davent said:
Come on then RR, answer his question then.
Way I see it is that a mono coil, is one loop of wire , boundvin different ways, each has advantages, depending on who makes them. The mono coil looks through the ground in a cone shape, the deeper it penetrates, depends on the size of the coil. Bigger the coil, deeper it goes. At its maximum depth, you are hearing info from the tip of the cone. So a deep target can easily be missed, but shallower targets are heard from higher in the cone. The new monosvare very sensitive and hear small targets. Mono,s are more prone to electrical interference, and more effected by ground noise.
DD,s are two coils of wire, shaped like opposing D,s inside the coil. One transmits and one receives. It dosnt see through the ground like a cone, more like a a piece of plywood , or a rectangle, going from the front of the coil,to the rear. Did,s won't penetrate as deep as a mono the same size. On the same ground, however.....if , to run your mono in hot ground, you need to turn you stabaliser and gain down, and run in enhance, with quiet audio, you might be better off with a did, that you can run in normal, and crank the gain and stab. When swinging a did, you need to go sloe, and side to side, where with a mono, you can confidently push fwd and back as well as side to side.
There is heaps more to it. DD,s are not as sensitive ( although the new detechs sound encouraging) but are less effected by emi and ground noise. Hope this helps a bit, I'm seriously considering adding a good dd to my coils, maybe if detech do an11 or 12" did spiral wound, I'd get one. Actually, no maybe about it.
Looks like you covered it pretty well, Mono's and DD's are like Concentrics and DD's but in reverse.
When it comes to comparing DD's to Concentric's there was a time that Concentric coils could detect deeper in Mild to Medium levels of mineralization and when people use to test them others would shout Foul, But DD's have now caught up with Concentric's. However Now this is not the case because in term of depth Both are now equal.
Too many people slap on a DD thinking that their Ground is highly mineralized when in fact most of the time their soil is close to normal or just Above normal, If a person has access to a VLF with some form of a GB/Fe meter on it they can use that to help decide as to which coil will give them the best results, and as a General Rule the need for a DD should only be when the Ground GB/Fe meter starts to read 75 to 80% of it's scale, 75% means Oh S**t and 80% means Man the Lifeboats.
UNLESS ? you have a 6" Concentric then you can Cheat because the machine is not seeing as much of the Ground as a 10" Coil does,
So why use a 6" concentric on A VLF? Simple, It will see Gold well in to the range of LF (Low Frequency) Detectors Like the GMT and the Gold Bug II and the Minelab Eureka Gold and the Makro Gold Racer,
That 6" coil will see bits in the Ground down to 0.003 to 0.006 Grams..
So what other benefits does a Concentric have ?.....
Well for a Start when it comes to Tiny bits, What a DD will see at 1 to 1.5 inches a Concentric will see at 3" to 4" inches, But once those targets get up around 1 or 2 grams Both Coils are Equal-ish.
What else does a Concentric Offer ?.....
Well do any of you enjoy digging Crown Caps ? Yes/No ? As our friends from the US call them,,, If you like digging
Clad Coins,,With a DD, If you disc out Crown Caps ( Stubby Tops ) Then you will loose 90% of Coins maybe More,
On my MXT All Pro using the 10" Factory DD,,,, To wipe out Crown Caps, I have to set the DISC between 6.7 to 7+ and out of 6 coins tested Only ONE Coin sounded as a Keeper/Wanted Item,
So then I switched Coils to the New 950 / 9.5" (X Type) Concentric Coil and I turned the DISC to Zero and I raise the Disc level slowly until the Crown Cap gave a LOW Tone,,,, Now Checking the Disc Level it is Now reading 4 and Testing all the Coins Once again ?,,,,, This Time 5 out of 6 Coins Gave a Keeper / Wanted Signal, Now that is just the results of the Coins I tested,,, With a DD, To Avoid Crown Caps you have to Increase the DISC by 75%, From 4 to 7.
When you think about using a DD when you are using the Disc you have to think about all the Gold Rings and Jewellery that you would be missing.,, DD's are really not that Great and they LOVE Flat IRON, Apart from Ground handling and some separation, They Offer very Little, On a PI they also offer some form of Disc, but that is about it,
When it comes to Concentrics,,,, They are 3 X Hotter than a DD on Tiny Items like Nuggets and Micro Jewellery, Giving you 3 X the depth of a DD on such things,
The Disc levels are more controllable because you do not have to be so heavy handed using much Lower levels of Disc means more Good Finds, Pin Pointing is about 90% more Accurate and about 90% Quicker.... and they Unmask Targets very well too Or they do on my machine,,, VDI readout are more Accurate,,,, And Concentric do not suffer with EMI like DD's do Allowing a person to run much Higher Gain levels.
Classic example of this,,, Now everyone thinks that little Whites 4x6 Shooter Coils is a hot one, Well The standard 950 Factory Concentric will Smoke It On Tiny Targets and the Little 5.3 (6") Concentric will Chew the Arse off it even in Hot Aussie Ground, I Know because I Tried it there.
A while back someone here was using their Deus and they had Dug dozens and dozens of Crown Caps because if they upped the Disc then they would have lost their Good Finds,,,, Now the Deus is a Hot machine Now, Can you imagine what a 9 or 10" Concentric would do for it's finds Ratio not to mention it's ID capabilities,
Personally I have very little respect for Detectors that only use DD's, because the best disc system in the world will not help that machine as long as they keep stuffing DD's on detectors, IF Only they would make Concentric Coils for a Certain Two top of the line machines then you would see some huge changes in the detecting world,
I have at leased 6 Coils for my MXT All pro and another one should be here on Monday or Tuesday,
A word to the Wise Dave,,,, If a Machine can not use DD's and Concentric's Then Don't Buy It because you are only buying half of a detector, Just look how good the GPX's are and they Use Both.
PS I hope this Answers your Question Dave. HH.
John.
