Was all excited to try my remote shack (rpi3 controlling ft-891 over wifi) but unlike my in-house testing with pi powered off a wall wart, when I power it off battery through a 12v->5v converter I get noise that (at least on 20m) raises an s1 floor to s9. Basically the rig is in my car powered off a lifepo (not the car battery), I mention because space is tight.
I believe it is mostly coming from the converter, this one: https://www.amazon.com/
It seems to send noise through cables connected to it (well technically the usb power hub I made), but also through the pi and into the radio via the usb cat cable. But any cable plugged into seems to sort of act like an antenna.
If I power the pi off of a 5v cellphone battery pack, noise drops down (seems like maybe a little, but at least S6 floor drop). As I say, I tested this pi in close proximity to the radio before off a wallwart, so I don't think pi itself is creating the noise.
Only thing I want to mention is that I created my own little USB power hub to connect to the converter using some jacks I have, and I assumed it is correct or at least harmless to ground the usb jack cases, was that wrong?
For now I am assuming the converter is noisy.
Anybody have experience with that one? Is there a better go-to? Besides ferrites (will try in the morning) any other way to quiet this one down? I have a few buck converters lying around and will see if I can come up with something, but open to any suggestions.