This Circuit is a low gain wideband Tunrd Radio Frequency receiver detecting from 500KHz to 600MHz. Upon detecting a signal the LED will illuminate. The detection range from a BUG is variable between 1 and 10meters by adjusting the 47K Preset. OA71 germamium detector diode can be replaced by a 1N4148 silicone rectifier diode but the range is less. If a 4.7uH choke is unavailable wind 5 turns of 22SWG enambled copper around a 5mm Air former. The LED limiting resistor can be lowered to 330R (ohms) if 6Volts is being used. To increase the range of the detector use a 20cm telescopic antenna and another for a ground plane connected to the 0ve(negative).
This page was updated on 20th March 2000.