I picked up a cheap charging cable for my Baofeng UV-9S. (https://www.amazon.com/gp/product/B07TSDSQ4Z/). It .. well, it works.
But it messes up operating my radios! I heard super strong interference on my HF receiver and my VHF receivers.
So, let's take a look. I setup a little antenna in my shack. The baofeng was about 6ft away.
Here's DC to 120MHz. Those peaks to the right? Broadcast FM. The marker is at 28.5MHz.
Ok, let's plug in the baofeng and charger.
Ok, look at that noise. Ugh. That's unfun.
What about VHF? Let's look at that. 100-300MHz.
Ok, that's expected too. I think that's digital TV or something in there. Ok, now, let's plug in the charger, without it charging..
Whaaaaaaaaattttttt oh wait. Yeah, this is likely an unshielded buck converter and it's unloaded. Ok, let's load it up.
Whaaaaaa oh ok. Well that explains everything.
Let's pull it open:
Yup. A buck converter going from 5v to 9v; no shielding, no shielded power cable and no ground plane on the PCB. This is just amazing. The 3ft charge cable is basically an antenna. "Unintentional radiator" indeed.
So - even with a ferrite on the cable, it isn't quiet.
It's quiet at 28MHz now so I can operate on the 10m band with it charging, but this doesn't help at all at VHF.