The "Prospecting" Forum

I'm borrowing a friend's GPX-4000 to use at a site that has produced a number of very early coins, and am trying to go as deep as I can. I've already dug 2 silver sixpences with this machine at the incredible depths of 18" and 22". But my question is in regard to why the machine responds to targets with either the hi-lo or lo-hi tones. Right now I'm using the inverted response setting, so the coins are coming in as a faint hi-lo tone. But fairly small and deep iron is also responding the same. I know this question does not have a simple answer, but what is the general relationship between target size, conductivity and depth with how the detector responds (hi-lo or lo-hi)? Even though I can afford to dig every signal at this site since its almost trash and iron free, I'd like to take the GPX elsewhere and be able to at least partially determine what to dig or not dig by properly interpreting the tones. I'd also like to hear some suggested settings to see if they match up well with what I'm currently using at the coin site. I'm using the 11" mono coil, and have all the settings hot due the clean and low mineralized ground. Appreciate any help you can provide. Thanks ..... Bill

Bill look to your PMs, I don't have time to do this twice.

JP

the hi-lo tones are your normal tones. If you have a large target it will sound off lo-hi. The inverted mode should be used if you know you are hunting in an area that produces big gold nuggets. Big nuggets sound off with a lo-hi and the inverted feature is meant to hunt for them with a normal sounding tone of hi-lo. If you are hunting coins don't use the inverted feature. hunt in deep mode and adjust the gain acc ording to how hot the ground is with the mineralization. I hunt with a GPX4000 and a x-terra 705. I know alot about the 4000. Any questions just ask. By the way if you are using the standard 11' DD or any other DD coil, you can use the iron cancel but it only works down to six inches. You cannot use the iron cancel with a mono coil. You can also use a DD coil in mon with the 4000 but you will only be using half of the coil. Keep this in mind.

I think that hi-lo are low conductor or tiny objects, low-high are high conductor, or big stuff...approx...
I.e. Big iron - silver coin, brass, bronze, copper = low- high
Gold nuggets, tiny pieces of iron or nails, mixture alluminium, some 12 cal shells = high-low
Also long nails or iron have a low-high-low tone.
A bullet has a low-high-low-high tone, that sound is a radiography of the material of the shell, copper with capsule and lead bullet at the top.
Also these tones depend on point of ground balance.
Take r.

---

Alessandro



Edited 4 time(s). Last edit at 04/02/2011 03:53PM by akille68.

I use the 5000 but the sounds are the same, if you get a solid hi sound dig. I found a mans thick heavy band & 9in at the beach in dry sand and the sound about blew out my ear drums.

That is one of the problems with Whites detectors. they are not user friendly. Get a Minelab! You will be alot happier.

I've got the 5000 and from what I've seen, all the GPXs from the 4000 on up have very similar features, so I'm going to say that what I've found is going to hold true to them as well.

The soil timings that you choose can have a major bearing on how the detector responds to targets in the ground via signal strength and tone. I'm using my machine to relic hunt with and I've yet to really find any good surefire help other than trial and error and guess work.

Minelab is trying to provide info on their website, via their classrooms there. Jonathan Porter and some of the other guys with many man hours on the GPX are writing articles and such over there, and that is a very good place to start. The problem is, is that the GPX machines are gold prospecting machines and most of the people using them are talking about settings for finding more gold. This differs from the way a relic hunter using a gold prospecting machine to find relics, should set the machine up! So that is the major problem there: lack of info for relic/coin hunters to get the most out of this power.

What I'm having difficulty in determining, is how to figure out what soil timings to choose for your given sites. There is a chart that Minelab has came up with, that you can sort of pick the size target you are after and it shows you which timings would be most sensitive to it in varying degrees of mineralization...BUT it still don't help in determining HOW to figure out how bad or good the soil mineralization is!!! So every time I go out to detect a site, I am always wondering in the back of my mind if I have the correct timing selected to get the most out of the machine.

I've dug deep minie balls with my 5000 that didn't even give a low-high tone or vice versa. The deep ones will just give a low tone and wont have a tag end tone to it. You really have to be listening to hear them break the threshold too; and I'm talking 18-20 inch deep bullets. The shallower ones are harder for me to figure out, because if they are shallower than 6 inches or so, they will actually start to overload the circuitry and you will get a broken signal, kind of like it is nulling out over a piece of iron (if you are using the DD coil and iron disc). I've found out that I can raise the coil and determine whether its a bullet or iron, by the iron will continue to be broken and a bullet will start to smoothen out the further the coil gets from it. So that said again, there is no sure fire way of tone ID on it By doing your inverted target response on the real deepies that don't give a tag end signal, you are missing those.

Why not clear the top 1-7 inches with a VLF (MXT 705, ATPRO) , then search deep with the GPX

Target response is dictated by a few things, size and distance from coil, timings used and to a certain extent the ferrous or non ferrous properties of the target. If you are having trouble deciding on a timing the best bet is to detect the area first in Normal timings which is the most balanced timing (optimised for maximum depth in the majority of ground conditions) on the GPX 5000, if the ground response is problematic (ground noise etc) then another timing such as Enhance might be a better option. From a relic hunting point of view it needs to be understood the Minelab GPX detectors have the ability to find tiny 1/10 gram nuggets in even extreme mineralisation as well as punch deep on large targets in all the timings available. A savvy operator will soon learn to ignore the small target responses as generally it is the larger coin like responses they are chasing. There are a couple of ways to cut down on the tiny ferrous targets whilst still maintaining decent depth on the larger ones, first you can use a Smooth type timing which is very effective in ignoring the very rusty items often found near or on the surface or if maximum depth is required then try using a deeper punching timing such as Normal but instead run the Quiet Audio filter with a combination of lower Gain levels. The idea is to maintain depth on sought after targets whilst ignoring the tiny responses.

Hope this helps,

JP

(This message does not contain any text.)