Metal Detecting Forum

It seems that way in my cellar when air testing. EMI is always present in my cellar and it produces mostly mid tones in the 3 detectors I tested. In Disc mode when the coil is passing over a deep dime some sweeps (maybe 40%) will produce an extra loud beep, some sweeps may give a higher tone. Not all sweeps will do it but it seems when the coil is passing over the coin at just the right moment the signal is boosted by the EMI. Any experts out there have any thoughts on this. (The coil is kept at a consistent distance using a cardboard box.)

When the spike caused by the emi is in phase with the target signal it can. The opposite if out of phase. Same with discrimination. If a discriminator is set to just break up on tabs, for instance- a coin near or underneath will be picked up better that full tab disc. The partial signal of the partially rejected tab will add to the coin signal. One of Jack Gifford's best tips in trash.l sometimes use that in high trash areas.

Sling. Thanks for the explanation. I noticed the EMI phenomena too. Just never knew why it did that.

I have interference in my home when trying air tests. I get a variety of false signals, noisy threholds and generally erratic behaviors that don't seem to be benficial in any way. In fact, just confuses the tests.
BB

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North Idaho - A bunch of Tesoros, 3 Whites, Gray Ghosts, Sunray probe
If you don't dig it, you'll never know!

Do know that EMI has never been beneficial to me out in the field, in fact it has always had just the opposite effect ( very poor depth).

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slingshot
When the spike caused by the emi is in phase with the target signal it can. The opposite if out of phase. Same with discrimination. If a discriminator is set to just break up on tabs, for instance- a coin near or underneath will be picked up better that full tab disc. The partial signal of the partially rejected tab will add to the coin signal. One of Jack Gifford's best tips in trash.l sometimes use that in high trash areas.

Slingshot - would it not also depend on the frequency? I would think, for it to be beneficial, it would have to be at the same frequency and in phase. Also, a lot of EMI is just plain noise. I would think that virtually all EMI is not helpful. I'm no md expert, but this seems logical to me.

Mike.....

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woodennickel

Quote
slingshot
When the spike caused by the emi is in phase with the target signal it can. The opposite if out of phase. Same with discrimination. If a discriminator is set to just break up on tabs, for instance- a coin near or underneath will be picked up better that full tab disc. The partial signal of the partially rejected tab will add to the coin signal. One of Jack Gifford's best tips in trash.l sometimes use that in high trash areas.

Slingshot - would it not also depend on the frequency? I would think, for it to be beneficial, it would have to be at the same frequency and in phase. Also, a lot of EMI is just plain noise. I would think that virtually all EMI is not helpful. I'm no md expert, but this seems logical to me.

Mike.....

Sorry if I implied it could be good in any other way than a split second spike. It's so rapid and unpleasant it's hard to discern a true signal.