+1. If you are trying to detect surveillance by considering RF emissions but only some of the time, a sane attacker will simply have the bug record what it need

+1. If you are trying to detect surveillance by considering RF emissions but only some of the time, a sane attacker will simply have the bug record what it needs and transmit it in a burst later when you will not find RF activity suspicious. You need to prevent the thing from recording you in the first place.