Volumio primo, turn WiFi really off

Volumio Information

Volumio Version:2.779
Hardware: volumio primo hifi
DAC:Ess primo dac

I noticed that the WiFi networks close to me stay visible with WiFi turend off, and that the signalstrenght is lower with antenne disconnected. This tells me wifi stays on and still emits high frequency noise. I would like to be able to really completely turn the signal off.
Any tips or is this a hardware thing?
I know it is nitpicking, but it would make the audiophile standpoint of volumio even more logical to me.