Arduino Menu Code:  MultiDigi_Menu_v0.1


EZ RFI Filter – Get the RF out!

In the development phase of the MultiDigi, there was a need for RFI filtering discovered. Not just on power, but also on data and audio signal lines. The solution after much investigation, experimentation, and trial was found to be a very simple LC filter based on a ferrite bead and capacitor. The Z is such that serial digital, audio and DC power are passed without degradation yet frequencies above 3MHz are attenuated and therefore rejected by the MultiDigi. Sometimes the most simple solution is the best.

L1 is a ferrite bead in 1206 SMD package with an impedance of 100 ohms, C1 is a 100 nano-farad capacitor, rated to 50VDC  to ensure stronger signals will not overload it.

Tested results showed that an RF signal of up to 1.5V p-p induced on the patch cables were successfully reduced to less than 30mv after the filter, putting those signals into the noise floor for the digital circuits and therefore ignored.

RFI Filter EZ


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