Antenna Gain & Beamwidth Calculator
Parabolic dish gain, half-power beamwidth, and pointing-loss sensitivity. G = η · (π·D/λ)². Pairs with the link budget calculator — this gives the antenna terms that feed it.
Inputs
Antenna
Typical: 0.55 prime-focus, 0.65–0.70 shaped Cassegrain, 0.50 offset-fed with strut blockage.
Frequency
Pointing
Loss ≈ 12·(θ_err / θ₃dB)² dB — the standard quadratic approximation near boresight.
Result
Need the full link budget — G/T, C/N₀, rain fade, and margin against a real ground station schedule?
Sign up →Frequently asked questions
How is parabolic antenna gain calculated?
G = η·(π·D/λ)², where η is aperture efficiency, D the reflector diameter, and λ the wavelength. In decibels, G[dBi] = 10·log₁₀(G). Gain rises with the square of both diameter and frequency, so doubling either adds about 6 dB.
Why does a higher-gain antenna make pointing harder?
Beamwidth is inversely proportional to D/λ, so every dB of gain narrows the beam. A 13 m X-band dish has a beamwidth of roughly 0.2° — which means the ADCS and the ground pedestal both have to hold pointing to a small fraction of a degree or the link margin evaporates.
Where does the 70λ/D beamwidth constant come from?
It is the standard engineering approximation for a uniformly-ish illuminated circular aperture with typical edge taper. Values between 65 and 70 appear in the literature depending on the illumination profile assumed; 70 is the common conservative choice and the one used here.
What does this tool NOT account for?
Feed spillover and blockage in detail, cross-polarisation, sidelobe envelopes and ITU-R S.580 masks, radome loss, surface-roughness (Ruze) loss at high frequency, or near-field effects. Those matter for regulatory filings and are covered in the Aerospace Pack's RF suite.
Upgrade for the full RF chain
- End-to-end link budget with G/T, C/N₀, Eb/N₀ and margin
- Rain fade and atmospheric attenuation by band and elevation
- Ruze surface-loss and pointing-budget rollup
- Ground station scheduling with real contact windows
- ITU filing support and frequency planning