An open, remotely tunable magnetic loop antenna for 40 / 20 / 15 / 10 m with automatic SWR optimization.
⚠️ Status: early development — not a finished project or product. Everything in this repository is design documentation, research, and an unbuilt/unbenched firmware skeleton (see Project status below). Nothing here has been validated on real RF hardware yet: numbers are calculated, not measured, and the firmware has not been run against an actual antenna. Don't build this expecting a working antenna today — track Sprint 1 for bench progress, and read Safety before touching any of it with a transmitter.
EasyLoop is a WiFi- and Bluetooth-controlled magnetic loop antenna system built around an ESP32. It tunes itself to minimum SWR on command — from a web browser, a smartphone app, or automatically by following your transceiver's VFO via flrig / hamlib.
The project has two explicit goals:
- Easy-to-build prototype — a proof of concept any reasonably experienced ham can reproduce from the documentation in this repository.
- Product + DIY documentation — evolve the prototype into a sellable product and keep a fully documented DIY build path in this repo (open hardware / open firmware).
Magnetic loops are the go-to antenna for restricted spaces (balconies, HOA lots, portable ops), but they have a razor-sharp bandwidth — a few kHz on 40 m — so every QSY means retuning. Commercial answers are either fully manual (~€300, you walk to the antenna) or premium remote-tuned (~€2000+, proprietary controllers). Almost none offer app control, open firmware, or automatic follow-the-VFO tuning. EasyLoop targets exactly that gap. See research/market/gap-analysis.md.
- 7.0–29.7 MHz continuous coverage (40/20/15/10 m, 30/17/12 m come free)
- Motor-driven butterfly/vacuum capacitor, sub-100 Hz effective tuning resolution
- Built-in directional coupler + log detectors: live SWR on every interface
- Automatic tuning: calibration-table pre-set + SWR hill-climb fine tune
- Control via web UI (WiFi, works on any device), BLE (app / offline portable use), and REST/WebSocket API
- Follow-the-VFO: polls flrig or rigctld (hamlib) and retunes as you spin the dial
- RF-quiet design: stepper driver disabled outside tuning, linear analog supply, shielded control electronics (see docs/hardware/electronics.md)
- Per-band tuning memories, backlash compensation, safe-power interlock during tune
| Path | Contents |
|---|---|
| docs/ | Engineering documentation (architecture, hardware, firmware, app, rig integration) |
| research/ | Market, technical, and community research backing the design decisions |
| firmware/ | ESP32 firmware (PlatformIO) |
| hardware/ | Schematics, mechanical design, bill of materials |
| app/ | Mobile app concept and (later) implementation |
| web/ | Web UI served by the ESP32 (source lives in firmware/data for now) |
| agile/ | Product backlog, sprint plans, working agreements |
Start reading here:
- docs/architecture/system-architecture.md — the big picture
- docs/hardware/antenna-design.md — the RF design with all calculations
- agile/product-backlog.md — what we build, in what order
Sprint 0 (inception) — complete. Research done, architecture defined, PoC firmware skeleton in place. No hardware has been built or tested yet — nothing has touched an antenna, a transceiver, or RF at power. The firmware compiles and its host-testable logic passes unit tests, but it has never run on real motor/capacitor/coupler hardware. All RF numbers in the docs are calculated, not measured.
Next: Sprint 1 — first bench prototype of the control electronics (motor + SWR sensing on a dummy load, no antenna involved yet).
A transmitting magnetic loop develops several kilovolts across its tuning capacitor even at QRP levels, and field strengths close to the loop are high. Read docs/hardware/safety.md before building or operating.
- Firmware & software: GPLv3
- Hardware design files: CERN-OHL-S v2
- Documentation: CC BY-SA 4.0
This combination keeps the DIY path open forever while still allowing us to sell assembled units. Details and license texts: LICENSE.md.