Field Strength Estimator

The program Field Strength and Power Estimator calculates power flux density, electric and magnetic field strength from the transmitted power, associated frequency and gain of the transmitting antenna.

Additionally the input power into a receiver with 50 Ohm input impedance is calculated from the gain of the receiving antenna.

The program automatically converts power flux density into electric and magnetic field strength.

Depending on the transmitted frequency, various parameters influence the received power and field strength, such as non-line-of-sight propagation, changes in polarisation, reflections, and multi-path propagation affect the true values. Additionally antenna VSWR and cable losses have to be considered.

The program Field Strength and Power Estimator does not consider these impairments. It assumes conditions, that are close to the best possible theoretical values. This is why we say the program is an Estimator, not a Calculator.

Quick Start

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To start calculation, just select a row by touching it and change a specific value.

After touching the "Estimator" button in order to return to the main menu, the dependent values are calculated automatically.

The results are displayed with 3 decimal places only (except the antenna gain values, which are displayed with 1 decimal place).

If you change a unit, the corresponding numerical values are converted.

For example: 1 mW gives 0 dBm if the unit is changed from mW to dBm. Be careful not to change a zero linear value to dB.

It is also possible to enter the values with "m" for milli, "M" for mega, "u" for micro, etc.

When changing the values for Frequency, Antenna Gain Transmitter, Antenna Gain Receiver or Distance, all other values are recalculated using the set Transmitted Power.

When changing one of the other values however, Frequency, Antenna Gain Transmitter, Antenna Gain Receiver and Distance will keep their values (the "Persistant Data" values).

Be careful: If you enter a Distance value, which is smaller than 0.159 times the wavelength

( D < Lambda / (2*Pi) ), the distance field becomes yellow as a warning for leaving the far-field condition.

This application is based on the application note:

"1MA85: Field Strength and Power Estimator"

by Rohde & Schwarz GmbH & Co. KG

( http://www.rohde-schwarz.com/appnote/1MA85 )

Rohde & Schwarz GmbH & Co. KG Web Site >> Field Strength & Power Estimator Support