Antenna Guide
ISM band devices (433 / 868 / 915 MHz)
Stock Telescopic Antenna
- 433 MHz: Extend to ~17 cm (quarter-wave). Stock antenna works but isn't ideal
- 868/915 MHz: Extend to ~8 cm. Stock antenna is nearly tuned for this
Quarter-Wave Ground Plane (Best)
- 433 MHz: Vertical element 17.3 cm + four 17.3 cm radials at 45°
- 868 MHz: Vertical element 8.6 cm + four 8.6 cm radials
- 915 MHz: Vertical element 8.2 cm + four 8.2 cm radials
- Material: Stiff copper wire soldered to an SMA connector
- Placement: Outdoors or near a window. Higher is better for range
Quick Reference
| 433 MHz λ/4 |
17.3 cm |
| 868 MHz λ/4 |
8.6 cm |
| 915 MHz λ/4 |
8.2 cm |
| Typical range |
50–300 m |
| Polarization |
Vertical |