I have simulated and measured the voltage noise of a buck converter at its input side in the previous post. This time I have sodlered a wire on different positions to create radiation from it. The position of the wire is at both sides of the chip ferrite which filters the input voltage of the buck regulator. This should demonstrate the efficiency of the chip ferrite to attenuate unwanted noise.
The picture shows the two positions of the antenna wire.
The difference in radiation is about 8 dB. The noisefloor is too high to give accurate results. At least it demonstrates the effectiveness of the chip ferrite.
As experiment I have tuned the decoupling caps to increase the radiation at a certain frequency. Therefore I have changed the value of one capacitor from 100 nF to 100 pF. And I have increased the inductance of the 22 µF capacitor by adding a wire to get a value of about 15 nH. This could be archieved by placing the capacitor further away or by a through hole type, too.
A simulation gives a peak at 100 Mhz. This should be able to interfere with the reception of a local radio station.
This is the photo of the setup.
The result is in the form of a short video this time. It shows the spectrum in combination with the audio received from a radio.