Calculates half-power and other beamwidth levels for parabolic antennas on all EME bands
To calculate dish gain click here
Half-Power Beamwidth (HPBW, 3dB) approximation:
where λ is the wavelength and D is the dish diameter. This approximation is valid for typical parabolic dishes with ~60% efficiency.
Beamwidth at an arbitrary (X) Beamwidth Level:
where X is the corresponding Beamwidth Level (for instance, 1dB, 0.5dB or 0.1dB)
| Beamwidth Level | Power Remaining | Power Lost |
|---|---|---|
| 3 dB (Half-Power) | 50% | 50% |
| 1 dB | ≈ 79.4% | ≈ 20.6% |
| 0.5 dB | ≈ 89.1% | ≈ 10.9% |
| 0.1 dB | ≈ 97.7% | ≈ 2.3% |
These values are exact by definition of the contours. In practice, remaining well within the 0.5 dB or 0.1 dB beamwidth on lower EME bands, and within 0.05 dB or 0.1 dB on higher EME bands, ensures negligible loss.
For a given frequency, an antenna becomes electrically small when D ≈ 2λ. In this region, the corresponding beamwidth becomes very large (on the order of ~30–40°). The orange dashed line at ~35° marks this practical limit.