18" N/F Mono / 16" N/F Mono ?

Hi All,
Will be buying a new GPX 5000 soon . Would like your oppinion on wich coil to use as a general use coil .
16" N/F or 18" N/F Mono , Sen/Depth. Is there much difference between them .

thanks Charlie c
West Oz

G'day Charliec.

Welcome to the forum.
You can't really go wrong with the 16 round,as a general purpose all rounder.Slightly more sensitive and quieter,than the 18 round and almost goes as deep. Keep in mind that the type of ground you intend on searching,
basically determines the type of coil to be used also.

Cheers kon61.

.

Just my experiences here:
NOTE that I've only used the 16" Round NFA and the 14" Elliptical NFA Monoloop coils on the GPX-5000
The others were used on the GPX-4500.

IMPORTANT: I have observed my 14" Elliptical NFA to be more sensitive on the GPX-5000 than it was on the GPX-4500.
This means I have had to seek fit a longer shaft (I used an OTTO 800mm shaft) to extend the coil further from my person when detecting.


18" NFA Mono Round =
* SLIGHTLY Deeper than 16" NFA.
* Less Stable than 16" NFA Round Mono.
* A little unwieldy and prone to instability.
* Requires longer shaft to extend away further from body.
* Gets the deepest nuggets.
* Less sensitive to smaller subgram nuggets than smaller coils.

16" NFA Mono Round =
* VERY Good Depth - More depth than 17" NFA mono Elliptical (and smaller coils)
* Not quite as deep as the 18" NFA but close.
* More stable than 18" NFA.
* Requires longer shaft to extend away further from body.

14" NFA Mono Round =
* EXTREMELY sensitive to very small targets.
* Shallower than 16" + 18" NFA. But VERY deep compared to similar sized coils.
* DEEPER than similar coils including 14" NFA Elliptical.
* Benefits from longer shaft to extend away further from body.

14" NFA Elliptical =
* VERY sensitive to subgram nuggets... more so than similar coils.
* MORE sensitive than the 14" NFA Mono Round coil (Almost as deep too)
* Excellent depth per size ratio.
* Much Better depth than an average 11" round mono.
* My personal favorite.
* Benefits from longer shaft to extend away further from body.
* Extremely compact and lightweight.


When I was playing around last year with a Coil Strength Field Meter, it showed that the NF coil with the most punch for the size at the time was the 16" NFA Round Mono. The 18" put out a stronger field but only slightly more. I think that it should be mentioned that the testing Meter was flawed - in that some coils that tested weaker than they ought to showed normal results when turned around 180 degrees on the platform. So the machine used to measure field strength was in some way compromised by the coil windings and/or orientation. For this reason, don't rely on a Coil Strength Field Meter unless you consider the other variables. But I was impressed by the punch from the 16"... enough to buy one at the time. I don't use it nearly as much as I use the 14" coil as the smaller one is more practical as an all-purpose nugget-hunter.



If I was recommending a coil to anyone, I'd suggest the 14" NFA Elliptical first and let them decide if they can handle a 16" or 18" NFA Round Mono. The 17" Elliptical would be easier for them to handle although all large coils are HARD to pinpoint with.

14" NFA Elliptical =
Much Better depth than an average 11" round mono.

Id like to protest, and say not on your nelly.

Hi Kon61 & Nero ,


Thanks for the replys.I think i will go with the 16" NF & 14" Elip Mono. I normally use 18" DD C/T,
17" DD C/T,& 24" UFO. I will get a full length OTTO shaft.
Not very good with computer but will keep learning. Thanks for the info .

regards Charlie C

Narrawa wrote:14" NFA Elliptical =
Much Better depth than an average 11" round mono.

Id like to protest, and say not on your nelly.

I'm not going to disagree at all ... and I did state "average" because I've found almost all 11" coils (of either configuration) to be average (ie. They aren't necessarily specialist coils)
If they weren't, we'd see a lot of others using them in spite of all the other options available out there.

Narrawa... give us some insight into your own observations. I know you do very well with the 11" coils.

And whilst it's not everyone's cup of tea, I think that the Double-D coils are immensely underrated by users of the GPXs.
In my mind, the Double-D coils have a considerable benefit although there are fewer being used out there at the moment on the recent machines.

I LOVE the 18" round NF monos and feel it walks all over the 16" round in so many ways, BUT there is no point to swinging an 18" if the conditions won't allow (shallow ground, tight terrain, unwieldy weight etc). The more windings there are in a coil the more sensitive it is, the smaller the coil the more windings it requires to get up to snuff on inductance therefore smaller coils have greater sensitivity (signal strength for size of target), however with greater sensitivity comes increased ground noise (and EMI in some cases), so the larger coils can run quieter to some extent on hotter ground which means even though they are less sensitive the signal that is there is more obvious.

Lastly there is outright depth, even though the field strength generated by a 16" is not that different to the field of the 18" the people doing the measurements sometimes forget it is not the transmit field that is so important but the surface area of the receive coil that is picking up on the millions of times smaller field created by the nugget after it has been stimulated by the powerful transmit field, ergo greater depth due to greater receive area. It is in this area the larger coil will always win hands down over smaller coils and to my mind the 18" round hits right on the sweet spot of outright sensitivity relative to less impact from surface mineralisation relative to outright depth. An 18" Mono will require careful concentration from the operator to pick the tiny nuggets but requires a hell of a lot less concentration to pick the larger deeper gold compared to the smaller coils.

JP

Pic of a tiny piece I found yesterday with my 18" Advantage Nugget Finder coil.

No probs Marco....
I have put a few newbies onto the 11" coil, mostly because they have one in there kit, and the coil they are using has been of the larger 15x12 or even bigger. Many are unable to distinguish whats going on because of the ground there on/settings/no training ect. But when they feel at home with your attitude, and welcome the info your giving, they soon learn your not pulling there leg, especially when looking down to see the coil you have on is smaller than theirs. Watching a noob trying to pinpoint with an 18" mono is like listening to someone playing the guitar,,,,,,,,that cant!

The 11" mono would have to be the best all-round coil I have ever used. This ML branded coil has won me much gold over the years and I have dug many a nugget with this coil at unbelievable depths.
Compared to the 14x9 and 14x7 which I have owned both of, and my partner still uses the 14x7 with much success, I have found little use for the size because the 11" will in most cases out perform it in depth...9" vrs 11" ...7" vs 11", not forgetting how the elips are wound vs that of a round.

I regularly find gold down to a poofteenth of a gram with the 11" ML mono, yet am able to dig targets including gold to depths of up to 23" with it as well, and certain members of this forum have been witness to such digs. I am just about due for a new one as the older model GP3000 vintage is starting to thin. This ONE coil has served me well from the 3000 4000 and 4500, and growl at the good women if she even looks in its direction while im playing with other coils.

Have seen and read many stories of the 14x-elips coils doing very well, and have no beef with this, and in many cases would prove more useful than a 11" round on certain ground types, coverage, creeks, rocky out-crops ect.. but they are an easy coil to use off the bat, even for a beginner.
Teaching a newbie to pinpoint with a round coil means they will have little trouble with an elip when the time comes.

As for the 11" DD, it has lost its love from prospectors and detectorist ( there is a difference ) simply because of the newer timings being offered with the ML detectors, but you will still find many witty operators using them, mine has scratches on it simply because it has its place.

To the newbie, the 11" or the 14x elip mono's will get you gold, and you will find them much easier to use while you familiarize yourself with the detector, and learning the many different types of target responses / ground types.
And there would be nothing wrong with using the one size coil for an extended length of time while you do. ( your manhood wont be effected )

Having said all that, the 17" elip, 14" round, 16" round, the trusty 11" DD and 10X5DD are well used coils of mine, and looking into an 18" round when I move state, Re what JP has said above, conditions here hamper the size.

Awesome replies!! Anyone browsing this thread is going to have a wealth of information to pick over. I always found that coil choice is a hotly debated topic. Can anyone who have been using the early PI machines chime in to say if coils were always such a point of conversation? Nowadays, there's a lot of differing opinions so I always try to mention that there are many reasons for people to have preferences for particular coils. I think I bought a number of my Coiltek Coils based solely on user's recommendation on the forums. Any recent NF coils have simply been personal preference for me (ie. I wasn't reading anything online about them at the time and wanted to experiment).

Gday


I would also have to say that the coil that I would still use the most is the minelab 11' commander round mono coil on my 4500, simply because its the best coil I have found for general use whether it be sniffing about old scrapings or getting around trees and shrubs, it really shines on rubbly eneven ground because it has really good depth and even when swung over the rubble it stick picks up on the buried pieces.

A larger coils like the 14" round nuggetfinder mono or eliptical mono are both great at this too but they are harder to manouver on this sort of ground so its easy to miss the bits and pieces, the other thing is that with the larger open spoked coils its harder to find the little bits and pieces once you have them out of the ground, but with the 11" you can put handfulls of dirt on the flat surface of it and easily find the nugget.

I only use about 4 coils, the two I use the most are the 11" commander mono and the 14" round advantage mono, this would be about 80% of the time out, my next favourite coil is the minelab 8" mono for the really tight spots like creeks and particularly around quartz blows and large rubble where I want to get in close, lastly I have an 18" commander mono for the open ground or where I know there have been deeper bits found, I did have the 20" round commander mono but found that a bit noisy, where as the 18" is more stable.

In regards to the longer otto shafts, I have the otto set up on my 4500 and have used the longer shafts on it as well, particularly with the bigger coils, but I found that the head section of the shafts are narrower than the standard minelab ones and you have to really tighten the nut/bolt to get it to clamp up, I found that it was deforming the bracket on the top of the coil and I believe placing stress on the base of the mount where it attaches to the coil, so I went back to the standard minelab lower shaft section.

Just wanted to add that the issue with the deforming of the mounting bracket was with the "Nuggetfinder Advantage" coils but all the others were ok.

cheers

stayyerAU

This is a good thread!

Marco(nero_design), in your very well written report above you did not evaluate the NFA 24" EM. I think you did own this coil. Can you give us a brief evaluation on this coil please ?

JP, what do you think about the NFA 24" EM as compared to the NFA 18" RM ?

Also very briefly on what approximate size gold surface area(just for an example like 2" or 3" across) does the NFA 25" RM kick-in as a depth advantage over the 18" or 20" RM's ?

Both of your inputs are very valuable and appreciated.

Got these today with my 18" NF ADV mono on the 5000 using Enhance, missed them with the 17" elliptical with the 4500 in Enhance, why? I'll let you people make your own minds up on that one.

JP

Bit over 5 grams of the good stuff for a couple of hours work

G'day gents.

JP,nice little finds.Judging by the type of ground that you're working in,nuggets of that size would have sung Dixie in the hands of a good operator with a finely tuned 4500,using the 8 or 11 inch Commander coils, the 12 round or 14x9 Nugget Finder Advantage coils,or even the 14x9 Gold stalker.

Cheers kon61.

Beer Beeper wrote:This is a good thread!

Marco(nero_design), in your very well written report above you did not evaluate the NFA 24" EM. I think you did own this coil. Can you give us a brief evaluation on this coil please ?

I agree, this is a great thread - mostly because there are few hands-on coil threads online. Just remember than this is only my opinion. Other people's experiences may differ.

The NFA 24" Coil is a LARGE coil and therefore was not ideal for my uses where I currently detect. My thoughts are that if you want a LARGE coil to go DEEP, then you need a round coil for maximum depth. An Elliptical tends to be slightly shallower seeking than a round of the same size but is often slightly more sensitive to smaller bits of Gold. I wanted more depth but not the tiny bits. Also, a larger ELLIPTICAL coil is easier to swing because the sides won't clip the ground like those on a large ROUND coil are prone to doing.


Now that's a freak huge, honkin' coil!



14" NFA Elliptical coil alongside the larger 24" NFA Elliptical coil.

But NSW is not ideal for the REALLY large coils though they can be applied almost anywhere. There's less open ground and much more rocky and hilly surfaces in our goldfields. There were several reasons why I chose to remove the 24" NFAE from my coil collection: One reason was that I found it to be very sensitive and incapable of being used quietly on a standard shaft with standard settings (I wear a bit of metal on my person when i detect). It was functional and I liked the way it looked on my detector - how can anyone fail to notice such a monstrous coil on a detector? I entertained the idea of using it to find deep meteorites in benign ground ...but in the end I chose to sell it because I use my other NFA coils more often and with greater ease. It didn't hurt that the week that i chose to sell it, these coils were commanding prices 6 times their original value for used coils. That was more of an agreeable coincidence.

Do/did I like the coil? Yes. I thought it was a great coil with ideal dimensions for it's depth and capability. Hard to say how it rates against the others from the same family but I miss it a little: I did not get to use this coil often enough to be able to give it a fair comparison as I enjoyed the 14" NFA coil more and therefore was using it more often on my GPX-4500.

* * * * * *

JP: Tell us more about your results with the 18" NFA coil and why you felt it was better on the 5000 than the 17" was on the 4500 in "Enhance". I assume it was the extra punch and stability from the GPX-5000 that gave you an advantage over the smaller coil on the slightly less stable GPX-4500. But I'm guessing. I know you liked the 17" NFA coil when you were using it last year.

kon61 wrote:
G'day gents.

JP,nice little finds.Judging by the type of ground that you're working in,nuggets of that size would have sung Dixie in the hands of a good operator with a finely tuned 4500,using the 8 or 11 inch Commander coils, the 12 round or 14x9 Nugget Finder Advantage coils,or even the 14x9 Gold stalker.

Cheers kon61.

I worked this gully last year with my 4500 and only managed to score a 4 gram piece using a 17" elliptical in both Normal and Enhance timings. The gully is too noisy to work effectively with Normal timings and masked the nuggets that were not loud enough to break through the ground noise, going to Enhance the outright performance of the timing coupled with the size/shape of the coil did not offer enough to bring the responses up to audible levels (the two larger pieces were down in the pug 14" or so). The other issue is the amount of EMI present due to two major coal mines in the district which reeks havoc unless the detector coil is held dead flat, as soon as you go onto a slope (gully edges etc) the noise starts up, in this regard the 5000 is very stable, couple that with improved timings and the 18" round Mono and the nuggets did "sing dixie" even in my hands. Could I have found those nuggets using the 4500 with Enhance and an 18" mono? Possibly but the EMI would have driven me to distraction and its possible the old Enhance might not have been up to the task, otherwise we'll never know as I only had 2 cracks at that gully with the 4500.

nero_design wrote:
JP: Tell us more about your results with the 18" NFA coil and why you felt it was better on the 5000 than the 17" was on the 4500 in "Enhance". I assume it was the extra punch and stability from the GPX-5000 that gave you an advantage over the smaller coil on the slightly less stable GPX-4500. But I'm guessing. I know you liked the 17" NFA coil when you were using it last year.

Marco I love the 17" elliptical but only when conditions allow, if the ground is no more than 12" deep and the bulk of the gold on or near surface there is no better prospecting coil for the weight to ground coverage to sensitivity to tiny targets ratio (especially using Fine Gold or Enhance), going up to the 24x12 loses some sensitivity to sub gram bits and increases the weight which causes fatigue when galloping across the country side, but for outright depth relative to size and shape along with receive surface area relative to inductance, the 18" round has no peers it really does hit the sweat spot.

JP

Thanks to everyone for their input here especially nero and jonathan for their detailed explanations.This has been a question on my mind for a while and really helps as its exactly what I need at the moment.
The only thing I can add here is the 14x9 just got me 50 tiny nugs in inglewood in the last couple of weeks in well worked ground in various locations that I had covered before,its a proven small gold finder for me,not much in the way of larger gold or targets though.
Steve

Good explanation JP. That's exactly what most of us want to hear,the reasons as to how you could've missed those small nuggies with the smaller elliptical coil from the start.

Cheers kon61.

nero_design wrote:.

Just my experiences here:
NOTE that I've only used the 16" Round NFA and the 14" Elliptical NFA Monoloop coils on the GPX-5000
The others were used on the GPX-4500.

IMPORTANT: I have observed my 14" Elliptical NFA to be more sensitive on the GPX-5000 than it was on the GPX-4500.
This means I have had to seek fit a longer shaft (I used an OTTO 800mm shaft) to extend the coil further from my person when detecting.


18" NFA Mono Round =
* SLIGHTLY Deeper than 16" NFA.
* Less Stable than 16" NFA Round Mono.
* A little unwieldy and prone to instability.
* Requires longer shaft to extend away further from body.
* Gets the deepest nuggets.
* Less sensitive to smaller subgram nuggets than smaller coils.

16" NFA Mono Round =
* VERY Good Depth - More depth than 17" NFA mono Elliptical (and smaller coils)
* Not quite as deep as the 18" NFA but close.
* More stable than 18" NFA.
* Requires longer shaft to extend away further from body.

14" NFA Mono Round =
* EXTREMELY sensitive to very small targets.
* Shallower than 16" + 18" NFA. But VERY deep compared to similar sized coils.
* DEEPER than similar coils including 14" NFA Elliptical.
* Benefits from longer shaft to extend away further from body.

14" NFA Elliptical =
* VERY sensitive to subgram nuggets... more so than similar coils.
* MORE sensitive than the 14" NFA Mono Round coil (Almost as deep too)
* Excellent depth per size ratio.
* Much Better depth than an average 11" round mono.
* My personal favorite.
* Benefits from longer shaft to extend away further from body.
* Extremely compact and lightweight.


When I was playing around last year with a Coil Strength Field Meter, it showed that the NF coil with the most punch for the size at the time was the 16" NFA Round Mono. The 18" put out a stronger field but only slightly more. I think that it should be mentioned that the testing Meter was flawed - in that some coils that tested weaker than they ought to showed normal results when turned around 180 degrees on the platform. So the machine used to measure field strength was in some way compromised by the coil windings and/or orientation. For this reason, don't rely on a Coil Strength Field Meter unless you consider the other variables. But I was impressed by the punch from the 16"... enough to buy one at the time. I don't use it nearly as much as I use the 14" coil as the smaller one is more practical as an all-purpose nugget-hunter.



If I was recommending a coil to anyone, I'd suggest the 14" NFA Elliptical first and let them decide if they can handle a 16" or 18" NFA Round Mono. The 17" Elliptical would be easier for them to handle although all large coils are HARD to pinpoint with.

Hi Nero, thank you for the informations about the most popular NF coils, you have not mensioned the 12" NFA round mono coil, what do you think about it?, I all ready have a 14" NFA elliptical, wich would you buy next a 16" NFA round or a 18" NFA round?
Cheers
Goldquest

Fantastic thread, clearly a wealth of knowledge here.

great thread and some great reading

im gonna put the cat amongst the pigeons here

On noisy high mineralized ground to get deeper targets out using a 4500 or 5000
is it better to use a smaller (quieter) coil say 12"nf with the gain turned up high 12 - 15 ?
or use a bigger (noiser) coil say 18"nf with the gain turned down lower to keep the coil quiet say 6 - 10 ?
assuming all other settings are ajusted to best suit the coil being used
and assuming flat open ground

just interested as to what your thoughts are on this

kind regards
mick

Hi Mark
The larger mono's are actually quieter,Ive been using the 17"elliptical and 16"round which run very well in mineralised ground.The problem is with receiving interference (EMI) in some areas.The smaller coils are definitely more immune to this but this also differs with brands.
The best option I've found is to run a few coils over good ground if you've found something,there are just too many variables involved.
Steve

Good question mickb...now a 12 inch NF round mono can punch in deep on a variety of nugget sizes...I`ve had one since January and it has found me 0.1 to 9.3 grams bits...and other multi gram pieces in between...Last week a 0.1 and 0.2 and a 2.7 gram nugget....and today just the one,but a 8 gram nugget at 7 inches

Now in regards to settings on my 4500,i find a gain of 10 and stabilizer at 7 works for me as i find in noisy ground that`s all i need as the detector is sensitive enough without increasing the noise from mineralization...If you turn up the gain too much you just start digging more ground noise...and yes i`m looking to buy a much larger coil,probably a bigger elliptical or round one.

Cheers Eureka Dreams

I have used my 12" NF for approx 18 months now and it is an awsome coil it finds all sizes at all depths.
I have recently hit on a good patch digging nuggets up to 8 or 9 inches down with the 12"NF and I just know there are deeper nuggets there.
So I tried the 18"NF and found it really noisy unless I turned the gain right down to 6 or 7 and the stabilizer down to 5 or 6.
Just wondered if reducing the settings would decrease the depth finding capability of a larger coil or is the difference negligible
Or is it just a case of run as large a coil as the ground mineralization and EMI will allow

thanks in advance

Kind regards
Mick

Hello Mick

I will have a go at answering,i think the larger coil say 18inch is still punching deeper on larger sized nuggets even with the gain set lower at 6 or 7...As i understand it the gain affects the signal receive response,and as you said run a larger coil as the ground mineralization and EMI will allow..By using say the 12 inch and then the 18inch you have covered your bases for a variety of nugget sizes at different depths...

I`m sure there are much better explanations on this topic and i am also very interested to learn more on this..
ATB..to you Mick....and sounds like your patch is proving to be a beauty.

Cheers Bill

G'day Mick.

Bingo.Unless your strictly into "coil crevicing" that last sentence of yours should be made universal law.
Reducing gain on any metal detector reduces the coil sensitivity on all targets to some degree regardless of coil configuration or size.This means some reduction in depth also.More so with VLFs than pulse.More so on faint target signals at depth as well as on the smaller gold nearer the surface.In the case of the NF18 mono,reducing the gain to between 6&7 will cost you some sensitivity and depth loss on the smaller targets but little or negligible depth loss on the larger multy ounce targets even at depth.As JP stated on one of his previous posts and as Bill stated before me,Its the target receive signal that's picked up better on the larger coils than on smaller ones.

Cheers kon61.

So if i read this correctly i am better off using my 16"round coil at a gain of 10-12 than my 14"eliptical with the gain set at say 14-15.
When refering to depth? I run a 5000 having just upgraded from my trusty old 4500
Is this right or have i miss read earlier posts.

Cheers
Marty