10.5" DD 18.75 kHz Search Coil

[Little Richard]

Is anyone using this 10.5" DD at 18.75 kHz? I have tried 2 and both are doing the same thing. In the prospecting mode I'm finding that the iron mask doesn't work the same as the standard coil and the elliptical DD 18.75. These last 2 coils will blank the threshold on all my test iron but the 10.5" DD give a positive signal on the large spike. I have talked to Minelab and they are going to get back to me with an answer. I was hoping my some else might shed some light on this.

 

[Jackpine Savage]

Iron mask is not designed to eliminate all of the large iron signals. If you were to elminate all iron you would be losing a lot of the gold responses as well. My guess is that what you are seeing is simply the difference in characteristics between coils and that the 10.5" DD just happens to accept more iron than the others. Have you tried adjusting the iron mask setting when switching coils to see if a pattern develops? Do the other 2 coils give the same response over a piece of iron using the same iron mask setting?

Tom

 

[bfodnes]

I agree with Savage, I found the 1-20 range iron mask sttings to be more then enough anyway.

I use 1 in iron mask and that seems enough on both the stock and elliptical 18.75.

I dont prospect though, I just use it to get the better feeling of iron when I use it together with the allmetal disc mode.

I suggest you just adjust your Iron mask to a point where it hints you that there is rust or ferrous under the coil. Thats far before you see the 20 mark.

 

[B.T]

I agree Tom. Different coils can respond in slightly different ways.
I only run my Iron mask when hunting for gold on 1. I have found some gold (it can be from varying shapes, impurities, the type of ground and so on) can be wiped out if the Iron mask is set too high. Many ironstone species will try real hard to blank on the preset of just 5. I personally, where I hunt in OZ , wouldnt trust it higher than 1. Thats not to say that the rest of the range is useless as there will be places which it would be good to increase it and its a good option to have. Gold too when associated with iron pyrites is even worse and will actually try to blank at times on just 1. Im yet to see a totally foolproof discrimination system on gold but having said that the 70s is pretty damn good.

 

[Little Richard]

Yes both the standard coil and elliptical coil knock out all my iron samples. The 10.5 DD will not knock out the 14" spike and the other due at the default iron mask setting in the prospecting mode