VFO-Knobby RF.GuruVFO-Knob is a 66 mm touch-screen tuning knob for AetherSDR, the free, open-source app for FlexRadio transceivers. Tune, pick the step, key the transmitter and watch the S-meter — over one USB-C cable or over WiFi. The firmware is already on it, and versions for more radios and apps are on the way.
Receive and transmit, shown to scale in the 66 mm body. The readouts follow the bars — just as they do on the knob.
It isn't polling — it's told. VFO-Knob speaks TCI v2.0, the open control protocol built into AetherSDR. Tune at the desktop and the knob follows; turn the knob and the desktop moves.
Tune, key, listen and read the meters without looking for the mouse.
Tap a digit to set the step to that decade. Acceleration rides on top: a flick crosses a band, a slow turn lands on 10 Hz.
Tap to key, tap along the bottom to unkey. A transmit time-out, a haptic nudge every 10 seconds and a screen that goes amber with a red PTT bar keep you aware you're on the air.
An S-meter on receive. SWR and auto-ranging forward power — up to 2 kW full scale — on transmit, with the mic level riding inside the power arc.
Receive audio from the 3.5 mm jack, transmit audio from the built-in microphone, each with its own level.
Tap to open, turn to choose, tap anywhere to accept. No menus to dig through.
Tap the meter arc and the knob shows its network addresses — no digging through your router to find it.
A configuration page on the knob itself: status, AetherSDR host, WiFi, audio levels, transmit time-out, password and updates.
Every firmware image is RSA-3072 signed and checked before it's accepted — and a failed update rolls back by itself.
Both arrive with the firmware installed and do everything on this page. The difference is how they're powered — and so where they like to live.
Cordless, on your WiFi
A built-in battery means no cable on the desk. Set up your WiFi once over USB-C, then put the knob wherever your hand falls — beside the keyboard or at the operating position — and it reaches AetherSDR cordless.
€99
Firmware preinstalled
One USB-C cable for power and data
Plug it into the computer running AetherSDR: it shows up as a network adapter, gets its address by itself and connects — no WiFi to set up. Want it cordless? Run it from a power bank and it goes over WiFi instead.
€99
Firmware preinstalled
| Feature | Blue | Black |
|---|---|---|
| Price | €99 | €99 |
| Power | Built-in battery, charges over USB-C | USB-C — computer, charger or power bank |
| USB-C link to the computer | Yes | Yes |
| WiFi | Cordless, on battery | From a power bank or charger |
| Display, knob, haptics, audio | Yes | Yes |
| Windows · macOS · Linux | Yes | Yes |
| Firmware preinstalled | Yes | Yes |
€99 either way, firmware preinstalled. Plug it in, turn on TCI in AetherSDR and follow the setup below.
The knob chooses for itself: the cable whenever there's a computer on the other end of it, WiFi when it runs from a battery, charger or power bank.
One cable for power and data
The knob shows up on your computer as a USB network adapter, gives it an address and talks TCI over the cable. No WiFi and no IP addresses to type in: it connects to AetherSDR on the computer it's plugged into.
Anywhere on your network
Enter your network and the AetherSDR computer's address once, on the knob's configuration page. From then on it connects by itself whenever it isn't plugged into a computer — cordless on the blue edition's battery, or from a power bank or charger on the black.
AetherSDR is the free, open-source, native amateur-radio workstation for FlexRadio 6000, 8000 and Aurora transceivers. VFO-Knob talks to it directly through its built-in TCI v2.0 server — no plug-ins, no bridge software, no virtual serial ports.
AetherSDR runs natively on Windows, macOS and Linux — and so does the knob, over USB-C or WiFi on all three.
AetherSDR is where VFO-Knob starts. Versions for other radios and SDR apps are in the works.
The firmware is already on the knob. Two steps and you're tuning — the other two are optional.
Install AetherSDR if you haven't yet — it's free for Windows, macOS and Linux. Then open its Settings menu and switch on Autostart TCI, so the knob finds it every time.
Connect the knob to the computer running AetherSDR with a USB-C cable and give it about ten seconds — nothing to install on Windows, macOS or Linux. If the knob says FLIP USB-C, flip the connector upside down.
Browse to http://10.55.42.1 and sign in with admin / admin to set audio levels, the transmit time-out and updates.
On the same page, set your own password first — on WiFi your whole network can reach the knob, and it can key a transmitter. Then add your WiFi network and the AetherSDR computer's address, and run the knob from its battery or a power bank.
Over the cable there's nothing to set up. On WiFi the knob connects to AetherSDR across your network, so the computer's firewall has to let it in:
USB-C Plug in and tune: Windows brings the knob up by itself — nothing to install, nothing to allow.
WiFi If you allowed AetherSDR on private networks when Windows first asked, you're set. Otherwise make sure your home network is set to Private, then open AetherSDR's TCI port to it once, from an administrator PowerShell:
PS> New-NetFirewallRule -DisplayName "VFO-Knob TCI (WiFi)" `
-Direction Inbound -Protocol TCP -LocalPort 50001 `
-RemoteAddress LocalSubnet -Action Allow -Profile PrivateUSB-C Works out of the box — plug in and tune.
WiFi Works by default too. If you've switched the macOS firewall on, allow incoming connections for AetherSDR: System Settings → Network → Firewall → Options.
USB-C Binds the knob by itself — nothing to install, nothing to allow.
WiFi If your firewall drops incoming connections (ufw, or firewalld's public zone), let your local network reach AetherSDR's TCI port once. Use your own range — a /24 like 192.168.1.0/24 or a /16 like 10.0.0.0/16:
$ sudo ufw allow proto tcp from 192.168.1.0/24 to any port 5000150001 is AetherSDR's default TCI port. More help on GitHub: if the page doesn't open · if the knob says NO LINK.
Latest firmware: v1.4.0
Firmware images are RSA-3072 signed and verified before they're accepted. On WiFi the knob checks once a day while it's on and installs quietly — it never reboots on its own; the new image waits until you next restart it. Over USB, the configuration page fetches the update and hands it over. If a new image ever fails to boot, the knob rolls back to the one before.
PTT is a toggle, so the radio stays keyed when you let go. That's why there's a transmit time-out, a haptic reminder every 10 seconds and a screen that goes amber with a red PTT bar. If something goes wrong, the knob steps down in stages — unkey, close the connection, tear it down, and finally restart itself. AetherSDR unkeys as soon as it sees the connection close.
Safety notesApache-2.0
Read it, build it, change it. The source, the build instructions and the full setup guide live on GitHub.
Which edition, your station, your operating system — ask the RF.Guru team and we'll help you get tuning.
