In the VLF-HF frequency range 9 kHz to 30 MHz the magnetic field strength is measured preferably, but often expressed in the unit of the electric field strength as the "fictive E field-level" ( dBμV/m).

In the undistorted far-field both units are linked by the characteristic impedance of free space 120 pW = 377 W. Practical EMC/EMI measurements however are carried out in the near-field zone (D

The magnetic loop antenna described here may be operated with up to 100 W input power for short periods and with 30 W continuously. An external 50 Ω power termination with the proper dissipation is required. A 50 Ω 20 Watt termination is part of the scope of delivery of HFRA 5149. It is more than sufficient for the maximum output of laboratory power signal generators. The HFRA 5149 has a 3/8" camera thread at the box.

Specifications:

• Nominal frequency:  9 kHz – 30 MHz
• Impedance at „Input“ and „Monitor“:  50 Ohm
• VSWR at „Input“:  < 2 (0.02 – 20 MHz) < 4 (0.009 – 30 MHz)
• Loop diameter: 500 mm 
• Terminals:  Type N (f) 2x
• Mount (camera thread):  3/8"UNC
• Weight:  1.25 kg