Category: Applications

VibeSDR Jr: Apple Watch RTL-SDR, KiwiSDR, UberSDR Client now Available

Back in July, we posted about VibeSDR, an AI vibecoded open-source mobile SDR client for rtl_tcp and UberSDR/KiwiSDR/OpenWebRX servers developed for iOS and Android. In that post, Stuart also mentioned that he was developing an Apple Watch app version of VibeSDR that runs directly on an Apple Watch, allowing you to view and listen to the spectrum on your wrist.

The Apple Watch version, called VibeSDR Jr, is now available as a full standalone Apple Watch App, meaning that no iPhone is required. The app costs £0.99 (~US$1.35). As before, Stuart has provided us with 20 free giveaway codes for the VibeSDR Jr App, so be sure to comment on either this post, the Facebook post, or the X post for a chance to win one of the codes.

Stuart has also noted that he now has a live VibeSDR demo running at demo.vibesdr.net, allowing users to see VibeSDR's DSP and server functionality in action. Stuart writes, "There is an RTL-SDR V4C, SDRPlay RSP1B, and AirSpy HF running on that demo server, all connected to the same AirSpy YouLoop with LNA antenna setup. The RSP1B is locked to 2.8MHz - 10.8MHz and can handle 10 users and the RTL-SDR & AirSpy are unlocked frequencies but 1 user at a time, each user gets a 30 minute time slot to play with. All the built in decoders are available and for the FM-DXers there is a full advanced RDS suite measured against a professional broadcast analyser too."

He also notes the following to avoid confusion with the software in the VibeSDR family:

VibeSDR + Buddy: The Main VibeSDR app and the Apple Watch Remote control companion app for that app.
VIbeSDR Jr: The full standalone Apple Watch SDR client no iPhone required
VibeServer: Built in to Android and standalone apps which allow you to quickly and easily share your SDR’s on a network

Use VibeServer to connect your radio and serve it and then use Jr to listen to it on your wrist, or if you don’t have your own radio Jr is compatible with almost all the same servers as the main VibeSDR app, the only thing it cannot do due to bandwidth/processing requirements is anything that is RAW IQ such as RTL-TCP or SpyServer.

Finally, Stuart notes that the Android version is coming soon and is currently just pending acceptance on the Google Play Store.

VibeSDR Jr - SDR Client for the Apple Watch
VibeSDR Jr - SDR Client for the Apple Watch

Carshepherd: An Android RTL-SDR App For the Early Awareness of Nearby Emergency-Service Vehicles

Thank you to Cees for writing in and sharing his Android app, "Carshepherd," which is currently in the pre-release stage. Carshepherd works with a connected RTL-SDR and TETRA antenna to give drivers early awareness of nearby emergency-service activity (such as police, ambulance, fire) by detecting the TETRA uplink signal.

Cees notes that this is essentially the same as what hardware devices like 'Target Blu Eye' do to detect emergency services. Laser/radar detectors are illegal in most European countries, and while not advertised as such for legal reasons, Carshepherd could be a legal alternative for detecting laser/radar speed traps, detecting ProViDa video-based pacing vehicles, or just for general awareness.

The app works by continuously sweeping the TETRA bands, looking for the signature of a TETRA carrier. Once it detects a confirmed uplink carrier, it estimates proximity, which then triggers a readout and audible alert. The TETRA uplink is not always active, but emergency service vehicles often send bursts of uplink data every few seconds with GPS position updates, and, of course, during voice PTT.

The algorithm is based on a large labeled dataset from dozens of real-world test drives. The dataset trains an AI classifier that can even tell you whether an emergency unit is keeping pace with you (e.g., traveling down the same stretch of motorway as you) or whether you are approaching a stationary unit.

Carshepherd currently only works in countries whose emergency services use the TETRA communications protocol, which includes most of Europe and various other countries, but notably not the USA. However, Cees notes that they are working on a US version that will listen to the P25 network.

While Carshepherd has not yet been released, the pricing is indicated as €3.99 per month. You can sign up for the waitlist at www.carshepherd.nl.

Carshepherd Android UI
Carshepherd Android UI

Building a Homemade Weather Radar with a HackRF or PlutoSDR and Salvaged Automatic RV Dish

After nearly being hit by a tornado that NEXRAD didn't see coming, Koakno decided to build his own DIY self-contained mobile weather radar built from a $5 salvaged RV satellite dome, a HackRF or PlutoSDR, and open-source software. 

Koakno notes that NEXRAD (the US weather radar system) data is typically 4-6 minutes old, and from a radar station that is often 100+ miles away, resulting in warnings coming in too late or not being detected at all. Only professional local mobile Doppler radar trucks have the capability of detecting local tornadoes rapidly enough to take action. Koakno set out to recreate this capability on a budget.

His antenna consists of a salvaged Winegard Carryout Anser GM-5000 automatic satellite dome built for RV motor homes. The dish carries an LNB that radiates an 850 MHz signal at 10.4 GHz, which is a perfect wavelength for weather radar. The SDR hardware can either be a HackRF or PlutoSDR. As the HackRF is only half-duplex, it uses pulsed timing, whereas the full-duplex PlutoSDR uses a continuous FMCW chirp. Open-source Python software processes the results, producing a live radar display showing color-scaled reflectivity.

Importantly, Koakno addresses the licensing concerns around this project. He notes there are clauses in the amateur radio FCC legislation that support the use of automatically controlled beacons for the observation of propagation, and experimental activities in the 3cm 10.0 - 10.5 GHz amateur radio band, but he is not an attorney, so this activity may still exist in a grey area.

The screenshot below was generated via the simulation the software provides for testing the UI.

A Demo of the Weather Radar Display
A Demo of the Weather Radar Display

9GRadio: An Android RTL-SDR App for Spectrum Monitoring and Decoding Analog/HAM/Aviation/Marine Radio Traffic

Thank you to Richard (9G5AR) for writing in and sharing with us the release of his open source Android app called 9GRadio. Richard writes that 9GRadio is an app designed for spectrum monitoring/analysis and the decoding of analog/ham/aviation and marine radio traffic.

In terms of demodulation it supports AM, FM, NFM, WFM, WFM Stereo, USB, LSB, CW, CWR, DSB and RAW IQ modes.

For digital decoding, it supports APRS, digital voice modes such as DMR, D-STAR, YSF, dPMR, NXDN, and aircraft, marine, and datalink modes such as ADS-B, AIS, ACARS, RDS, and multilateration.

Richard also notes that 9GRadio includes a full multilateration stack for locating transmitters, which works with 2+ networked 9GRadio receivers. Interestingly, the multilateration stack is noted to be protocol-agnostic, meaning it should work not only with ADS-B, but also with any mode that provides a digital identity for a transmission, such as AIS, ACARS, RDS, and digital voice modes.

The app is not available on the Google Play Store, but the APK is available for sideloading on the project's GitHub Releases page, along with the open source code.

9GRadio GIF of various screens
9GRadio GIF of various screens

Scanner Command: Mapping Incidents from Live Radio Calls and ADS-B to Airband Voice with AI

Recently, we posted about DeepSDR, which is a program that automatically transcribes voice data from public safety radio communications and uses an LLM to categorize and plot incidents on a map as they happen.

In that post, we noted that we expect to see more projects like this soon, and sure enough, another program called "Scanner Command" with a similar angle has been submitted to the blog by author Benjamin Blood. Like DeepSDR the software listens to public safety and then uses voice transcription and an LLM to automatically understand, categorize and map incidents on the map. One additional feature that Scanner Command has is a fun tool that correlates ADS-B data with airband voice. Benjamin explains it best:

Scanner Command turns a radio scanner into a live AI incident map. A Uniden SDS200 covers the trunked digital public safety side (the LA area's P25 Phase II system, with ProScan driving the scanner and handing off every recording), and two $45 RTL-SDR dongles handle the rest, one decoding ADS-B with readsb, one capturing VHF airband transmission by transmission. Everything gets transcribed locally with Whisper, an AI extraction pass works out what happened and where, and about 30 seconds after a call ends it's a color-coded pin on the map with the audio one click away. Location matching is honest on purpose: an exact intersection match gets a solid pin, an area-only match gets a dotted one, and it tells you which.

Here's the design idea underneath it, and what I think separates it from the other transcribe-and-map projects out there: this is built for tactical situational awareness when the grid's down. The system does its learning while it's online, building its own gazetteer of local streets and places, learning unit callsigns and talkgroup names, priming the transcriber's vocabulary from real local traffic, precisely so it's more capable when it's cut off. Map tiles, geocoding, and hazard data are all cached locally with that scenario in mind.

The picture in my head has always been: grid's down, the box is running on backup power serving wifi, and my neighbors connect with their phones and everyone can see what's happening around us, instead of one guy hunched over a scanner relaying it. It's not shelf gear you dust off when something happens; the whole point is that running it every day is what trains it for the day you need it. Transcription is already fully local, the LLM extraction step currently uses a hosted model when online (it runs me about a dollar a day at 24/7), and the next build phase is a GPU box that closes that last gap with a local model.

The feature people are having the most fun with is the airband/ADS-B correlation. The system pulls spoken callsigns out of airband transcripts and matches them to ADS-B tracks by time and geometry, with match windows scaled by altitude and speed, plus hex-to-tail-number derivation. Click a plane on the map and hear what its pilot actually said, with a confidence badge when the match came from a partial readback. Beyond that: an ATAK feed (CoT/KML/GeoJSON), twice-daily AI briefs, a BOLO board, incident threading with a unit activity board, and helicopter orbit detection.

ADS-B aircraft position data automatically linked to airband voice transcripts
ADS-B aircraft position data automatically linked to airband voice transcripts

Benjamin adds that a public demo is available at https://demo.scannercommand.com. But he notes that "the public demo is a replay of two real days of traffic from my setup".

The software has not yet been released, and it does not appear to be free or open-source. There is a signup waitlist available on the scannercommand.com website.

This is an exciting time with AI not only helping to rapidly develop new software, but now being used to summarize and condense the vast amount of information about the state of the surrounding world available in the RF spectrum. 

Scammer Command example mapped incident report
Scammer Command example mapped incident report
I Turned My Police Scanner Into a Live AI Incident Map (24/7)

Testing Airspy’s New WebSpy Web SDR Interface with an RTL-SDR

A couple of weeks ago we posted about "WebSpy", a new web client for Airspy software defined radios. Developer @lambdaprog, (aka Youssef Touil) has kindly provided us with an early beta of the server to test.

WebSpy is built into SpyServer, and SpyServer is an existing program that streams data from Airspy and RTL-SDR devices directly to SDR#. This new beta SpyServer now incorporates WebSpy into it, so once SpyServer is running on the server, all you need to do is run the binary and browse to https://SERVER_IP_ADDR:5555 in a browser, and the WebSpy interface will show.

As SpyServer supports RTL-SDR dongles, WebSpy also works as intended with RTL-SDRs. So in our test, we used a remote RTL-SDR connected to a networked Pi 5 and started up WebSpy. As the default includes self-signed certificates, you will get an unsecured warning from your browser, but this is safe to ignore. If you were to share your WebSpy publicly, you would want to generate your own certificates. Youssef recommended using acme.sh for that.

Clicking the power icon in the web interface starts the SDR connection, and then you can tune to frequencies using the top tuning interface like you would with SDR#. Audio is extremely clear, as if you were running the SDR directly. As Youssef explained in our earlier post, WebSpy uses some proprietary IQ compressors that preserve spurious-free dynamic range, and it does all the IQ decoding directly in the browser to avoid audio codec compression artifacts.

With an Airspy and RTL-SDR receiving a narrowband 12.5 kHz voice channel, we got about 25 kb/s network usage. Reducing the channel size to 2.4 kHz LSB reduces the usage to around 13 kB/s. A wideband FM signal at 200 kHz uses about 240 kB/s. Of course, expanding the channel size to the max 2.4 MHz of the RTL-SDR results in a much higher network bandwidth of 1.2 MB/s, but there are not many situations that would require that.

We tested in Chrome, Edge, and Firefox, and all browsers worked fine. In terms of CPU usage, it barely touched 10% on any core with a single user. Youssef mentioned that a single Pi 5 should be able to serve up to 40 simultaneous sessions for WFM users, and hundreds for SSB/AM users (and we suspect NFM too).

WebSpy CPU Usage
WebSpy CPU Usage

The implementation of WebSpy is still pretty bare in this beta. Most of the features present in SDR# are not there, but Youssef mentioned that these are being worked on, and plugin support may even be added in the future. You also can't tune individual frequency digits with the mouse wheel like you can in SDR#, and there are no squelch or bias-tee controls.  But as this is still in development, we expect more features and tweaks in the future. 

WebSpy Running an RTL-SDR
WebSpy Running an RTL-SDR
WebSpy Running an Airspy
WebSpy Running an Airspy

Radio Silence: A Native iOS App for Listening to Public KiwiSDRs

Thank you to 'Radio Silence Dev' for writing in and sharing the beta release of his iOS native app, Radio Silence, designed for listening to public KiwiSDR receivers around the world on an iPhone or iPad.

The app streams live audio from the KiwiSDR network, with a live directory showing each node's signal quality, load, and online status. If a receiver drops out mid-session, the app will automatically fail over to another one. There is also a tap-to-tune live spectrum waterfall.

Radio Silence also includes CW, RTTY and FT8 decoders, which all run on-device rather than on the receiver, printing text under the dial as it comes in. Audio keeps playing with the screen locked, and captures are saved to a logbook tagged with frequency, mode, node, S-meter reading and UTC timestamp, with export to ADIF, CSV and WAV. Captures can also be shared as QSL-style reception report cards stamped with the solar flux and Kp index at the time of the catch. NAVTEX and SSTV decoders are in development.

The developer notes that the app is written to be a good citizen on the KiwiSDR network, releasing its channel slot when listening stops and handing it back automatically if playback is left running unattended. Streaming uses about 22 MB per hour.

Radio Silence is free during the beta, and listening is set to remain free at launch, with any future subscription covering software features only. Beta invites can be requested via radiosilencesdr.com.

Radio Silence: Waterfall View
Radio Silence: Waterfall View
Radio Silence: Decoding FT8
Radio Silence: Decoding FT8

TunerScope: A Browser App to Help Optimize HDTV Antenna Positioning with an RTL-SDR

Thank you to Luke Berndt for writing in and sharing with us a new RTL-SDR browser-based app he's created called TunerScope. TunerScope is a spectrum analyzer program that focuses on helping users in areas with ATSC digital TV achieve perfect HDTV antenna positioning.

The app runs entirely in a Chrome browser, so you can just connect your RTL-SDR to your device, browse to https://tunerscope.com, and start using the app instantly. 

TunerScope has a few interesting features, including the use of spectrum stitching to visualize the full 6 MHz + wide ATSC signals as the RTL-SDR only provides 2.56 MSPS max, multipath detection via in-channel flatness, a snapshot reference trace to see how well your antenna movements are helping, an SNR reading, location-aware channel labeling and a tower map, and a channel list view.

We note that from what we can gather, this app appears to be designed for the US only and may only support ATSC signals and FCC lookups for the location aware features.

AI-Disclaimer: From a comment on the YouTube video it appears TunerScope was developed with Claude. 

I got better HDTV using an SDR