Antenna Gain Calculator for Construction

Calculation mode

Frequency

Dish diameter

Aperture efficiency (%)

Use manufacturer data when available.

Directivity (dBi)

Directivity excludes radiation efficiency.

Radiation efficiency (%)

Accounts for conductor/dielectric losses.

Antenna gain

Net gain = gain(dBi) − losses.

Input gain value

Input type

Cable loss (dB)

Connector loss (dB)

Other losses (dB)

Polarization loss (dB)

Use if antennas are cross-polarized.

VSWR (optional)

Mismatch loss is derived from VSWR.

Apply VSWR mismatch loss

Include mismatch loss in totals

Reset

Modes that include losses will calculate net gain by subtracting losses from the calculated or entered antenna gain.

Example data table

These examples use the parabolic dish formula and ignore losses.

Frequency (GHz)	Dish diameter (m)	Efficiency (%)	Estimated gain (dBi)
2.4	0.6	6	21.36
5.8	0.9	65	32.89
11	1.2	7	41.27

For field work, subtract cable/connector losses and validate with a site survey.

Formula used

Parabolic dish gain (in dBi):

G(dBi) = 10·log10( η · (π·D/λ)² )

η = aperture efficiency (0 to 1).
D = dish diameter (meters).
λ = wavelength (meters), where λ = c / f.

Directivity to gain (in dBi):

G(dBi) = D(dBi) + 10·log10(η)

VSWR mismatch loss (optional):

Γ = (VSWR−1)/(VSWR+1), Loss(dB) = −10·log10(1−|Γ|²)

How to use this calculator

Select a calculation mode that matches your antenna data.
For a dish, enter frequency, diameter, and efficiency.
For directivity, enter directivity and radiation efficiency.
To get net gain, add cable, connector, and other losses.
Optionally include VSWR to estimate mismatch loss.
Click Calculate to see results above the form.
Use CSV/PDF export to share the calculation with your team.

Construction tip: Keep antenna height, obstructions, and multipath in mind; gain is only one part of reliable coverage planning.

Professional notes for construction wireless planning

Antenna gain describes how effectively an antenna concentrates radio energy in a preferred direction compared with an ideal isotropic radiator. On construction sites, gain matters because temporary layouts change frequently, obstructions appear without notice, and noisy RF environments can reduce link reliability. This calculator helps you estimate theoretical gain for parabolic dishes, convert between gain units, and apply practical losses so your design reflects field conditions.

For parabolic dishes, gain rises with larger diameter and higher frequency because the aperture becomes electrically larger. The calculator uses the standard aperture formula G(dBi) = 10·log10(η·(π·D/λ)²), where η is efficiency, D is dish diameter, and λ is wavelength. Efficiency captures feed illumination, surface accuracy, and blockage; use manufacturer data if available. If you only know directivity, the tool estimates gain by applying radiation efficiency, which represents conductor and dielectric losses.

Example data can guide quick decisions. A 0.60 m dish at 2.40 GHz with 60% efficiency estimates about 21.36 dBi. A 0.90 m dish at 5.80 GHz with 65% efficiency estimates about 32.89 dBi. If your coax and connectors add 1.50 dB total loss, the net gain becomes roughly 31.39 dBi, which is the value to use in link budgets. Higher gain narrows the beamwidth, so mounting stability and precise alignment become more important as you increase dish size or frequency.

Losses are where many site deployments miss their targets. Cable attenuation increases with frequency and length, connector quality varies, and polarization mismatch can quietly remove several dB. The optional VSWR-based mismatch loss estimates power not delivered to the antenna due to reflections; treat it as a screening value and confirm with instrumentation when possible. After calculating, export results to CSV or PDF so supervisors and installers can verify the exact assumptions used on-site. As a final step, compare your net gain with regulatory limits, safety clearances, and the radio’s EIRP settings before commissioning the link.

FAQs

1) What is the difference between dBi and dBd?

dBi references an isotropic radiator. dBd references a half-wave dipole. Convert with dBi = dBd + 2.15 dB for typical engineering calculations.

2) Why does dish gain increase at higher frequency?

As frequency increases, wavelength decreases, making the dish electrically larger. The same physical diameter produces a narrower beam and higher directivity, increasing gain.

3) What efficiency value should I use?

Use manufacturer-reported aperture efficiency when available. If unknown, 50–75% is common for many dishes. Surface accuracy, feed design, and blockage can change efficiency significantly.

4) Should I include cable and connector losses?

Yes. Net gain should reflect real installed performance. Measure cable length, check datasheets for attenuation at frequency, and add realistic connector and accessory losses.

5) What does VSWR mismatch loss represent?

Mismatch loss estimates power reflected back toward the transmitter due to impedance mismatch. It reduces delivered power. Use it as a practical estimate and verify with a meter if critical.

6) Is higher gain always better on a job site?

Not always. Higher gain usually means narrower beamwidth, which can be harder to align and more sensitive to movement. Balance gain with mounting stability and expected site changes.

7) How do I share results with my team?

After calculating, use the CSV or PDF download buttons in the result summary. This captures inputs, losses, and outputs for quick review during installation and troubleshooting.