Digital BFO Metal Detector

[Lake]

Are there any real digital bfo metal detectors ever made?
I didn't find much information about this Zenith Radio Corp..

There you is the complete document at "Alkuperäinen julkaisu" -> Save full document.
http://v3.espacenet.com/origdoc?DB=E...QPN=US4321539#

http://www.freepatentsonline.com/4321539.html

What if we hook coil oscilator circuit directly to microcontroller which implements frequency counter, averaging, sound generating etc. What could be the maximum detection distance for a coin?

[kt315]

has released up. on Atmel+NE555 TX stage. Tracker-FM by Andrej Schedrin & Jurij Kolokolov.

[amtech2005]

Digital BFO Metal Detector

Here is link for the Tracker FM. http://www.metdet.ru/FM.htm Eugene