Schwarzbeck HFRA 5156 Transmit Loop Antenna For Calibrations

The Transmit Loop Antenna HFRA 5156 was designed to generate well defined magnetic fields with moderate fieldstrength levels (< 0.1 A/m) in the frequency range DC to 5 MHz. With slightly reduced performance the loop can be used in the frequency range up to 10 MHz. The loop, consisting of ten turns in series with a 480 ? resistor, is shielded against E-fields. The loop can be mounted at its female large camera thread.

The generated magnetic field is proportional to the loop current. A tabular indicates the fieldstrength values in A/m and dBµA/m to be expected with the maximum permissible current of 100 mA. Additionally the relative decrease of magnetic fieldstrength referred to the center of the loop antenna can be found. Lower magnetic fieldstrengths can be achieved by scaling the current to the respective value. With a feed current of 10 mA instead of 100 mA the tabular values decrease by a factor of 10, which corresponds to a reduction by 20 dB in logarithmic measure. All specified magnetic fieldstrengths refer to the component which is perpendicular to the loop-plane.

Application:

Both female BNC-connectors are directly wired with each other. One of them can be used to feed the loop, the other can be used to monitor the voltage with a voltmeter (high impedance). The measurement distance to apply for the calibration of RX-loops depends on the RX-loop dimensions. For large loop antennas a higher calibration distance is required in order to obtain a uniform field distribution over the complete loop area. The shorter the distance, the smaller the uniform area and the size of antennas to be calibrated. The following table indicates the recommended minimum calibration distances, depending on the loop diameter of the loop under calibration and the wanted field uniformity.

The error to be expected caused by the decay of fieldstrength within the RX-loop area is less than the specified field uniformity, because of the averaging characteristics of the loop area exposed to the magnetic field.

Magnitude of Impedance	Transmission between TX-Loop HFRA 5156 and RX-Loop HFRAE 5162
Relative Decay of Fieldstrength versa Distance	Relative Decay of Fieldstrength versa Distance
Absolute Decay of Fieldstrength versa Distance with 100 mA Loop Current	Absolute Decay of Fieldstrength versa Distance with 100 mA Loop Current