Strange Happenings

[Txop]

So it's been raining all day so I was doing some inside testing with coins and ran across something weird. Maybe you guys can tell me what's going on.

I was in the BASIC program waving different clad coins across the coil. Zinc penny, copper penny, dome, and quarter. I decided to see what it would do with a stack of quarters. I stacked 5 together. It nailed them as you would expect. It read a TID of 99.

So then I decided to try the SIFTER program waving the same coins. All sound as expected with single coins. Then I stacked my 5 quarters together and nothing. I mean no sound at all like it was nulled. It is not the overload tone just nulled.

So I tried to figure out the difference between the 2 programs. I brought the frequency down to 11. No go. I even changed the tones from full to 3 tone. Still nothing. The horse shoe is also not registering anything. I played with just about every setting in the sifter program and couldn't get it.

I flipped through the other default programs and some would get it and some would not. I even tried varying the distance from the coil. I tried one coin, then two and so on up to 5. It started going away at 3 tones and totally gone at 5.

I am stumped. It's probably a combination of settings.

Any ideas??

 

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[Txop]

I just tried 9 quarters and with that many the BASIC program loses them also. Really strange.

 

[Txop]

OK, I found out what the deal is. It's the frequency. If I take the 9 quarters and wave them across the coil while changing the frequency it hears the coils perfect at 7khz and 4khz.

The problem I have is that it shouldn't null out at the 17khz. I can see it getting weaker but totally gone and nothing on the horse shoe doesn't see right to me. Makes me wonder would would happen if I had the HF coil. If the pattern holds it would not hear these coins at all. I guess since I hunt for coins I will have to stay at 7khz. I would hate to miss a jar of coins.

I am going to try this same test in the ground and see what it does. I am going to stack 9 quarters at about 5 inches and see what happens.

Anybody else seen this?

Edit: When I stack the coins I am putting the flat side (heads or tails) of the stack towards the coil. If I just grab a big hand full of coins and wave them it works. It's just when you stack them. Really weird.

 

[vferrari]

Now that explains why I haven't found a roll of quarters. I was wondering....

 

[Tedyoh]

I have actually heard of this phenomenon before a while back....never looked into it though....probably because of what VF said....chances of finding (walking over) a roll of quarters standing on end in a perfect vertical position are slim and none...for me and my luck anyway

 

[RW]

Probably thinks it is iron wrapping around in the higher frequencies. Wonder how a bar of silver would react?

 

[SD51]

Just for fun, put a piece of insulating material in between each coin, like a small piece of paper and see if that changes your result. Wondering if the fact that all the coins are contacting each other, changes the way the detector senses the stack?

 

[Calabash Digger]

Ive heard of it before too...don't know why though

 

[gamiller]

Inquiring minds want to know have you duplicated this effect with different detectors ?

 

[RW]

Could it be the "chain link effect"? So many different pieces that the detector might think it is the ground? Would like to watch the GB on auto track.

 

[Txop]

I did get a chance to try it on my X-Terra with a 18khz DD coil. It did the same thing. I put on a 7.8khz and it worked fine.

Something happens at the higher frequencies. I doubt you would ever find a roll of coins standing on end in a hole but it would be interesting to know why it does. What’s weird is both sides of the horse shoe are clear like it’s not seeing anything. I wonder if it’s how DD coils work at higher frequency?