Technical Details on an SDR Supercluster with Eight HackRFs

A few weeks ago we posted about Reddit member u/OlegKutkov who used his HackRF supercluster to receive Starlink beacons, but details on the HackRF supercluster project itself were a little sparse. Now Oleg has posted a full description about the HackRF supercluster, noting that the 8 HackRF's in the system can provide up to 160 MHz of live monitoring bandwidth.

Oleg shows how each of the boards are connected to the same GPS disciplined 10 MHz clock source, how it uses an RF splitter with LNA and how it requires 8 separate host controllers connected to individual PCIe lines in his computer system to overcome the USB2.0 data bandwidth limits. He also shows the GNU Radio script he's created that combines the 8 sources into one.

Oleg writes how he's using the HackRF supercluster together with a TV Ku-Band LNB and satellite dish for wideband satellite monitoring.

HackRF Supercluster Block Diagram
The HackRF Supercluster

Multichannel ALE and GMDSS Decoding with Black Cat Systems Software

Black Cat Systems have recently released two new programs that may be of interest to HF monitoring enthusiasts. The first is a multichannel capable ALE decoder and the second is a multichannel GMDSS-DSC decoder. Both programs are not free, with an (introductory) price tag of $29.99 each for three parallel input channels, and $99 for up to 24 parallel input channels.

With an appropriate HF capable SDR, like a SDRplay, Airspy HF+ Discovery, or even an RTL-SDR V3 in direct sampling mode, these programs allow you to set up a home monitoring station. 

ALE or Automatic Link Establishment is a digital RF protocol that enables users to initiate a reliable call over HF frequencies, by automatically choosing the best frequency based on propagation conditions, allowing for telephone like calling operation, and enabling short text messages.

GMDSS or Global Maritime Distress and Safety System is a set of radio protocols that enables digital text communications between ship to ship and the shore, as well as weather broadcasts, and distress beacons. 

Over on his blog Nils Schiffhauer (DK8OK) has been testing these two programs out. In his first post about the ALE decoder, Nils explains ALE in more depth, and demonstrates how he uses the multi-channel capable SDR-Console with Virtual Audio Cable to feed 16 ALE channels into the decoder. He goes on to show how to filter by callsign and provides some tips for best reception. He notes that with ALE you might receive messages from:

... forces, diplomatic services, emergency agencies, police, militia, UN missions, drug enforcement, border control and even amateur radio. It is used from aircraft like AWACS, as from aircraft carriers, from mobile units to fixed stations. 

In his second post Nils tests out the GMDSS decoder noting that it is an "extraordinary sensitive decoder" and "it also includes smart processing of the data – from looking up vessel’s complete data from ITU’s Ship Station List (internet connection needed) to saving all data to a fully-fledged database". His post goes on to explain the GMDSS format in more detail and demonstrate multichannel decoding.

Black Cat Systems ALE and GMDSS Decoders demonstrated by Nils Schiffhauer (DK8OK)

Receiving Starlink Beacons with an RTL-SDR and LNB

Derek OK9SGC has recently posted a write-up of how they’ve been able to receive the Ku-band beacon signals from the Starlink constellation of communication satellites continually launched by SpaceX since 2015. While we recently covered Starlink Beacons being captured with a HackRF Supercluster Derek has noted that receiving the beacons requires little more than an LNB, a low-cost SDR such as the RTL-SDR V3 and a power injector to provide 12V DC to the LNB. Derek notes that a dish is not even required as the beacons transmit with high power.

Starlink Beacon Receiver Setup

Due to the low earth orbit and thus high speed of travel of the Starlink constellation you’ll notice strong Doppler effect drifts in your received signal. Derek notes that it may be interesting to perform Doppler analysis on the satellites with the satellite tracking toolkit for radio observations (strf) software. He also noted that in the 30 minutes he was receiving for, there was almost no point in time where a beacon was not being received, indicating that the Starlink constellation is close to achieving 100% sky coverage. 

Derek has made the process easy to understand and illustrates just how easy it is to listen to these beacon signals. Of course we note that these are just the beacons, and they carry no data. Still they are fun signal to receive, and doppler analysis could reveal interesting information about orbits. 

Starlink beacons shown in a fast FFT (LEFT), and slow FFT (RIGHT)

TechMinds: Testing Off-Grid LoRa Radio Mesh Text Messaging with Meshtastic

Low cost ESP32 based LoRa capable boards have been available from marketplaces like Aliexpress for some time now. They typically include features such as LoRa, WiFi or Bluetooth and GPS all on a PCB board with small screen and battery holder for mobile use. LoRa is a modern IoT communications protocol that is designed to be operated with low power, and in a networked mesh-way for extended range. One application of this hardware is to use it as a mesh based text messaging system, using the Meshtastic firmware. This might be useful for teams of hikers, pilots, or skiiers who operate in remote areas without cell phone reception.

In his latest video Matthew from the Tech Minds YouTube channel shows how to install and use the Meshtastic firmware on a TTGO board. He uses the alpha firmware which has a web app, allowing users to send text messages through a web based GUI that users can connect to locally via WiFi.

OFF-GRID LORA Radio Mesh Text Messaging - Meshtastic

SignalsEverywhere: Spectrum Analyzer and Tracking Generator with Pluto SDR

In the latest video on the Signals Everywhere YouTube channel, Sarah investigates how a PlutoSDR can be used as a Spectrum Analyzer with the SATSAGEN software. The SATSAGEN software is able to work as a spectrum analyzer by rapidly sweeping over multiple frequencies and stitching the spectrum slices together. It support SDRs like the HackRF, PlutoSDR and RTL-SDR (in receive mode only). The PlutoSDR can transmit, so it is able to work as a full spectrum analyzer with tracking generator, allowing users to measure RF devices such as filters, tune antennas, and work as a frequency generator.

In the video Sarah demonstrates how to use the PlutoSDR and SATSAGEN to measure our RTL-SDR Blog Broadcast FM filter, and to tune our multipurpose dipole antenna.

Spectrum Analyzer and Tracking Generator with Pluto SDR

KrakenSDR Crowd Funding Campaign Ends Fully Funded

Thank you to everyone who has backed or been following our KrakenSDR project on Crowd Supply. The initial funding campaign has now concluded with almost 5x our minimum funding goal! If you missed out, please don't worry as the product is will still be available for sale on Crowd Supply at the campaign price, but later orders may receive units from the second batch produced a few months after the first.

Thanks to the successful funding campaign we now have all the required parts on order and we expect the factory to receive them in a few weeks time. The final confirmation prototype is in production now, finishing touches to the enclosure are being worked on, a QC process is being developed and EU compliance certification and logistics details are being worked through.

At the same time work on on the DFing software is continuing to progress as well. If you are testing the software with the older KerberosSDR units, please note that the software is still in beta and that a thorough reading of the documentation is required to understand the DAQ control parameters. As direction finding with an SDR can involve learning a lot of new technical information, we are aiming to significantly simply the knowledge that is needed to understand the DAQ parameters, and hope to have a simplified version released with a tutorial by mid-December. So if you have a Kerberos, and are struggling with the setup, please kindly wait until the official release, unless you are interested in learning the nitty gritty technical details.

Recently we have also been working on improvements to the intermittent signal squelch handling and we are also working on multichannel DFing capabilities. We have a new developer starting work on a multiplatform networked mapping program too.

We are also looking to sponsor some accelerator projects such an GNU Radio integration and beam forming investigations for applications like radio astronomy. If you have DSP programming skills, and you're interested in helping on this, or have the DSP skills and interest in developing another project, please email us at [email protected] with details.

The KrakenSDR
KrakenSDR Latest Prototype Enclosure

Black Friday Sales on Airspy and SDRplay Products

Black Friday is upon us again. This year we were not expecting any major sales as the component supply chain crisis has meant that many electronic products, including SDRs are very low in stock. However, there are two great sales that we have found:


Airspy is holding a 25% off sale for this years Black Friday event. Discounts should track across most of their distributors and their main direct sales platform on iTead. On our own store we resell the YouLoop and have also discounted it there, however stock may be backordered by a few days (discount only available via direct sales, or via Aliexpress).

Airspy HF+ Discovery: $169 $126.75
Airspy Mini: $99 $74.25
Airspy R2: $169 $126.75
SpyVerter: $49 $36.75
YouLoop: $34.95 $26.21

Airspy are also holding a #Freebie promo via Twitter.

Airspy Sale Banner


Direct sales from the SDRplay website appear to have no discount and the RSP1A is backordered until Jan.Feb, but Ham Radio Outlet are holding a site-wide sale including their SDRplay stock.

SDRplay RSP1A: $119.95 $99.95
SDRplay RSPdx: $239.95 $199.95
SDRplay DUO: $279.95 $239.95

Did you find any other great Black Friday sales? Please let us know in the comments. Unfortunately this year due to low stock we will not be holding our own sale for our products, but over the next year as the situation hopefully improves we hope to drop prices naturally.

CaribouLite Crowd Funding Launched: A $119 30-6000 MHz 13-bit 2.5 MHz Bandwidth TX/RX SDR Hat for the Raspberry Pi

Back in June of this year we first posted about the upcoming CaribouLite product which is a software defined radio HAT for the Raspberry Pi. The project has just launched on Crowd Supply with a price tag of $119 for the CaribouLite, and $69 for a CaribouLite ISM only band version. The product is expected to ship in May 2022. CaribouLabs write:

CaribouLite is an affordable, open-source, dual-channel software-defined radio (SDR) platform—and an SDR-focused FPGA development framework—implemented as a Raspberry Pi (RPi) HAT. CaribouLite turns your Raspberry Pi single-board computer (SBC) into a self-contained, dual-channel radio Tx/Rx that spans a wide tunable frequency spectrum up to 6 GHz.

The CaribouLite RPi HAT

The CaribouLite is entirely open source and designed for makers, hackers, educators, and researchers. It comes in two versions, the full and ISM band only versions. For most people the full version will be most desirable as it covers the full 30 MHz - 6 GHz range. However, certain projects may want to make use of the ISM band only version as they note that it may easier to obtain regulation compliance.

The full version comes with two TX/RX half-duplex channels, with channel one covering 30 MHz to 6 GHz, and channel two covering sub 1 GHz only. Both channels use a 13-bit ADC, capable of a bandwidth of up to 2.5 MHz maximum. The unit is capable of up to 14 dBm of transmit power.

The libcariboulite drivers support Soapy API, meaning that many SDR programs including SDR++, GQRX, CubicSDR and GNU Radio will be able to support the CaribouLite. 

One interesting design feature is that the CaribouLite does not interface with the Raspberry Pi via USB or Ethernet which is how most SDRs interface. Instead they make use of the SMI (Secondary Memory Interface) connector, which is a high bandwidth interface available on Raspberry Pi's. This is a very fast interface allowing the IQ samples to stream back and forth, however the disadvantage is that the CaribouLite will only work on Raspberry Pi devices. Although it should be possible to use the Raspberry Pi as a host device if you wanted to use the SDR on a PC.

One problem is that we note that most Raspberry Pi resellers are out of stock and the component supply crisis appears to have slowed Raspberry Pi production. So this may be an issue for purchasers who do not already have their own Raspberry Pi. However, given that the CaribouLite ships in May 2022, there may still be time to obtain a Pi.

Given the low cost, specs and features, this appears to be quite an interesting SDR that we are excited to get our hands on. Combined with a Raspberry Pi Zero we can imagine multiple portable use cases and projects that will come from this product.