Most of today’s digital-based products create a large amount of on-board RF harmonic “noise” (EMI). While this digital switching won’t usually bother the digital circuitry itself, that same harmonic energy from digital clocks, high-speed data buses, and especially on-board DC-DC switch-mode power supplies can easily create harmonic interference well into the 600 to 850 MHz cellular phone bands and even as high as 1575 MHz GPS/GNSS bands, causing receiver “desense” (reduced receiver sensitivity).
