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Detecting In Hot Rocks, Coke, And Slag


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On 6/22/2020 at 4:42 PM, kac said:

Unfortunately the are of interest there the farm house had burned down and back of it they had buried all their coal ash so it is almost impossible to detect anything there deeper than 6".

Have you read some of Mark Gillespie's posts about using the TDI/SL in a school yard loaded with coal waste?  Here's one.

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I have a couple of options since I don't have a PI. If i use the Tejon I can set my discrim to crackle on the hot rocks and usually doing that, like iron, anything substantial in with it will still sound off but their signal gets dragged down. The smaller concentric coil seems to do better than the dd for some reason, maybe because it has less target separation?

Other option is to use my Multi Kruzer in 19kzh all metal mode and watch my numbers. I did try the MK out there in 14kzh 2 tone and 3 tone and did find a shallow ear ring but it was really exhausting. Make matters worse, some of the coal hits upwards of pennies in id. Those large spikes can sound good too. Wonder if a gold machine would do better with much higher frequency?

Almost got a TDI last fall to poke around old foundations and do a dig all except some iron approach. Now that Whites is shutting down I'll pass.

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42 minutes ago, kac said:

Wonder if a gold machine would do better with much higher frequency?

 

42 minutes ago, kac said:

I don't have a PI.

What you (and Mark Gillespie in similar circumstances) are experiencing sounds a lot like what native gold detectorists deal with in areas with very high mineralization (much of Australia and some parts of Western North America, for example).  Maybe they can help you tune your VLF's but I doubt you are going to get deeper than a few inches even then.  Some of them use PI's (or ZVT's) exclusively as the IB/VLF just don't produce in those difficult conditions.

You mention that since White's is going under that you won't get a TDI.  Well, in about a year (fingers crossed) you may have the option of a dry land version of the soon to be released (toes crossed) Fisher Impulse AQ.

 

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Don't want to hijack your thread here, sorry about that.

I did a quick test using a gob of metal shavings from my grinder. I placed a nice thick layer over a 9" plastic lid. Next I put the lid over an open parts drawer that is 5" tall.

I gb my machines and used that clean spot to do the following test using zero mode on AT Pro wtih 9x12 concentric, All metal mode Tejon 8x9 concentric and Gen Mode on the MK stock 7x11 dd. Note discrimination modes failed this test as repeatable signals or lack of any made them useless.

Tested items were a Barber quarter, seated dime, copper wheatie, buffalo nickel, med sq iron nail, square tab and vintage ring tab with tab still on it.

The Tejon I could barely hear the dime, the penny was better could hear it to about 6", nickel and quarter hit around the same 12" or so.

The MK did way better even with the isat dropped to 5 from factory 6. Lower is less correction so may drop it down more in the field if it doesn't false out too much.

Dime hit in the 7" mark there abouts, penny bit better, quarter and nickel did well and better than the Tejon.

Between both Tejon and MK aluminum was off the charts. On the MK the audio was clear as I could hear the targets but had no ID's except on aluminum targets that would spike the machine to numbers higher than silver and often maxed at 99 but didn't alarm out. Iron nail on both those machines was silent which is good and if anything caused the machines to false on either side of the nail.

Knowing that good targets don't have an id is going to be really helpful to me in the area as I know that if I get a spike with number it's most likely aluminum. Little blind hunting but think it may work out. Not sure how the big coal pieces will react.

Last bit, the 19kzh did better and had a better crisper response on the targets vs the 14 and 5 kzh. 5khz seems to do poorly for me in heavy iron.

If it's not blistering hot this weekend I'll take a run out there and make some holes.

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