Prof. Dr. Michael Hartje, DK5HH, and Markus Heller DL8RDS, Organizers
From my Microphone to the Ether – An example-based introduction to SDR
Marcus Müller, ETTUS
When we talk about Software Defined Radio, we look at systems that implement functionality that's usually done in hardware by processing a digital signal in software. But: what is a digital signal? How can I get the radio wave off the air, into my PC? And what about the other way around? What are the limits of doing things in Software, and how can we make sure our digital system works at least as well as its analog counterpart?
This talk strives to take the audience on a journey from the audio to a digital signal, over to some digital signal processing basics and finally approaches on how to actually transmit something that was nothing but 0's and 1's in a computer.
We'll start by describing what's coming from a microphone as a band-limited voltage signal that we can digitize, learn a bit on sampling (and a guy called Nyquist) on the way, show how all the magic can be done in GNU Radio and what tricks an Ettus USRP does, internally, to bring the resulting signal to the air!
An update on the mcHF SDR Transceiver and Microwave SDR
David Minchin, VK5KK, Wireless Institute of Australia (past President VK5)
At SDRA 2015 in Friedrichshafen,the author presented an overview of the mcHF SDR HF transceiver and a discussion on using SDR for microwave operation. The SDRA 2016 presentation will provide a more technical discussion on the mcHF including the expanded feature sets and firmware development over the past 12 months. To assist current and potential mcHF project participants a summary of modifications, upgrades, test results and experiences will also be presented. The second part of the presentation will discuss utilising the mcHF UI controller hardware and source code with VHF/UHF SDR platforms. The current development of a stand alone 144 MHz transceiver incorporating an imbedded FREEDV 2400A decoder/encoder will be presented to promote more interest in this area. Some results from using this experimental "Digital VHF SDR" radio with microwave transverters, with both FREEDV 2400A and JT65a weak signal operation, will be tabled.
Debunking Direct Sampling Receiver Performance Myths
Gerald Youngblood, K5SDR, President of FlexRadio
With the rise of direct sampling receiver technology, the future of the now 100 year old superheterodyne technology is coming into question. As with the rise of any disruptive technology, misconceptions are propagated both through lack of accurate knowledge and from those who have a vested interest in the old approach. This presentation will take both intuitive and analytical approaches to understanding the truth about directly sampling receiver performance measurements in the lab apply to the real world. This discussion will include such concepts as Interference Free Signal Strength (IFSS) and ADC overload probability in the real world.
Red Pitaya - Measurement device and emulation of SDR-Transceivers
Prof. Dr. Michael Hartje, DK5HH, HS Bremen
Red-Pitaya is a combination of a two channel 14 bit AD / DA converter with 125 MS/s and a FPGA. It consists of a dual core arm processor, which can operate the FPGA and peripheral devices via network or usb.
There is a very active developer community and special, Pavel Demin, who made some special solutions for ham radio application. One of these solutions does implement a HPSDR hardware protocol with 1 TX and 2 RX chains. This includes the abiltity to use the famous PowerSDR including diversity receiver or digital predistortion during transmitting. The direct output power is limited to about 10 mW but can be easily amplified up to several hundred watts or used direct for the beacon mode WSPR.
Some more predefined images are for use with gnuradio in the range up to 60 MHz with two independant TRX-Chains or as an embedded TRX.
This paper shows and demonstrates some features of the radio emulation and gives an overview how to use this equipment for different purposes.
OpenHPSDR: Stand-alone HPSDR Transceiver using low-cost processors
John Melton, G0ORX/N6LYT
Software, specifically written to run on low-cost ARM processors such as the Raspberry Pi 2, Odroid C1+ and Pine 64, supports all HPSDR/Apache Labs radios using both the original Ethernet protocol and the new protocol. The software uses a version of WDSP that has been ported to Linux and has been written in C, using GTK+ for the GUI toolkit, to work with a small touch screen display (typically 800x480) and supports rotary encoders and push buttons along with the touch screen for a "Knobs and Buttons" user interface. John will present a powerful direct-sampling SDR solution for QRP and portable operation.
OpenHPSDR: Direct Fourier Conversion (DFC) – An alternative architecture for Software Defined Radios
Phil Harman, VK6PH
Most of the latest SDRs use an Analogue to Digital Converter (ADC) close to the antenna followed by Digital Down Conversion (DDC). DDC is usually performed in an FPGA or ASIC and is used to reduce the bandwidth and data rate of the samples that are subsequently processed by a microprocessor, PC or single board computer. However, with the availability of low cost and high performance Graphics Processing Units (GPUs) an alternative architecture can be used that has a number of advantages over the current DDC approach. Phil will present the theory and some practical examples of this alternative architecture.
OpenHPSDR: Advanced Algorithms for Noise Blanking and Noise Reduction
Dr. Warren C. Pratt, NR0V
Wideband noise-blankers and LMS noise-reduction algorithms are commonplace in modern SDRs. With today's CPU power, more advanced algorithms offering superior performance are also available. Warren focuses on two such algorithms implemented in 2015 in the WDSP library used for the openHPSDR program: 1. The Spectral Noise Blanker uses linear predictive coding and often removes impulse noise under conditions where wideband blankers are ineffective. Impulses are detected by comparing the observed waveform with a predicted waveform. Impulses are corrected by recreating an estimate of corrupt portions of the original waveform using spectral information. 2. The Spectral Noise Reduction algorithm operates in the frequency domain and, based upon statistical models of speech and noise, reduces random noise much more effectively than LMS algorithms. The seminal work for this approach was published by Yariv Ephraim and David Malah in 1984. However, the state of the art has advanced substantially over the past thirty years.
OpenHPSDR: Evaluating Digital Receivers
Adam Farson, VA7OJ/AB4OJ
The second and third-order intercept points (IP2 and IP3) are figures of merit for TRX specifications and allow distortion products to be computed for various signal amplitudes. Advanced SDR designs employing the ADC close to the antenna, require modified test methods to characterize strong signal performance. Terms like IP3 or intermodulation-free dynamic range fail and also terms like dither or random noise get meaning. Noise Power Ratio (NPR) an old test procedure can be very useful to benchmark SDRs and legacy analogue concepts as well. Adam will explain some fundamentals and test results.
Signal Intelligence with Software Defined Radio
Sebastian Müller, Univ. Karlsruhe
Signal intelligence describes the gathering of information out of intercepted radio signals with unknown origin and unknown parameters. Due it’s universal character, software defined radio seems to be predestinated for this task. The current leading SDR framework GNU Radio and compatible hardware products will be introduced. Also, information about the IEEE Signal Intelligence Challenge will be given and the typical signal intelligence workflow shall be described with two to three examples.
OPEN matters! A critical perspective on proprietary systems
Frank Werner-Krippendorf, HB9FXQ
A brief showcase of SDRplay & Flex 6K APIs on linux. Both systems stand for non-open hardware while allowing perfect control by providing fully loaded APIs. The practical part is embedded in a critical discussion around the relevance of OPEN soft- and hardware interfaces for our hobby.
SDR in Contest Practice
Prof. Dr. Harald Gerlach, DL2SAX, HS Neu-Ulm
As the SDR technology is now generally available on the market and since there has been a multitude of SDR transceivers in a wide price range, light will be cast on the question of additional functionality for operating requirements, particularly in contests.
This talk will address the question of hardware requirements, operating consoles, the integration into a station's concept, and the performance of the entire scenario under the strain of a contest.
GQRX as a Graphical Frontend for Digital Receivers
Bastian Blössl, DF1BBL, Univ. Paderborn
Developed by OZ9AEC, GQRX is a SDR with a graphical user interface that is very intuitive for radio amateurs. The waterfall plot, together with demodulators for FM, AM, and SSB, makes it a great tool for analog modes. GQRX is, however, not limited to analog transmissions, but is an excellent tool for digital modes too. Much like a conventional radio, it doesn't aim to implement all digital modes internally, but provides means to export signals to audio files or stream them through network sockets. In this talk, we will show how this functionality allows to connect GQRX to other software, using it as a graphical frontend for various digital receivers. In particular, we will use a bit of format conversion to connect GQRX to multimon, custom GNU Radio receivers, and inspectrum, a new tool for offline signal analysis. Using the GUI of GQRX has the advantage that common functionality to find, filter, and demodulate a signal does not have to be reimplemented, allowing for rapid development of new receivers. Furthermore, the possibility to switch between storing and streaming data allows to develop offline receivers and later switch to live data seamlessly. I hope this talk gives some new ideas on how to get the most out of GQRX and how to combine it with other tools to ease receiver development.
Recent work on OpenWebRX and csdr
András Retzler, HA7ILM, Univ. Budapest
OpenWebRX is a multi-user, web-based SDR receiver application, which uses the libcsdr library through the csdr command-line tool for DSP processing. During the last year many improvements were made to the software package. The waterfall diagram and the audio are now streamed in a compressed form. Several ways of accelerating the digital downconversion were investigated, which include a multi-band filter bank based on fast convolution. The csdr tool has been extended with functions for transmitting AM/FM/SSB. A new GUI application, qtcsdr has been released, which uses csdr under the hood. It can turn a Raspberry Pi and an RTL-SDR into a transceiver. It also uses the rpitx project by Evariste Courjaud, F5OEO to generate modulation on a GPIO pin of the Raspberry Pi.
Reversing digital signals with inspectrum
Reverse engineering an unknown signal is a fairly manual process and common methods are time consuming, requiring an array of tools to discern all the parameters of a signal.
This talk introduces inspectrum; a new open source program for analysing captured radio signals. I'll explain how inspectrum's unique features improve the process of reverse engineering a signal and conclude with a demonstration of how to use these features on signals captured from an example device.
The Panoradio: A wideband direct sampling SDR with 250 Msps
Stefan Scholl, DC9ST, Univ. Kaiserslautern
Direct sampling receivers are considered as the "holy grail" of SDR, because the signal is digitized directly after the antenna. The Panoradio SDR (www.panoradio-sdr.de) features a sampling rate of 250 MHz resulting in a 100 MHz aliasing free bandwith for spectrum monitoring and reception from short wave to VHF at the same time. With an additional frontend direct sampling reception of the 70cm band is possible. The SDR hardware is build upon the Zedboard, containing a modern Xilinx Zynq device, that combines FPGA and a dual ARM A9 processor on a single chip. It runs a linux operating system and therefore works in standalone mode - with only a mouse and monitor connected. The purpose of the Panoradio SDR is to demonstrate the capabilities of today's technology for signal monitoring and reception.
Chris Kuethe, KJ6GVE
Summary and Outlook
Prof. Dr. Michael Hartje, DK5HH and Markus Heller, DL8RDS, Organisation Committee