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Looking at the RF currents on the power line from a digital LED panel. The noise from the PWM switching is all sub-5MHz, and noise from the communication bus / internal state updates runs from 1MHz to 100MHz. The measurement numbers were not corrected and are only useful for relative comparisons.
The goal here was to determine what kind of filtering the board needed- it looks like a few hundred uF of bulk capacitors does a good job for the 0-3MHz PWM noise, and series resistors on the communication cable reduces the higher frequency bits by 5-15dB.