Direction finding

A Direction finder estimates signal arrival direction from a coherent array. It shows a bearing, confidence, and angular response. Triangulation combines bearings into a position estimate.

Set up a finder

1. Add a multi-lane Device or an Array.
2. Add Direction finder. Set Geometry to your antenna layout and Elements to its count.
3. Connect every lane to the matching iq, iq2, and subsequent inputs. All must come from one source.
4. Set Offset and Bandwidth to cover the signal.
5. Calibrate the array.
6. Connect GPS position for map output or triangulation.

Geometry supports a circle with radius, a line with element spacing, or explicit element positions.

Algorithm

For one transmitter, start with Sources set to one.

Read the compass

The compass shows response peaks, the selected bearing, and confidence. Bearings run clockwise from north at 0°. The strip below shows calibration quality per lane.

Phase unknown suppresses bearings. Check clock connections and the calibration reference.

Listen along a bearing

Connect beam to a channel. Follow bearing steers toward the current estimate. Fixed azimuth holds a chosen direction and starts at the beam's current bearing.

Crossing bearings from several finders

1. Add Triangulation and connect the finders' events outputs.
2. Give each finder its own position source, using GPS or fixed coordinates.
3. View the estimate, error ellipse, guidance, and age of each bearing. Clear resets the estimate.

Bearings from different positions constrain the transmitter location. A finder alone provides bearings; position estimates and driving guidance require Triangulation.

On the map

Connect finder events to Map for bearing rays that fade with age. Connect Triangulation events for the estimated location, uncertainty ellipse, contributing stations, and next waypoint.

Guidance

For a long, narrow uncertainty ellipse, guidance suggests moving across the bearing to improve the intersection angle. Once the estimate converges, it suggests approaching the location.

The first converged fix emits an event that connected webhook, MQTT, or Matrix outputs can forward. Use field mode for phone guidance and navigation.