Back in June and January, we posted about QuadRF and ScaleRF (previously known as open.space) and their mission to unlock affordable open-source Earth-Moon-Earth (EME) bounce communications for the amateur radio public.
Their core product, QuadRF, is a 4-element coherent antenna tile with built-in SDR and processing on a Raspberry Pi 5. Apart from being able to be chained together to make a massive coherent beam-steering antenna capable of working with EME, a single tile can also be used for C-band (4.9–6.0 GHz) direction finding and spatial signal visualization. QuadRF can also transmit, enabling point-to-point communication and the creation of mesh networks.
Recently, their product was launched on the CrowdSupply crowdfunding platform, and it has already far exceeded their $100,000 funding goal. The QuadRF kit is priced at $499 and includes the required Raspberry Pi 5, a tripod, a 32GB microSD card, and a power supply. The QuadRF Mobile expansion pack costs $149 and lets you take the QuadRF on the go. They are also selling a QuadRF six-pack for $594, although as this is designed for research, it does not include the enclosure, antennas, Pi 5, or phased-array structure.
QuadRF - A 4x4 MIMO SDR tile for spatial RF vision & beamforming that scales as a phased array
Back in January, we posted about open.space and their mission to unlock affordable open source earth-moon-earth (EME) bounce communications for the amateur radio public. Recently, we've seen that the project has been renamed to ScaleRF, with the EME system renamed to MoonRF, and the invisual tile renamed to QuadRF. They've also put out a new update post with a lot of interesting information and demonstrations. In the latest update, they also announced that the QuadRF 4-element tile will soon come to Crowd Supply for crowdfunding.
MoonRF is a software-defined radio-based tiling system that enables users to easily create large phased arrays by combining multiple smaller 'QuadRF' tiles consisting of four tile elements, a custom SDR, and a built-in Raspberry Pi 5. Although the ultimate goal is to produce a large system capable of working EME bounce communications, they show that a single QuadRF tile has considerable utility on its own.
An interesting application they show is the ability to visualize and track RF signals using a single QuadRF and their augmented-reality smartphone app. QuadRF appears to be limited to the C-band (4.9–6.0 GHz), but many modern devices, such as smartphones and drones, operate at these frequencies, and in the video, they are able to track these devices with perfect accuracy.
They also show that QuadRF has built-in web browser access to various programs, including a wireless camera decoder for drones.
Thank you to Gary Schneider from workingwithwildlife.org for writing in and submitting news about the release of his Android App called "SDR Direction Finder (RTL-SDR)" which currently costs US$9.99. Gary is a wildlife conservationist who has been using RTL-SDRs and his Android app to track animal beacons in the wild. Gary writes his story best:
I run a conservation project in South Africa conducting wildlife monitoring, and I’ve spent the past 7 years out in the field tracking wildlife. To make tracking more practical and affordable for researchers and NGOs, I’ve spent much of my time outside of fieldwork developing an Android app to replace traditional receivers, and I’ve recently published it on the Google Play Store.
While other apps exist, I’ve found them practically too difficult to use in field conditions and very limited in range. My focus was maximizing VHF range while keeping the interface simple.
By using the app’s custom IQ filter settings with an RTL-SDR V3 and LNA combo, my old spare Xiaomi phone now outperforms my $1,200 Comm Spec R-5000 receiver. The most challenging part of development was optimising the high-resolution waterfall to run smoothly at a high sample rate without any stuttering on low-end devices.
I added a built-in mapping feature to log bearings and automatically calculate estimated signal locations. The map also allows users to import their own custom KML/KMZ files. This has been incredibly helpful for me to quickly locate my tracked animals, and to subsequently export my data for further analysis. The waterfall makes it easy to handle signal drift or monitor multiple collars simultaneously (e.g. when I’m searching for a pack of African wild dogs which might have two or three working VHF collars fitted).
While wildlife tracking here is exclusively CW in the 148–152 MHz range, the app isn't limited to this. It also supports AM, NFM, WFM (Mono/Stereo), LSB, and USB across the full range.
Even though I developed this with wildlife tracking in mind, it should work equally well for falconry, fox hunting, or simply for general SDR enthusiasts.
Back in June 2025, we posted about SDR ProTrack, a radio direction-finding app that uses an RTL-SDR and directional antenna to determine a bearing towards a transmitter. Alex has recently written in to note some major updates to the app.
He notes that the app has been redesigned for user-friendliness and to be as relevant as possible for signal-tracking purposes. The main upgrades include:
New hardware compatibility: SDR Lime Mini & Airspy now supported.
Enhanced signal & pulse detection
New track states, UI and in-app guidance
Now available in 14 languages
Hunt sharing on social media with pictures and map included
Thank you to Janble for writing in and sharing with us their new software called "RDF-J / ECM-J SYSTEM". These are two distinct programs in a package.
The software is not open source, and it appears that Janble wishes to sell the software to interested parties. Currently, they do not have a website, and they wish to refer interested parties to their X post for more information on pricing and how to obtain the software. As with any closed-source software, we can only recommend that interested parties do their own due diligence on the safety of the software.
RDF-J is a Time Difference of Arrival (TDoA) and signal strength-based radio direction finding program, which utilizes multiple HackRF software-defined radios spread out over an area. Janble writes that the radio direction finding system can operate using either TDoA and signal strength methods independently or together, with a minimum of three nodes being required, and ideally five.
We clarified with Janble that the TDoA system uses a GPS synchronization approach to achieve the required timing accuracy.
The second program, part of the same package, is ECM-J, which is an electronic countermeasure system. It appears to use a HackRF to transmit a jamming signal. Obviously, jamming is illegal in most countries, so this is to be used at your own risk.
Janble has sent us a PDF showing the software in more detail, and they have uploaded a YouTube video, shown below.
Over on YouTube, we've seen a talk by Mark Jessop that may be interesting to some readers, as it covers Amateur Radio Direction Finding / Fox Hunting with the KrakenSDR, as well as various other radio tools. If you are unaware, KrakenSDR is our 5-channel coherent RTL-SDR based software defined radio system, designed for coherent applications like radio direction finding.
In the talk, Mark explains the amateur radio fox hunting sport, which involves the organizer hiding a transmitter somewhere in a defined area and having participants search for it using just its radio emissions. He goes on to show the different types of antennas, radio systems and vehicle setups participants used.
Mark further explains that on his particular vehicle, he uses a KrakenSDR as the primary receive system. He explains how the KrakenSDR works, how he integrated it into this vehicle and the custom software and LED display that he is using with it.
ARDF at Mt Gambier - by Mark VK5QI and Grant VK5GR - AREG September 2025 Presentation
Thank you to Alexandre Gellibert for writing in and sharing his new Android App, "SDR ProTrack." SDR ProTrack is a radio direction-finding app that uses an RTL-SDR and directional antenna to determine a bearing towards a transmitter.
Interestingly, Alexandre notes that this app was initially developed to track Asian hornets, a bee-killing pest. With hornet tracking, a miniature RF transmitter is attached to a caught hornet, and the hornet brings it back to the nest. RF tracking techniques can then be used to find the nest.
It's possible to determine the bearing toward a transmitter by using a receiver such as an RTL-SDR paired with a directional antenna like a Yagi. Directional antennas have high sensitivity in one primary direction and significantly lower sensitivity in all others. By rotating the antenna until the strongest signal is identified, you can establish the precise bearing angle. Typically, following this bearing will guide you directly toward the signal's origin.
Alexandre wrote in an email to us the following:
Just to let you know we just launched a new Android app compatible with RTL-SDR dongles (though mostly tested on RTL-SDR v4).
App is free to use. Advanced features (like Compass to point the signal potential source) are for premium users.
It's plug and play, easy to use, much more user friendly than SDR++.
Any feedback is really appreciated :)
If you want to know more about the project or the 2 developers behind it (we develop it in France to be able to track asian hornets that kill all the bees), please feel free to contact us.
And the Android page describes SDR ProTrack in the following way:
Unlock the power of radio tracking with SDR ProTrack! Transform your Android smartphone into a signal-tracking powerhouse using an RTL-SDR dongle and a directional antenna. Affordable, versatile, and perfect for enthusiasts, researchers, pros or anyone tracking signals—like Asian hornets or wildlife.
★ Key Features ★
• Automatic RTL-SDR dongle recognition and connection (free) • Spectrum Visualization (Free): View signal shapes in the frequency domain effortlessly. • Compass (Premium): Pinpoint the strongest signal direction with precision. • Signal Strength Display (Premium): Monitor signal power with an intuitive interface. • Custom Settings (Premium): Adjust bitrate, sample rate, and frequency sensitivity to your liking.
★ Requirements ★
• Requires an external RTL-SDR device. • Check compatibility: https://osmocom.org/projects/rtl-sdr/wiki
Need an RTL-SDR dongle, emitters, receptors, or antennas? Visit our website: https://www.intuite.fr/en_GB/pricing
★ About Us ★
Intuite is a company specialized in locating Asian hornet nests. We developed SDR ProTrack to provide a robust, cost-effective solution for radio signal tracking, combining innovative technology with our expertise in signal detection.
★ Open Source Community ★
Join our mission to advance radio tracking! Our open-source library, RTL-SDR Bridge Android Lib, powers SDR Pro Track. Contribute to development, report issues, or explore the code at https://github.com/alexandreGellibert/RTL-SDR-Bridge-Android-Lib. Support our work and help shape the future of signal tracking!
Download SDR ProTrack today and start tracking signals like a pro!
The talk focuses on using SDR hardware such as the RX888, RTL-SDR, and Airspy devices combined with directional antennas for radio direction finding. Interestingly, they also discuss using ultrasonic microphones to find power line noise from bad transformers or insulators. The talk also focuses on ensuring that your SDRs receive real signals and what noise might look like on the spectrum.
This talk provides a comprehensive guide to identifying and locating radio transmitters. Learn about practical techniques, common tools, and methodologies from decades of combined experience finding, squashing, and mitigating against radio frequency interference.
Supercon 2024: Justin McAllister and Nick Foster - How to Track Down Radio Transmissions
