[RFI] RFI-free Vehicle 5v USB Adapter?

[Jim Brown]

On 3/15/2020 5:41 PM, Greg Troxel wrote:
> I have a few Anker dual-port lighter/USB devices.  WIth them in the
>    shack, charging phones, and running an esp8266, I don't hear them.
>    That of course doesn't prove totally quiet; it means less than my
>    other noise.

What matters is proximity to ANTENNAS, not to radios. It also matters 
what OTHER noise we're hearing -- the typical home has DOZENS of noise 
sources. We hear our own and we hear our neighbors, so one noise is 
buried by the combination of those others. I generally discount 
observations that xy device is quiet unless they have been made in a 
location that is already relatively quiet, or the device is very close 
to antennas used for observation.

Our 7QP and CQP county expedition team ran into the issue of a logging 
computer that could be used while mobile, with HF antennas a few feet 
from the computer and the inverter and computer's power adapter! I have 
a similar situation in my shack, with a 160M vertical only 20 ft from my 
operating desk.

To evaluate a potential noise source, I use a battery operated RX that 
can tune to the ham bands, and use it to probe around that source and 
the wiring connected to it.

NA6O has gone several big steps better, setting up noise sources in a 
test lab that he's built and qualified!

73, Jim K9YC