Originally Posted by
Uplinker
But some receivers can unintentionally "leak" certain frequencies - even when only receiving. They shouldn't do if the circuit design is proper, but some might, or they might be damaged. Hence, for really critical situations, it might be requested to switch the whole device off.
Automotive radar detectors have been notorious for this - and it doesn't take damage, just cheap design/construction. Basically, some receivers - looking for a particular incoming frequency (e.g. radar detectors) - create a reference frequency that they compare to the incoming signal. If not well shielded, that reference signal gets transmitted out and can corrupt other receivers. Some cheap auto radar detectors would set off other detectors as much as a quarter mile away.
One of the reports I saw of suspected PED related interference was blamed on a Gameboy - pretty sure they don't have a designed transmit mode...