Bruce, basically just step a). We are sniffing for noisy lights, switching power supplies, or leaking/arcing capacitors on the AC line inputs to most electronic devices.
I once had an AM noise problem (not with TMCC/Legacy, but just my AM radio) that was due to arcing contacts on a neighbor's aquarium heater. The noise would cycle on and off as the heater turned on and off. (We share the same power transformer.)
A somewhat related problem is desensitizing. If there is a strong unwanted signal that gets into the front end of a radio receiver, that signal can activate the Automatic Gain Control circuitry that normally avoids overload with loud (desirable) signals. In this case, the gain is also turned down for our wanted signal, desensitizing the receiver. The R2LC has a tuned input stage that narrows the reception band to keep out unwanted signals, and there is no AGC.
