CCO Metal Detector

[gigabyte]

Greetings
I am an Electronic Hobbyist having experimented in a great many different types of projects.
Right now I have become quiet interested in Metal Detectors having already built about all the circuits that are online all work but the one I am most interested in is the CCO coil coupled oscillator. I have both the LM386 and Transistor model built and love the sensitivity but I am very diss-appointed that it needs a pocket radio to work. Does anyone have a circuit I could add on that will receive it?
Preferable one tuned that does not require an tuning capacitor they are very hard to come by
Any help in this matter would be greatly appreciated.
This is a link to the design using the LM386 but I can use the transistor model as well.
**broken link removed**

Thank you.
Ken

 

[MikeMl]

Dont you just need a BFO (Beat Frequency Oscillator) and a mixer driving an audio amp?

 

[gigabyte]

Not really sure I guess I really do not understand the exact workings of this circuit it has me kinda in the dark.
Its not really a BFO or is it?

 

[MikeMl]

Not really sure I guess I really do not understand the exact workings of this circuit it has me kinda in the dark.
Its not really a BFO or is it?

Your circuit just oscillates at some starting frequency, say 1000kHz (middle of the AM band). Coupling some metal to it causes the frequency to shift by a few Hz to tens of Hz. You need to make that frequency shift audible.

Building a fixed oscillator that runs at say 999kHz or 1001kHz and mixing it with your metal detector oscillator at 1000kHz will make an audible signal of 1kHz. The human ear is very sensitive to pitch change, so you can hear the metal pull the frequency of the metal-locator oscillator.

The new fixed-frequency oscillator is the BFO.

 

[gigabyte]

Thank you MikeMI.
This gives me something to work on and a starting point. I understand BFO, PI and the others.
I guess the simplicity of the circuit just had me misled.

 

[Revolver11]

hey can yo please post the schematics of the metal detectors that you have made then worked properly? I'll really appreciate it. Thanks!