How to use Antenna Factors
What is an Antenna's "Antenna Factor"?
An antenna's antenna factor (AF) is a comparison between the field level presented to the antenna and the actual voltage produced by the antenna at it's connector. The antenna factor varies with frequency, that is for the same presented field strength, but at a different frequency, the voltage produced at the connector is not constant.

Creating the AF Data
By way of further explanation, a not particularly accurate yet simple way to generate AF data for an antenna would be to illuminate it with a known field strength at a specific frequency, and use a receiver to measure the volts produced at the antenna connector. The reason it is not particularly accurate in this example is because we will use the RF train used in an immunity system to create a known field strength (say 10V/m) over the antennas frequency range (covered in equally spaced spot frequencies). The field probe is then replaced by the antenna in question, the spot frequencies stepped through and the voltage at the antenna connector measured and recorded.

Using the AF Data
Far more accurate AF data is supplied in plot form by the antenna supplier. This data is input to the EMC emissions software so it can add the antenna factor to the entered cable loss etc. All the data entered into the software is in dB's.

The field level emitted by the EUT can then be determined by simple algebraic addition of the voltage reading on the receiver and the entered data.

That is the voltage reading in dBuV is added to the AF at that frequency and the cable loss at that frequency to obtain the actual field strength measured by the antenna.

Welcome to A.H. Systems, inc.
A.H. Systems has been established since 1974 and manufactures a complete line of affordable, reliable, EMI test equipment. Our individually calibrated EMI Test Antennas, Preamplifiers, Current Probes and Low-Loss Cables satisfy many test standards including CISPR, MIL-STD, FCC, EN, VDE, IEC and SAE. With a wide variety of mounting configurations, we can also offer tripods and accessories that compliment other EMI testing equipment used to complete your testing requirements. We are also committed to providing all of our clients with no cost prompt and professional technical support. Manufacturing high quality products at competitive prices with immediate shipment plus prompt technical support are our goals to improve the quality of your testing requirements