GPS Fix Capture Tips

The NEO-6M needs a clear sky view before it can report a position. Most “no fix” reports are placement problems, not hardware problems. This page is the practical routine.

Placement

• Put the ceramic antenna side up, away from metal and away from the body.
• Keep the antenna away from the ESP32, battery and wires; the module is most sensitive at its top face.
• Outdoors: a pocket at the shoulder of a pack beats an inner coat pocket. A chest harness is better still.

Sky view

The fix time depends on satellites in view:

Environment	Typical time to fix
Open sky	30-90 s (cold), under 10 s (warm)
Window sill	Minutes, unreliable
Indoors	Usually never

See GPS Testing Indoors for why indoor testing fails, and GPS Warm vs Cold Start for the timing details.

The routine

1. Boot the beacon outdoors and wait for the GPS WAIT screen to complete. The beacon waits up to the configured timeout for a fix before transmitting.
2. Watch the satellite count on the OLED. Three or more valid satellites produce a valid fix; more satellites mean better accuracy (see GPS Coordinate Accuracy).
3. Confirm the fix over serial: the bridge prints AEGIS:POS: lines automatically, or send POS.

Keeping the fix

• The RTC cache persists the last fix across deep sleep, so a beacon that fixed outdoors boots with a position even if the next boot is indoors (see Firmware GPS Handling).
• If you move far between boots, the cached fix is stale. Re-acquire outdoors before relying on coordinates.

When it fails

Symptom	Likely cause
Never reaches 3 sats	Indoor, or antenna blocked by battery/wires
Sats valid but position jumps	Reflected signals; hold still during acquisition
Fix lost mid-use	Antenna covered; keep it facing up

Related

• GPS Failure Contingency
• GPS Warm vs Cold Start
• Configuring the NEO-6M over UART