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Coil Choice For Compact Detector To Search Inside Structures


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I'm contemplating modifying a standard size (discriminating) IB/VLF detector into a compact form factor to search inside old structures.  Thinking small concentric, but how small?  Tesoro has a 5 3/4" concentric.  Other manufacturers have 6" diameter concentrics.  Both Fisher and Bounty Hunter (well, First Texas now) have made 4" concentrics.  (Note:  I've decided to go with a concentric instead of a DD because of the freedom of motion symmetry they offer.)

Any thoughts/opinions are welcome.

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The 4 inch BH coil is cheap, that's one good thing. It will fit a fair range of machines, including the Fisher F2/F4. These have all the electronics self-contained, so they can easily be refitted onto a custom shaft. I have this coil, and it does seem to pick up electrical interference, though. Maybe the screening/shielding is a bit minimal, being a low-end BH product.

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I have the Tracker IV that I have used with the small gold coil to get into some of the old buildings such as barns that are missing a few of their boards over the past 100 years.

I had the shaft as short as possible so I could swing it around some objects and it surprised me with how well it did do the job.

Hope this helps and good luck.

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Good replies so far.  I'm wondering if my strong preference for a concentric coil is too hindering.  Coil size is another thing I emphasize (within the already tight range of 4" to 6").  Am I making too big of a deal over that?  Here's a Q&D scorecard covering the considerations among 4 current options:  Minelab X-Terra 705, Tesoro Vaquero, Fisher F2, Bounty Hunter X (many BH detectors can operate with the 4" hockey puck).  I'll lump all the First Texas (FT) detectors together.

1) Detector availability:  I already have both the 705 and the Vaquero.  Other two I should be able to pick up pretty cheaply on Ebay (especially BH since so many models will work):  705 and Vaq score a 2; others a 1.

2) Coil availability:  I already have a 6" concentric (7.5 kHz) for the 705.  NEL Snake / Cors Shrew are available now on Ebay for $122, but with Tesoro OOB I wonder for how long....; that FT 4" coil is available (cheap) both new and used, and I might find the detector&coil combination for reasonable (both for about the price of the Snake/Shrew?):  705 gets a 2, others get a 1.

3) Detector performance:  I'm calling this a tie since all will do what I need (simple ferrous-vs-non-ferrous discrimination; tonal response).  All score a 2.

4) Coil size:  FT 4" hockey puck wins; Shrew (3.5"x6.5") next; 705 last:  FT = 2; Vaq = 1; 705 = 0.

5) Coil type:  since I currenly prefer concentric over DD, Vaq comes in behind the others with a 1; FT and 705 get a 2.

6) Detector compactness:  Vaq wins hands down.   Those micromax control units are tiny and they are mounted right on the shaft.  Vaq gets a 2.  705 gets a 1 (because it can be remounted in a prone position), FT = 0.

7) Ease of modification:  Vaq is practically grab and go -- just needs a shortened lower shaft.  Vaq = 2; FT = 1; 705 = 0.

8 ) Overall looks/feel/impression:  Vaq with its compactness and similicity gets the nod here.  Vaq =2; others = 1.

Weighting all of these criteria equally (not necessarily the best method for a final decision...):  Vaq = 13; 705 = 10; FT = 10.  Easiest path is to just buy the Snake/Shrew for the VaqCheapest solution is the 705 since I already have everything, just need to do the mods.  FT is a bit of hassle to first find the detector, the coil, and then doing the modification.  However, FT has the most desirable(?) coil with the tiny 4" round concentric.  Decisions, decisions.

Final comments:  Above I didn't include the option of the 5 3/4" round conentric Tesoro factory coil.  Those are getting hard to find (even used).  If I were to go now with the Snake/Shrew coil on the Vaquero I still have the option of adding that concentric coil in the future.  It's obviously more expensive buying two coils but I like options.  Also, I see from the thread Steve H. linked that Tesoro also made a 4" round concentric, but I think only with a 5 pin ('Epsilon') connector, not the 4 pin ('Delta') which is used on the Vaquero.  Thus I would need to buy a detector and coil to go this route.

 

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A few thoughts.

One, do these units need to be extra durable or waterproof? I don't know how or where you'll be hunting, but being in tight and possibly damp quarters means getting at least a weather resistant machine might be something to consider? If so, maybe an AT Pro with the 4 inch hockey puck coil is an option? Or is that coil a DD?

Two, the F2's control box is fairly big. Not sure if you've used one before.

Three, how about a Deus with a specially modified sniper coil? More info here: https://md-hunter.com/sniper-5-coil-for-xp-deus-homemade-photos-video/

Four, how about a special pinpointer, like the N/M PulseDive or Quest Scuba Tector Pro with a special coil, attached to a separate shaft?

 

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35 minutes ago, mh9162013 said:

A few thoughts.

One, do these units need to be extra durable or waterproof? I don't know how or where you'll be hunting, but being in tight and possibly damp quarters means getting at least a weather resistant machine might be something to consider? If so, maybe an AT Pro with the 4 inch hockey puck coil is an option? Or is that coil a DD?

Two, the F2's control box is fairly big. Not sure if you've used one before.

Three, how about a Deus with a specially modified sniper coil? More info here: https://md-hunter.com/sniper-5-coil-for-xp-deus-homemade-photos-video/

Four, how about a special pinpointer, like the N/M PulseDive or Quest Scuba Tector Pro with a special coil, attached to a separate shaft?

Good questions and thanks for the thoughtful reply.  Here are my quick answers:

Waterproof?  Ziplock bags do pretty well as long as you don't drop the control unit in water....

F2 control box?  Thanks for that tip.  I've been thinking about control box size all along but have never seen an F2 (and don't remember seeing a BH up close).  The X-Terra 705 control housing is pretty substantial, too, particularly compared to today's smallish units like XP Deus/Orx, ML Equinox, and the upcoming N/M Legend (and especially compared to the legacy Tesoro Micromax housings).

XP Deus?  Now you're talking real money!  (Ditto buying a Garrett AT.)

Pinpointer?  Typically these don't have discrimination.  I think some of the Minelab pinpointers are advertised as such but my limited knowledge (YouTube, forum reports, etc.) is that this feature is marginal.  Could be wrong there.  But those ML pinpointers don't have a circular coil like the Nokta/Makro Pulsedive, for example.

Obviously what I'm considering is going to be a specialty detector which gets used infrequently.  Thus I don't want spend much.  I don't see my 'solution' being even a backup detector -- I have enough of those already.

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I understand the Deus and AT Pro might be expensive options, but I wasn't sure what you budget was.

As for the Ziploc bag, that won't be as nice as a purpose-designed detector that's weatherproof,  but I get how it's a lot cheaper.

I wasn't sure if you needed discrimination and if so, how much you needed. But if you need a small amount, using a pinpointer probably wouldn't be a good option.

Whatever you decide to do, good luck!

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Most people are likely getting tired of this topic already, and that assumes those who were even interested in the first place.  🙄

I'm reminded of something a mentor (not detector related) told me long ago:  Ugly/sloppy workmanship doesn't necessarily mean poorer performance, but those who take enough pride in their work to make things look nice tend to build better performing / more reliable devices.

So how does this apply here?  The question is, will the better looking, compact, easy to use Tesoro solution pay off in its ability to squeeze into tight places?  Peripherally, will I be more likely to make maximum use of the Tesoro because of its appearance?  Maybe.

I'm going to wait about half a day or so longer to see if anyone has something further to add before I go with my current leaning of just ordering the NEL Snake / CORS Shrew.  So far no one has taken on the concentric vs. DD question.  Basically, my thought is that you can move a concentric in any direction (left-right, forward backward) and get the same response whereas a DD coil has an azimuthal dependence because of its internal assymetry.  There are ways around this (just rotate the entire unit 90 degrees, or remount the shaft 90 degrees from standard orientation and rescan) but those aren't quite as easy/quick as just changing the sweep motion.

BTW, in playing around with the Tesoro Vaquero I discovered (something I'm sure many here already know) that the shafts of my White's TDI are compatible with the Tesoro Vaquero.  I don't know how many other models of those two companies this holds for, but I suspect quite a few.  So I can shorten the Vaquero shaft permanently but if I ever want to use that detector in its standard configuration then I'll just plug in the White's TDI lower shaft (of which I have a spare).

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If you have an Equinox and 6" coil why not just put it on a telescopic shaft, plenty of options available then you don't even need a special detector or coil.  Just use what you've got and the added bonus is you can pop it out to full length in a few seconds and carry on detecting elsewhere.

minelab-equinox-custom-telescoping-carbon-rod-herschbach.jpg

 

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