WiFi Antenna Rotator Controller on a Raspberry Pi Pico

Every shack with a beam has the same little ritual: glance at the map, work out roughly where the DX is, and nudge the rotator until it feels about right. I wanted something better than about right — and I wanted it to run without a PC bolted to the desk. So I built one.

Rotator Master is a complete antenna-rotator controller that runs entirely on a single Raspberry Pi Pico 2 W — a microcontroller that costs around £7. There's no companion computer, no app to install, and nothing in the cloud. The Pico serves its own control page, so you simply point a browser at it and drive the antenna from a compass dial on your phone.

What it does

• Point-and-go. Type a heading and press Go — the antenna swings there on the shortest safe path.

• Grid-square pointing. Enter a Maidenhead locator (say FN30as) and it works out the great-circle bearing and the distance in km and miles, then rotates onto it. No more guessing where a square actually is.

• Home and field. At the shack it joins your Wi-Fi. Out portable, it becomes its own hotspot — connect your phone straight to it and carry on.

• Cable-wrap protection. It knows where north is and refuses to over-wind the feedline. If the short way round would take the cable past the limit, it calmly goes the long way instead.

• A proper REST API. Position, targets, homing and bearings are all available over simple web requests, so it drops neatly into logging software or your own scripts.

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The clever bits

The dial you see on the phone is drawn live: a green needle for where the antenna is, a grey one for where it's heading, and a faint red wedge marking the ±15° no-wrap zone around north.

Behind that, the firmware tracks position by counting motor steps — it's open-loop, with a one-tap Set Home to re-reference it to true north whenever you like. The motor is an 18°-per-step geared unit, and those big, torquey steps will happily stall if you slam them to full speed from a standstill. So the driver ramps: it starts gently, accelerates to a cruise, and eases back into the target. The result is a move that's quick but never drops a step.

All of it runs cooperatively under MicroPython's asyncio, so the antenna keeps moving smoothly while the web page stays responsive.

The hardware

• Raspberry Pi Pico 2 W — the brains, the web server and the Wi-Fi, all in one.

• Kitronik 5331 (DRV8833) motor driver board — drives the stepper and regulates power for the Pico, so there's no separate supply to fuss over.

• MOONS' PG22L45.2 geared stepper — a 20 mm motor with a 45.2:1 planetary gearbox, giving roughly 0.4° of resolution at the mast.

It's a genuinely small, tidy build and we will be producing a version already built to compliment our antennas.

Free software — and kits and complete units if you'd rather not build

Here's the part I care about most: the software will soon be free and open source. The firmware, the web UI, the wiring notes and a full user manual are all on GitHub for anyone to download, flash, study, modify and improve.

If you've got a Pico and a stepper in the junk box, you can be pointing at grid squares this weekend for the price of nothing.

I know, though, that not everyone wants to source parts, identify coil wires and flash microcontrollers — and that's completely fair. So alongside the free code I will be offering two things through radio-stuff.com:

• Kits — the board, the geared motor and everything you need, ready to assemble, with the firmware pre-loaded. A relaxing afternoon's build.

• Completed rotators — fully built and tested, ready to mount and run. Open the box, point your phone at it, and go.

Buying a kit or a finished unit is the easiest way to support the project and keep the free software coming — but you're never required to. The code stays open either way.

The 1st kit will be launched in August 2026 you will just need to buy a Pico, Stepper Board and Stepper motor.