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#1

PhaseTech
Phase Technical
From: Adelaide, SA
Joined: 29 May 2014
Posts: 1,939
Phase Technical
13 November 2019 11:45 am

This coil doesn't have it's own thread, so thought I better start one.

1573605673_18_concentric_sm.jpg

A short session to report on the Detech 18" CC. Disclaimer - no I didn't find gold, but learnt a few things I'd like to share.

What I wanted to do is just swing it around, and get some more time on it - unfortunately I only had a couple hours to spare, but better that than nothing. No point doing comparison testing against other coils before knowing how it performs, and what likely settings can be used in different areas.

The spot I took it to was the Small Gold Patch that is in some of my YouTube videos. This has since been flogged with the Zed, SDC and GPX with a variety of coils. The reason I wanted to try it here was 1) this spot is pretty worked out, and 2) It is quite mineralized. A spiral/flat mono can only be used in smooth timings here. Regular monos can also be a pain but a larger mono such as a Minelab 18" is almost workable but a few tweaks are necessary. So I wasn't too sure what to expect with the Detech Concentric.

I switched on the 5000 with my normal settings but switched the front panel to Normal and DD. After ground balancing, the threshold was very stable, a welcome change from using big monos on a windy day! As I started to detect, I was on the edge of my seat waiting for the expected ground noises to come in. But they didn't. I even threw my test nugget on the ground a few times to make sure all was okay. I wasn't expecting to find much but I got a couple small bits of iron trash, most likely ignored by smooth timings on the GPX.

As I detected I was mucking around with Gain and Motion settings just sort of auditioning a few things, so I did hear a few ground noises. These were easily identified by using common techniques, i.e. comparing signals with sweep speed, ground balancing around the response area etc. I still checked a few to be sure. One which sounded a little sharper, and was still there even after re-balancing ended up being a .22 lead. "Wow, how is that still here?" was my first thought. I decided to put it back in the hole to have a play with some settings. With DD on the coil switch, I got a sharper response than in Mono. Switching the timing to Sens Extra sharpened up the response again. In DD, the coil works as a Concentric so the response is like using a smaller mono, very sharp and "tight". Imagine an 8" mono sitting inside a 18". I found that pin-pointing on a shallow target is on the outside of the inner ring (winding).

With targets virtually non-existent on the patch proper, I started working the fringe area to try and dig something. On the edge of a connecting track I got a nice sweet signal, that I expected to be a fairly shallow bullet. Before digging, I tried Mono, and the target was lost in the sudden increase in ground signal. I flicked into Enhance and I could hear it now, but the response was very faint. Back to DD and Normal and the signal was really clear and sharp. Into Sens Extra and it was sharper again, so I was pretty excited at this point. I was even more excited when it was still in the hole after two good digs, and all this crunchy wash was coming out of the hole! I thought for sure I pinged one of the right colour. When I got it in my hand it even felt good, heavy and hackly, but unfortunately it was lead.

1573604743_18_cc_find.jpg

Other general observations:

- It handled EMI like a champ, very stable
- Very light for its size
- I really liked having the option of switching between Mono and DD for different performance characteristics
- It's neither mono, nor DD, probably closer to a DD, but it can be a big mono or a bit of a hybird depending on your settings.

Thanks 10fp for letting me use your coil while I waited for more stock to arrive. Your closed skid is here now as well. Here's what it looks like fitted

1573605701_closed_skid.jpg

All 18" Concentric coils supplied now include the black fitted/open skid, as well as the white closed skid. This is not a flat bottom skid, bit still prevents sticks and vegetation from getting caught in the spokes.

Last edited by PhaseTech (13 November 2019 11:47 am)


Agent for Minelab, Nugget Finder, Nokta & Makro, Quest, Detech, SteelPhase - Phase Technical Website

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#2

Jarrod84
Member
Joined: 08 October 2017
Posts: 109
Member
13 November 2019 12:13 pm

So in DD it transmits on the big winding and receives with the small, in Mono it transmits on the big or small? And then receives with both?
It would be interesting if these type coils took off and you could get an in line switch to isolate the individual winding so you could select concentric, 18" mono and 8" mono.

#3

Dignit
Member
From: Melb Eastern Suburbs, VIC
Joined: 15 May 2015
Posts: 1,684
Member
13 November 2019 12:27 pm

Great report Phasetech.
Please excuse my ignorance but would you please explain how a concentric coil works and the benefits.
I’m sure others like me know how monos and DD’s work but aren’t sure about CC’s.
Thanks Dignit


GPX 4500, pick, Jeep Cherokee and gold fever

#4

PhaseTech
Phase Technical
From: Adelaide, SA
Joined: 29 May 2014
Posts: 1,939
Phase Technical
13 November 2019 01:25 pm

I'm in the same boat Dignit, Concentric on a PI is still very new to me.
I don't exactly know how these coils are wired up, but from how it performs it seems like:

When in Mono, it transmits using the larger outer winding, and receives with the outer winding (or both?). I would think the receive is likely done by both windings (as is the case with a DD coil in Mono mode) but I could be wrong. Either way, it goes deeper in Mono on larger targets, and the outside edge of the coil is the sensitive part. It still pin-points in the centre on a larger target at depth, as with a traditional mono coil.

When in DD, it transmits using the outer winding, then receives on the centre smaller winding. This provides extra sensitivity, like using a small mono, but you get more depth as you still have a very large transmit field.

I'll try get some confirmation from Detech on this, and next time I'm out providing it isn't windy, I'll do a video on some different targets.

Just as a bit of a dummy check, I hooked it up to a 3500, and have a very textured nugget that I found with a GPZ that recently came out of an acid bath. In mono I can't get a signal off it. In DD I can, and it's even better in Sensitive, so this confirms my findings from the field.


Agent for Minelab, Nugget Finder, Nokta & Makro, Quest, Detech, SteelPhase - Phase Technical Website

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#5

Leroy
Member
Joined: 26 May 2016
Posts: 199
Member
13 November 2019 01:49 pm

Here is another one for you Nenad, going on your recent testing on the CC. How do you think it would go on a GOOD 2000. I understand that’s probably a difficult question to answer but I thought maybe you could give an experts opinion on this awkward question. Should I stick to running it on the 5000 inDD Normal?

#6

PhaseTech
Phase Technical
From: Adelaide, SA
Joined: 29 May 2014
Posts: 1,939
Phase Technical
13 November 2019 02:12 pm

Should actually be a good match on the old 2000. The 2000's not being as sensitive as the 2100, ran mono's pretty successfully in all but really bad mineralisation, so a concentric which handles ground better than a straight mono should be a great match. The SD's just run Normal/DD (no coil switching like the GP's and up), so you'd be running it as a concentric all the time.


Agent for Minelab, Nugget Finder, Nokta & Makro, Quest, Detech, SteelPhase - Phase Technical Website

#7

PhaseTech
Phase Technical
From: Adelaide, SA
Joined: 29 May 2014
Posts: 1,939
Phase Technical
13 November 2019 06:37 pm

Pete's video going across some targets on a test patch, posted in another thread, but some may not have seen it:


Agent for Minelab, Nugget Finder, Nokta & Makro, Quest, Detech, SteelPhase - Phase Technical Website

4 users like this post: Dolphin, robmoto, Dignit, Happy Jack

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