I take my product to EMC test and we found some noise at 228.81Mhz. I'm using an SDC2130. It is installed near a miniatx box. Do you have any idea where this noise come from and what should we do to decrease it?
You can see the result with motor on:
You can see the test result for both motor on and off on attached files.
Most of the noise would come from the motor wires. When the motor is on, the motor wires will carry a PWM signal with extremely sharp edges (<100ns rise and fall time). Reducing EMC is an art which we are not expert at. Consider reducing wire leghts as much as you can. Twist the two motor wires. Shielding them. Look for more tips on the net.