Frugal Radio: Decoding Fire, Ambulance MDT and Hospital Pagers with SDR++ and PDW

On this weeks Frugal Radio YouTube video, Rob explores how to decode Fire, Ambulance and Hospital pager data using SDR++ and PDW. In the video Rob first explains what applications pagers are used for in 2021 and how they're typically received with pager or MDT hardware terminals mounted in fire and ambulance trucks.

He then goes on to show how we can receive and decode these pager messages using an RTL-SDR, SDR++, VB-Cable and the PDW pager decoder. The tutorial shows how to set up SDR++ settings for pager reception, how to install and setup PDW and how to interface the two programs with VB-Cable. Finally Rob explains how to fully understand some of the messages that you might receive.

Decoding Fire & Ambulance MDT data & hospital pages with a $10 SDR Radio

KrakenSDR Update: New Prototypes, Software Updates, Campaign to Release Soon

KrakenSDR is our 5-tuner coherent software defined radio based on RTL-SDR. It is the successor to the KerberosSDR and will be crowdfunded on Crowd Supply with the campaign due to begin soon. Please sign up to the KrakenSDR Crowd Supply mailing list to be notified as soon as the campaign begins, and to check out our previous videos demonstrating the unit in action.

With a 5-channel phase coherent RTL-SDR interesting applications like radio direction finding (RDF), passive radar and beam forming become possible. It can also be used as five separate RTL-SDRs for multichannel monitoring.

KrakenSDR Updates

Like many other projects we have been severely delayed by COVID work restrictions and the effects it's having on the supply chain, and I'd like to thank everyone who is keen to get a hold of a KrakenSDR for their patience. But the ball is rolling faster now and we have finally received our latest KrakenSDR prototypes! Testing has been ongoing for the last few days, and apart from a few minor issues everything is working brilliantly. At this stage we are confident in the design and are making plans to begin the crowdfunding campaign soon.

The latest KrakenSDR Prototype PCB running on a Pi 4.

Supply Chain Constraints

The first batch will unfortunately be limited to 1000 units maximum due to supply constraints and we expect this first batch to be ready 2-3 months after the campaign finishes. So if you are after a unit ASAP, please ensure you are on the CrowdSupply mailing list as we fully expect demand for the first batch to outstrip the supply.

But if you are willing to wait, batch 2 will be still be available at the campaign special price. we will have a second batch available for early preorder at a discount (sorry due to higher than expected shipping and skyrocketing component prices we can't discount the second batch at the moment). Please keep in mind that the second batch will be at least 6 months away due to the long supply chain resulting from the pandemic.

Next Steps

The next stages in hardware development will involve finalizing our custom milled aluminum enclosure, testing one last prototype, and beginning mass manufacturing when the crowd funding campaign is over.

Work on the software is ongoing, but the beta version of our new DAQ firmware and direction finding DSP software layer is stable and already available on the krakensdr GitHub at Everything resides in the development branches and there is full documentation on the code structure available in the Documentation folder. This code can also be used on the KerberosSDR by editing the configuration files to specify 4 receivers instead of 5.

By the time the units ship out we will have a ready to use SD card image for the Raspberry Pi 4 and a quickstart guide available.

KrakenSDR DAQ and DOA DSP Web Interface

Android App

We have also been working at improving the Android direction finding companion app. This app was made during the KerberosSDR release a couple of years ago, and is used to plot and log the direction finding bearings being generated by the Kerberos/KrakenSDR unit, combining it against the GPS and movement data generated by the Android phone. This Android phone + KrakenSDR combination results in a powerful multipath resistant radio direction finding tool, and once enough data has been collected (usually after a few minutes of driving) it is able to determine where the most likely transmitter location is.

The upgraded app makes use of the full 360 degrees of direction of arrival and multipath data that is generated by the KrakenSDR, resulting in a more accurate determination of the transmitter location, and a better understanding of the uncertainties. It also allows users to visualize multipath. There are also various bug fixes and improvements made overall. We are planning to transition this app into a paid app, but all KrakenSDR backers will receive a license for free and the older KerberosSDR app will remain free.

KrakenSDR Android App Improvements

KrakenSDR Antennas

To work as a radio direction finder, KrakenSDR needs five antennas. If you plan to use them in a circular array, they need to be omnidirectional antennas such as whips or dipoles. So to go along with the KrakenSDR we will be selling an optional set of five magnetic whip antennas which can be mounted on for example, the roof of a car. (Please note the magwhips shown in the photo may differ slightly from the final ones sold).

KrakenSDR Magnetic Whips on a Car Roof

We have also been working with Arrow Antennas in the USA, who are producing a KrakenSDR 5-element dipole array antenna which is great for use in fixed sites (for example on the roof of a house). The antenna will be sold by Arrow antennas (not by us), and the future link (not active yet) will be We expect them to generate this page within the next few days. This antenna has been used in all our fixed site experiments as you can see in some of the YouTube videos, and works very well. (The image below show a prototype, we're told the final version may look slightly different.)

Arrow Antenna 5-element antenna array for the KrakenSDR

Future Work

DAQ & Direction of Arrival (DOA / Radio Direction Finding) :
Work on the DAQ and DSP software is coming along well and this is mostly complete and runs stable on a Raspberry Pi 4. There are just now bug fixes and minor features being added. Intermittent 'bursty' signal handing is already working, but we are working on improving it's sensitivity to weak bursty narrowband CW signals which can still be problematic to detect. The Android app is also currently being field tested.

Passive Radar:
Work on new passive radar software is also ongoing and we expect to have something ready for experimentation and with quickstart guides before shipping. At the moment it is also still possible to use the older KerberosSDR software for passive radar, but we believe the new DAQ core software will run things much smoother. The goal for the new software is to not only plot a range-doppler map, but to combine it with direction finding and be able to plot radar detections on a map. This feature may require operation on a device faster than the Raspberry Pi 4, such as GPU based device like a NVIDIA Jetson.

Beam Forming, Interferometry:
One application we think the KrakenSDR would be great with is amateur radio astronomy via interferometry. The ability to combine multiple small hydrogen line dishes spread out over several meters of area should result in much greater radio imaging resolution, without needing to deal with a single huge dish. It may also allow for electrically steering a beam without needing to rotate the dishes.

Advanced Direction Finding + Advanced Log Management:
At the moment networked direction finding (direction finding via multiple fixed or mobile sites spread out around a city or area) is possible via the third party RDF Mapper software, but we aim to create our own advanced platform in the near future. The goal is to have software that will automatically log and alert when a signal of interest appears. For some examples we can see this being used to help coastguard locate distressed marine pleasurecraft that typically do not have AIS via their VHF radios, locate emergency beacons, for animal/wildlife/asset tracking, and monitoring for illegal/interference transmissions.

At this stage the core DAQ+DSP software will also be updated to support monitoring multiple simultaneous channels within the available 2.56 MHz bandwidth, and with a scanning and beacon ID detection feature.

Research into field applications:
One example we hope to test is the operation of KrakenSDR on a drone. With great line of sight from up in the sky, localizing a transmitter should be fast. Another example could be actually visualizing signals like light via augmented reality.

Some of our previous KerberosSDR and KrakenSDR posts might also be of interest.

TechMinds: Testing SDR++ The Bloat Free SDR Software

Over on YouTube TechMinds has recently released a video where he overview SDR++, dubbed as the "bloat free SDR software". We've been following the development of SDR++ for a while, and recently posted about the release of version V1.0.0. SDR++ is an open source, cross platform, C++ based GUI general receiver program for various SDRs including the RTL-SDR. In another recent post we also saw a video review from Sarah at SignalsEverywhere.

The the video TechMinds gives an overview of the SDR++ features and GUI, and also shows DSD+ and WSJT-X running together with it. He notes that SDR++ lives up to it's expectations and lives up to it's bloat free tagline.

SDR++ Multi Platform SDR Application

SDR Talks from the SDRMakerspace Online Presentation

Thank you to Robert for letting us know about these videos from the "ESA ARTES SDR MakerSpace Presentations" from September 6-8, 2021 which are now available on YouTube. 

Libre Space Foundation ( Greece) and the Institute of Reconfigurable & Embedded Digital Systems(REDS) of the Haute Ecole d’Ingénierie et de Gestion du Canton de Vaud – HEIG-VD (Switzerland) have been implementing a number of smaller projects as part of an Software Defined Radio MakerSpace of the European Space Agency.

This activity is part of the ARTES programme of ESA that supports innovation in satellite communications.

The findings were presented in three 2-hour slots in the afternoon at 15:00 CEST (for which you are requested to register separately) on Mon 6, Tue 7 and Wed 8 September 2021.

  • Monday 6 Sep was focused on the evaluation of various SDR boards and FPGA tools chains. High-rate direct sampling by SDR’s and SDR on Android will also be presented.
  • Tuesday 7 Sep was dedicated to building blocks that have been implemented as open source developments for Gnuradio, such as gr-leo, gr-ccsds, gr-soapy etc.
  • Wednesday 8 Sep was mainly about the combination of SDR and AI/ML to do signal detection and classification. In addition, an SDR testbed and spectrum monitoring will be presented.

The talks cover various SDR topics related to satellite observing. Some talks we were interested in are highlighted below, but the full list can be found on the SDRMakerspace website, or the SDRMakerspace playlist on the Libre Space Foundation YouTube channel.

SDRMakerspace - SDR on mobile

TAPR/ARRL DCC 2021 Talks Available on YouTube

The TAPR/ARRL Digital Communications Conference (DCC) was held virtually during September 17 - 18 2021 and the live streamed talks are now available on YouTube. DCC is a yearly conference with many SDR and RF related talks, with a focus on ham radio science.

The talks include various updates on the development of the TangerineSDR (an SDR designed for citizen science experimentation), talks on the development of a magnetometer board for citizen science, as various other talks regarding ham radio and ham radio science experiments.

The two days of talks are all lumped into the two videos below, and a list of all the talks presented can be found on the TAPR schedule website.

TAPR DCC 2021 Friday session

TAPR DCC 2021 Saturday session


Comparing the Malahit DSP-2 Russian Original vs Chinese Clone

Over on the blog guest poster Dan Robinson has posted an article comparing  the Russian made original "Malahit" DSP-2 (~$200) vs the Chinese clone who have upped the version number to DSP-3, but will be referred to as the "HFDY V3" (~$180). The original Malahit DSP-2 from "Malahiteam" is a portable SDR with built in speaker and touchscreen. It has a frequency range spanning between 50 kHz to 50 MHz, 50 MHz to 250 MHz and 400 MHz to 2 GHz.

There are several clones out there, but Dan notes that the Chinese "HFDY V3" version appears to be superior in terms of build quality with its high quality metal construction, high quality knobs, two antenna jacks for AM and FM, good internal shielding, and front firing speaker with beautiful gold grill. These are all improvements over the Russian made version, however it's important to note that the Chinese clone version comes with older firmware that must be carefully updated first, in order to obtain the same features as the original DSP-2.

Overall in terms of performance, after the firmware upgrade, Dan finds no difference in performance between the two. Dan goes on to mention that both the clone and original suffer from grounding problems and sensitivity to touch especially with shortwave. 

Finally he notes how Malahiteam are planning a new higher end more expensive product which will include an optional add-on for enabling reception up to 6 GHz. The estimated cost of the new version will be $480 with the 6 GHz add-on, and $42o without.

The HFDY Malahit DSP SDR V3 (Chinese Clone)

SDRUno 1.41 Released: Scheduler and ADS-B Plugins Added

Last week SDRplay released version 1.41 of their SDRUno software platform. SDRuno is the official software for the SDRplay line of low cost software defined radio devices. The main new feature is the addition of the scheduler facility which allows users to easily schedule recordings. This is great if for example you wish to automatically record a shortwave programs playing overnight.

SDRuno V1.41 was fully released today. It includes the much requested full scheduler facility which allows you to set up numerous recording events for your RSP. As well as providing all the expected calendar options (time of day, date, start and stop times, repeating options and so on), you can also set the ‘profile’ for each recording – this allows you to pre-set frequencies, bandwidths, demodulator options (AM/FM/USB/LSB etc.), choice of filters and antenna port selection. Additionally you can choose the settings for connectivity to other third party software or the running of a specific plugin.

Introduction to SDRuno 1 41 - Scheduler & Profiles (VID597)

The new version also includes a finalized version of their ADS-B aircraft tracking plugin. Last month TechMinds tested the ADS-B plugin beta, noting that it worked well, but there were bugs with the built in mapping feature. In the official tutorial video the ADS-B plugin is demonstrated and shows that the mapping problem is fixed.

SDRuno ADSB Plugin (VID599)

Is the Titus II Portable Android Tablet Shortwave SDR Close to Release?

The PatronX Titus II SDR is something we've been posting about several times since 2016, but in the end it was never released and assumed to be vaporware. However, we found that the website for the Titus II SDR was updated only a few weeks ago, and pricing details have been added advertising $120 and $150 for two versions of the product. But on the new website there is no store, just an email link to contact sales for ordering information. We contacted that email two weeks ago for more information but have not received a reply back yet.

The PantronX Titus II was advertised to be a portable Android tablet based SDR that would feature a 100 kHz - 2 GHz tuning range, and software that focuses on HF digital DRM decoding, as well as DAB on VHF. Computer rendered images show the tablet housed in a portable carry enclosure with two speakers. Their new website writes:

The design of rTablet / rTab defined radio receiver started in 2014. It soon became evident that electronic products available on the market could not be modified to incorporate the advanced features requested by potential buyers. This initiated the process of the innovative design of the Titus SDR (Software Defined Radio) unit. The engineering team started with a general purpose computer unit and embedding it in a broadband radio receiver module.

All types of applications, including RF software, could be installed. For example, DRM capabilities could be added as DRM is an open source. Dream Linux app was converted to run under Android mobile operating system.

The Titus rTablet / rTab being introduced to the market, is a low cost, high performance platform with many RF and PC factory installed applications.

Key feature of rTablet / rTab is the compatibility with analog (SW, AM, FM) and digital standards (DRM, DRM+, DAB, DAB+, HD). Consequently the market of rTablet / rTab is global.

The updated website with pricing and an ordering email makes us think that it might be finally on the way, but the lack of email reply is concerning. If anyone has any further information about the rTab/Titus II please be sure to share with us in the comments!

Titus II SDR updated website
Titus II Specs