Extreme RFI From a Small SMPS!

Here I am demonstrating the extreme radio frequency interference from a small switch mode power supply (SMPS) powering the external speaker of my laptop. You can see the bandspread increases as the volume on the speaker is increased and RFI disappearing when the SMPS is switched off. Difference between RFI pick of different antenna-cable system is also shown. More interference is seen with endfed half wave antenna using thin HLF 200 cable while it is less with RG 213 cable connected to 40/10m inverted V fan dipole antenna. EFHW has an ‘ugly balun’ or 10 turns of coax wound on a 3 inch diameter PET bottle near the feedpoint. Fan dipole has a 1:1 current balun purchased from a local ham. EFHW has a 49:1 balun at feedpoint which was bought from the same source. I do work good DX with both antennas, though each has different propagation characteristics.