KIWI Antenna Tracker
Antenna tracking module for the KIWI Ground Station Kit. Receives MAVLink telemetry from the UAV and automatically points the antenna toward the aircraft. Based on the KiwiF405-12S flight controller running ArduPilot AntennaTracker firmware.
Features
- Automatic antenna tracking — receives GPS coordinates from the UAV via MAVLink and drives a yaw servo to keep the antenna pointed
- Precision encoder — high-resolution heading sensor for accurate yaw position feedback
- GPS — onboard GPS for tracker’s own position reference
- TBS Fusion VRX control — built-in serial integration for remote frequency control, RSSI monitoring, and band scanning
- Single-servo yaw — continuous rotation servo on output 1
- Plug-and-play — pre-configured defaults, connects directly to the Ground Station Kit
Connections
| Port | Function | Default Protocol |
|---|---|---|
| USB | GCS / Configuration | MAVLink2 |
| SERIAL1 | RC Input | SBUS/CRSF |
| SERIAL2 | MAVLink Telemetry | MAVLink2 (460800) |
| SERIAL3 | GPS | GPS (115200) |
| SERIAL4 | TBS Fusion VRX | VRX Serial (115200, half-duplex) |
| SERIAL5 | MAVLink2 GCS (RS422) | MAVLink2 |
| PWM1 | Yaw Servo | Continuous rotation |
Modes
| Mode | Description |
|---|---|
| MANUAL (0) | Direct servo control from RC |
| STOP (1) | Hold current position |
| SCAN (2) | Sweep back and forth searching for vehicle |
| AUTO (10) | Track vehicle automatically using MAVLink GPS |
Default startup mode is MANUAL.
Video Receiver Control
The tracker supports remote control of 5.8 GHz video receivers over SERIAL4. Two receivers are currently supported:
| VRX | VRX_ENABLE | Frequency Control | RSSI | Band Scan |
|---|---|---|---|---|
| TBS Fusion | 2 | Yes | Yes (dual RX) | Yes |
| SteadyView X | 3 | Yes | No | No |
TBS Fusion VRX Integration
The tracker has built-in support for controlling a TBS Fusion 5.8 GHz video receiver over a single-wire UART connection (SERIAL4). No CAN bus or additional boards required.
Wiring
One wire from TBS Fusion UART TX/RX to the tracker’s SERIAL4 pad. Half-duplex is pre-configured (SERIAL4_OPTIONS=4). Power the Fusion separately — only the data wire is needed.
Features
Real-time RSSI monitoring — dual-receiver signal strength (Receiver A and B) and current frequency are polled at 2 Hz and streamed to GCS as MAVLink NAMED_VALUE_FLOAT messages:
| Message | Description |
|---|---|
VRXF | Current frequency (MHz) |
VRXA | RSSI Receiver A (0.0–1.0) |
VRXB | RSSI Receiver B (0.0–1.0) |
Remote frequency control — change the VRX operating frequency from GCS by setting the VRX_FREQ parameter (in MHz, e.g. 5800). The tracker confirms the change and reports back via GCS status message.
Frequency range scan — trigger a full-band scan from GCS to find active video transmitters. Scan results (RSSI per frequency) are delivered as a binary MAVLink TUNNEL message (payload_type 60100) for GCS-side visualization.
VRX Parameters
| Parameter | Default | Description |
|---|---|---|
| VRX_ENABLE | 2 | 0=Off, 2=TBS Fusion, 3=SteadyView X |
| VRX_FREQ | 5800 | Operating frequency (MHz) |
| VRX_ADDR | 1 | TBS Fusion serial address |
Scan Parameters
| Parameter | Default | Description |
|---|---|---|
| VRX_SCAN | 0 | Set to 1 to start scan, auto-resets to 0 |
| VRX_SCANLO | 5200 | Scan start frequency (MHz) |
| VRX_SCANHI | 6000 | Scan stop frequency (MHz) |
| VRX_SCANST | 10 | Scan step (MHz) |
| VRX_SCANRX | 0 | Scan receiver (0=A, 1=B) |
Scan Results Format
Scan results arrive as a TUNNEL message with payload_type 60100. Binary payload:
| Field | Type | Description |
|---|---|---|
| start_freq | u16 LE | Start frequency (MHz) |
| step | u8 | Step size (MHz) |
| count | u8 | Number of entries |
| rx | u8 | Receiver (0=A, 1=B) |
| rssi[] | u8[] | RSSI value per frequency step |
SteadyView X VRX Integration
Remote frequency control for the ImmersionRC SteadyView X receiver over SERIAL4. Set VRX_ENABLE=3.
Wiring
Same as TBS Fusion — single wire from SteadyView X UART to SERIAL4 pad, half-duplex.
Features
Remote frequency control — change the VRX channel from GCS by setting the VRX_FREQ parameter (in MHz). RSSI monitoring and band scanning are not available on this receiver.
Parameters
| Parameter | Default | Description |
|---|---|---|
| VRX_ENABLE | 3 | SteadyView X serial backend |
| VRX_FREQ | 5800 | Operating frequency (MHz) |
Firmware
ArduPilot AntennaTracker firmware for KiwiF405-12S-Tracker. Flash via Mission Planner or apj upload over USB.