I have been to multiple locations and my 390 has not dipped below 1.8mg and average readings in multiple locations is 3.5mg. I picked locations where there are no power lines within a 200 feet and I turned off my phone just to make sure but still 3.5mg.
So i purchased another 390 and this meter is also reading 3.5 average and it has not dipped below 2.
What gives? I live in northern new jersey so what could it be? Is 3mg background for this location?