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You are right, ch1 is a piece of wire with a ferrite tube molded around it. You can get the size from the pcb layout, but these usually are the size of a 1/4 W or 1/2 W resistor. An alternative is a small ferrite tube with one or two holes through the length and a separate wire threaded through and looped around. These have a larger diameter but better performance. Longer, thicker, whatever - the more ferrite, the better. It is acting as the series inductor in an LC filter.
A common mode version might work better, but only if you are dealing with common mode noise. But you no longer are working with the original circuit as designed, and you now have a series impedance in the GND that can create the effect of noise where there was none before. Been there, watched another guy do that, learned.
ak
A common mode version might work better, but only if you are dealing with common mode noise. But you no longer are working with the original circuit as designed, and you now have a series impedance in the GND that can create the effect of noise where there was none before. Been there, watched another guy do that, learned.
ak
