You Have Got To Listen To That Threshold...

[Critterhunter]

As you slowly move the coil back and fourth hunting. If you hear the threshold change in the slightest way then home in on that spot and do short slow to fast wiggles or short sweeps over that spot to try to get a deep target to sound off and ID properly. It's been a while since I've hunted a known deep target location like I did today, and it made me remember that often the real deep stuff won't do anything at first but change the threshold a bit. That's when you have to center right over where you heard that threshold change and do short sweeps or wiggles. Sometimes they want them fast and sometimes they want them slow...I think it depends on the soil matrix and how high you have the sensitivity. It seems like the higher sensitivity is set the slower the wiggles or short sweeps over the deep target should be, and the lower the sensitivity the faster it wants it. But, as said, I also think the soil matrix can cause this to change. It's wierd....you just have to try those short sweeps or wiggles slow and fast to see which seems to lock onto the deep target and bring out the proper ID the best.

I was really taking my time and slowly crawling the coil around for the short hunt today. It seems that the higher you set sensitivity (had it at about 11PM) the slower you want to work the coil. If I have sensitivity set to say 3PM then it seems like the machine wants a faster sweep speed as I hunt to hit harder on targets. I've noticed this many times before and have heard it mentioned by other people. But for sure if you are running a high sensitivity you need to slow down your sweep speed even more. Almost to a crawl. Especially if you are riding the very edge of sensitivity to where things are a bit unstable. Also, if you don't keep your sweep speed super slow at this high of a sensitivity you'll have the threshold drop out on you more often. A sure sign that you are sweeping too fast. Don't think it's just iron if the threshold is nulling out. Try slowing your sweep down more. Too high of sensitivity can also cause the threshold to drop out, but again before lowering sensitivity try slowing your sweep to a crawl.

A good way to see if sensitivity is too high is to hold the coil perfectly still on the ground or in the air. Is the machine acting eratic (doing things like reseting the meter off and on or having the threshold make noises)? Then you've got the sensitivity set to high. Lower it until this stops. However, if it's stable with the coil being held still on the ground or in the air that doesn't mean the the threshold still isn't set too high. As you hunt you'll often see that the machine becomes unstable again. This tells you that you are riding the very edge of sensitivity...Stable when the coil is held still but somewhat unstable while you hunt. Now is the time to slow your sweep to an absolute crawl. That will help keep it more stable. You will still have to put up with the threshold going in and out here and there or the meter reseting but if you can tell the difference (you can with experience) between those false "hits" and a real hit. A real hit will of course repeat while this unstable chatter won't. Now you are riding the edge of stability and pushing depth to the limits.

Today I wasn't in the mood for the somewhat unstable threshold. At max sensitivity it was riding this edge...stable when the coil was held still but unstable when hunting here and there. So I had to lower the sensitivity to about 11PM until the threshold was rock solid stable all the time (unless hitting iron) because that's what I was in the mood for. You just have to learn how to hunt that edge when you want to and put up with a somewhat in and out threshold or falsing. One tip about this...when you are hunting at a somewhat unstable setting getting the ID to lock on with targets can be harder to do. The machine keeps reseting and so the ID will appear somewhat jumpy as you try to lock onto it. You can correct this by making sure your short sweeps or wiggles back and fourth over the target are constant and non-stop. In other words, you have to "fight" the machine and keep force feeding it the signal over and over for it to lock onto the proper number for it. Don't assume it's iron or junk because the ID is hard to lock on. It's the somewhat too high sensitivity setting that is causing that. With practice and effort you can tell that it's a good target that the high sensitivity is making jumpy, and not a bad target that is causing the eratic ID.

Also, riding the edge of sensitivity like this will cause you to get false coin hits off of iron or junk more than with a lower sensitivity setting. You might want to be a little more picky about what semi-good coin hits you want to dig when riding high like this...Unless it sounds very deep and should be giving you that kind of trouble.

 

[GunnarMN]

good discription of what the GT does, I often check deep targets by turning up the sens to 1:00and turning up the threshold a bit more if i operate in pinpont i can tell the depth by strength of signal and then try disq if it still nulls on a medium dpth target good chance its Iron

 

[Critterhunter]

One other thing...The deep stuff isn't going to give you a good response unless you are directly over it. Often you're not hitting deep stuff as you hunt with the very center of the coil. You may just nick the edge of something deep and the threshold will just change a tiny bit. You need to home in on that "ghost signal" to see if it was a deep target or just the threshold randomly changing due to the sensitivity being real high. Once directly over it you need to do the short sweeps or wiggles to try to draw the best ID out of it.

 

[Rick(ND)]

n/t

 

[Raven69]

Good advice there critter.

I have been using a Garret AT Pro which has no threshold tone. Just got my Excalibur a couple of weeks back and having a threshold tone is so much nicer. Takes me back to when I started detecting over 25 years ago with the Minelab GS 15000. On the gold fields you would be listening for that faint increase in tone to tell a piece of gold was down deep.



Raven

 

[Tin Fin]

Good description Critter - I was working with this whole idea my self today after work. Went to a park near by work and started working it. In some areas, the GT was chatty; a couple of times, that was due to underground electrical lines, but sometimes it was that I needed to adjust the Threshold and Sensitivity until it was stable again. Found about 10 Cents in pennies, one was a Wheatie, several has been chopped up by lawn mowers.

But more than finding a lot of coins, I learned some of what you were discussing here, and that is going to pay off in the long-run. Soil was mostly dry, and it's solidly packed. I was running Sensitivity at about 3:00 o'clock, sometimes 1:00 o'clock, once or twice worked it up to 12:00 o'clock but had to back it down again to about 2 or 3:00 o'clock before it would get stable. Learning to push the envelope; spending the time, but learning is more important to me right now. Then, when I do get into some of the better areas, I will have a better idea of what I'm doing. The Threshold shifting was what clued me into playing with the adjustments; find an area that the Threshold shifted, make adjustments, play with the wiggle, see what I can make the sound/numbers do or not, determine if I had an actual target or not, and then find the thing.

Being in a park, there were some targets I eventually had to pass on because I didn't want to make too big a plug and had already dug down over 8 inches. At that point, I figured that I wasn't going to find the target without making a bigger hole in order to go deeper - rather than do that, I will refine my skills elsewhere, and come back to this location when I'm more comfortable with that ability.

Thanks for the info though - sometimes repetition by reading the same thing presented multiple ways can help me.

 

[Critterhunter]

Glad to was useful. With practice you'll be able to tell how deep a target is by how loud the audio is and how easily the target IDs. When you guesstimate that it's going to be deeper than say 6 or 7" then it's better to begin with to dig a plug that is bigger in diameter (but not too big) so that you can get deeper. A normal plug for me is about the size of a small soup can. If I think I'll need to dig a deeper plug then I'll dig one maybe twice that big around. It does less damage then trying to widen a plug you already dug.

 

[lumacurve]

Hello,all, I'm reading this thread with great interest ( still learning on my GT) So if i get a change in threshold and want to hone in on that area I can adjust sensitivity AND Threshold ? I understand the sensitivity part but I thought the threshold was to be set at where its just audible? So what kind of adj. can or should be made to the threshold to help with the target ? Thanks John.

 

[Critterhunter]

Most people don't touch the threshold once it's set. Just high enough to hear. Sometimes when hunting I'll go over a different target and find (probably due to my hearing) that I can no longer hear the threshold anymore. When that happens I simply increase it a tad until I can comfortably hear it again.