hello friend aft, bfo is critic for stabilice the coils, you can build one simple project how bfo home clara", is the best and most simple bfo, in google you can find, bfo home clara', these project accept all transistors npn and is very versatile for modifications you put green cap. put in paralell whit speaker indicator ( analogic )of neddle very sense whit resistence
want you the major turns of coil reference, for stabilizacion, near 340 turns, most or less, in coil rastreo near 3 ohms wire groos grueso ( not thickness )
bfo is the best for little objects discrimination, whit big coils
best whises
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