Getting started with an RTL-SDR in the browser

ATS Mini Controller has a second mode for RTL-SDR receivers: the cheap USB sticks built around the Realtek RTL2832U chip. The browser talks to the stick over WebUSB, so there is no program to install. Samples come in over USB and are demodulated inside the tab, and nothing about the signal leaves your computer. The mode is marked Experimental in the app, so expect rough edges.

What you get: a spectrum and waterfall, up to six VFOs listening at once inside the captured band, audio and IQ recording, a scanner, bookmarks, the EiBi schedule, and a set of decoders. What you do not get: an rtl_tcp or network source, transmitting, or anything outside the browser tab. The RTL-SDR overview lists all of it on one page.

What you need

• An RTL2832U stick with an R820T, R820T2 or R828D tuner: the RTL-SDR Blog V3 and V4, Nooelec NESDR sticks and most generic ones. Sticks with an E4000, FC0012, FC0013 or FC2580 tuner open in a basic mode: you see the spectrum and can record, but the app cannot tune or set the gain. The RTL-SDR Blog V4L (R828S tuner) has basic support for now: it tunes from 24 MHz up, but shortwave on it is not supported yet. See choosing a stick.
• An antenna on the stick’s SMA socket. The telescopic dipole that comes in most kits is fine to start with.
• Chrome, Edge or Opera on a computer, or Chrome on Android. Safari and Firefox have no WebUSB, and neither does any browser on iPhone or iPad. You can still open an IQ file there (see recording and IQ files).
• A free USB port. A USB 2.0 port is enough, but it must be a real high-speed port: low-speed hubs and USB isolators cannot carry the sample stream.

Switch the app to RTL-SDR

Open the Device menu in the header and choose RTL-SDR. The controller page now shows the RTL-SDR connect card instead of the ATS Mini one. Each device keeps its own settings, and you can switch back at any time; only one of them can be connected in a tab. Switching between the ATS Mini and an RTL-SDR covers what changes.

The driver step, per system

The browser needs to open the stick as a plain USB device. On some systems another driver grabs it first. The connect card shows the steps for the system it detects; here they are all in one place.

Windows

Windows installs a TV-tuner driver for the stick, and the browser cannot open it through that. Replace it with WinUSB using Zadig (opens in a new tab): plug the stick in, start Zadig, choose Options → List All Devices, pick Bulk-In, Interface (Interface 0), make sure the driver on the right says WinUSB and press Replace Driver. Then unplug the stick and plug it back in. SDR# and SDR++ use the same driver, so they keep working. Pick the entry carefully: replacing the driver of your keyboard or another device by mistake is the one way to make this step painful.

Linux

The kernel’s DVB driver claims the stick as a TV tuner. Block it with echo 'blacklist dvb_usb_rtl28xxu' | sudo tee /etc/modprobe.d/rtl-sdr.conf, then unload it once with sudo modprobe -r dvb_usb_rtl28xxu (or reboot). Your user also needs access to the device: put SUBSYSTEM=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="2838", MODE="0660", TAG+="uaccess" in a file such as /etc/udev/rules.d/20-rtlsdr.rules, run sudo udevadm control --reload-rules, and replug the stick. The connect card has copy buttons for both lines.

macOS

Nothing to install. Open the page in Chrome, Edge or Opera, plug the stick in and choose it. If GQRX or SDR++ already has the stick open, quit it first: only one program can use it at a time.

Android

Plug the stick in through a USB OTG adapter (USB-C to USB-A on most phones), open the page in Chrome and choose the stick. If it keeps dropping out, the phone cannot supply enough current: power the stick through a powered USB hub.

ChromeOS

Nothing to install. Open the page in Chrome, plug the stick in and choose it.

Pair and connect

1. On the connect card, press Choose your receiver.
2. The browser opens its USB dialog. Pick the stick (it usually shows as RTL2838UHIDIR or Blog V4) and press Connect.
3. The stream starts at 1.8 MS/s, a sample rate most sticks handle without dropping data. You can change it later under Source.

The browser remembers the permission. Next time the card lists the stick under Receivers this browser may use, with one Connect button per stick that is plugged in. Unplugged sticks are listed too, so you can see what you paired before.

If the stick drops out

A loose cable, a hub that runs out of power or a revoked permission ends the stream. The workspace stays as it was, the status strip says No stream, and a banner says when it happened. Your settings and bookmarks are kept, and a recording that was running is saved up to that moment. Plug the stick back in and press Reconnect, in the banner or in the connection menu at the left of the status strip. The app looks for the same stick and opens it in the same mode. It never reconnects by itself, and when it cannot tell two identical sticks apart it opens the browser’s USB dialog so you can pick the right one.

No stick at hand: open an IQ file

The connect card also has Open an IQ file. It plays a recording (WAV, RF64, SigMF or raw IQ) through the same workspace, with the spectrum and the VFOs; you can only tune inside the band the file captured. It needs no WebUSB, so it is also the way in on an iPhone or iPad and in Safari or Firefox. The file is read in the browser and never uploaded. See recording and IQ files.

Your first station

The easiest test is an FM broadcast station. Click the frequency readout, type a frequency such as 98.8M and press Enter, then pick WFM as the mode (the W key does the same). The station appears as a wide block on the spectrum. If you hear nothing, check the volume in the Output bar and that the VFO is not muted. If the spectrum stays flat, check the antenna.

From here, the workspace guide explains the spectrum, VFOs and squelch, the status strip guide what the strip under the header tells you, and the keyboard shortcuts how to run it all from the keyboard. When the stick misbehaves, see troubleshooting.