Antenna Gain Calculator
Calculate parabolic dish antenna gain from frequency, diameter, and efficiency. You can also convert gain values between dBi and linear scale.
Parabolic Dish Gain
dBi ↔ Linear Converter
What Is Antenna Gain?
Antenna gain tells you how well an antenna focuses energy in a particular direction compared with an ideal isotropic radiator. Higher gain does not create extra power out of nowhere; it concentrates the available power into a narrower beam. That means better signal strength in the desired direction and weaker radiation in others.
How This Gain Antenna Calculator Helps
This page gives you a quick planning tool for common RF work. It can help you size links for Wi-Fi bridges, microwave backhaul, satellite experiments, and point-to-point telemetry.
- Compute dish gain (linear and dBi) from frequency and diameter.
- Estimate wavelength and approximate beamwidth.
- Convert between dBi and linear gain instantly.
Formula Used in the Calculator
Dish Gain Equation
G(linear) = η × (πD / λ)2
Where:
- η is antenna efficiency (as a decimal, e.g., 0.65),
- D is dish diameter (meters),
- λ is wavelength (meters), with λ = c / f.
To convert to dBi:
G(dBi) = 10 × log10(G(linear))
How to Use the Calculator
1) Dish Gain Section
Enter operating frequency in GHz, dish diameter in meters, and efficiency in percent. Click Calculate Dish Gain to get:
- Wavelength
- Gain in linear scale
- Gain in dBi
- Approximate 3 dB beamwidth (degrees)
2) dBi and Linear Conversion Section
If you already have one gain format, you can convert it immediately:
- Use dBi to Linear when reading datasheets listed in dBi.
- Use Linear to dBi for engineering equations that start in linear form.
Example Calculation
Suppose you have a 0.6 m dish at 5.8 GHz with 65% efficiency:
- Frequency = 5.8 GHz
- Diameter = 0.6 m
- Efficiency = 65%
The result is roughly in the low- to mid-30 dBi range, depending on exact assumptions and rounding. That is a very directional antenna, ideal for point-to-point links where alignment matters.
dBi vs dBd (Quick Reminder)
This calculator outputs dBi, referenced to an isotropic radiator. Some specifications use dBd, referenced to a half-wave dipole.
- dBi = dBd + 2.15
- dBd = dBi - 2.15
Always check units before comparing antenna specifications.
Real-World Factors That Affect Gain
- Feed and connector losses: Cable and connector loss reduce effective system performance.
- Manufacturing tolerance: Surface errors can reduce dish efficiency.
- Pointing accuracy: High-gain dishes require precise alignment.
- Frequency drift: Off-frequency operation can degrade expected gain.
- Weather and obstruction: Especially relevant at higher microwave bands.
Practical Tips
- Use realistic efficiency values (50% to 75% for many practical dishes).
- Keep feedline short and low-loss for better end-to-end link quality.
- Combine gain calculations with link budget analysis (EIRP, FSPL, fade margin).
- For narrow beams, include a stable mounting system to maintain alignment.
Final Note
A gain antenna calculator is best used as a planning tool before deployment. For final validation, always compare with measured performance in your actual environment. If you pair this with a complete link budget and field test, you will get much more reliable RF designs.