Radio Horizon Calculator
Calculate maximum line-of-sight distance for radio/microwave links.
K Factor Reference
| K Value | Condition | Use Case |
|---|---|---|
| 0.67 | Subrefraction | Worst-case planning |
| 1.0 | No refraction | Optical LOS |
| 1.33 (4/3) | Standard atmosphere | Typical conditions |
| 1.5-2.0 | Superrefraction | Tropical/coastal |
| > 2.0 | Ducting | Anomalous propagation |
Radio Horizon Theory
Horizon Distance Formula
d = sqrt(2 * K * R * h)
Total LOS = d_A + d_B
Where R = Earth radius (6371 km), h = antenna height, K = refraction factor
Total LOS = d_A + d_B
Where R = Earth radius (6371 km), h = antenna height, K = refraction factor
Radio waves bend due to atmospheric refraction, effectively increasing the horizon distance. Standard K=4/3 accounts for typical temperate conditions.
Design Considerations
- Use K=4/3: Standard planning value
- Check K=0.67: For worst-case clearance
- Fresnel zones: Need additional clearance
- Terrain: May block before horizon
- Tropical paths: Consider variable K