How to Calculate Fresnel Zone
What is Fresnel Zone?
Calculates first Fresnel zone radius for wireless links. Ensures line-of-sight clearance for optimal signal strength.
Formula
Formula: radius = 548 × √(d ÷ (4 × f))
Step-by-Step Guide
- 1Distance between transmitter and receiver (d)
- 2Frequency in GHz (f)
- 3Formula: radius = 548 × √(d ÷ (4 × f))
- 4Typical target: 60% first zone clearance
- 5Formula varies by distance units
Worked Examples
Input
Distance 1km, freq 900MHz
Result
Radius 8.2m
Common Mistakes to Avoid
- ✕Ignoring Fresnel zone and assuming straight line-of-sight
- ✕Not accounting for earth bulge over long distances
Frequently Asked Questions
Why is Fresnel zone clearance important?
Obstruction causes signal fading; proper clearance ensures line-of-sight performance.
How much clearance do I need?
Minimum 60% first zone clearance; 100% clearance ideal; 80% typical compromise.
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