#### Nomograph

###### for the antenna gain of a symmetrical parabolic antenna

Figure 1: Preview of the nomograph

#### Nomograph for the antenna gainof a symmetrical parabolic antenna

This nomograph is used to determine an antenna gain of a symmetrical parabolic antenna from the data of a frequency (or wavelength λ) and the diameter d of the antenna (alternatively in meters or in feet.) The nomograph is based on the approximation:

 G = 20log(d/λ) + 9.94 dB - 10log(η) (1)

The example describes a satellite receiving antenna with a frequency range of 10.7 to 12.75 GHz and a diameter of 80 cm. For more oval reflectors of offset antennas, use the smaller dimension.

However, the nomogram can only consider two variables. Therefore, the efficiency η is assumed to be equal to 1 and must be corrected as follows:

• for η= 0.79 subtract 1 dB from the nomogram result;
• for η= 0.5 subtract 3 dB (standard value for parabolic reflectors);
• for η= 0.25 subtract 6 dB from the nomogram result.

Please print out the nomogram as an individual image.