This is very simple EMF detector. Modified (by Melih Karakelle) from here. Two Schottky diode (BAR10, 1N5711, etc.) for rectifier, an Op-Amp (LM10), a cap (100 nF), a resistor (1 Mohm), triger level adjust trimpot (220 Kohm), a driver transistor (BC550). Operated with 3 V battery (2 x AA). Very simple and working good. Can detect/find a cell phone (GSM) about 30-50 cm (when RF propagation), electricity cable (on load), tv/monitor etc…
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