replaced 12V power plug with 12V-to-USB, now have radio static

Vehicle: 2009 Expedition

Background: swapped rear power point (12V "lighter" socket) with a 12V-to-USB adapter as shown below:

via spade terminals crimped to existing wires. Now, when the adapter is plugged in, there is static through the car audio speakers when the radio is on.

It happens whether the engine is running or not running, so I think eliminates the alternator as a contributor to the issue. To figure whether or not it was related to the wiring, we went directly to the battery via test leads to the adapter. Connected = static. Not connected = no static. So i think this eliminates the wiring / grounding as an issue. Seems like we need some kind of filter but i suck at electrical and don't know where to get an appropriate filter.

UPDATE: It's an antenna issue, apparently, as it only affects radio. CD plays with no static with the 12v-to-USB adapter connected to vehicle wiring.

anyone seen this problem / know the solution?

I don't have a solution, but I am watching this with interest because I have the same problem. One of my adapters makes a high-pitched noise while a phone is plugged in to the 2.1A slot but then quiets down when a second phone is plugged in to the 1A port. It also puts a ton of interference into the radio along with its squealing. I solved that problem by putting that adapter in the wife's car and using the other one in mine, but that probably isn't the fix you're looking for.

You installed a part producing interference. Not much you can do about it besides remove or replace it.

you could try one of these filters http://www.amazon.com/Magnum-XLF20C-Filter-Radios-Prong/dp/B005AUMLAW/ref=sr_1_1?ie=UTF8&qid=1420309058&sr=8-1&keywords=cb+radio+power+filter but it would probably be cheaper to just get a higher quality usb power supply.