LST sensitivity

[keverett]

I posted this in the Metal Detecting for Gold forum too, but I figured since it is specific towards Tesoro LST, then I might as well post it here too. I have a few questions about the LST's sensitivity. First off, let me state that I have only had the machine for about a month. Secondly it is my second machine next to the Minelab X-Terra 70. I read the manual, and watched some of the videos on youtube and whatnot, and figured it would be a snap to figure out. My first hunt with the LST was mixed at best. I had the sensitivity set at about 8.5, and was running discrimination off and on, but the disc. was never set above 3. The LST was finding pieces of small wire no more than 1/2 inch long at about 3-4 inches depth. This sensitivity is a double edged sword.....seems to be great in relatively clean ground, but if there was any trash at all, it would scream. My question is, can I find a happy medium between sensitivity and depth for smaller targets. I understand that most nuggets found here in my part of California are relatively small (match head size up to .dwt or so), so a PI machine isn't going to do any better than the LST, especially in the mineralized ground we have here. I don't want to negate the machines abilities by turning the sensitivity down too far, or turning the discrimination up too high. Any advice you guys can give would be great.

 

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[Sandman]

"This sensitivity is a double edged sword.....seems to be great in relatively clean ground, but if there was any trash at all, it would scream."

You have discovered the thing that bothers everyone. Because all ground is different you have to keep readjusting the sens. along with the GB. This depth can not be increased well by the sens and expect to find small nuggets and not the small copper wire. You can do well by trying small samples of gold flake or those match head size things and see where they drop out with disc at certain sens settings. It helps to use a smaller coil too and you can use more sensitivity but you will lose a small amount of depth.

 

[Adrian SS]

Do not use the Disc mode in the gold fields, the mineralisation will render the discrimination almost useless with small gold causing you to think the target is ferrous.
Any setting above one will lose small gold.
The sensitivity can be set down around 5 without losing much depth or sensitivity to small gold within a few inches of the surface while smoothing out the operation of the detector.

It is worth trying the Alkali mineral setting in all metal mode when you are having difficulty with GB and hot rocks in gold field conditions.
The sensitivity of the LST can be set quite low and still allow you to hear those small gold nugget signals.
In very bad ground I have set my LST Sens to as low as 4 and selected Alkali mode which quietened the ground noise very well and was still able to find match head gold at near 4 to 5 inches but because the threshold is very smooth and sens is low, at those settings you have to listen carefully for the signal changes.

 

[keverett]

Thank you Adrian for your helpful advice. I always worried about turning the sensitivity down too far, and losing depth. I will try running the detector a little less sensitive and see if the finds improve

 

[Adrian SS]

Hi Keverett,
When you GB the LST, make sure the sens is at max and then turn it back to where you want it after you have achieved GB.

It is unusual to have to select anything other than Normal Ground Minerals to achieve good GB.

The Black Sand Mode will reduce Sensitivity a lot, so only use it when absolutely necessary, although even in this mode you will still be able to hear coin size targets at around the 6 to 8 inch mark in moderate mineralisation if you slow your sweep speed down to around 3 foot per sec and listen carefully.

Adrian SS

 

[keverett]

Thank you Adrian for your help on both of the posts! The problem is the area I have been hunting was home to two very productive mines up until the 1920's. It is all private property now, and I have permission to hunt I have found a couple pretty nice pieces, but it was working a highbanker along the edge of the river on the property, and nothing more than maybe .5 gm. I know there are some nice nuggets up there, but the area is covered with iron trash and blasting wire. It was impossible to run the machine higher than 5 sens. I know this is gonna be a problem up in that area, but there are a few patches of ground that seem relatively free of trash and such. Thanks for everyone's insight and help.