Little coil that goes deep

[Woody.au]

There has been a lot of people tell me that Red clay is a real problem on detector depth, it seems that the Red clay either distorts or attenuates the flux lines. I carried out a test using red brick clay with a mix of soil and iron filings to make a barrier layer, I used an 11 inch coil and adjusted the distance so that I could just detect a 5 cent coin. Next I carried out the same test with a small 6 inch coil and the signal increased by around 20% at the same detection distance. This I think demonstrates that a more concentrated flux gets through these barriers better than with a larger coil.
My thoughts on this may be utterly wrong, I hope more people try out various experiments so see if they can also get this effect.

[sharky]

U should even see to the damping and also the pulse width, freq, Delay and sampling before u comment on the depths and sensitivity

[Stefan]

Hi Woody,

You are absolutely right. I have a range of coils I use on highly mineralized ground right down to 6 inches and have observed the increase in sensitivity on small nuggets using small coils.. It takes quite some time to search a large area using such a small coil so I only use the coil when I suspect that there a small deep nuggets.

Regards,

Stefan

[Woody.au]

These small coils can punch down through adverse soil much better than a larger coil, even on a large target. I know of a place in Western Australia where a group detected over red clay and only got a couple of Nuggets on the surface, when they scraped of 6 inches with a dozer the found a few large 2 to 6 oz Nuggets that should of been detected in the first surface sweep. It has to be this red clay stopping the signal.

[Stefan]

I'm from the Pilbara region of W.A and we have plenty of red clay ( red loam) and it really prevents deep penetration. I had one situation where a 4 ounce nugget about 18 inches deep just sounded like a ground balance anomally. This ground balance signal is quite common. Many times have I dug a hole based on this signal and found nothing but red loam.

Any way back to the nugget. I had passed my detector a couple of times over this section of red loam and got the ground balance signal. It was early on a summer morning and not too hot so I decided to do some digging. I scrapped of a few inches of red loam and the signal was more localized. Once I was down about 4 or 5 inches I knew I had something. After I got through the surface loam the ground was very hard and it took me close to an hour to dig out the 4 ounce nugget. Most happy.

The other aspect of the red loam is that if you use a sensitive coil that works quite well in slightly mineralized ground it won't work well at all on the red loam. The ground balance response will drive you crazy. What I have learned is to listen to the variations on ground balance and this means increasing the threshold so you always have a background signal. Variations of this ground balance signal can signify the presence of a nugget especially on deep targets. This is the same for small coils also. However with small coils you are able to discriminate a lot better.

Regards,

Stefan