DD Coil Issues With Shallow Targets

[mh9162013]

I love coinshooting, and I'm often in my local parks or private permissions searching for clad and silver coins. But I noticed that when digging up shallow clad coins (3 inches or less), my AT Max with the stock coil would say the coin is 6 inches down. Sometimes, a surface coin would read at being 4 inches deep. I didn't think this was that big of a deal, b/c I could always pull out my F-Pulse and see if the assumed coin target was truly shallow or not. Also, the incorrect depth reading wasn't keeping me from digging a desired target.

Tonight, I read:

 and

http://www.fisherlab.com/hobby/davejohnson/SearchcoilfieldshapeApril2012.pdf

Both of these mentioned anomolies or issues with DD coils and shallow targets. Is what I'm experiencing with my shallow coins and AT Max one of these anomolies? Or is there something else going on?

[phrunt]

My Equinox gives less stable target ID's on very shallow targets, I just lift the coil a bit higher off the ground to clear it up. 

I've not used my Garrett AT much at all, well for about an hour in total so I'm unsure about your issue, hopefully someone else knows but I do know my Garrett Ace detector doesn't have that problem.

 

[Valens Legacy]

4 hours ago, phrunt said:

My Equinox gives less stable target ID's on very shallow targets, I just lift the coil a bit higher off the ground to clear it up. 

I have noticed the same thing on mine, and if I think a target is close to the top I will lift the coil up a few inches to make sure.

I also noticed that if the soil is wet enough it also gives a different depth also.

[geof_junk]

5 hours ago, phrunt said:

My Equinox gives less stable target ID's on very shallow targets, I just lift the coil a bit higher off the ground to clear it up. 

I've not used my Garrett AT much at all, well for about an hour in total so I'm unsure about your issue, hopefully someone else knows but I do know my Garrett Ace detector doesn't have that problem.

 

As phrunt said with more information below.

I always lift the coil to a height that still give a definite but low audible volume when using a VLF detector. This give a signal a much more readable signal that is not over-load by size, depth and mineralize ground. I have been doing this since hitting the gold fields since the late 1970s and it helped me find good targets that people have walked a way from or wasted time and effort digging rubbish. 

[Steve Herschbach]

Coin depth reading is nothing more than a signal strength indication, usually calibrated to a dime size target. You are not seeing a depth reading, you are seeing a signal strength indication. This is why it only works on coin size targets, and not real small or real large items. Anything that affects the signal strength, including coil anomalies, EMI, other targets under the coil (including dished out targets) will affect the “depth reading.”

[mh9162013]

9 hours ago, Steve Herschbach said:

Anything that affects the signal strength, including coil anomalies, EMI, other targets under the coil (including dished out targets) will affect the “depth reading.”

Could mineralization in the soil have an effect? In many of the parks I hunt at where I see this issue, I'm often digging clad coins straight out of mineralized clay.

[Steve Herschbach]

50 minutes ago, mh9162013 said:

Could mineralization in the soil have an effect? In many of the parks I hunt at where I see this issue, I'm often digging clad coins straight out of mineralized clay.

If it affects signal strength, it affects depth reading, so yes.

[Mike_Hillis]

   Dave J confirms DD coil anomalies with shallow targets here....in the Search Coil Field Shapes article.

http://fisherlab.com/hobby/dave-johnson-essays.htm

HH
Mike

[JCR]

Thanks Mike. It's good to read all those again.

[locator]

I think recovery-delay/recovery-speed, sweep-speed and real sweep-speed will take affect, too. To me it helps a lot to lift the loop on shallow targets to get better ID.