Given that the frequency response of this is probably << 5khz I would guess most of the EMI being picked up is from the inductors in the phone's voltage regulators, not RF transmission.
I also I assume the minimum threshold is set fairly high given the shape and location of the antenna. Arduinos and USB links, especially from laptops, are rather noisy themselves.
I also I assume the minimum threshold is set fairly high given the shape and location of the antenna. Arduinos and USB links, especially from laptops, are rather noisy themselves.