Ghost Signals, OH Heck!

[Cody]

I often see a post where a signal is detected, can be pinpointed, but no target found. If something is actually detected, not just ground noise or stray RF, a hot rock will cause this problem. The detector looks at least two major events to determine if the target volume consists of soil only or soil and metal. Soil presents a predictable constant signal to the receiver. Metal targets present an abrupt change. A hot rock presents an abrupt change as does a cold rock. Hot and cold rocks are composed of high iron content. One is hot and one is cold based on the type of ferrite.

A general rule is a hot rock is detected and when we go to pinpoint we can pinpoint the rock. I have collected several just to have them around. A cold rock can be detected but cannot be pinpointed. There are contaminants in the soil that will mimic a hot or cold rock. When coal is used for heating there is left in the cold fired stove what we called clinkers. These clinkers were dumped in particular around homes for various reasons. We can get into a yard full of clinkers and it sounds like popcorn going off. I have seen this many times and think that is what is often posted as iron problems. You see a lot of this around old homes. Also, some fertilizers are very conductive and will give a positive hit. When we try to find the target we end up chasing the signal as we stir the fertilizer. Another problem is roots that have a high concentration of mineral. We get our detector set up just the way we want it and start to get hits around an old tree. The sound just right but we dig down and find a bit tree root. This really is a problem as I have found a lot of good coin beneath tree roots but minerals in tree roots can respond like a hot rock. Old bricks can be hot like a hot rock. If we are hunting an area where they laying around at various depths they can drive us up the walls.

I am not sure what to suggest when we run into these problems. We are going to chase

 

[Buzzz (Southern Tier NY)]

Another good Post Cody ! But I am not sure about the Tree roots and minerals, Couple years back we had a discussion about Tree roots. Anyway, The roots will eat anything that get in the way..........A guy posted a before and after picture of a coin inside the root. Cody, could you Please explain more fully why you think they are minerals and your experience with the roots......THANKS !!!

 

[Cody]

Roots in some soil will have a fairly heavy concentration of water that has salts and other minerals. I have many times got a hit that I thought was very deep coin only to dig down and find a root. You can cut the root out and lay it on the ground and still detect the root. It acts like a very low conductive hot rock. The problem is I have also found coins beneath roots around trees. The roots will grow over deep old coins and I have found them right next to a root. I have to be very sure that a faint target is in fact a root. One way is the closer we get to the target is should increase in strength. Minerals in roots don't do that. We get that low conductive sound of a wet salt pocket. If I can what I do is cut the root out of the hole if the target id looks really good. I don't think I miss most of the good hits but this one is more difficult than some of the others. I did not mention it but the high frequency component of the signal will also detect a hole in the soil. I have dug up more than one gopher hole and large spider hole. The higher the frequency of the detector the greater this is a problem.

These comments are intended to be general simple to help explain some of the "ghost" signals that are in fact true hits. It took a few years where I first started out to figure out a lot of these thing as there was just me and a detector. I guess I was slow but after a few thousand bottle caps I said one day "OH that sounds just like a bottle cap." Ha ha

Jump in a help as I sure enjoy your posts.

 

[AK in KY]

Cody - You are right on about the holes. When I was out yesterday I dug a signal and then found the hole. I thought crap, the coin went in the hole. Same thing happened two more times and I figured the hole somehow was giving off the signal.

AK in KY

 

[AK in KY]

The the holes give a signal because of the sudden change in minerals?

AK in KY

 

[Cody]

I am not sure exactly why. I know that high frequency detector are used to detect holes in the soil. I think however in our case it is similar to when I put the detector down and the coil now sees most air as the matrix. It will sound off at times and stay that way unless I push the take it out of pinpoint. Glenn may have a much better answer on this as I have not thought much about it other than when I push the digging tool in the soil and feel that resistance and then it breaks through to an underground hole I think "OH no". I have dug some homes and had some pretty ugly spiders come crawling out.

 

[Captain Kirk]

The question is "How would the detector respond to a small hole under the ground?".

If there are no minerals in the soil (if that were possible), then you would not be able to detect a hole. If you place a lot of iron filings in the soil (See NOTE #1) and then bury a small balloon (blown up with air) in the midst of the iron filings, then you would be able to detect the balloon. What would the balloon sound like? I am not sure about this. The magnetic field would certainly be distorted, but the target would not be conductive. Therefore, I suspect that the target would show up somewhere along the bottom edge of the Smart screen (perhaps to the right of the left edge because it is less inductive).

NOTE #1

The iron filings would have to be spread over a region of at least a couple of coil diameters. This would allow the detector to adjust the target environment reading to account for the iron filings. When the detector sees the change in the environment (caused by the balloon filled with air), then the detector says "I see a change in the target matrix.".

HH,
Glenn