# Calculate small loop Antenna Factor

This calculator allows calculation of the Antenna Factor of a small loop. Antenna Factor is a sensitive calibration parameter commonly used for field strength measurement.

 Inputs: Frequency (MHz) Loop type Circle Square Hexagon Octagon Loop perimeter (m) Wire diameter (mm) Wire conductivity (S/m) Directivity Load resistance (Ω) Other loss (dB) Received power (dBm) Results: Antenna factor (dB/m) Field strength dBμV/m Field strength dBμA/m Gain (dBi)

Assumptions:

• perimeter<0.3λ;
• wire is round;
• wire is bare;
• wire is non-magnetic;

The calculator depends on an assumption that the current is uniform around the loop. It is most accurate for small loop perimeter, accuracy suffers for perimeter>0.1λ, but is usable up to about 0.3λ.

The calculator assumes that the ratio E/H is equal to that of free space (3.76730313461771e+002), measurements within a half wavelength of a radiator may have significant error.

In practice, a thin layer of insulation does not introduce significant error.

The calculator assumes a free space value for radiation resistance. Copper conductor is assumed, but the results are not very sensitive the the material resistivity.

A receive power level may optionally be specified, and field strength will be calculated for that scenario. If you set receive power to 0dBm, the field strength values will be those values to add to receive power level to calculate the respective field strenths.

The calculator does not do a lot of error checking, if you enter nonsense, it will produce nonsense.

# Example

Using the Example 1 button calculate the scenario.

# References / Links

• Grover, F. 1945. Inductance calculations.
• Kraus, J, and Markefka R. 2002. Antennas for all applications, 3rd ed. New York: McGraw Hill.

# Changes

 Version Date Description 1.01 10/06/2014 Initial. 1.02 18/12/2014 Revision. 1.03 1.04 1.05