I have two 12vDC - 19vDC converters; one is an Itekiro, the other a PWR+. Both are noisy, interfering with broadcast FM and HF SSB
when in use. I have been able to silence both by putting a clamp-on ferrite choke on the 12v and another on the 19v wire and also wrapping the brick in aluminum
foil. The foil made a noticable difference. I intended to replace the aluminum
foil with copper foil so that I could solder on a ground wire, but with the problem gone, I've never done it.
My clamp-on chokes are Fair-Rite 31 material from Mouser.com. The newer (and of course more expensive) 75 material may be a better option.