RF Sniffer and Interference Tester


This was published in "Circuit Ideas", Electronics World, March 1994, page 213.  

The author says that it was  "intended to indicate the presence of r.f. emissions with the 1996 EMC directive in mind, this circuit has been used for many other purposes, including testing car alarm keys and as a bug detector.  It detects fields down to 1mW at 1m and from 100kHz to 500MHz."