A handy formula…..plot your antenna gain vs. frequency and convert to AF vs. frequency

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-Charlie

?W5CDT

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Thanks Charlie!

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I've been a Ham since 1960 and I never recall hearing about something called "antenna Factor".? Hardly a day goes by when I don't learn something new and you've supplied that wonder today!

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So I decided to ask my favorite AIl service about antenna factor.? I use a service from Google called Gemini (gemini.google.com).? Here is "it's" answer proving that AI can sometimes be very useful!

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The term "Antenna Factor" refers to the ratio between the electric field strength of an electromagnetic wave and the voltage that the antenna receives from that wave. It's a way to quantify how efficiently an antenna converts electromagnetic energy into a measurable voltage.

Key points about Antenna Factor:

• Units: Antenna factor is typically expressed in decibels per meter (dB/m).
• Frequency dependence: Antenna factor varies with the frequency of the electromagnetic wave. Antennas are designed to be most efficient at specific frequencies or frequency ranges.
• Use in measurements: Antenna factor is crucial in electromagnetic interference (EMI) testing and other applications where it's necessary to determine the actual electric field strength. By adding the antenna factor (in dB/m) to the voltage measured at the antenna output (in dB?V), you can calculate the electric field strength (in dB?V/m).

Example:

Let's say you're measuring the electric field strength of a radio wave using an antenna. The voltage measured at the antenna output is 50 dB?V, and the antenna factor at the frequency of the radio wave is 10 dB/m. To calculate the electric field strength, you would add these two values:

Electric field strength = 50 dB?V + 10 dB/m = 60 dB?V/m

This means that the electric field strength of the radio wave is 60 decibels above 1 microvolt per meter.

In summary, the antenna factor is a critical parameter that helps relate the voltage received by an antenna to the actual electric field strength of an electromagnetic wave. It's essential for accurate measurements in various applications, including EMI testing, wireless communication, and radar systems.

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Thanks again Charlie!

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Dan N1DH

Hi Dan,

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The reason antenna factor is not well-known is because the only technical folks that care about it are EMC test people doing FCC and European compliance measurements. ?Broadcast engineers and hams care more about antenna gain. ?

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One of the reasons EMC test antennas are so expensive is because they usually come with an antenna factor calibration chart often custom for each serial number shipped.

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Fun stuff! ?Now all I need is an anechoic chamber. ?;-)

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-Charlie

?W5CDT

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