At the 1420.405 MHz hydrogen line, the SETI Horn of Plenty is generally quoted at about +20 dBi gain (roughly +18 dBd).
For comparison:
| Antenna | Approx Gain (dBi) | Approx Gain (dBd)* | Notes |
| SETI Horn of Plenty | 20 dBi | 17.9 dBd | Broad bandwidth, low sidelobes |
| 1 m dish | 20.9 dBi | 18.7 dBd | Similar overall gain to Horn of Plenty |
| 1.5 m dish | 24.4 dBi | 22.2 dBd | About 4 dB stronger than Horn |
| 2 m dish | 26.9 dBi | 24.7 dBd | Common amateur H-line size |
| 3 m dish | 30.4 dBi | 28.3 dBd | Typical serious amateur radio telescope |
| 17-element patch Yagi | 15 to 17 dBi | 12.9 to 14.9 dBd | Depends on boom length and optimisation |
| 86 cm Ptarmigan Triffid 4×4 dipole array | 16 to 18 dBi | 13.9 to 15.9 dBd | Wide beam, good sky coverage |
- dBd is referenced to a half-wave dipole.
dBi is referenced to an isotropic radiator.
Conversion: dBd = dBi – 2.15
A few useful comparisons:
- The SETI Horn of Plenty is approximately equivalent to a good 1 metre dish.
- A 2 m dish has roughly 7 dB more gain than the horn, which means about 5 times the received power.
- A 3 m dish has about 10 dB more gain than the horn, or roughly 10 times the received power.
- The horn often performs better than its raw gain suggests because of very low ground pickup and sidelobes.