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Robot
Lawn Mower noise filtering
Robot lawn mowers are becoming very popular. That seems to be a problem for ham radio because they may radiate RF noise. 
Robot lawn mowers themselves
don't seem to cause any interference (Husgvarna in my case).
But the charging station with the boundary wires is the source
of the noise, especially when the mower is in the charging station.
The power supply was the worst in my Husgvarna
case and the filter choke in power cable was a remarkable improvement. The
boundary wires are using 5kHz to 40kHz signal so RF ferrite chokes can be
installed to them too. I added filter chokes to all the three cables and
the interference is now gone.
I used material 31 snap-in ferrites Fair-Rite 0431176451 with
5 turns in each. It provides enough impedance to attenuate RF noise. The
choke in the power supply cable is the most important.
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