Calculation of antenna factor and gain

The calculation equation useful for mutual conversion of an antenna factor and gain is presented.

Application

Solution

• When measuring the electric field strength by com bining a spectrum analyzer with an antenna, calcul ating an antenna gain from an antenna factor, or the contrary may be needed. The calculation equation is shown below. In MSA438 , the electric field strength can be read directly by registering the antenna gain in it.
• The following equation is used to calculate the ant enna factor Af (dB/m) from the antenna gain Ga (dBi) in a 50-ohm system.

• Similarly, the following equation is used to calcula te the antenna gain Ga (dBi) from the antenna facto r Af (dB/m) in a 50-ohm system.

• The following table is a calculation example.

Frequency [MHz]	30	50	100	200	500	1000	1500	2000	3000
Antenna factor [dB/m]	38.5	32.5	27.8	22.6	23.3	29.5	40.2	47.3	50.5
Antenna factor [dB/m]	-38.7	-28.3	-17.6	-6.4	0.9	0.7	-6.4	-11.1	-10.7

System configuration

Spectrum Analyzer MSA438	×1
MSA438 calibration set	×1
Biconical Antenna［MAN150]	×1

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