Field strength calculator.
Use this calculator to determine the field strength at the three major distances used in EMC immunity testing, in V/m, using a standard power level of 100W into the antenna and a moderate antenna gain found in most of the EMC antennas that are able to create a field compliant to the EN-61000-4-3 FUA (Field Uniform Area, see standard EN 61000-4-3) requirements.
Be careful with your choice of an antenna in an RF immunity test in relation to the gain. High gain numbers produce a narrow beam, making it difficult to create a 1.5 x 1.5 meter FUA according the standard EN61000-4-3.
The E-Field is calculated for three distinct distances 3, 5 and 10 meters you often find in Radiated Immunity tests in EMC testing. Under development we have at the moment a brand new EMC immunity system calculator with which you can determine what amplifier power and antenna gain is required to generate the required field for your EMC immunity testing.