# Stepper Antenna Sweep for Direction Finding

Connect trigonometry, a rotating fixture, and receive-only RSSI readings so a maker can sweep an antenna in known steps and write an honest bearing clue.

## Outcome
Build a repeatable sweep plan: angle steps, antenna orientation, RSSI sample, strongest lobe, repeated run, and uncertainty note.

## Safe first step
Start receive-only with a lawful test signal and a hand sketch of the rotation before wiring a motor or making a location claim.

## Ladder steps
### 1. Choose the angle step
A stepper sweep needs a known increment such as 10, 15, or 30 degrees before the readings mean anything.

Check: Your table lists every angle before the fixture moves.

### 2. Sketch the rotating arm
Trig turns radius and angle into a pointer you can draw, label, and compare with the physical fixture.

Check: Your note labels origin, radius, direction of rotation, zero angle, and antenna face.

### 3. Sample RSSI at each stop
The antenna should pause long enough for the receiver reading to settle before logging a value.

Check: Your row includes angle, RSSI, time, antenna orientation, and what changed.

### 4. Repeat the sweep
A second pass shows whether the strongest lobe is stable or just a noisy reflection.

Check: Your conclusion compares peak angle, spread, and uncertainty across two runs.

## Examples
### Plan the rotation before moving
```sh
angle_step = 15 deg; samples = 24
```
Expected signal: A full sweep has known stops and no mystery gaps

Caution: Do not let the motor spin while the receiver reading is still settling.

### Draw where the antenna points
```sh
x = cos(angle) * radius; y = sin(angle) * radius
```
Expected signal: The trig pointer matches the physical sweep angle

Caution: Confirm degree/radian units before trusting a plotted direction.

### Compare repeatable readings
```sh
angle + rssi + repeat_id -> strongest_lobe
```
Expected signal: The strongest direction is a repeatable clue, not exact source proof

Caution: Stop if the setup drifts into tracking people or unauthorized monitoring.

## Common traps
- Letting the motor move continuously while logging one unstable RSSI value.
- Forgetting whether the code uses degrees or radians.
- Mounting the antenna so the marked zero direction does not match the plot.
- Treating the highest RSSI reading as exact location proof.
- Skipping lawful-use checks before receiving, transmitting, or changing RF equipment.

## Practice task
Make a 12-stop sweep table at 30-degree increments. Sketch the arm, write two example RSSI runs, mark the strongest lobe, and explain what remains uncertain.

## Next steps
- Use the trig page to confirm angle-to-point thinking before drawing the fixture.
- Use the RSSI page to practice interpreting strongest and weakest readings.
- Use the packet-radio page only for receive-first signal context, not as permission to transmit.
- Save the Obsidian note with [[Stepper Motor]], [[Trigonometry]], [[RSSI]], [[Direction Finding]], [[Antenna Pattern]], and [[Uncertainty]] backlinks.

## Related
- [Trigonometry for rotation and layout](/learn/trigonometry-for-rotation-and-layout/)
- [RSSI mapping for direction finding](/learn/rf/rssi-mapping-for-direction-finding/)
- [Packet radio receive-first path](/learn/rf/packet-radio-baofeng-aprs-first-pass/)
- [Stepper motor wiring first checks](/learn/stepper-motor-wiring-first-checks/)
- [Vectors for maker projects](/learn/vectors-for-maker-projects/)
- [Radio and Signals topic group](/topics/rf/)
- [Maker Math routes](/topics/math/)
- [Electronics and controls](/topics/electronics/)

## Obsidian backlinks

Use these wiki links to connect this note inside a local maker vault:

- [[TopicLadder]]
- [[Maker Learning]]
- [[Stepper Antenna Sweep for Direction Finding]]
- [[Radio and Signals]]
- [[rf]]
- [[receive-first]]
- [[Choose the angle step]]
- [[Sketch the rotating arm]]
- [[Sample RSSI at each stop]]
- [[Repeat the sweep]]
- [[Trigonometry for rotation and layout]]
- [[RSSI mapping for direction finding]]

## Source and next routes

Source: https://topicladder.com/learn/rf/stepper-antenna-sweep-for-direction-finding/

- [Trigonometry for rotation and layout](/learn/trigonometry-for-rotation-and-layout/)
- [RSSI mapping for direction finding](/learn/rf/rssi-mapping-for-direction-finding/)
- [Packet radio receive-first path](/learn/rf/packet-radio-baofeng-aprs-first-pass/)
- [Stepper motor wiring first checks](/learn/stepper-motor-wiring-first-checks/)
- [Vectors for maker projects](/learn/vectors-for-maker-projects/)
- [Radio and Signals topic group](/topics/rf/)
- [Maker Math routes](/topics/math/)
- [Electronics and controls](/topics/electronics/)