Category: Applications

QIRX SDR Updated: Legacy DAB, DAB Transmitter Identifications and more

Back in May of this year we posted about QIRX SDR, which back then was a brand new multimode SDR program compatible with the RTL-SDR. One of its defining features is that it has a built in DAB+ decoder. Recently QIRX SDR has been updated to version 0.9.1, the new features are quoted below:

General:

  • Updated Documentation
  • Device Frontend: Manual Center Freq. Correction in kHz
  • Waterfall Spectrum
  • Raw Recording: Playback Control, for a timed positioning (“seek”) in “arbitrary” large (GBytes) recorded raw files.

DAB:

  • Legacy DAB, intended for users where DAB+ is not generally available, like in the UK or Spain. As this could only be superficially tested here in Germany (no standard DAB any more, I used some raw samples recorded in Madrid), I would be very interested in feedback of users about it.
  • Synchronization of raw files recorded with central frequency offset
  • Enhanced manual synchronization control, mainly for tests in mobile environments
  • Detection of the Transmitter Identifications (TII). However, as this is a feature only useful for specialized applications, it is not included in the distribution. To my knowledge, qirx is the only DAB SDR having this feature.

Some Bug fixing.

The QIRX team have also added a new Quickstart Guide to help users get set up with their software quickly. In addition QIRX author Clem also writes that the QIRX software will be demonstrated during this weekends Ham-Radio fair in Friedrichshafen, Germany.

QIRX SDR Updated
QIRX SDR Updated

OpenWebRX Updates: 3D Waterfall and BPSK31 Demodulator

OpenWebRX has recently been updated and now includes a 3D waterfall display and a BPSK31 demodulator. OpenWebRX is a popular program which allows you to stream an SDR like the RTL-SDR over the internet efficiently. A number of clients can connect to your server and tune anywhere within a predefined bandwidth. Many examples of OpenWebRX running on RTL-SDRs and KiwiSDRs can be found on sdr.hu.

The 3D waterfall is quite an interesting feature as it allows you to visual signal strength, frequency and time all at once. BPSK31 is a popular amateur radio digital mode for making QSO’s (contacts). The new decoder allows you to zoom in closely on the band with high resolution and select with the mouse which BPSK31 channel you’d like to decode.

András Retzler, creator of OpenWebRX also writes that he’s now completed his Masters Thesis (congratutions!) on the topic of “Integrating digital demodulators into OpenWebRX”. His thesis is available for download here and looks to be an interesting read.

OpenWebRX BPSK31 Mode
OpenWebRX BPSK31 Mode

Demonstrating an RTL-SDR Based Metal Detector

Over on YouTube user Ancient Discoveries has uploaded a video showing a prototype of his RTL-SDR based metal detector. The metal detector appears to consist of a coiled detection loop antenna powered by an AM transmitter and an RTL-SDR running in Q-branch direct sampling mode.

Ancient discoveries uses SDR# to tune to a low medium wave frequency of around 898 kHz while in direct sampling mode. Then as a piece of metal is moved closer and further from the detection coil the signals on the spectrum move around in correlation with the metals distance. A whining sound just like a real metal detector is also produced by SDR#.

!!! RTL SDR Metal Detector !!! dancing with signals !!! modified latest project

Running Windows & x86 SDR Decoding Apps on the Raspberry Pi 3: Unitrunker, WinSTD-C, WXtoIMG, DSDPlus and more

There is a great advantage to running SDR decoder apps on a single board PC like a Raspberry Pi 3. For example instead of committing a whole PC to become a dedicated decoder, a cheap Pi 3 can be used instead. However, unfortunately many decoder apps are written for the x86 CPU architecture and/or Windows, making them impossible to run on ARM and/or primarily Linux devices like the Raspberry Pi 3.

That is unless you use an emulator combination like Eltechs Exagear and Wine. Exagear is an emulator that emulates an x86 environment on a device like a Raspberry Pi 3 which uses an ARM CPU. Wine is a Windows compatibility layer that allows you to run x86 Windows apps on an x86 Linux installation. So by combining Exagear together with Wine it is possible to run Windows apps on ARM Linux devices.

Exagear is not free (although there is a free trial). It currently costs $22.95 USD for a Pi 3 licence, and $16.95 USD for a Pi 2 licence and $11.45 for a Pi 1/Zero licence. They also have versions for Odroid, Cubieboard, BananaPi, Jetson and many other ARMv7 and ARMv8 devices like the super cheap and powerful Orange Pi’s. There are free alternatives out there like QEMU, however when we tested QEMU it was far too slow on the Pi 3 to even run notepad responsively, let alone a decoder. Exagear on the other hand seems to run apps at near native speeds, without much lag at all. So in this respect the price seems to be worth it.

We decided to test the Exagear + Wine combination on a Pi 3 and were successful in running a number of apps including Unitrunker, WinSTD-C, WXtoImg, DSDPlus, PC-HFDL, MultiPSK, Orbitron and Sondemonitor.

Trunking setup with Unitrunker on a Raspberry Pi 3

With Unitrunker we were able to set up a full trunk tracking system using two RTL-SDR dongles, rtl_fm, rtl_udp and a custom script to control rtl_udp.

Unitrunker running on a Raspberry Pi 3
Unitrunker running on a Raspberry Pi 3

In the future we may put up a full double checked tutorial with images, but for now a roughly written tutorial is presented below. The tutorial is fairly involved and assumes decent Linux experience. The tutorial starts from a fresh install of Raspbian.

The basic idea of operation is based around the fact that the RTL-SDR cannot be used directly within Wine (or so it seems). So the control signal audio is routed from rtl_fm running on one dongle into Unitrunker on Wine using alsa loopback. Then we use the old Unitrunker remote.dll method to generate a sdrsharptrunking.log file which is a text file that contains the current frequency that the voice receiver should tune to. A simple shell script continuously reads this file and extracts the frequency, and then commands an instance of rtl_udp running with the second dongle to tune to that frequency.

Continue reading →

Using a TV Dipole Antenna for NOAA Satellite Reception

Over on YouTube icholakov has uploaded a video showing how effective a simple old TV bunny ears antenna can be at receiving NOAA satellite images. The old TV antenna is telescoping so it can be adjusted to be resonant for many frequencies, and for NOAA satellites about 20 inches makes it resonant. Using the antenna as a V-Dipole and placing it in a North to South direction optimizes the radiation pattern towards the sky, allowing for good reception of the NOAA satellite. Using it this way also helps to null out strong vertically polarized stations. More information on the V-Dipole can be found on our previous post where we posted about Adam 9A4QV’s idea to use the V-Dipole for satellite reception.

2017: TV Antenna vs. NOAA Satellite

Also related to this post is a sneak preview on our new product: We’ve also caught onto the idea that TV antenna dipoles are extremely versatile, and are in the final stages of releasing a simple telescopic dipole product similar to the TV antenna used in this video. It will be released as an antenna set that comes with some portable mounting solutions like a suction cup and bendy tripod, and 3M of RG174 coax so that the antenna can be used anywhere. Target price is $10 -15 USD incl. shipping from China. This will probably also replace the stock telescopic whip antenna currently used in our dongle sets since the telescopic dipole is simply much more versatile.

Skylark Image for Outernet’s Dreamcatcher RTL-SDR

About two weeks ago we posted our review of the Dreamcatcher, a new RTL-SDR and full ARM based computing platform built onto a single PCB. Back then the only OS available for it was a standard Armbian build, and no Outernet decoder was available. So we reviewed the Dreamcatcher with the Armbian OS and tested to see how well it worked as a general purpose RTL-SDR and computing platform.

Recently the Outernet team released a new build of ‘Skylark’ for their Dreamcatcher board. Skylark is their customized Outernet signal specific operating system that was available on the C.H.I.P. Skylark is essentially turnkey as it is much easier to setup and use. Just burn the image to an SDcard, insert the card, connect to the automatically generated Outernet WiFi hotspot on a PC or mobile device, and then browse to outernet.is to see the Skylark interface.

Unfortunately it is unclear how long some of the high bandwidth features such as the nice weather app may last. The Outernet Inmarsat L-band signal runs at a bandwidth of almost 20mB a day and appears to cost quite a bit of money to operate, so Outernet appear to be considering moving to a lower bandwidth signal in the near future. This will probably reduce content to data like text articles (news/APRS/Wikipedia/books) only. But even if it is text only it will still continue to be a very useful and interesting service.

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QIRX SDR Updated: Legacy DAB, DAB Transmitter Identifications and more

Back in May of this year we posted about QIRX SDR, which back then was a brand new multimode SDR program compatible with the RTL-SDR. One of its defining features is that it has a built in DAB+ decoder. Recently QIRX SDR has been updated to version 0.9.1, the new features are quoted below:

General:

  • Updated Documentation
  • Device Frontend: Manual Center Freq. Correction in kHz
  • Waterfall Spectrum
  • Raw Recording: Playback Control, for a timed positioning (“seek”) in “arbitrary” large (GBytes) recorded raw files.

DAB:

  • Legacy DAB, intended for users where DAB+ is not generally available, like in the UK or Spain. As this could only be superficially tested here in Germany (no standard DAB any more, I used some raw samples recorded in Madrid), I would be very interested in feedback of users about it.
  • Synchronization of raw files recorded with central frequency offset
  • Enhanced manual synchronization control, mainly for tests in mobile environments
  • Detection of the Transmitter Identifications (TII). However, as this is a feature only useful for specialized applications, it is not included in the distribution. To my knowledge, qirx is the only DAB SDR having this feature.

Some Bug fixing.

The QIRX team have also added a new Quickstart Guide to help users get set up with their software quickly. In addition QIRX author Clem also writes that the QIRX software will be demonstrated during this weekends Ham-Radio fair in Friedrichshafen, Germany.

QIRX SDR Updated
QIRX SDR Updated
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OpenWebRX Updates: 3D Waterfall and BPSK31 Demodulator

OpenWebRX has recently been updated and now includes a 3D waterfall display and a BPSK31 demodulator. OpenWebRX is a popular program which allows you to stream an SDR like the RTL-SDR over the internet efficiently. A number of clients can connect to your server and tune anywhere within a predefined bandwidth. Many examples of OpenWebRX running on RTL-SDRs and KiwiSDRs can be found on sdr.hu.

The 3D waterfall is quite an interesting feature as it allows you to visual signal strength, frequency and time all at once. BPSK31 is a popular amateur radio digital mode for making QSO’s (contacts). The new decoder allows you to zoom in closely on the band with high resolution and select with the mouse which BPSK31 channel you’d like to decode.

András Retzler, creator of OpenWebRX also writes that he’s now completed his Masters Thesis (congratutions!) on the topic of “Integrating digital demodulators into OpenWebRX”. His thesis is available for download here and looks to be an interesting read.

OpenWebRX BPSK31 Mode
OpenWebRX BPSK31 Mode
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Demonstrating an RTL-SDR Based Metal Detector

Over on YouTube user Ancient Discoveries has uploaded a video showing a prototype of his RTL-SDR based metal detector. The metal detector appears to consist of a coiled detection loop antenna powered by an AM transmitter and an RTL-SDR running in Q-branch direct sampling mode.

Ancient discoveries uses SDR# to tune to a low medium wave frequency of around 898 kHz while in direct sampling mode. Then as a piece of metal is moved closer and further from the detection coil the signals on the spectrum move around in correlation with the metals distance. A whining sound just like a real metal detector is also produced by SDR#.

!!! RTL SDR Metal Detector !!! dancing with signals !!! modified latest project

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Running Windows & x86 SDR Decoding Apps on the Raspberry Pi 3: Unitrunker, WinSTD-C, WXtoIMG, DSDPlus and more

There is a great advantage to running SDR decoder apps on a single board PC like a Raspberry Pi 3. For example instead of committing a whole PC to become a dedicated decoder, a cheap Pi 3 can be used instead. However, unfortunately many decoder apps are written for the x86 CPU architecture and/or Windows, making them impossible to run on ARM and/or primarily Linux devices like the Raspberry Pi 3.

That is unless you use an emulator combination like Eltechs Exagear and Wine. Exagear is an emulator that emulates an x86 environment on a device like a Raspberry Pi 3 which uses an ARM CPU. Wine is a Windows compatibility layer that allows you to run x86 Windows apps on an x86 Linux installation. So by combining Exagear together with Wine it is possible to run Windows apps on ARM Linux devices.

Exagear is not free (although there is a free trial). It currently costs $22.95 USD for a Pi 3 licence, and $16.95 USD for a Pi 2 licence and $11.45 for a Pi 1/Zero licence. They also have versions for Odroid, Cubieboard, BananaPi, Jetson and many other ARMv7 and ARMv8 devices like the super cheap and powerful Orange Pi’s. There are free alternatives out there like QEMU, however when we tested QEMU it was far too slow on the Pi 3 to even run notepad responsively, let alone a decoder. Exagear on the other hand seems to run apps at near native speeds, without much lag at all. So in this respect the price seems to be worth it.

We decided to test the Exagear + Wine combination on a Pi 3 and were successful in running a number of apps including Unitrunker, WinSTD-C, WXtoImg, DSDPlus, PC-HFDL, MultiPSK, Orbitron and Sondemonitor.

Trunking setup with Unitrunker on a Raspberry Pi 3

With Unitrunker we were able to set up a full trunk tracking system using two RTL-SDR dongles, rtl_fm, rtl_udp and a custom script to control rtl_udp.

Unitrunker running on a Raspberry Pi 3
Unitrunker running on a Raspberry Pi 3

In the future we may put up a full double checked tutorial with images, but for now a roughly written tutorial is presented below. The tutorial is fairly involved and assumes decent Linux experience. The tutorial starts from a fresh install of Raspbian.

The basic idea of operation is based around the fact that the RTL-SDR cannot be used directly within Wine (or so it seems). So the control signal audio is routed from rtl_fm running on one dongle into Unitrunker on Wine using alsa loopback. Then we use the old Unitrunker remote.dll method to generate a sdrsharptrunking.log file which is a text file that contains the current frequency that the voice receiver should tune to. A simple shell script continuously reads this file and extracts the frequency, and then commands an instance of rtl_udp running with the second dongle to tune to that frequency.

Continue reading →

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Using a TV Dipole Antenna for NOAA Satellite Reception

Over on YouTube icholakov has uploaded a video showing how effective a simple old TV bunny ears antenna can be at receiving NOAA satellite images. The old TV antenna is telescoping so it can be adjusted to be resonant for many frequencies, and for NOAA satellites about 20 inches makes it resonant. Using the antenna as a V-Dipole and placing it in a North to South direction optimizes the radiation pattern towards the sky, allowing for good reception of the NOAA satellite. Using it this way also helps to null out strong vertically polarized stations. More information on the V-Dipole can be found on our previous post where we posted about Adam 9A4QV’s idea to use the V-Dipole for satellite reception.

2017: TV Antenna vs. NOAA Satellite

Also related to this post is a sneak preview on our new product: We’ve also caught onto the idea that TV antenna dipoles are extremely versatile, and are in the final stages of releasing a simple telescopic dipole product similar to the TV antenna used in this video. It will be released as an antenna set that comes with some portable mounting solutions like a suction cup and bendy tripod, and 3M of RG174 coax so that the antenna can be used anywhere. Target price is $10 -15 USD incl. shipping from China. This will probably also replace the stock telescopic whip antenna currently used in our dongle sets since the telescopic dipole is simply much more versatile.

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Skylark Image for Outernet’s Dreamcatcher RTL-SDR

About two weeks ago we posted our review of the Dreamcatcher, a new RTL-SDR and full ARM based computing platform built onto a single PCB. Back then the only OS available for it was a standard Armbian build, and no Outernet decoder was available. So we reviewed the Dreamcatcher with the Armbian OS and tested to see how well it worked as a general purpose RTL-SDR and computing platform.

Recently the Outernet team released a new build of ‘Skylark’ for their Dreamcatcher board. Skylark is their customized Outernet signal specific operating system that was available on the C.H.I.P. Skylark is essentially turnkey as it is much easier to setup and use. Just burn the image to an SDcard, insert the card, connect to the automatically generated Outernet WiFi hotspot on a PC or mobile device, and then browse to outernet.is to see the Skylark interface.

Unfortunately it is unclear how long some of the high bandwidth features such as the nice weather app may last. The Outernet Inmarsat L-band signal runs at a bandwidth of almost 20mB a day and appears to cost quite a bit of money to operate, so Outernet appear to be considering moving to a lower bandwidth signal in the near future. This will probably reduce content to data like text articles (news/APRS/Wikipedia/books) only. But even if it is text only it will still continue to be a very useful and interesting service.

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SatNOGs No-Rotator Setup

Thank you to Silvia P. for writing in and letting up know about the SatNOGs “No-Rotator” project, which looks a lot easier to build compared to their motorized rotator. SatNOGs is an idea and organisation that is trying to make it easier to set up a low cost networked RF ground stations for monitoring various satellites. The idea is to increase satellite ground station coverage all over the world and collect and share received satellite data over the internet so that anyone in the world can view and make use of up to date satellite data.

An original SatNOGs station is built as a motorized antenna rotator, with directional antennas that point and track satellites as they pass over the ground station location. The gears and most internal plastic parts are 3D printed, with the rest of the items like bearings, frames and motors being available on eBay. The problem is that building the rotator is quite a big project, and takes a lot of research, purchasing and building to get started.

Recently over on their Wiki a new type of non-rotator ground station has appeared. The no-rotator ground station still consists of the basic SatNOGs electronics including an RTL-SDR and Raspberry Pi. But instead of using high gain directional motorized antennas this ground station uses a much simpler turnstile antenna tuned to about 137 MHz. Unlike the rotator, the turnstile probably doesn’t have enough gain to pick up some of the weaker amateur satellites, but should be good enough for NOAA/Meteor weather satellites and ISS APRS etc.

We’ve also recently seen similar no-rotator builds discussed over on their forums and on Twitter.

SatNOGS turnstile no-rotator implementation
SatNOGS turnstile no-rotator implementation
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Listening to and Tracking NXDN/IDAS Trunking Systems with two RTL-SDRs

Over on YouTube user radiosification has uploaded a video tutorial that shows how to decode, follow and listen to NXDN/IDAS trunking radio signals. NXDN/IDAS is a narrowband digital voice protocol commonly used with handheld radio terminals.

In the tutorial radiosification explains how to set up DSDPlus and its frequencies text file to automatically listen to and track conversations using the control channel. SDR# is initially used to find the NXDN control and voice channels, which are then entered into the text file. Using this method only DSDPlus and its corresponding receiver FMP is used. Trunking software like Unitrunker is not needed.

Radiosification also notes that the method he presents can also be used for other digital trunking systems such as P25 as well.

How to track NXDN trunking with RTL SDR & DSDPlus

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