ETI561, a BFO revitalized, beginer's project

[darkkitten2000]

Here goes another one in my collection, a fairly good and simple, chip BFO siutable as a begginer's project. I'll use this one as a shallow skimmer for recently lost items.

Have fun,
d.

feel free to e-mail for schematics and PCB

[darkkitten2000]

Hi,

assembled modules available.

d.

[NGE]

Is it possible to make a BFO machine that would detect much deeper (say 6 - 8 inches deep) I have always wondered that since 1960 when I had my first Radio Shack detector........NGE

[darkkitten2000]

this one can detect a very large target (refrigerator) at 70cm in air, a 10cm diameter target at 20cm (soil) and 20cm diameter target at 25cm (soil), 1 EUR coin at 10cm (soil). Are we in range yet? The drift is however always present (needs temporary readjusting i.e. on every 30 to 60 seconds), and it useless in weat grass.

regards,
d.

[NGE]

Yes, I seem to remember the problem with drift. On my R.S. machine it was like re-adjusting every 5 to 10 seconds.......NGE

[Frankn]

I use to love that motor boating sound of the BFO. I had an old one for one of my first detectors. It was so old it had tubes. It would only reach about 2".
Your circuit, if small enough, would make an interesting pinpointer. You only need about 1" reach, and the motor boating sound variance would tell you when you got closer. It would be more accurate than the hit or miss of present day pinpointers.