Interference suppression filters and ferrite cores

Every electrical device is a source of interference or may be interfered with by other devices. Radio amateurs deal with signal reception, whose level is many times weaker than in the commercial sphere. Weak signals can thus overlap others, even unwanted signals from other devices, which emit HF energy. Typically, these are power supplies, for example, chargers, computers, etc..

On the contrary, the transmitted radio signal of an amateur station must meet the quality criteria. However, even a good signal from an amateur station can inadvertently cause interference to another device. This usually happens if the manufacturer of the device, in an effort to save a few cents, omits the necessary filter circuits or omits some other requirements of electromagnetic compatibility., EMC.

Although it sounds like a joke – save a few cents – so it is quite a common practice, which unfortunately complicates life. In this case, it is possible to help by adding such filters. Which, however, is appropriate? Which ferrite material or filter design better suppresses unwanted signals?

Video “Filters and ferrite cores for interference suppression” (Drirr90) worth a look. While the beginning talks mainly about network filters, the other half contains practical measurements with a toroid or snap-on filter.