biquad antenna calculator

How this biquad antenna calculator works

A biquad antenna is built from two connected square loops. In the classic design, each side of each square is approximately one-quarter wavelength. This calculator converts your frequency into wavelength, then computes practical build dimensions: square side length, total driven element wire length, reflector spacing, and suggested reflector size.

What you get from the calculator

• Wavelength: Full free-space wavelength for your selected frequency.
• Square side length: The core biquad segment length (approximately λ/4 adjusted by velocity factor).
• Total wire length: Estimated length for the full two-square driven element.
• Element-to-reflector spacing: Typical starting point around λ/8.
• Reflector size: Suggested square/plate size based on wavelength multiplier.
• Feed gap: Small central gap where your feed is connected.

Formulas used

The script uses these standard relationships:

• λ = c / f where c = 299,792,458 m/s
• Side length = (λ / 4) × velocity factor
• Total wire length = 8 × side length (for two connected squares)
• Reflector spacing ≈ λ / 8
• Reflector size = λ × reflector factor

Build tips for better real-world results

1) Start slightly long, then trim

If you have a VNA or antenna analyzer, cut a little long and trim small amounts. Tiny changes can move resonance significantly at higher frequencies.

2) Keep bends sharp and symmetric

Uneven corners and mismatched square sizes can distort pattern and impedance. Use a jig to maintain identical segment lengths and 90° bends.

3) Maintain spacing accurately

Reflector spacing affects gain and impedance. Nonconductive standoffs and careful measurement help maintain repeatability.

4) Use a solid feed connection

A poor solder joint at the feed can waste signal and create intermittent behavior. Keep leads short, clean, and mechanically stable.

Common frequency examples

• 2.4 GHz ISM / Wi-Fi: popular DIY biquad build range.
• 5.8 GHz FPV: physically smaller dimensions; tighter tolerances required.
• Other microwave links: same math applies; fabrication precision becomes critical as frequency rises.

Limitations and practical notes

This calculator gives excellent starting dimensions, not final guaranteed dimensions for every material and environment. Nearby objects, enclosure effects, connector style, wire diameter, and construction tolerances can shift performance. For best results, validate with measurement tools and adjust iteratively.