Category: Other

DesktopSDR MATLAB RTL-SDR Text Book Released

Back in August we posted about an RTL-SDR related text book called DesktopSDR that was due to be released later in the month. The text book discusses technical SDR topics, with the RTL-SDR used as the radio receiver and MATLAB used as the digital signal processing tool. It looks to be very useful to students of radio or communications engineering. There were a few delays with the release, but it is now out at www.desktopsdr.com. The eBook version is free whilst the print version is soon to be released on Amazon for about $68 USD for the paperback and $89 USD for the hard back. 

To go along with the book they have also released several accompanying videos that are available at desktopsdr.com/videos.

The books blurb reads:

The availability of the RTL-SDR device for less than $20 brings software defined radio (SDR) to the home and work desktops of EE students, professional engineers and the maker community. The RTL-SDR can be used to acquire and sample RF (radio frequency) signals transmitted in the frequency range 25MHz to 1.75GHz, and the MATLAB and Simulink environment can be used to develop receivers using first principles DSP (digital signal processing) algorithms. Signals that the RTL-SDR hardware can receive include: FM radio, UHF band signals, ISM signals, GSM, 3G and LTE mobile radio, GPS and satellite signals, and any that the reader can (legally) transmit of course! In this book we introduce readers to SDR methods by viewing and analysing downconverted RF signals in the time and frequency domains, and then provide extensive DSP enabled SDR design exercises which the reader can learn from. The hands-on SDR design examples begin with simple AM and FM receivers, and move on to the more challenging aspects of PHY layer DSP, where receive filter chains, real-time channelisers, and advanced concepts such as carrier synchronisers, digital PLL designs and QPSK timing and phase synchronisers are implemented. In the book we will also show how the RTL-SDR can be used with SDR transmitters to develop complete communication systems, capable of transmitting payloads such as simple text strings, images and audio across the lab desktop.

Download the book at desktopsdr.com
Download the book at desktopsdr.com

4NEC2 The Definitive Guide Book

4NEC2 is a freeware antenna simulation software program. The program can be used to model an antenna, and then determine through simulation properties such as the radiation pattern and SWR of the modelled antenna. It is very useful for those designing home made antennas for their RTL-SDR or other radio, or for those just trying to understand how antennas work. 

4NEC2 can be a complicated piece of software and to get the most out of it a guide is needed. We’ve recently been informed that Mark Schoonover KA6WKE, is writing an eBook guide on this topic. His guide is currently only 20% complete, but a free sample of his book in its current state can be downloaded from leanpub. The guide already shows what the main windows of 4NEC2 do, and shows you how to model and simulate a simple dipole antenna.

4NEC2: The Definitive Guide
4NEC2: The Definitive Guide

Building an active wideband antenna for your SDR

As the RTL-SDR and other SDRs are wideband, we recommend that people use a wideband antenna if they want to scan over all the frequencies. Normally a discone or a scantenna is suggested as the wideband antenna of choice, however there are alternative designs such as the Dressler ARA-2000 which is a type of log spiral antenna that can receive from 50 – 2000 MHz. This particular product is no longer for sale, but an article detailing the breakdown of its construction can be found online. 

The dressler ARA-2000
The dressler ARA-2000

The article shows how to build the antenna from scratch. The active element consists of a thin copper sheet (or copper foil) in the shape of a wedge which is rolled into a cylinder around a plastic sheet. It is then connected to a low noise amplifier (LNA), which is powered through a bias tee. For the LNA something like the LNA4ALL could be used if building it yourself.

This antenna may be something to consider if you are thinking about building your own wideband antenna. It has the advantage of being much smaller than a discone and it can also be fully enclosed in a plastic radome to that fully protects it from weather elements. The author of the article also writes that he saw better performance from this antenna than when compared with a discone.

Inside the ARA-2000
Inside the ARA-2000

Frequency Manager Suite Plugin for SDR#

Recently the popular Frequency Manager + Scanner plugin set for SDR# has been upgraded and renamed to the “Frequency Manager Suite”. The plugin can be downloaded from their new website at www.freqmgrsuite.com. The plugin suite includes a frequency scanner and manager, a scanner metrics recorder, a scheduler, an activity logger and a frequency entry plugin.

Apart from plugins the suite also now includes a plugin manager program called “Pluginator” which can help you to install and delete plugins without needing to edit the Plugins.xml file directly. There is also a new database manager tool which can help you to import frequency databases from online or other sources.

We have posted the full feature release below:

The Frequency Manager Suite (FMS) adds 4 more plugins to the previous set of 3:

  • Scheduler – allows you to schedule listening activities by date and time.

  • Activity Logger – records scanner activity to a file for later use.

  • Scanner Decisions – now a first-class plugin and also available as the classic stand-alone window. And you can change the position of the plugin without restarting SDR#.

  • Frequency Details – displays details about a frequency from your database. And you can change the position of the plugin without restarting SDR#.

New standalone applications also come with FMS:

  • Data Tools – this significantly upgraded import/export application lets you import data from 6 popular internet databases as well as generically-formatted files, and permits you to export your FMS databases to standard file format.
  • The Pluginator – an application that lets you add, delete, and change the order of plugins without ever having to hand-edit the SDR# file Plugins.xml. Just fill in the blanks.

New features in Frequency Manager + Scanner:

  • The new Preferences dialog allows customization without hand-editing a configuration file.
  • FMS configurations are now kept in a file separate from those of SDR#, permitting easier upgrades to SDR#.
  • You can have multiple frequency databases, and can change to a different database without restarting SDR#.
  • When tuning manually you can optionally change the radio settings (mode, BW, etc.) according to what’s in the database for the tuned frequency.
  • Scan resolution – high-res or low-res to favor speed over accuracy or vice versa.
  • Adjacent Frequency Rejection now displays its bandwidth on the spectrum analyzer.
  • Plus many other improvements and bug fixes.

fms_1v2   fms_3   fms_2   

pluginator

GNU Radio Conference 2015: Presentations

The GNU Radio conference (GRCon15) is a yearly conference discussing all matters related to GNU Radio, an open source graphical block based DSP programming application that is compatible with most SDR’s, including the RTL-SDR. The conference started on August 24 and is due to close this Friday August 28, however many of the presentation slides are now available for viewing on their website.

This year there are many interesting talks, including a speech by Balint about radio direction finding, RF sniffing and digital FPV on drones. There are also several tutorial presentations that show how to install GNU Radio, how DSP sampling works, an intro to analog RF concepts and how to build a software radio from scratch.

gnuradio

Seeing through walls with WiFi signals and USRP software defined radios

Researchers at the University College of London have found a way to use WiFi signals to see through walls, using a USRP software defined radio and software written in LabView. The researchers have shown that they are able to utilize local WiFi signals to detect and monitor moving objects such as people behind a wall in a similar fashion to how radar systems work. The advantage over traditional radar is that their system is completely passive, requiring no transmitter, other than the already ubiquitous WiFi signal.

In a demonstration the researchers showed how they were able to not only detect the presence of a person behind a wall, but also detect small hand gestures that were made.

Detecting body gestures from WiFi signals in LabView.
Detecting body gestures from WiFi signals in LabView.

It appears the researchers are patenting their work and are looking to market their technology towards military and security surveillance operators as well as towards other applications such as traffic monitoring and the monitoring of children and the elderly.

We aren’t sure what type of radio accuracy is required for a system such as this, but it may be possible that SDR’s that cost less than the USRP may also work, assuming the software technology can ever be replicated/licensed.

wifi_hostage
A proposed application of the technology: Allowing police to see through walls in a hostage situation.

Painting on the RF Spectrum with a HackRF

Last week several people from the Chaos Communication Camp conference and others on the #hackrf IRC channel were playing around with the idea of painting pictures on the RF spectrum with the HackRF – a low cost transmit capable software defined radio. This idea works simply by modulating a signal so that it produces a desired image pattern on a frequency domain waterfall display.

To make this easier to do, GitHub user polygon has authored a Python program called Spectrum Painter which easily converts an image into an IQ file which can be transmitted with a HackRF. In addition as described in the Reddit thread linked above, a Windows program called Coagula can also be used to convert images into .wav files, which can then be transmitted on any capable radio. The RF painted images can then be received on another SDR radio like the RTL-SDR.

As always remember to only transmit at a frequency you are licensed on, or at low power in a RF controlled environment.

Below is an example image and video showing images being painted on the RF waterfall.

Spectrum painter transmitted output image
Spectrum painter transmitted output image

hackrf transmitting images in the frequency domain

SDR Talks from the 2015 Chaos Communication Camp

The Chaos Communication Camp (CCC) conference was recently held in Germany this year. The conference is a five day event that focuses on topics such computer security, hacking, electronics and other similar related topics. The full list of talks can be found here, but on this page we list all the SDR related talks which we could find. If you know of any more SDR related talks from the CCC please let us know in the comments.

“The Rad1o: Listen to all the things”

This year participants of the CCC were all given a Rad1o badge, which is a HackRF variant. In this talk the creators of the Rad1o explain their experience with creating the Rad1o and give an overview of it’s hardware and software options.

“Satellite Open Ground Station Network: open source ground station, optimized for modularity, built from readily available and affordable tools and resources.”

(Audio broken until 2:50) The SatNOGS project aims to provide low cost satellite ground stations (where one critical component is currently an RTL-SDR dongle) along with free networking software in order to create a crowd sourced satellite coverage network. The SatNOGS project was also the grand prize winner of the 2014 Hackaday prize which saw them take away almost $200k US dollars of prize money. This talk introduces the SatNOGS project.

“Iridium Hacking: please don’t sue us”

Iridium is a satellite service that provides global communications. This talk discusses how the presenters were able to decode the Iridium pager network with a simple software defined radio like the RTL-SDR. At the end of the presentation they show a live demo of the Iridium signals being decoded.