Anyone made a metal detector?

I'm planning on making one, and I found a very simple circuit. The problem is that this circuit transmits the signal to an AM radio receiver that you need to carry with you set at a certain frequency.

Anyone knows how to improve this design so that it's all integrated in the same circuit, maybe with an indicator for depth, etc... or has anyone a better, yet still simple, design that I can make at home?

I don't understand how this one works, so can anyone explain? (I can't even see where is the AM radio transmitter in there)

 

This page will provide you with the information you're seeking.

 

This page will provide you with the information you're seeking.

Thanks again.

 

This link (about half way down the page) give a bunch of metal detector circuit. Some of which you can even buy the PCB board already etched.
http://chemelec.com/Projects/Projects.htm

 

This link (about half way down the page) give a bunch of metal detector circuit. Some of which you can even buy the PCB board already etched.
http://chemelec.com/Projects/Projects.htm

Thanks, I'll try that one too.