A four week free class on signal analysis using SDR’s like the RTL-SDR will be taking place in the “Unallocated Space” technology community center in Baltimore-DC area. It starts on Tuesday September 20, 2016 at 7pm to 10pm. The class will help participants set up their systems, and cover locating, identifying, demodulating, and decoding common RF signal types. On the final week they will host a wireless capture the flag competition, where students will use their skills to solve problems and earn points.
You will need to bring your own SDR hardware such as an RTL-SDR, as well as an omnidirectional antenna and a PC/laptop capable of running your SDR.
Recently a new Linux based tool called RFTap has been released. RFTap acts as a bridge between GNURadio flow graphs and Wireshark. GNU Radio is a visual based programming environment for digital signal processing applications, such as RF signal decoders. GNURadio supports many different SDR’s including the RTL-SDR. Wireshark is a network packet analyzer/dissector that aides with troubleshooting and analysis of network protocols. RFTap also supports other DSP languages like Pothos, liquidsdr, LuaRadio as well as other packet analyzers like TShark, tcpdump, Scapy.
CubicSDR is a relatively new SDR program, which is similar in operation to programs like SDR#, HDSDR and SDR-Console. Recently CubicSDR has been updated to V0.2.0. This version seems to be a new stable version which incorporates many changes and improvements built up over the past months. Currently CubicSDR supports the following SDR’s:
SoapyRemote
RTL-SDR
AirSpy
SDRPlay** (only AppImage supported for Linux currently)
Over on YouTube Adam 9A4QV (creator of the LNA4ALL and other products) has uploaded a video that explains Friis formula for noise, using simple calculations and theory. These calculations explain why an LNA can significantly help reception on L-Band with an RTL-SDR. In his video he uses graphs and tables provided in this document released by the US Naval Academy. At the end of this post we attached images of the graph and table that he uses in the videos calculations for easy access.
The calculations show how the noise figure and gain of the first LNA in the system dominates the result. The final result of his video shows that using an LNA with a noise figure of 1 dB and 16 dB gain can give an improvement in SNR of about 7.8 dB over a standard RTL-SDR which has a noise figure of 6 dB. This is the improvement on L-band from simply placing the LNA by the dongle, and it does not take into account the extra improvement that could be had by placing it by the antenna, if a run of coax is used. The equations can also be adapted to other frequencies, and they show that as the frequency decreases, the effect of the noise figure of the LNA becomes less important.
NOTE: This tutorial is no longer valid as Outernet discontinued their L-Band service in late 2017. Please consult www.outernet.is for news on their latest delivery methods.
Outernet is a relatively new satellite service which aims to be a "library in the sky". Essentially their service is going to be constantly transmitting files and data like news and weather updates from geostationary satellites that cover almost the entire world. Geostationary means that the satellites are in a fixed position in the sky, and do not move over time. By simply pointing a small patch antenna at the sky (with LNA and RTL-SDR receiver), it is possible to download and decode this data from almost anywhere in the world. Their aim is to provide up to date information to users in locations with little to no internet (rural, third world and sea), or in countries with censored internet. It may also be of interest to disaster preppers who want an "off-grid" source of news and weather updates. It can kind of be thought as a kind of one-way download-only internet service.
Currently the L-band service is being tested, and while they are not yet sending actual Outernet files, they are already sending several daily test files like small videos, images and text documents as well as GRIB files for mariners. At a maximum you can expect to receive up to about 20 MB of data a day from their satellite. Previously they had C-band services but these required large satellite dishes. The C-band service is due to be discontinued at some point in the future.
In this guide we'll show you how to set up an Outernet L-band receiver with an RTL-SDR dongle. If you enjoy this guide then you might also enjoy our Inmarsat STD-C EGC Decoding Tutorial which has similar hardware requirements.
A four week free class on signal analysis using SDR’s like the RTL-SDR will be taking place in the “Unallocated Space” technology community center in Baltimore-DC area. It starts on Tuesday September 20, 2016 at 7pm to 10pm. The class will help participants set up their systems, and cover locating, identifying, demodulating, and decoding common RF signal types. On the final week they will host a wireless capture the flag competition, where students will use their skills to solve problems and earn points.
You will need to bring your own SDR hardware such as an RTL-SDR, as well as an omnidirectional antenna and a PC/laptop capable of running your SDR.
Recently a new Linux based tool called RFTap has been released. RFTap acts as a bridge between GNURadio flow graphs and Wireshark. GNU Radio is a visual based programming environment for digital signal processing applications, such as RF signal decoders. GNURadio supports many different SDR’s including the RTL-SDR. Wireshark is a network packet analyzer/dissector that aides with troubleshooting and analysis of network protocols. RFTap also supports other DSP languages like Pothos, liquidsdr, LuaRadio as well as other packet analyzers like TShark, tcpdump, Scapy.
CubicSDR is a relatively new SDR program, which is similar in operation to programs like SDR#, HDSDR and SDR-Console. Recently CubicSDR has been updated to V0.2.0. This version seems to be a new stable version which incorporates many changes and improvements built up over the past months. Currently CubicSDR supports the following SDR’s:
SoapyRemote
RTL-SDR
AirSpy
SDRPlay** (only AppImage supported for Linux currently)
Over on YouTube Adam 9A4QV (creator of the LNA4ALL and other products) has uploaded a video that explains Friis formula for noise, using simple calculations and theory. These calculations explain why an LNA can significantly help reception on L-Band with an RTL-SDR. In his video he uses graphs and tables provided in this document released by the US Naval Academy. At the end of this post we attached images of the graph and table that he uses in the videos calculations for easy access.
The calculations show how the noise figure and gain of the first LNA in the system dominates the result. The final result of his video shows that using an LNA with a noise figure of 1 dB and 16 dB gain can give an improvement in SNR of about 7.8 dB over a standard RTL-SDR which has a noise figure of 6 dB. This is the improvement on L-band from simply placing the LNA by the dongle, and it does not take into account the extra improvement that could be had by placing it by the antenna, if a run of coax is used. The equations can also be adapted to other frequencies, and they show that as the frequency decreases, the effect of the noise figure of the LNA becomes less important.
NOTE: This tutorial is no longer valid as Outernet discontinued their L-Band service in late 2017. Please consult www.outernet.is for news on their latest delivery methods.
Outernet is a relatively new satellite service which aims to be a "library in the sky". Essentially their service is going to be constantly transmitting files and data like news and weather updates from geostationary satellites that cover almost the entire world. Geostationary means that the satellites are in a fixed position in the sky, and do not move over time. By simply pointing a small patch antenna at the sky (with LNA and RTL-SDR receiver), it is possible to download and decode this data from almost anywhere in the world. Their aim is to provide up to date information to users in locations with little to no internet (rural, third world and sea), or in countries with censored internet. It may also be of interest to disaster preppers who want an "off-grid" source of news and weather updates. It can kind of be thought as a kind of one-way download-only internet service.
Currently the L-band service is being tested, and while they are not yet sending actual Outernet files, they are already sending several daily test files like small videos, images and text documents as well as GRIB files for mariners. At a maximum you can expect to receive up to about 20 MB of data a day from their satellite. Previously they had C-band services but these required large satellite dishes. The C-band service is due to be discontinued at some point in the future.
In this guide we'll show you how to set up an Outernet L-band receiver with an RTL-SDR dongle. If you enjoy this guide then you might also enjoy our Inmarsat STD-C EGC Decoding Tutorial which has similar hardware requirements.
Cloud-SDR is a new tool currently in beta testing which enables remote streaming access of SDR receivers, such as the RTL-SDR and Airspy. In a way it is similar to rtl_tcp in that it allows IQ samples to be streamed over the network, however Cloud-SDR appears to be a much more developed solution that can support more SDR’s and has many more features, as well as better performance. Cloud-SDR is not free, and during these beta stages of release the pricing does not appear to be public. However they have licences for personal/hobbyist use, which we assume will be reasonably priced.
They describe their software in the following blurb:
Cloud-SDR can collect real-time IQ complex samples from an SDR hardware device connected on one machine, stream the samples to a second machine for demodulation or analysis, then send the resulting stream to third machine for storage.
In standalone mode, Cloud-SDR can execute signal processing tasks described with embedded JavaScript DSP engine.
Because network bandwidth is limited compared to SDR receiving bandwidth, the core concept of Cloud-SDR is to move the processing along the cloud to where it is required or possible : the DSP chain is divided in sub-tasks that are spread between computers interconnected through Internet.
For example a “signal scanner” application can be programmed with a script and stored on the SDR server for execution. Only found signals will threshold stream transmission through the TCP/IP network. Remote Client will only receive the IQ stream if a signal is detected by the DSP task. In “cloud mode”, the same script can be broadcasted to several SDR nodes located at different places, enabling parrallel signal search.
Server software SDRNode receives IQ streams from the different SDR hardwares, extracts the different bands, processes them and transmits the RF data using compression algorithms to limit TCP/IP network bandwidth.
Recently the popular SDR# (SDRSharp) software has had several improvements made to it (changelog). One of the most noticeable improvements is a decent reduction in the amount of CPU usage required by the software. We tested the new version on an i7 CPU and compared it against an older version using an Airspy. We saw 12% CPU usage on the older version and 7% on the newer version. With the RTL-SDR the older version showed 5% CPU usage which reduced to 3% on the newer version. Using an older i5 PC resulted in even larger improvements, going from about 35% CPU on the older version down to 25% or lower usage on the new version with the Airspy. The improvements are especially noticeable when decimation is used with the Airspy. These performance updates may help users on older PC’s and tablets run the software, or help users who run many programs at one time. The SDR# author is also testing out a 64 bit version of SDR#, which may be released in the future.
Recent versions over the past few months have also made improvements to the included noise blanker plugins and they have also added a default band plan plugin which shows the various frequency bands visually on the FFT spectrum.
Showing the very low CPU usage obtainable with the latest SDR# versions.
At this year’s hacker themed Eleventh Hope conference, Stefan “Sec” Zehl and Schneider gave a talk which discusses their latest work on decoding data from Iridium satellites using SDR’s. Iridium is a truly global satellite service which provides various services such as global paging, satellite phones, tracking and fleet management services, as well as services for emergency, aircraft, maritime and covert operations too. There are currently 72 operational satellites operating.
In their talk they discuss how Iridium security is moderate to relaxed, pointing out that Iridium claims that the majority of ‘security’ comes from the complexity of the system, rather than actual security implementations. They then go on to discuss how the Iridium system works, how to receive it with an RTL-SDR or HackRF/Rad1o, how the gr-iridium decoder implementation works, and how to use it to actually decode the data. Later in the presentation they show some interesting examples such as an intercepted Iridium satellite phone call to a C-37 aircraft.
