A MD question 4 the tech-oriented

[Jason in Enid]

Very interesting. If this is the case then I can't imagine a way to counteract the phenomena. Permeability & Lines of force are lines of force...period.
Now...how about a theory on why fine gold chains are invisible.

My CZ's have a strange quirk I've formed a theoretical answer for...they give a squawk after you click them off. I think it's an inductive or transient spike formed in the coil (inductor) when the EM field collapses.

I can answer about the chains. Metal detectors do not see chains as one single unit, it sees individual links, and some chain do not even have individual circular "links". How well a detector sees it's prey is based on the signal load that can build in the target, how fast that load decays and the sampling rate of the detector. Some detectors are better at tiny gold, others are better at deep silver and copper. Everything in the hobby is a trade off. If you want depth, you sacrifice small targets. If you want silver you sacrifice small gold.

 

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[eddiecurrent]

That's interesting.
I've read that other factors that effect detection of small gold is frequency and the return signal sensitivity.
I know that gold detectors use closer tolerance parts and are highly tuned. I'm sure that those qualities have their own tradeoffs.
When I use my fisher cz in all metal mode and the sensitivity cranked till I get a threshold, it will detect a small gold chain if it's bunched up. Real small gold pendants too, grain of wheat-sized.

 

[Jason in Enid]

That's interesting.
I've read that other factors that effect detection of small gold is frequency and the return signal sensitivity.
I know that gold detectors use closer tolerance parts and are highly tuned. I'm sure that those qualities have their own tradeoffs.
When I use my fisher cz in all metal mode and the sensitivity cranked till I get a threshold, it will detect a small gold chain if it's bunched up. Real small gold pendants too, grain of wheat-sized.

there is no difference in the tolerance or tuning, it's the nature of the circuit design. Gold detectors use different frequencies and timing which affects the signal loading in the target. That same detector that is sounding on grain-sized gold will be terrible on a deep silver dime.

The comparison of VLF to PI gets even more complicated. The newest Minelab PI gold hunter will hit tiny gold at unbelievable depths. I have heard they are being used very successfully at relics hunting sites in heavily mineralized grounds too.

 

[eddiecurrent]

Higher frequencies are more sensitive to gold. Gold detectors use closer tolerance parts. They also have a more highly tuned receive circuit, maybe even a harder driven transmit oscillator. This is per several manufacturer's published claims.