July 30, 2026

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).

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.

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July 29, 2026

Building a $50 BOM Software Defined Radio with a HT9201 20 MHz ADC and an FX2LP USB Controller Clone

Over on Hackaday, we've seen that Anders Nielsen gave a talk at Hackaday Europe 2026 about his effort to build a software-defined radio with 20 MHz of bandwidth on a bill of materials of under US$50. We've posted about his work before, first with the PhaseLoom quadrature sampling front end, and later with PhaseLatch, which combined a 20 MSPS ADC with a 50-year-old MOS 6502 CPU. In this latest work, the 6502 is still part of the stack, but for the wideband work the samples bypass it entirely.

The RF side is a discrete Tayloe detector built around a TLV3253 analog switch, sampling the signal four times per local oscillator cycle to give downconversion and quadrature in one step. A Si5351 provides two clocks offset by 90 degrees from the same PLL, an ADA4891 op amp buffers into a HT9201 dual 20 MHz 10-bit ADC, and an FX2LP clone streams the parallel data over USB 2.0, avoiding the cost and tool chain of an FPGA. USB bandwidth forces a choice between 20 MHz at 8 bits or 10 MHz at 10 bits, and he notes that PCB design was critical in getting a flat frequency response.

Anders ran a live demo streaming 19.375 MHz into GQRX and showing the whole FM band at once, with tuning handled by firmware running on the FX2LP's own 8051 core. Still to come are bias and offset calibration to suppress the mirror images, better filtering and layout, and a front-end mixer to get past the roughly 100 MHz ceiling of the Si5351. He is also looking for help with the SoapySDR driver, so take a look at his GitHub if you have the skills.

Hackaday Europe 2026: Anders Nielsen - High Performance SDR on the Cheap

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Below, we're also embedding the video from his YouTube channel, which covers the same project.

Cheapest 20MHz SDR You Can Build

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July 29, 2026

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.

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July 29, 2026

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

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July 29, 2026

DeepSDR Updates: Live Public Safety Incident Map with an RTL-SDR, Whisper and an LLM

Last week we posted about Hubquhq's DeepSDR project (project contact page), which collects transcribed voice data from multiple public safety radio channels and then uses an LLM to summarize and plot incidents on a map.

Recently, he wrote in again and wanted to share additional information about the project and how it works after receiving a few questions from interested parties. He writes:

I run every stage in a separate docker container: Capture (I capture audio as longer sessions for archiving, and separately just short sessions where there's no silence for further processing. I tried using VAD to detect voice, but with radio it was missing some talk, so I just use ffmpeg) > Transcribe > LLM > Finding latitude and longitude for addresses > Grouping connected conversations.

He has also provided a PDF explaining how DeepSDR works in more detail, which you can download here.

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July 28, 2026

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

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July 28, 2026

SDROxide: A New SDR Client for HAMs and SWLs written in Rust

Thank you to Josef (OE3JJS) for writing in and sharing with us the release of his new open-source software called SDROxide, an SDR client designed for HAMs and SWLs (short-wave listeners), written in Rust. The software supports Linux, Windows, macOS, and also has a web client. As it supports SoapySDR, RTL-SDR dongles are supported for RX. Josef writes about SDROxide:

It's a completely new project written in Rust, supporting many SDR interfaces (CAT/Audio, CAT/IQ, SoapySDR, HPSDR, TCI) and with loads of features built in that used to require extra programs: FT8/FT4, SSTV, RTTY, PSK, OLIVIA, THOR, FSQ, a CW/RTTY/PSK skimmer, there's dx cluster and sota/pota spotting, a logbook with integrations for QRZ.com, HamQTH, eQSL, LoTW, there's neural-network noise reduction, a 3D "hamclock" that visualizes QSOs, satellites, Aurora, CME cones, with up-to-date images of the sun's surface, and you can run the client locally, remote with native binary, or remote via the web (WASM).

Josef notes that the project is fully open-source and available on GitHub.

AI-Disclaimer: The author notes the use of local and hosted LLMs in the development of this software.

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July 28, 2026

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.

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