Do Modern Detectors see into Rock and Quartz?

[Ben78]

Now Ben78, I think I should get some background info' from you- where do you get your information on this from?? Are you simply speculating, or did this information come from a particular source??

A combination of a university electronic engineering education and experience.

Next time you are out detecting wave the coil at your car from a couple of metres away = detecting an object at 2m

Maybe next time you hear a lightning spike, look for the storm, see that one building on the horizon - you are detecting something 150km away.

The quote I refuted claimed that a AT Gold (a VLF machine) detected a pulltab at 1m deep. Not possible.

 

[BumbleB]

Now Ben78, I think I should get some background info' from you- where do you get your information on this from?? Are you simply speculating, or did this information come from a particular source??

A combination of a university electronic engineering education and experience.

Next time you are out detecting wave the coil at your car from a couple of metres away = detecting an object at 2m

Maybe next time you hear a lightning spike, look for the storm, see that one building on the horizon - you are detecting something 150km away.

The quote I refuted claimed that a AT Gold (a VLF machine) detected a pulltab at 1m deep. Not possible.

Mate I believe you said "No detector currently made will detect a pull tab a metre deep". I then questioned the statement against my 5000 & 18-20" coil, & u stated "With a 20" coil on a 5000 you would detect a pull tab at a metre deep - if it was still attached to the beer can". I don't think I misunderstood your comments or took them out of context.
Anyway, I emailed Nugget Finder last night for clarification, so will see what they come back with.

I haven't got an electronic engineering education, but I can confirm to you that with a standard 11" mono on my 5000 in highly mineralised soil in Clermont, dug a 3g nugget at approx' 500+mm (the hole was past my knee), so as I said, it would surprise the hell out of me if an extra 61% in size of coil didn't equate to a substantial increase in depth- why else would people spend $500+ on a 18" or 20" coil?? With all due respect to you Ben, either you are plain wrong, or thousands of prospectors around the country are being fed a crock of crap & Nugget Finder, & Retailers are selling rubbish........I'm pretty sure Nugget Finder aren't selling worthless rubbish.

In your opinion, generally speaking, what increase in depth should that extra 61% coil size achieve?

 

[Ben78]

In your opinion, generally speaking, what increase in depth should that extra 61% coil size achieve?

Depends on the size of the object, but if it was say a pulltab (square modern type) a 61% increase in coil size might buy you a couple of inches. On a can sized object going from a 11" coil to a 20" coil would be a big jump maybe a foot or more. I don't know the specific calculations, and wouldn't be able to calculate anyway as I don't know a lot of the specifications of that 20" coil.

so as I said, it would surprise the hell out of me if an extra 61% in size of coil didn't equate to a substantial increase in depth- why else would people spend $500+ on a 18" or 20" coil?? With all due respect to you Ben, either you are plain wrong, or thousands of prospectors around the country are being fed a crock of crap & Nugget Finder, & Retailers are selling rubbish........I'm pretty sure Nugget Finder aren't selling worthless rubbish.

Maybe I am wrong, maybe I'm not. Its been a long time since I studied.

There is a relationship between size of object and size of coil, as you would know small coils = small objects and large coils = large objects but there becomes a point at which as the coil size grows there becomes a depth/size cut off point that the coil can no longer respond to it. People buy the BIG coils to find BIG nuggets that are deep - hence the metre deep holes on multi ounce nuggets that you see.

If the question posed to Nugget Finder was "Will a 20" NF coil detect a pulltab at 1m in the ground" I would be very interested to see their response. I don't believe any of the coil retailers are selling rubbish, nor are they lying to you. I have honestly never seen an advertisement from any retailer that buying their super sized coil will have you digging pulltabs at a metre, they probably wouldn't want to either - the mere thought of digging a metre into goldfields ground for just a pulltab makes me shudder.

Now this isn't an accusation or a question of your character so do not take it that way please. I have seen personally seen, and seen in video where people have dug whopping great holes in search of their item and then whilst widening the hole to go deeper are able to locate their item. All of a sudden Detector XYZ is able to detect a bobby pin on the beach three feet deep. It happens, I've done it, people you know have probably also done it. If you don't know the physics behind it, it is easy to believe.

I've been trying to write a response that explains the decay of electromagnetic pulses and how it relates to depth, but it is difficult to keep it basic and not have gaping holes. With a bit of searching I was able to find a document written by Bruce Candy that explains it near perfectly. - http://www.minelab.com/__files/f/11043 go to page 14. For anyone that is even remotely interested in the theory of detectors I have just read it and it is a fantastic resource and will go a long way to explain the "what the hell?" moments we often have when detecting.

 

[trenchfighter]

well after about 3 hrs of digging rubbish out of concrete hard rocky soil, i personaly THANK THE LORD that i cant detect to 1 meter...

 

[BumbleB]

In your opinion, generally speaking, what increase in depth should that extra 61% coil size achieve?

Depends on the size of the object, but if it was say a pulltab (square modern type) a 61% increase in coil size might buy you a couple of inches. On a can sized object going from a 11" coil to a 20" coil would be a big jump maybe a foot or more. I don't know the specific calculations, and wouldn't be able to calculate anyway as I don't know a lot of the specifications of that 20" coil.

so as I said, it would surprise the hell out of me if an extra 61% in size of coil didn't equate to a substantial increase in depth- why else would people spend $500+ on a 18" or 20" coil?? With all due respect to you Ben, either you are plain wrong, or thousands of prospectors around the country are being fed a crock of crap & Nugget Finder, & Retailers are selling rubbish........I'm pretty sure Nugget Finder aren't selling worthless rubbish.

Maybe I am wrong, maybe I'm not. Its been a long time since I studied.

There is a relationship between size of object and size of coil, as you would know small coils = small objects and large coils = large objects but there becomes a point at which as the coil size grows there becomes a depth/size cut off point that the coil can no longer respond to it. People buy the BIG coils to find BIG nuggets that are deep - hence the metre deep holes on multi ounce nuggets that you see.

If the question posed to Nugget Finder was "Will a 20" NF coil detect a pulltab at 1m in the ground" I would be very interested to see their response. I don't believe any of the coil retailers are selling rubbish, nor are they lying to you. I have honestly never seen an advertisement from any retailer that buying their super sized coil will have you digging pulltabs at a metre, they probably wouldn't want to either - the mere thought of digging a metre into goldfields ground for just a pulltab makes me shudder.

Now this isn't an accusation or a question of your character so do not take it that way please. I have seen personally seen, and seen in video where people have dug whopping great holes in search of their item and then whilst widening the hole to go deeper are able to locate their item. All of a sudden Detector XYZ is able to detect a bobby pin on the beach three feet deep. It happens, I've done it, people you know have probably also done it. If you don't know the physics behind it, it is easy to believe.

I've been trying to write a response that explains the decay of electromagnetic pulses and how it relates to depth, but it is difficult to keep it basic and not have gaping holes. With a bit of searching I was able to find a document written by Bruce Candy that explains it near perfectly. - http://www.minelab.com/__files/f/11043 go to page 14. For anyone that is even remotely interested in the theory of detectors I have just read it and it is a fantastic resource and will go a long way to explain the "what the hell?" moments we often have when detecting.

Ben, just had a quick read of that article- & yes it is a bit of a 'mind-bender'. I will have to read it a couple of times to get my head around the language- thanks for the link.

I have actually found sub-grammers (tiny fly poo size) nuggets with my 18" at 5-6 inches depth, which was a big surprise, as I was of the understanding that you lost those small ones with the larger coils. It's all a bit confusing to be honest- there seems to be all these 'physics rules' which are set in stone, but that can be 'bucked' at anytime.

My way of thinking, now, to pay $500+ for an extra few inches on a 'maybe' larger nugget is wasted money unless you're in an area that is known for larger nuggets- ie WA. I truly wish I had known this before, or that these wonderful retailers, that win these Minelab awards, would atleast try to be honest.

I now know that I was obviously misled by Clermont Detectors in this regard (in hide-sight, not that surprising actually)!! His indications with his hand gestures to his rib-cage & then over his head was NOT accompanied with any explanation, or qualification of can sized nuggets only. Now I'm pissed!!

Everyone please learn from my experience here- if ever traveling to Clermont, BEWARE the BS is very thick up that way!

Thanks Ben for the clarification, it would appear that you have at very least prevented me from continuing to walk around with false ideas & false hopes (head up my ***).

It will be interesting what Nugget Finder respond with- what their testing has produced. I will relay that to everyone.

 

[WalnLiz]

You may have been ripped off with some of the info BB, but don't underestimate that 18" NF. It and the 14" NF are in my opinion a must in every 5000's arsenal. Wouldn't be without them. I recently pulled a 40 grammer (very flat and wide), with the 18" at very close to a metre.

Pull tab at a metre with 18" or even 20".....no way

Cheers Wal

 

[BumbleB]

40 Grammer! That will do Wal- I can feel all my stressessssss drifting away...........

I appreciate & understand what u r saying- I just despises being lied to, especially when it's not necessary- I probably would have bought the 18" anyway, but deserve to be told its true capabilities, instead of mouthwatering hand gestures of unattainable & misleading depths.

Telling newbies rubbish & leading them astray like that is just as bad as telling them the swimming pool is the best place to find Gold.

 

[WalnLiz]

Hearing what you say BB .....But if you pick up few small bits with the 11"...always run your 18" over it before someone else does.

You will get a lot of good gold with that NF18......don't bother with getting the 20" though.

Cheers Wal.

 

[nuggetino]

Soil type must play a role in depth penetration too. Testing a detector (waving a coil) in the air makes it much more susceptible to emi. I tried running air tests on targets for theoretical depth and was very disappointed in the results. It seems at least in quiet ground on my test patch I can detect targets much deeper than in the air perhaps due to a more stable threshold and coil swing. My 24' DD coil does go much deeper than the 11" dd by around 50% which is in line with jack langes predictions http://www.kamakazi.com/docsplace/jlange/confusion.html but struggles on shallow targets as expected. Have detected a four ounce lead lump at 75cms. The 11" DD struggled for a whimper at 50cms on the same test. The fact that our hearing plays a role in how deep we can detect targets is another factor. I'm sure my detector picks up nuggets much deeper than I'm able to decipher with my hearing. If I had a detector that could find a pull tab at a meter I'd be a rich man.

 

[trenchfighter]

air tests are a absolute waste of time. PI's need a ground matrix around the target to detect it properly

 

[lost a bit]

Hearing what you say BB .....But if you pick up few small bits with the 11"...always run your 18" over it before someone else does.

You will get a lot of good gold with that NF18......don't bother with getting the 20" though.

Cheers Wal.

this may be the answer to the question I have been going to ask, I have been running my 11" mono on the 5000 and picking up small pieces from sub gram to 5 grams I have a 15x12 elliptical and have been toying with the idea of running it over the spot also, how much more depth would I expect to get with the 15x12 or would it be a waste of time. also say there was a largish nugget( 1 ounce up ) at 2 to 3 feet could you detect it with the 11" or would all the stars have to line up
cheers lab

 

[WalnLiz]

Depth is gained from radius dimensions, so your elliptical 15x12 is only really as good as as a 12" round. Gives you a larger sweep area but not much added depth. I would jump to at least a 16" round or 18" round. If you don't own an 18" round i would certainly recommend adding one to your arsenal. ...one ounce up at 2' with an 11" round....very achievable with no stars lining up.

Cheers Wal.

 

[HeadsUp]

You may have been ripped off with some of the info BB, but don't underestimate that 18" NF. It and the 14" NF are in my opinion a must in every 5000's arsenal. Wouldn't be without them. I recently pulled a 40 grammer (very flat and wide), with the 18" at very close to a metre.

Pull tab at a metre with 18" or even 20".....no way

Cheers Wal

I am still using standard 11 inch coils on my GPX5000 , coz i didnt form a clear idea on which coil to buy in the larger range

there have been many posts on that topic .

what is the current view on the best large coil people ?

( exclude the 36 inch drag coil as i will probably get one for a trip later this year - thats a different category )

( and i will probably get the waterproof platypus at some point too )

 

[WalnLiz]

My personal opinion on the best coil range, and this will vary for many depending on where you detect, is, firstly i wouldn't be without an 8x6, or the standard 11" round, as these are your bread and butter coils for the abundant sub grammers and up to around the 8gram mark.

The 14" round is probably the most versatile size if you're over in WA and in the GT. The 18" round i wouldn't swap for all the tea in China, and accounts for 90% of my larger nuggets.....but it has its limitations on the East coast where undergrowth limits its use.

I have a few ellipticals for fast coverage of WA ground, and the best of these is the NF 17 x 11. Coils are a very personal choice and determined by the locations you most work. Each will have their own favorites, and should use a coil suited to their location rather than somebody elses suggested favorite. ....Tip.... Don't bother with the 36" drag.... unless you're following dozers. Have two mates with them and both resold them. :/

Cheers Wal.

 

[HeadsUp]

My personal opinion on the best coil range, and this will vary for many depending on where you detect, is, firstly i wouldn't be without an 8x6, or the standard 11" round, as these are your bread and butter coils for the abundant sub grammers and up to around the 8gram mark.

The 14" round is probably the most versatile size if you're over in WA and in the GT. The 18" round i wouldn't swap for all the tea in China, and accounts for 90% of my larger nuggets.....but it has its limitations on the East coast where undergrowth limits its use.

I have a few ellipticals for fast coverage of WA ground, and the best of these is the NF 17 x 11. Coils are a very personal choice and determined by the locations you most work. Each will have their own favorites, and should use a coil suited to their location rather than somebody elses suggested favorite. ....Tip.... Don't bother with the 36" drag.... unless you're following dozers. Have two mates with them and both resold them. :/

Cheers Wal.

Is that 18 inch round coil a mono or DD ?

NF or other brand ?

thankyou

 

[lost a bit]

next question
what is the best brand in the 18" coils or are they all much of a muchness
lab

 

[Guest]

Hey Lab - had been looking at 18" coils myself but decided not to get one until I upgrade the detector.
From what I read the price is the biggest difference in them & most stick with their preferred brand.
Nugget Finder over $500, Minelab Commander $450 & the Detech one's about $415 off ebay. Have seen some good reports on the Detech coils but nothing specifically for the 18".
A couple of the GPX4500's I'm looking at come with 18" commander monos so if I end up with one in a few weeks & ya haven't got anything by then I'll give it to you to test out before ya buy one.

 

[WalnLiz]

My personal opinion on the best coil range, and this will vary for many depending on where you detect, is, firstly i wouldn't be without an 8x6, or the standard 11" round, as these are your bread and butter coils for the abundant sub grammers and up to around the 8gram mark.

The 14" round is probably the most versatile size if you're over in WA and in the GT. The 18" round i wouldn't swap for all the tea in China, and accounts for 90% of my larger nuggets.....but it has its limitations on the East coast where undergrowth limits its use.

I have a few ellipticals for fast coverage of WA ground, and the best of these is the NF 17 x 11. Coils are a very personal choice and determined by the locations you most work. Each will have their own favorites, and should use a coil suited to their location rather than somebody elses suggested favorite. ....Tip.... Don't bother with the 36" drag.... unless you're following dozers. Have two mates with them and both resold them. :/

Cheers Wal.

Is that 18 inch round coil a mono or DD ?

NF or other brand ?

thankyou

Have both the ML solid and the NF Advantage spoked. (Only use monos myself). Both are equal in my opinion, though i use them in different situations. For creek bed checking i use the ML solid as I scrape this coil consistently on the ground.

The NF18 spoked is my preferred general hunting coil as the lighter weight makes it a much more pleasurable unit to use. If I had to choose between the two the NF18 spoked would be the number one choice, based on the ease to swing it substantially longer.

Cheers Wal.

 

[lost a bit]

thanks for that walnliz, I ended up buying the NF advantage in a 20" at a reasonable price here in Mudgee and mbasko can you hurry up and get that new ML so we can go test it out.

as for finding gold in quarts with the dectors me and a mate found some nice specimens today in large quartz rock mine was visible from the outside and even more visible when broke open, the piece that knuckles found was not visible until the quartz broken open

 

[penfooey]

My personal opinion on the best coil range, and this will vary for many depending on where you detect, is, firstly i wouldn't be without an 8x6, or the standard 11" round, as these are your bread and butter coils for the abundant sub grammers and up to around the 8gram mark.

The 14" round is probably the most versatile size if you're over in WA and in the GT. The 18" round i wouldn't swap for all the tea in China, and accounts for 90% of my larger nuggets.....but it has its limitations on the East coast where undergrowth limits its use.

I have a few ellipticals for fast coverage of WA ground, and the best of these is the NF 17 x 11. Coils are a very personal choice and determined by the locations you most work. Each will have their own favorites, and should use a coil suited to their location rather than somebody elses suggested favorite. ....Tip.... Don't bother with the 36" drag.... unless you're following dozers. Have two mates with them and both resold them. :/

Cheers Wal.

Hey Wal, the 8x6 is that the Sadie NF? and how often do you use this one? Is the 18" round the Nugget Finder or Minlab coil. The NF 18" Advantage is $530 and the Minelab is $475

We will be spending a bit of time later in the year in WA - only have the DD and Mono 11" which came with the GPX5000. Really starting to get a grip on using these now and as retirement is only two days away, want to get our prospecting arsenal sorted.