H-field and E-field-probes capture magnetic (H-) and electrical (E-) fields. For emv-compliance a device or circuit must not produce too much stray radiation. H-field and E-field probes together with a spectrum analyzer allow you to detect and evaluate the strength of electromangnetic stray fields. This way weak points in a design or a PCB layout can be found.

Beeing passive probes their design is basically simple. A H-probe in its simplest form is just a single wire loop. The more  elaborate shielded versions are formed from a semi-rigid coax cable loop or from multilayer PCB material. Even more simple is a E-probe which can be just a short piece of coax cable with its inner wire exposed for ca. 10mm. Alternatively multilayer PCB material is useable here also. The probes can be optimized in their performance by adding clip-on ferrites or a commonmode choke.

Commercial probes are build just this way. DIY can save a couple of hundreds up to several thousands of  Euros. The probes shown above cost ~25€ on ebay and are well manufactured from PCB-material. DIY doesn´t pay off here any more.

The probe signal typically needs some amplification to gain sufficient levels. The fitting RF-amplifiers and cables are also available from ebay at extremly low costs.