Ready for an advanced calculation
Choose a calculation mode, enter dish data, then calculate.
Formula used
Dish gain depends on diameter, wavelength, and realized efficiency. Surface errors reduce efficiency using the Ruze relationship. Beamwidth narrows as electrical dish size increases.
Variable definitions
How to use this calculator
- Select gain, diameter, frequency, or efficiency mode.
- Choose frequency input or direct wavelength input.
- Enter dish diameter and aperture efficiency assumptions.
- Add surface accuracy and geometric blockage details.
- Enter link losses when received power matters.
- Calculate, review warnings, then export the results.
Dish geometry illustration
Example dish configurations
| Application | Diameter | Frequency | Efficiency | Approximate gain |
|---|---|---|---|---|
| Ku satellite reception | 0.60 m | 12 GHz | 65% | 35.4 dBi |
| C-band earth station | 1.20 m | 4 GHz | 60% | 31.9 dBi |
| Microwave backhaul | 3.00 m | 8 GHz | 65% | 46.1 dBi |
| Radio telescope | 10.0 m | 1.42 GHz | 55% | 41.0 dBi |
| Ka satellite terminal | 1.20 m | 30 GHz | 60% | 49.3 dBi |
| Amateur microwave dish | 2.40 m | 10 GHz | 58% | 46.1 dBi |
Frequently asked questions
What does dish gain measure?
Dish gain compares focused radiation with an isotropic radiator. Higher gain concentrates energy into a narrower angular region. It does not create additional transmitter power itself.
Why is practical gain lower?
Real dishes lose energy through illumination and mechanical imperfections. Feed spillover and phase errors also reduce usable aperture. Surface accuracy becomes especially important at higher frequencies.
What efficiency should I use?
Many practical dishes operate between fifty and seventy percent. Offset dishes often avoid central feed blockage losses. Manufacturer measurements remain the best source for final design.
How does diameter affect gain?
Gain rises with the square of dish diameter. Doubling diameter ideally adds about six decibels. The beam also becomes substantially narrower after enlargement.
How does frequency affect gain?
Higher frequency increases gain for a fixed dish diameter. Surface tolerances become harder to maintain simultaneously. Atmospheric and rain losses may also increase significantly.
What is Ruze efficiency?
Ruze efficiency estimates loss from random surface deviations. It compares RMS error against the operating wavelength. Smaller wavelengths demand much more accurate reflector surfaces.
What is dBi versus dBd?
dBi references an ideal isotropic radiator. dBd references a half-wave dipole instead. Convert dBi to dBd by subtracting 2.15 decibels.
How accurate is beamwidth?
Beamwidth formulas are useful engineering approximations. Actual patterns depend on feed taper and reflector shape. Measured radiation patterns provide better final verification results.
What causes pointing loss?
Pointing loss occurs when antennas miss perfect alignment. Narrow beams increase sensitivity to mechanical positioning errors. Wind and mount flex can worsen tracking performance.
Can this calculate satellite links?
The link section estimates free-space and user-entered losses. Satellite calculations may require additional propagation models. Include realistic rain, atmosphere, polarization, and hardware losses.
Is this suitable for final certification?
This tool supports design estimates and educational checks. It does not replace calibrated antenna measurements. Verify critical installations against applicable engineering standards first.