What VLF to compliment PI?

Ok, after a recent detecting trip I am wondering about adding a VLF machine to my collection!
I was detecting an area in NQ, plenty of old workings, and I have a choice of an SDC or a Z, so finding targets was no problem, but...the areas contained so much "trash" it was seriously disheartening (not to mention bloody tiring!) I could get a signal about every couple of metres, and I know I was in the right area, some of them were broken miners pick tips. Some of these areas had obviously been pushed with dozers, so as well as that I was finding little scrapes off the blades up to whole broken off tines.
So now to my question, would a vlf machine with good iron dicrimination help to 'sort out' the targets, and if so, what might be the best (and most economic!) choice?
Obviously I have 2 good machines for finding targets I just want an option to discriminate the more obvious ferrous targets out of them

VLF = Very Low Frequency. The SDC and GP machines are PI or Pulse Induction. I gather that PI machines cannot discriminate but I am no expert.
Best and most economic usually don't go together.

I would look at the XP Deus as a serious contender. It handles the hot ground quite well with very good manual ground balance showing you the numbers from the ground, yet to find gold with it but found lead shots and bullets in amongst some very iron infested ground. The new version 4 goes right up to 56khz which will make it very sensitive to the small stuff too. And it is also one of the best coin shooting machines you can get.

Hi Ramjet, PI machines can discriminate but only with a double D coil. Most of the ML PI machines are run with mono coils which are more sensitive on small/deep targets.
I agree with goldwright on the Deus, my suggestion would be a ML 705. I can lend you one to try if you wish?

Thanks Simmo. I have zero experience with PI machines. I would add my vote for the Deus. It weighs nothing compared to the others and is a very capable machine.

Thanks guys, I like the idea of the Deus, but really all I am looking for is the ability to discriminate out targets that I find with the sdc or z, and it looks like the 705 is a lot cheaper!
I would love to get together Simmo and at least have a look...are you going to the next meeting?

Nigel

cairnspom said:

I would love to get together Simmo and at least have a look...are you going to the next meeting?

Nigel

Click to expand...

Hi mate I don't know as yet. I'm going to try and get another shift or two in up North before we shut up for the wet.
You quite welcome to pop over and grab the 705 for a try mate, you're only just around the corner.

I purchased a cheap used Gold Bug Pro (19khz) for $400 for this purpose & doing junky creeks etc. but have found that I haven't used it as much as I thought I might. Summer might see me use it some more on the really hot days? Mostly I really don't want to put the Zed down & risk missing something.
My method for attacking these areas with a PI/Zed is to work a small area for a couple of hours until I'm sick of digging the junk then move on. Do some slopes or areas off the diggings for a break. I've found by doing short stints & concentrating on a small area it can help to maintain concentration + I've found a few bits in amongst the trash in some areas so know that they could be worth further searches now.
Having no discrimination on the SDC & GPZ can get a bit frustrating at times but many a wise man has told me that if your not digging everything then your missing gold. True but very hard to maintain in some areas!

I would be looking at either the MXT All Pro because there are over 30 Coils out there made for them, Or the Nokta Relic and the XP Deus. The XP is a fantastic Coin machine but the MXT and the Relic are the two that are closer to what you want, My sites are Heavily contaminated with junk were I can hit 20 to 30 bits of junk in one sweep of the Coil and any of these 3 would do well in such places.

John.

Simmo said:

Hi Ramjet, PI machines can discriminate but only with a double D coil. Most of the ML PI machines are run with mono coils which are more sensitive on small/deep targets.
I agree with goldwright on the Deus, my suggestion would be a ML 705. I can lend you one to try if you wish?

Click to expand...

Hey Simmo

Sorry but current PI technology can not offer discrimination with any coil. Unlike a VLF which is basically looking for a change in the transmitted signal, PI machines look at the decay signal from the target.

I can see it the future that there will be discrimination but as it stands its not possible with current designs.

The reason most PIs use mono coils is that they offer deeper penetration of the ground. DD coils are naturally quieter, less sensitive to ground noise but does not punch as deep.

cairnspom said:

Ok, after a recent detecting trip I am wondering about adding a VLF machine to my collection!
I was detecting an area in NQ, plenty of old workings, and I have a choice of an SDC or a Z, so finding targets was no problem, but...the areas contained so much "trash" it was seriously disheartening (not to mention bloody tiring!) I could get a signal about every couple of metres, and I know I was in the right area, some of them were broken miners pick tips. Some of these areas had obviously been pushed with dozers, so as well as that I was finding little scrapes off the blades up to whole broken off tines.
So now to my question, would a vlf machine with good iron dicrimination help to 'sort out' the targets, and if so, what might be the best (and most economic!) choice?
Obviously I have 2 good machines for finding targets I just want an option to discriminate the more obvious ferrous targets out of them

Click to expand...

Option to discriminate the more obvious ferrous targets.
From this I assume anything you doubt is not ferrous you would like to check with the pi? It's a tricky task, can you really forsee going back and forth between pi & vlf?
I believe to do what your asking you will want a few pre requisites. Lighter rather than heavier, ability to swap coil size and even potentially raise and lower sensitivity and discrimination and size of coils (mono to dd and small to large) on your vlf.

I would suggest target id and notching discrimination. All dollars. Most vlf will suffer the same fate they are set to detect a certain sized object usually coin to discriminate, so the ability to tell a piece of small steel vs small gold is really hard. Vlf will hit different content gold rings with accuracy but fail on nuggets localised.

Is it a hobby or does the vlf need to pull it's weight? Will you use it often enough?
It budget wasn't the issue then the dedicated relics are worth the money for accuracy and flexibility. MXT, Goldbug/F75. (My preference would be F75 except in real hot ground but as I'm selling one I've put in two other very capable macines)
If your only wanting to be less accurate, use it for this purpose only a 705 xterra will do, easy to buy and sell quickly.
Nenad would be worth a pm. Those Noktas look pretty good and I'm sure he would point you in the right direction regardless.

A little info from Nenad on the subject.

https://www.minelab.com/treasure-talk/prospecting-with-iron-reject-gpx-5000-gpx-4800

SteelPat said:

Hey Simmo

Sorry but current PI technology can not offer discrimination with any coil. Unlike a VLF which is basically looking for a change in the transmitted signal, PI machines look at the decay signal from the target.

I can see it the future that there will be discrimination but as it stands its not possible with current designs.

Click to expand...

SteelPat,

Sorry but what you have said is untrue.

Simply read the user manual from the Minelab SD 2200D right through until the GPX 5000 and within the first few pages, you will read about the discrimination feature.

It is indeed the reason that the GPX range still come with a DD coil - without one, they couldn't be advertised as being able to discriminate out of the box.

The only Minelab PI machines since the SD 2200D with no discrimatio feature are the GPZ and the SDC.

Another way to look at it: the "D" in SD 2200D actually stands for "Discrimination"

Nuggetbuster said:

SteelPat said:

Hey Simmo

Sorry but current PI technology can not offer discrimination with any coil. Unlike a VLF which is basically looking for a change in the transmitted signal, PI machines look at the decay signal from the target.

I can see it the future that there will be discrimination but as it stands its not possible with current designs.

Click to expand...

SteelPat,

Sorry but what you have said is untrue.

Simply read the user manual from the Minelab SD 2200D right through until the GPX 5000 and within the first few pages, you will read about the discrimination feature.

It is indeed the reason that the GPX range still come with a DD coil - without one, they couldn't be advertised as being able to discriminate out of the box.

The only Minelab PI machines since the SD 2200D with no discrimatio feature are the GPZ and the SDC.

Another way to look at it: the "D" in SD 2200D actually stands for "Discrimination"

Click to expand...

The discrimination they offer is not true discrimination. Its more of a blanket rejection of a range of signals (basically a notch filter). I think it was more of a marketing gimmick that they would not be able to get away with these days. The iron rejection that some pi machines used in the past is not proper discrimination.

If you would like to learn a little more on the technical aspects of PI machines try and get a copy of "Inside the Metal Detector" by Carl Moreland and George Overton. Its a pretty good book that explains a little more in depth about how the machines work. Carl was a designer with Whites but is now with First Texas who do Bounty Hunter, Fisher and Teknetics.

Iron reject/discrimination isn't something I'd 100% trust on any PI. For that matter I wouldn't trust it 100% on a VLF when looking for gold nuggets either & have personally seen them fail!
Just about all VLF's advertised as "gold" detectors will recommend when hunting for gold to use All Metal. Nuggets are tricky little buggers.

A small DD coil like a Detech 8" DD or a Minelab 10x5" Commander DD will reject iron quite well. Accuracy and your potential to miss gold suffers the higher the mineralisation and the higher you turn up your iron reject setting. While it is a great feature to have, if you don't have a GPX to start with, it probably isn't the best choice to purchase just for it's discrimination abilities.

The best discriminating machine is the CTX3030, but it's sensitivity to small gold isn't that crash hot. However, it will pick up a 0.7g if it's close enough to the surface.

If you are after "the most economic" option that will actually do the job, it'd be a toss up between the Eureka Gold $799, or a Nokta Fors CoRe $860. If it was me in that situation, I'd be grabbing the Fors Relic as it has a few extra tricks up it's sleeve, mainly iMask which is like a secondary ground filter. The Eureka Gold doesn't have a full discrimination mode like the 705 or Fors units, but the Iron Reject is quite good, and works in a similar way to the Iron Reject in the GPX series, but being VLF, does it a little bit quicker.

A few options there, you just have to weigh up features vs price.