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A couple pictures. Tried another where I filed, not better could try again if needed.

Found the smaller one in Alabama, the larger was sent to me from California as a hot rock. Both attract a magnet.

One battery backwards would cut the voltage in half.

The GB works fine. I've never had a problem getting it to balance anywhere I've used it. Jim Thanks for the reply. I'm just trying to learn something. Seems like a good detection distance for the 1grain bar.

Hi Jim Do you have some hot dirt to verify the detector does cancel ground? If I did my math right your bar would be about .012 inches thick.

Exactly, assume the target signal didn't decay and the second sample needed a gain of four to cancel the ground signal. The subtracted target signal would be minus 3times the target sample.

Some data with a PI I've been playing with. The timings were adjusted to cancel ground signal. Signal strength for the quarter is higher with ground balance on. Noise increased with ground balance on so detection depth is lower with the nugget and nickel and about the same for the quarter. If noise stayed the same, detection depth the same for the nugget, less for the nickel, increase depth for the quarter. Double signal strength increases detection depth about 1inch. Different timings different results.