New Raspberry Pi image preloaded with software available for the SDRplay

Over on their forums the SDRplay team have just released a new Raspberry Pi image which comes preloaded with the drivers and a bunch of ready to use software. They write

We have released a Raspberry Pi 3 image that has a number of SDR applications pre-built and tested that support the RSP. Periodically, we will update the image with software updates and new software.

The current list of software included on the image is:

SoapySDR/SoapySDRPlay, SoapyRemote, ADS-B (dump1090), CubicSDR and SDR-J DAB receiver

Please note: This is a complete OS with software image. Writing the image to a micro SD card will wipe the micro SD card of any other data that is on there, so we recommend you make sure you have backed up any data on your existing micro SD card or you use a new micro SD card.


1. Download image. There are two downloads provided, the 7zip version is just a smaller download but not everyone has 7zip which is why we also provide a zip download. The links are here: (2.7 GB) … 0.1.img.7z (2.0 GB)

2. Extract the contents of the compressed file. This will extract to a .img file which will be about 7.2 GB

3. Use an image writer such as Win32DiskImager ( to put the image onto the micro SD card.
WARNING: Please make sure that you use the correct drive letter for the micro SD card. The image writing software will completely remove any data that is on the destination media.

That’s it – put the micro SD card into the Raspberry Pi 3 micro SD card slot and boot the system. Allow the system to fully boot and you will see a GUI that will allow you to run each of the applications or read further information.

We also recommend that you use an active cooling system on your Raspberry Pi 3 to avoid any issues with over heating. In our tests, we have used heatsinks and a fan in a case. The CPU speed will be throttled if the temperature gets too hot, so for optimum use this is really recommended. These cases are available at reasonable prices from many Raspberry Pi stores.

If you are a developer of software that supports the RSP and you would like to be included on the image that we will release periodically, please contact us at [email protected] – currently we’re aiming to update the image every quarter, this will largely depend on software availability and what the demand is.

We are aware of other software that we are looking to get onto the next release such as Pothos and more SDR-J software. We will work with developers on any issues we’ve seen during this process so that we can get them onto future images.

Best regards,

SDRplay Support

Last week we posted about Kevin Loughin’s video where he showed how to get CubicSDR and an SDRplay running on a Raspberry Pi 3. This new ready to go image saves you from needing to perform the install process.

Testing the Outernet Dreamcatcher: Linux Based ARM PC with Built in RTL-SDR

Last week we posted about Outernet’s new Dreamcatcher unit which is an RTL-SDR + L-band LNA + computing board all on the same PCB. The Dreamcatcher comes with a new active ceramic L-band patch antenna, costs $99 USD (plus shipping) and can be bought directly from their store. Outernet were kind enough to send us a review unit, and we’ve been testing it for the past few weeks. This post is a review of the unit.


Outernet is a free data service that uses L-band satellites to beam down information like news, weather updates, Wikipedia articles, books and more.

In the past Outernet have used the $9 USD C.H.I.P computing board, an RTL-SDR dongle and an external LNA as the receiving hardware for their data service. However, popularity of the Outernet service has been severely hindered by the huge supply shortages of the C.H.I.P. Over the past year or so it has been almost impossible to get a hold of a C.H.I.P unit if you did not back the Kickstarter or buy one from Outernet’s first initial stock. By manufacturing their own PCB including the computing hardware, Outernet must be hoping to be able to control their stock situation, and not rely on third parties who may not be able to deliver.

At the moment the Dreamcatcher can only be run on their new Armbian image. The older Skylark image has been removed from their servers presumably because the Outernet signal is going to change in the near future and the old demodulator on Skylark may no longer work. The Armbian image is basically just standard Armbian and at the moment does not actually run any Outernet software, and cannot decode their signal, but this is being worked on. Eventually they hope to replace Skylark with a standard decoding app that runs on Armbian.

In this post we’ll review the Dreamcatcher with Armbian and consider it as a general purpose receiver (not just for Outernet), and we’ll also review the new active ceramic patch antenna as well.

Dreamcatcher Overview

The Dreamcatcher is a single PCB that combines an RTL-SDR, Linux (Armbian) based computing hardware, and an L-band LNA and filter. 

On first impressions we noticed that the PCB is relatively large square at about 12 cm by 12 cm. The most prominent chip is the Allwinner A13 SoC. The RTL-SDR circuitry is positioned in the upper right with the RF sections (R820T and LNA) both covered with RF shielding cans. There is no onboard WiFi circuitry, but a small ‘EDUP’ branded WiFi dongle is included and plugs into one of the USB ports on the PCB.

We measured the Dreamcatcher to be using about 400 mA – 600 mA while idle and 800 mA while utilizing the RTL-SDR and 100% CPU. Heat is not an issue as the Dreamcatcher stays relatively cool during its operation even at 100% CPU with the CPU only getting up to about 45 degrees C.

Continue reading

Testing the HackRF and Portapack with an LNA4ALL

Over on YouTube Adam 9A4QV has been testing out his HackRF and Portapack with his LNA4ALL. The LNA4ALL is able to be powered inline via the bias tee on the HackRF. In the first video Adam shows that the HackRF and LNA4ALL is capable of receiving L-band satellites easily. The antenna he uses is a homemade circularly polarized antenna with a cooking pot being used as the reflector.

In the second video Adam shows the HackRF, Portapack and LNA4ALL receiving a telemetry signal on 442 MHz.

Finally in the last video Adam shows himself making a full QSO contact using the HackRF, Portapack and LNA4ALL. The software he uses on the Portapack is Furtek’s ‘Havoc’ firmware which has microphone to TX functionality. The LNA4ALL is able to work in transmit mode without trouble. Adam has written instructions for modifying the LNA4ALL so that it can transmit and use the HackRF’s bias tee power at the same time over on his website

Forum Talk Videos From Hamvention 2017

During Hamvention 2017 several presenters and myself presented SDR or radio related talks. Some were filmed and put up onto YouTube. Unfortunately the 2017 SDR Forum video seems to be missing, or not yet uploaded yet.

The first set of talks was recorded by Gary KN4AQ at the TAPR Forum. The first talk in the set was from Michael Ossmann and Dominic Spill on “Low Cost, Open Source Spectrum Monitoring”. In this talk they discussed their recent improvements on creating a fast spectrum scanner mode on their HackRF. The second talk was “Advanced SDR Algorithms for Noise Blanking and Noise Reduction” by Warren Pratt NR0V. Here Warren discussed and gave examples of the effectiveness of some new noise blanker and noise reduction algorithms used in openHPSDR. Finally the third talk was “Introduction to RTL-SDR: Ultra cheap software defined radio” by Carl Laufer (myself). This was a brief introduction to the RTL-SDR showing some typical applications that they are used for.

The second set of talks was recorded by the Ham Radio 2.0 YouTube channel at the Digital Modes forum. The first talk was from myself again and was another introduction to cheap SDRs with some slightly different material. The second talk was by Uli with Wireless Holdings who discussed the latest developments in his DV4 digital mode transceiver products. Finally Mel K0PFX gave a talk on the latest developments in the FreeDV digital voice codec.

Finally I was interviewed by Gary KN4AQ of the HamRadioNow podcast and YouTube show and Marty KC1CWF of the PhasingLine podcast about and the V3 dongles.

Just a reminder that slides from all the talks presented by myself are available on this post.

First Renderings of the Airspy HF+ Revealed

Back in February of this year we first heard about the Airspy HF+, which is an upcoming product from the Airspy team that is intended to be a high performance HF receiver at a low price. Over on the Airspy HF+ website the first (rendered) image of the unit has recently been released. We’ve also managed to get some additional renderings from the Airspy team which we show in the image slider below.

The enclosure is CNC carved aluminum with two SMA ports on one side, and a USB port on the rear. Since the HF+ actually has the capability to tune up to 260 MHz it uses two SMA inputs, one for an HF antenna and one for a VHF antenna. Inside the RF circuit is shielded again with a shielding can to protect it from USB noise.

The tweet below also appears to show some grounding improvements made to reduce USB noise.

Other recent tweets from prog (the creator of the Airspy HF+) indicate that the hardware is ready, and show that streaming from with SpyServer from a RPi3 is functional. Hopefully we should be seeing this unit release for sale soon.

Decoding and Listening to HD Radio (NRSC-5) with an RTL-SDR

HD Radio is a high definition terrestrial digital broadcast signal that is only used in North America. It is easily recognized by the two rectangular blocks on either side of a broadcast FM station signal on a spectrum analyzer/waterfall display. Since HD Radio uses a proprietary protocol, finding a way to decode it has been difficult and so this signal has been inaccessible to SDR users for a long time. Back in February of this year we posted about Phil Burrs attempt, where he was able to create a partial implementation (up to layer 2) of the HD Radio standard, but didn’t get far enough to decode any audio in layer 3.

However, now cyber security researcher ‘Theori’ has created a full RTL-SDR based decoder for the HD Radio protocol. In his post Theori explains that the HD Radio system is split into three layers. Layer 1 finds the signals and does decoding and error correction. Layer 2 is a multiplexing layer, which allows various layer 3 applications to share the bandwidth. Layer 3 is the audio data layer. In his post he explains how these layers work in detail. 

One of the main findings was the discovery of the audio compression codec. Theori found that the codec was essentially HE-AAC with some minor modifications. The modifications were minor enough that he was able to adapt the open source FAAD2 library for HD Radio audio decoding.

Theori’s code is open source and available on GitHub. The code includes the patch to modify FAAD2 for HD Radio and it is automatically applied during the build. A sample file for testing the decoder is also provided and we tested the decoder with the sample and it worked well. The decoding can also be performed in real time and examples of that are also on the git readme.

HD Radio Spectrum
HD Radio Spectrum

Precisely Synchronizing Multiple HackRFs

Recently Marco Bartolucci & José A. del Peral-Rosado wrote in and wanted to let us know about their work in creating multiple precisely synchronized HackRF’s. They plan to use the synchronized HackRFs for solving at a low cost some interesting navigation problems which are described in detail in their academic paper (IEEE link). The abstract of the paper reads:

This paper describes a new method for the synchronisation of multiple low-cost open source software-defined radios (SDR). This solution enables the use of low-cost SDRs in interesting navigation applications, such as hybrid positioning algorithms, interference localisation, and cooperative positioning among others. Time synchronisation is achieved thanks to a time pulse that can be generated either by one of the SDRs or by an external source, such as a GNSS receiver providing 1PPS signal. Experimental results show that the proposed method effectively reduces the synchronisation offset between multiple SDRs, to less than one sampling period.

In simple terms, hybrid positioning is the process of using multiple signals such as WiFi, Bluetooth and cell phone signals etc together to get an accurate position of the receiver. By using several sources localization accuracy can be improved, but to do this each receiver much be precisely synchronized to the same clock source.

The system they created uses a 1PPS GNSS based time source connected to the SYNC_IN inputs on both HackRFs. The synchronization code is run in hardware on the HackRF’s onboard CPLD (complex programmable logic device). Furthermore they also write the following regarding the system and code which has been adopted into the HackRF repository:

A new time synchronization feature has been recently adopted in the HackRF official repository thanks to the collaboration between SPCOMNAV group, Università di Bologna, and the European Space Agency (ESA).

This contribution allows any user to precisely synchronize multiple HackRF devices below 50 ns, by means of a minor hardware modification and the firmware update. 

More information about the driver updates and instructions for use can be found in this Git pull request. The team also write that their work was presented at the NAVITEC 2016 conference.

HackRF Synchronization with a 1PPS GNSS Reference.
HackRF Synchronization with a 1PPS GNSS Reference.

PagerMon: A browser based app for displaying pager messages from multimon-ng

Thank you to Dave for submitting information about his new pager message display software called PagerMon. PagerMon is a web browser based tool for displaying POCSAG pager messages decoded by multimon-ng. It is based around nodejs and uses a sqlite database for storing the messages. Multimon-ng is an RTL-SDR compatible digital mode decoder which can decode multiple protocols including POCSAG pagers.

PagerMon and the features and future features are listed below:

PagerMon is an API driven client/server framework for parsing and displaying pager messages from multimon-ng.

It is built around POCSAG messages, but should easily support other message types as required.

The UI is built around a Node/Express/Angular/Bootstrap stack, while the client scripts are Node scripts that receive piped input.


  • Capcode aliasing with colors and FontAwesome icons
  • API driven extensible architecture
  • Single user, multiple API keys
  • SQLite database backing
  • Configurable via UI
  • Pagination and searching
  • Filtering by capcode or agency
  • Duplicate message filtering
  • Keyword highlighting
  • WebSockets support – messages are delivered to clients in near realtime
  • Pretty HTML5
  • May or may not contain cute puppies

Planned Features

  • Multi-user support
  • Other database support (MongoDB and DynamoDB planned)
  • Horizontal scaling
  • Enhanced message filtering
  • Bootstrap 4 + Angular 2 support
  • Enhanced alias control
  • Graphing
  • Push notifications
  • Non-sucky documentation

The GitHub readme has a getting started section which shows how to set up the server and get it running on your local machine.

PagerMon displaying POCSAG messages
PagerMon displaying POCSAG messages