VLF in Salt water

[Pat]

Can anyone tell me why a VLF/TR gets so eratic when near salt water, but yet Garretts old Sea Hunter VLF/TR worked so good in Salt water with out any problems. That machine was 15Kh. Thanks in advance.

[Qiaozhi]

Can anyone tell me why a VLF/TR gets so eratic when near salt water, but yet Garretts old Sea Hunter VLF/TR worked so good in Salt water with out any problems. That machine was 15Kh. Thanks in advance.

The reason is simple. The chemical name for salt is sodium chloride, and sodium is a metal.
Like any metal target, it is possible to adjust the discrimination to ignore it.

[Pat]

VLF Salt water

Thanks for the asnwer, But this is what I don't understand. If you take just say a Bounty Hunter,VLF a Whites Coinmaster VLF and go any where near salt water it'll get so erratic that you have to go back to dry sand or turn the sensitivity down to almost nothing, yet the old Garrett VL500 was a VLF/TR and you can walk into the salt water without any problems. I just can't understand why. was it the low kilihertz (15). again Thank you in advance.

[Qiaozhi]

Thanks for the asnwer, But this is what I don't understand. If you take just say a Bounty Hunter,VLF a Whites Coinmaster VLF and go any where near salt water it'll get so erratic that you have to go back to dry sand or turn the sensitivity down to almost nothing, yet the old Garrett VL500 was a VLF/TR and you can walk into the salt water without any problems. I just can't understand why. was it the low kilihertz (15). again Thank you in advance.

According to the Garrett website, they never made a VL500 detector. It appears to have been called the XL500 (VLF), as opposed to the XL500 (PI).
Here's a copy of the manual that explains using the Eliminator control. As far as I can ascertain, this is another name for a Discriminate control.

[Pat]

VLF Salt water

Thanks Guru you were really a great help. Thanks again.

[Carl-NC]

Salt water is conductive and looks like a target. In terms of raw phase, it comes in around +95 degrees, same as small bits of foil.

However, there is a little trick you can do to somewhat ignore salt water. Normally, the ground balance control is used to set up the sample points to ignore ferrous ground signals, which occur near a phase of 5 degrees or so. Most GB controls give enough adjustment to deal with 15-20 degrees of ground phase variation, not enough to balance all the way up to salt at +95. However, if you extend the GB to go that far, then you can balance out the salt.

This method still gives some falsing because, in addition to salt, there is usually still some ferrous minerals (black sand usually) and the combination of the two give a lot of phase variation. But it's better than nothing, and in most cases is very usable.

- Carl