RF Fresnel Zone Calculator

Fresnel Zone Formula:

\[ r_n = \sqrt{\frac{n \lambda d_1 d_2}{d_1 + d_2}} \]

Fresnel Zone Number (n):

(integer)

Wavelength (λ):

meters

Distance from Tx to point (d1):

meters

Distance from point to Rx (d2):

meters

Fresnel Zone Radius (r_n):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Fresnel Zone?

The Fresnel zone is an elliptical area between two radio antennas that must be kept free of obstructions to ensure optimal signal strength. The first Fresnel zone (n=1) is most critical, but higher-order zones also affect signal quality.

2. How Does the Calculator Work?

The calculator uses the Fresnel zone formula:

\[ r_n = \sqrt{\frac{n \lambda d_1 d_2}{d_1 + d_2}} \]

Where:

\( r_n \) — Radius of the nth Fresnel zone (meters)
\( n \) — Fresnel zone number (1 for first zone)
\( \lambda \) — Wavelength of the radio signal (meters)
\( d_1 \) — Distance from transmitter to point (meters)
\( d_2 \) — Distance from point to receiver (meters)

Explanation: The formula calculates the radius of the elliptical Fresnel zone at any point along the radio path between transmitter and receiver.

3. Importance of Fresnel Zone Calculation

Details: Maintaining at least 60% clearance of the first Fresnel zone is critical for optimal radio communication. Obstructions in this zone can cause signal attenuation, multipath interference, and reduced link quality.

4. Using the Calculator

Tips: Enter the Fresnel zone number (typically 1 for first zone), radio wavelength, and distances from transmitter to point and point to receiver. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is the first Fresnel zone most important?
A: The first Fresnel zone contains the strongest signal energy. About 60% clearance of this zone is typically needed for good signal propagation.

Q2: How do I calculate wavelength from frequency?
A: Wavelength (λ) = speed of light (3×10⁸ m/s) / frequency (Hz). For example, 2.4 GHz = 0.125 meters.

Q3: What happens if the Fresnel zone is obstructed?
A: Obstructions cause signal attenuation, phase shifts, and potential multipath interference, reducing link quality and reliability.

Q4: How does Fresnel zone radius vary along the path?
A: The radius is maximum at the midpoint between antennas and decreases toward each end.

Q5: Is Fresnel zone important for all radio frequencies?
A: It's most critical for line-of-sight microwave links (typically 1GHz and above) where wavelength is small compared to obstacle sizes.