Performance loss in Coils

hi
can anybody tell me how much less sensative is a 14"dd,used in mono,than a 14"x7" mono?
is there heaps of difference,or a little bit of difference. with my 4000,if i use it in high trash areas with the double d coil set in mono,i find some targets,that if i switch over to dd ,i cant hear them,so the mono setting is more sensative,but how much more sensative would a straight 14"x7" mono be.i`m sure someone here would have done such comparisons.
thanks

Since the 'Transmit' coil (on the left half of a DD coil) is only half the size of the coil, you're essentially using a 'mini-coil' by switching your DD coil to MONO. It's sometimes referred to as a 'Pseudo-Mono' coil when you use a DD coil in this manner.

But if a Dedicated or True-Mono coil is used, the Monoloop coil has a denser field and is therefore more sensitive and goes deeper than the DD coil of the same size. Also the size of the field is much larger than that of a DD coil of identical size. So a DD coil at 14" is going to be quieter than, but not deeper than a 14" Monoloop.

Gday

Although there may be a some of loss in depth, using a coil in the pseudo mono mode, rather than a dedicated mono coil of the same size there is the upside of the coil running more quietly and the descrimination feature will work to some degree as well.

Also you have to be aware that as the coil is operating only on the one side then if you are using it around trees and vegetation then you can miss targets as well, so its best used on clear ground where you have a clear swing.

It will perform similar to an eliptical coil, as far as the shape of the signal transmitted into the ground, so it would not achieve the same depth of a round coil of similar size.

This feature was only really designed so that a stock standard machine fitted with the 11" dd could have the added advantage of being switched into pseudo mono to give it a bit more sensitivity when the ground allowed it, basically providing two types of coils in one, it will of course work on most dd coils, even after market ones, but I feel that it works the best on the stock 11" minelab dd coil from my own use, rather than other makes of coil.


cheers

stayyerAU

Hey Dave,
So what was your result, I too would like to know as I use both depending upon the conditions at the time.... 14X9 mono when conditions permit and a 14inch DD when things get abit noisey... I dont like to use sensitive smooth timings on my 4000 as I believe u lose to much depth/sensitivity...

What about running a DD coil in Mono mode on the GP series?The transmit winding on an 11" DD is approximately 11" x 7", but the transmit winding of an11" Mono is 11" x 11" which is why it can achieve better depth. However, the 11" DD in Mono mode transmits using the left 11"x7" winding, but receives using the whole coil, which makes it more sensitive than the 11" mono, and because some DD characteristics are retained, it will provide better stability in mineralised soils. Those operators who have experimented with their GP’s have reported finding small nuggets at excellent depth in highly mineralised soils, using larger DD coils in Mono mode.There are other factors that can determine a coils performance, such as wire quality, crosssectional dimension of the winding, shielding quality,rigidity etc., and a coil cannot be built to be the best at everything, so every coil has compromises in some areas.
From an early Minelab Times article.
Knowing where & when to use it is the key, especially with a 4000/4500

You loose so much depth in mono mode that you're better off using a mono of an even lesser size. I used te 11" dd in mono mode for a while and you're getting bugger all depth. It'll still pick up hotrocks the size of a pea so no, it won't really be quieter. The only way to use that coil imo is in dd mode going a foot per 2 andahalf secs.

This just an estimate, I think a 10 elip mono would go deeper than the 11 dd in mono.

This might help:

The Searcher
Minelab GPX 4000 by Search Ed', March 08 Field Test
http://video.minivideos.co.uk/ja/minelabgpx4000fieldtest.pdf


In case that link above does not work, it can also be obtained at the very bottom of this page:
http://www.joanallen.co.uk/a_minelab_metal_detectors_uk.html