The HFRA 5149-60B H-field transmitting loop antenna is designed for immunity testing in the frequency range from 9 kHz to 30 MHz and is compliant with CISPR 16-1-4.

In the VLF-HF frequency range from 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 377 ohm. Practical EMC/EMI measurements however are carried out in the near-field zone. For that reason defined magnetic field sources are required. For Immunity Tests powerful H fields might be needed, but also general tests and measurements at an open site, in screened rooms and in absorber-lined rooms require well-defined powerful H field sources. Magnetic fields in the near-field zone decay with the inverse 3rd power of distance (ca. 18 dB at twice the distance). Even at 1 m distance at 30 MHz the transition from pure near-field to far-field begins, the exponent of degradation gradually reduces from 3 to 1 in the undistorted far-field.

The magnetic loop antenna described here may be operated with up to 100 W input power for short periods or with 30 W continuously. An external 50 ohm power termination with the proper dissipation is required. A 50 ohm 20 Watt termination is part of the scope of delivery of HFRA 5149-60B. It is more than sufficient for the maximum output of laboratory power signal generators. The HFRA 5149-60B has a 3/8" camera thread at the box for mounting it e.g. on a tripod. 

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: 590 mm 
• Terminals:  Type N (f) 2x
• Mount (camera thread):  3/8"UNC
• Weight:  1.25 kg