two related fields may not seem as transformative as some of the other electronic revolutions, but when you think about it, they really have transformed the world of radio communications. SDR means that complex radio transmitters and receivers, no longer have to be implemented strictly in hardware as a collection of filters, mixers, detectors, and amplifiers; instead, they can be reduced to a series of algorithms running on a computer.

Teamed with DSP, SDR has resulted in massive shifts in the RF field, with powerful, high-bandwidth radio links being built into devices almost as an afterthought. But the concepts can be difficult to wrap one’s head around, at least when digging beyond the basics and really trying to learn how SDR and DSP work. Thankfully, Dr. Marc Lichtman, an Adjunct Professor at the University of Maryland, literally wrote the book on the subject. “PySDR: A Guide to SDR and DSP using Python” is a fantastic introduction to SDR and DSP that’s geared toward those looking to learn how to put SDR and DSP to work in practical systems. Dr. Lichtman will stop by the Hack Chat to talk about his textbook, to answer your questions on how best to learn about SDR and DSP, and to discuss what the next steps are once you conquer the basics.

Our Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, November 11 at 12:00 PM Pacific time. If time zones baffle you as much as us, we have a handy time zone converter.

Etherify: Transmitting Morse Code via Raspberry Pi Ethernet RF Leakage

Over on his blog SQ5BPF has been documenting a TEMPEST experiment where he's been able to transmit data via RF being leaked from a Raspberry Pi's Ethernet connection. The idea was born when he found that his Raspberry Pi 4 was leaking a strong RF signal at 125 MHz from the Ethernet cable. He went on to find that it was easy to turn a tone on and off simply changing the Ethernet link speed with the "ethtool" command line tool. Once this was known it is a simple matter of creating a bash script to generate some morse code.

Quite amazingly the Ethernet RF leakage is very strong. With the Raspberry Pi 10 meters away, and a steel reinforced concrete wall in between, SQ5BPF was able to receive the generated morse code via an RTL-SDR connected to a PC. Further experiments show that with a Yagi antenna he was able to receive the signal from 100 meters away.

His post explains some further experiments with data bursting, and provides links to the scripts he created, so you can try this at home.

Update - SQ5BPF also notes the following:

The leakage differs a lot with the hardware used. The Raspberry Pi 4 is exceptional and also allows to switch the link speed quickly, so was a nice candidate for a demo, but other hardware works as well.

The first tests were done on some old laptops I had laying around, and they leak as well. Maybe someday I will publish this, but everyone of them behaves differently.

Etherify 1 demo receiving via SDR and decoding via fldigi

Frugal Radio: SDR Guide Ep 6 – Trunk Tracking Public Safety Systems with UniTrunker and SDRTrunk

In this episode of Frugal Radio's ongoing SDR Guide videos Rob demonstrates how he uses Unitrunker and SDR Trunk with SDRs like an RTL-SDR to monitor Public Safety networks in his area. Rob writes:

This is a video demonstrating how I use UniTrunker and SDRTrunk with Software Defined Radios to monitor multiple Public Safety networks in my area.

There is some information on how trunked systems work, and you can hear how my SDRs produce better P25 audio on a Simulcast (LSM) system than some scanners.

I use a couple of RTL-SDR v3s and an Airspy R2 in this episode.

2020 SDR Guide Ep 6 : Trunk tracking Public Safety systems with UniTrunker and SDRTrunk

RF Fingerprinting ADS-B Signals for Security

At this years ICNP 2020 IEEE conference a paper titled "Real-World ADS-B signal recognition based on Radio Frequency Fingerprinting" (pdf file) was presented by researchers from Harbin Engineering University in China. The idea presented in the paper is to use RF "fingerprinting" techniques to uniquely identify and confirm that the ADS-B signal originates from the correct aircraft source.

RF fingerprinting works on the premise that every transmitter has small manufacturing variances that result in slightly different signals be transmitted, resulting in a unique "fingerprint" that can be traced to a particular transmitter. The idea here is to use these fingerprints to ensure that a known aircraft is indeed transmitting an ADS-B signal and the signal is not being transmitted from a fake spoofer. ADS-B is completely unencrypted and not authenticated, so spoofing of ADS-B signals may be a real security threat.

In the teams research they use an RTL-SDR to collect ADS-B signals from five different aircraft. They then use that data to create "Contour Stellar Images" and train a deep learning neural network which after training accurately identifies which aircraft a signal comes from.

Aircraft ADS-B Fingerprinting

In previous posts we've seen the idea of fingerprinting used by Disney research and others to identify electronic devices, to authenticate RF IoT devices and to identify handheld transmitters via CTCSS fingerprints.

GOES Weather Satellite Images on an E-Ink Display

Thank you to a few users who have submitted links to u/ThePhotoChemist's Reddit post showing his e-ink display for his live GOES-16 weather satellite images. The post doesn't go into much detail about the setup, however it seems that he is using a Raspberry Pi, and displaying the images via a 9.7 inch E-Ink display which he notes does not come cheaply. He also notes that the resolution is quite low, and that it's limited to 16 shades of grey, however the images do still look good on it. The display is mounted into a picture frame which makes a very nice display piece.

If you're interested in receiving live GOES (or GK-2A) weather satellite images with an RTL-SDR we have a tutorial available here. 

An e-ink display with live GOES images from space

Happysat Reviews the QO-100 Bullseye LNB

Thank you to Happysat for reviewing the QO-100 Bullseye LNB which we have available in our store, eBay and Aliexpress. The Bullseye LNB is an ultra stable TCXO (temperature compensated oscillator) based LNB which makes it very good at receiving the narrowband signals on the QO-100 amateur geostationary satellite.

Standard LNBs that are sometimes used for QO-100 are not designed for narrowband signals and hence do not have temperature compensated oscillator which can result in the signals drifting in frequency significantly as the ambient temperature fluctuates. Happysat also notes that the extra stability seems to have increased signal strength on the more wideband DATV reception as well.

First test's on Es-Hail Narrow SSB transponder compared to my old regular sat-tv LNB clearly is showing more signal stability overall.

It does need some time for both the tuner and LNB to get stable, but that's only a few minutes.

Weather conditions shows less "drifting" of the pll where the old LNB was very sensitive of temperature changes, clouds before the sun did have immediately effect on the signal stability.

Some days with storms reception was impossible on SSB Narrow band.

Winter is coming over here so it gets a lot colder and more storms, but I don't expect any problems with this LNB.

Wideband testing DATV reception also shows a more stable signal although its a wider signal then narrowband, it also did increase the signal, e.g. a signal lock happens much faster.

More information about Happysat's setup and his use of the Bullseye QO-100 LNB can be found on his QO-100 website.

Other reviews of the Bullseye LNB include a YouTube video from TechMinds and F4DAV's in depth review on his website.

The Bullseye LNB for QO-100

RPiTX Beta for Raspberry Pi 4 Released

Evariste (F5OEO) has just announced the release of an update to RPiTX which allows it to now be used on a Raspberry Pi 4. If you are unfamiliar with it, RPiTX is a program for Raspberry Pi single board computers that allows you to transmit almost any type of signal on frequencies between 5 KHz up to 1500 MHz with nothing more than a piece of wire connected to a GPIO pin. Evariste also notes that the new version is compatible with the beta 64-bit version of Raspbian.

Some examples of signals you can transmit with RPiTX include a simple carrier, chirp, a spectrum waterfall image, broadcast FM with RDS, SSB, SSTV, Pocsag, Freedv and Opera. You can also use an RTL-SDR to record a signal, and replay the IQ file with RPiTX. However, please remember that transmitting with RPiTX you must ensure that your transmission is legal, and appropriately filtered.

RPiTX Logo

A Few More Demonstrations of the SDR# FM and AM Co-Channel Cancellers

Over on YouTube a few more videos showing the new AM and FM co-channel cancelling algorithms available in recent versions of SDR# have been uploaded. In the first video YouTuber channel "Peter .DXChannel" shows an example of broadcast FM Sporadic E signals (temporary long range reception due to Tropospheric ducting) being recovered with the FM co-channel canceller.

A demonstration of the SDRsharp FM Co Channel Canceller with Es signals

In the second video "icholakov" shows the AM co-channel canceller recovering a weaker signal being broadcast directly on top of a stronger one (zero carrier offset).

SDR Sharp Co-channel interference AM canceller. Several tests using Airspy HF+ Discovery