Category: Digital Signals

HamRadioWeb: A Browser-Based Remote FT8/FT4 Receiver with Live Heatmaps, Performance Metrics and DX Cluster

Thank you to Patricio for writing in and sharing with us his release of HamRadioWeb, a browser-based remote receiver with a focus on FT8 and FT4 reception. If you're not aware, FT8 and FT4 are amateur radio digital fixed-format modes that can be decoded even with very weak signals. 

The software works by running a small server bridge app alongside JTDX/WSJT-X on the shack PC. Users can then log in from anywhere in the world on any device via the browser-based system. Once logged in, you can transmit and monitor, just as if you were sitting in a ham shack.

HamRadioWeb is designed to streamline remote FT8/FT4 operating directly from any mobile browser or PC without requiring complex setups like VPNs or port forwarding. In addition to remote TX/RX control, it features:

  • Live FT8 geospatial heatmaps and signal footprint visualization.
  • Grid-level SNR benchmarking against nearby stations.
  • Azimuthal radar & path telemetry relative to the shack.
  • Automated DXCC and award hunting synchronized with logbook data.

It’s built to make remote digital mode operating visual, data-driven, and easily accessible on the go.

HamRadioWeb is free for unlimited decodes, but limited to 10 TX's per day. Premium is a paid service costing $4.99 per month, which provides unlimited access.

HamRadioWeb: A Demo of the FT8/FT4 Terminal Display
HamRadioWeb: A Demo of the FT8/FT4 Terminal Display

IC-SDR: A New Multimode SDR Software for Windows Written in Go

Thank you to Luis Lopez Martinez for writing in and sharing the release of his open-source software, IC-SDR, a new multi-mode SDR application for Windows written in Gowith a focus on performance and efficiency. Luis writes:

IC-SDR supports AM, NFM, WFM, LSB and USB demodulation, along with several integrated digital decoders:

  • AIS
  • ADS-B (1090 MHz and UAT 978 MHz)
  • Radiosondes
  • APRS
  • RTL_433
  • DMR
  • SSTV
  • TETRA

It also includes a memory bank, real-time spectrum and waterfall displays, an audio recorder with automatic silence removal, and a frequency-segment scanner with instant triggering.

The Windows release can be found on the project's GitHub Releases page.

FreeDV RADE: An Open-Source Digital Voice Mode for HF that Beats SSB at Low SNR

Thank you to Rebecca Key (KO4KVG) for writing in and sharing with us an article she's written over on the ARDC website about a relatively new amateur open-source radio digital voice mode called FreeDV RADE.

ARDC is a private foundation that issues grants that support amateur radio and digital communications technologies. FreeDV is an ARDC grantee, and it has been using the funds to develop "a digital voice mode that could compete with SSB across varying signal-to-noise conditions on HF while providing more natural-sounding speech".

Last year, they released the FreeDV Radio Autoencoder (FreeDV RADE), which is their flagship digital voice mode. FreeDV RADE incorporates both machine learning and classical DSP, resulting in working audio at SNRs as low as -2 dB, with only half the bandwidth of a typical 3 kHz SSB voice signal. The article goes on to describe how the audio quality, power, and bandwidth efficiency are superior to other digital voice modes. 

The article also mentions how FreeDV RADE is seeing increased adoption by hardware manufacturers, with FlexRadio now supporting the mode in several radios. It also mentions upcoming improvements, including a goal of reducing bandwidth use to under 1 kHz.

FreeDV Software
FreeDV Software

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.

Sept 5 2026 Update: Carshepherd is now live on the Google Play Store.

Carshepherd Android UI
Carshepherd Android UI

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

CellScope: LTE Sniffing on Windows

Over on YouTube, Sarah from the SignalsEverywhere YouTube channel has uploaded a new video showing a new open-source program she's developed called CellScope, which is used for LTE sniffing. She notes that CellScope is essentially LTE Sniffer, but ported for Windows. CellScope needs a wideband SDR, and it currently supports LibreSDR B210 Clone, HackRF and the Airspy R2/Mini

LTE (aka 4G) is a modern mobile wireless standard used by cellphones for data. While it is encrypted, there is still some data transmitted in the clear, such as the devices connected to the cell site and how much data they are pulling down, if there is an active call on the cell site, and of course the data activity can be useful to monitor too. 

In the video Sarah shows CellScope in action, demonstrating it detecting a call from her phone and visualizing the data transfer activity from her device when pulling down data.

CellScope is open-source and available on GitHub. If you don't want to compile it yourself, the Windows executable can be purchased from her site for a minimum $0.00 donation.

CellScope: LTE Sniffing on Windows

isTRAIN: Detecting if a Train is Blocking a Local Crossing By Listening to Railroad Frequencies

Jhestyr takes pride in being punctual, but a local railroad crossing keeps getting in the way. Trains sometimes park across it for hours at a time, and there is no way to know one is sitting there until you have already driven out to it. Every wasted trip to the crossing and back out to an alternative route costs him a significant chunk of time and fuel.

This is why Jhestyr used two RTL-SDR dongles to build isTrain, an open source program that decodes End-of-Train brake pressure and motion telemetry on 457.9375 and 452.9375 MHz, transcribes railroad voice traffic in the 160 to 162 MHz band via Whisper, and fuses both sources into a single live verdict on whether the crossing is blocked.

The program generates a webpage that can be accessed, providing a YES/NO verdict on whether there is a train blocking the crossing. A live public instance of Jhestyr's isTrain webpage is available here https://istrain.jhestyr.net.

AI-Disclaimer: Jhestyr notes that the code was developed with a 60/40 agentic/human split.

The isTrain Web Interface
The isTrain Web Interface

War Driving for DECT Devices with a HackRF and Android Device

Over on her YouTube channel SignalsEverywhere, Sarah has uploaded an interesting video showing her doing a wardrive for DECT devices, with an Android device connected to a HackRF, running her own Android version of DECT toolkit. In the past, we also covered her DeDECTive software, which is a fully DECT scanner and voice decoder for Linux and the HackRF.

DECT is a digital wireless protocol operating at around 1.9 GHz, which is typically used by modern cordless home phones, baby monitors, headsets, intercoms, and more. If you are unfamiliar with the term wardriving, this is when someone drives around in a vehicle and looks for interesting signals around the area. Wardriving is typically associated with mapping out the local WiFi environment and looking for security flaws, but it can apply to any signal.

During her wardrive, Sarah finds mostly VTech cordless phones, but a few other models like 'Binatone' and 'RTX' pop up, which she suspects are headsets, one possibly from a local McDonald's. She notes that only one active call was found, although the video has voice decoding stripped out for privacy reasons. She also notes that no encryption was found to be enabled on any device, despite DECT supporting it. The Android App also records the GPS position of any found DECT devices on a map.

War Driving for DECT Devices