DD coil information and questions

[Davent]

Yeah, understand the 15 detech is good, hard to carry.
Also really want something I can run in normal, in hot ground. Depth is also a big consideration.thanks heatho

 

[Heatho]

Pity they haven't made an Ultimate Spiral wound DD in an eliptical shape yet for better maneuverabilty in tight areas. Anyway hopefully a few other members give you some ideas about what to try.

 

[condor22]

I use a Commander 15x12 DD on occasions, good for covering new ground (new to me) quickly. Doesn't go as deep as a mono, but the signal pattern allows less overlap.

Also good for noisy ground, but can be difficult to swing in undergrowth, as any larger coil would.

 

[Davent]

Cheers condor, think I'll end up with an older style, like the platypus 17x11. The spirals seem a bit hot for what I want, don't need the sensitivity, just want to run it in normal, instead of enhance. I reckon that a bigger dd, in normal, gain pushed up, stab backed off, will get more depth than a mono with low gain and stab up. I can get the small shallows no prob, but need a way to get some more depth in hot, wet ground.

 

[condor22]

Davent, depending on ground I also sometimes run mine in deep mode, to look for the bigger deeper stuff, worth trying occasionally...

 

[Tubsy]

Hi All,

On a DD SEF coil is the signal strength the same across the entire width and length of the coil field or is the exact centre of the field still going to show the strongest signal?

Cheers

 

[Goldpick]

The signal strength does tend to taper off towards both ends of the DD coils, though should still pick up on most targets along the whole length of the centre axis. Have a go at running your MXT in pinpoint mode with the SEF coil, and try a few methods shown in the video below. That should give you a good idea on how the SEF reacts, and where the strongest response from that coil will be. Not all DD coils are of the same construction or shape, so they may vary in response between brands/models.

Either way, best method is to simply overlap your swings to ensure maximum depth and coverage, and efficient use of time.

Here's video illustrating methods of pinpointing, and it also gives you a good idea on how that centre axis of the coil reacts to a target.



Typical DD coil diagram

 

[Ridge Runner]

With a concentric coil you just pull the trigger and sweep left and right and then push the coil forward and backwards, with a DD you need to sweep across the targets and then turn 90* degrees to the target and sweep left and right again and draw a cross on the ground,

Using the push/pull method on a DD coil will lead you to either Damage more finds and digging bigger/wider Holes, The push pull method only really works accurately when using Concentric Coils,

Hope that helps.

John.

 

[Ridge Runner]

Hi All,

On a DD SEF coil is the signal strength the same across the entire width and length of the coil field or is the exact centre of the field still going to show the strongest signal?

Cheers

As GP posted in that picture the pickup are runs from front to back although they can also pickup signals from the side they are focussed to about an inch to about 2 inches wide front to back, With some DD's they can have a dead zone where the Two D's meet back to back which is at the Centre of the Coil,

The SEF Coils are not quite as hot as the Whites Coils which does help a lot with dealing with Aussie Dirt and that helps with ground balancing and being able to run the Gain a fraction higher which leads to more depth, And even using the same Gain settings the SEF coils seem to go deeper in Hotter Ground because being less sensitive they do not get over run with Ground Noise, In Noisy Ground the 8x6 SEF can go Deeper than the 6x10,

In anywhere else in the world I would try and stick with the Whites Coils, But in Oz I would have to say go with the SEF Coils, The 10x12 SEF is a great Coil and the 12x15 would be the biggest one I would want to use, But your 14x10 is about the Best overall Coil where it offers Depth and Ground Coverage Yet it is about the same weight as the whites factory 10" round DD, and the 14x10 goes a few inches deeper,

hope that helps.

John.

 

[isolation]

Since purchasing my 4500, I have only ever used the 11' supplied mono commander coil. I've been thinking of a few trashy areas that I'd like to revisit, and I'm keen to get the DD coil out of the box and give discrimination a go. I'm interested in hearing about any tips or tricks people find effective when using a DD coil.

I tend to run the mono pretty hot in Enhance. as running in Normal (even turned down) drives me crazy with false signals. I'm keen to try the DD in Normal and see how it goes. Would 'Custom > Hi-Trash' be a good place to start?

 

[Balmain Bob]

Gday Mate,
Next time that you drop into H.E I will go through the settings that I use. I've just bought the Detech 15 Ultimate spiral DD coil and I currently experimenting with it .

Bob

 

[isolation]

Oh nice one mate. There's a chance we could get there this weekend, but not sure so didn't want to commit.

 

[Moneybox]

Isolation I'm in the same situation with my settings. I've only ever had success using the mono in enhance. I've spent a while with the DD on both the GPX4500 and GPX5000.

I've not found a situation where it could be helpful. If you have the discrimination set low it only blanks out quite big bits of iron. If you set the discrimination high it blanks out big nuggets as well as the iron. I'm not prepared to risk losing that big nugget.

 

[Redfin]

These are the settings I use on the larger [24"] DD's with both the 4500 and 5000 in Victoria, mainly looking for the larger stuff down deep.
May need tweaking for a smaller coil.

Front end cap:

Search Mode: General
Soil Timings: Normal/Special
Coil/Rx: DD
Ground Balance: Tracking/Fixed

Menu Settings:

Main Menu:
Backlight: 0
Battery Test:
Volume Limit: 8
GB Type:Gen
Special: Sharp
Manual Tune: 128 (wherever threshold is stable)

General Menu:
Motion: Slow or Very Slow
RX Gain: 11
Audio: Normal
Tone: 60
Stabilizer: 20
Signal: 19
Target Volume: 8
Response: Normal
Tracking: Medium
Iron Reject: Off

 

[isolation]

Thanks Redfin!

Do you find those settings run pretty smooth in hot ground? Even in Special: Sharp? Do you ever use Audio: Deep or Boost when looking for those large deep targets?

 

[Redfin]

Those settings were posted many years ago by JP and have worked well for me on occasions.

 

[10fp]

iv just been playing with a big lump down at 16-18 inches today with a coiltech 14" DD in mild to medium gold country in Adelaide hills and the 4500 prefered Deep and normal on the front otherwise much the same as Redfin .

But my 17x11 Elite in Normal gave another 2-3" but stabilizer needed to be around 5-6 and RX around 8-10.
using Enhance was only bout same as the 14 dd

Dave

 

[PhaseTech]

Looking for big deep gold or wishing to reject iron are two very different things, so will require different coils and settings.

To work trashy areas you generally want a smaller coil so it can isolate better between ferrous and non-ferrous. The Custom Hi-Trash mode is a good place to start. I would only ignore any cleanly blanking signals. For best results, make sure you have the coil switch in DD, and use Fixed GB.

For running a big DD in Vic looking for big deep targets, you definitely want to get things happening in Normal, which usually needs a drop in Gain. I've been in spots where I've needed to run Rx as low as 4. Stabilizer 20 is too rattly for me, and my setting depends on which Audio Type is selected.

My general rule of thumb is:

Deep: Stabilizer 6-8
Normal: Stabilizer 9-12
Quiet: Stabilizer 13-16

Whenever I'm not using any of the smooth timings, I like to run in Tracking, preferably Slow, but Medium if needed.

The other thing I avoid when using DD's is Very Slow motion. It just isn't required and Slow or Medium will give you a slightly brighter response.

 

[isolation]

Thanks Nenad, very comprehensive as usual.

My focus for now is to try iron reject, but I'm definitely interested in any other advice people have. One of the areas I'm thinking about is shallow alluvial diggings, and not much ironstone from memory, so hopefully I won't be cancelling out any nuggets :Y:

 

[Dignit]

The thing I find with a DD and Iron Reject on, the detector will often still register a target but as you get closer to it it starts to blank. I expect this is just the limitation of the of discrimination signal processing.