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A Few Big Coil In Saltwater Notes...


cjc

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My CTX had been in the shop for quite a while–it had the old config and leaked more than once.  One bulkhead, one set of clips and two lithium cells later she was still drinking brine.  Thanks to  Minelab I’ve just gotten a like new machine and am very excited and grateful.  (This must be what it’s like to complete a jihad and be granted a virgin in the afterlife)!  Anyhow,  I do a lot of testing in my  basement in that the interference from furnace, household panel and dryer simulate actual tough salt surf conditions.  If you can tune a detector inside–you are doing something right.   This is especially true of big coils.  I have the large coils for my CTX, Equinox 800 and a WOT hardwired for my Blue Tubes Excal.  There is a ton to be learned about signal balancing big coils under these high interference conditions.  This kind of testing has gotten me a lot of deep, heavy gold in conditions where there is a lot of pro-level competition.   First, its amazing how much of a difference in performance loss (even in air) there is between large and stock coils.  These big coils just suck the interference out of the air (or water).  What I notice is that target sounds have a much more “inverse” .sound–as if the threshold was “taking over.”  The higher you turn the Gain–the quieter targets get.   In some instances–the stock coil actually hits targets further out.  (Talk about a “teachable moment!)”

One thing that’s worked well with the CTX has been to run a P2 version of one of the programs that features one or a couple of reject lines.  (Andy’s Beach for example)  This seems to balance the signal and reduce all the reverberation-type noise.   This works well in the field too–especially of you don’t pile on more interference from current and any incline.  This involves a slow sweep speed and working only North / South.  I’ve gotten some rings down at the 20″ level this way.  The Excalibur–as hard to tune with the WOT coil as it can be–is a simpler platform with less going on–electronically.  While it can’t be run that high–maybe at 1 to 2 o’clock is a balanced signal–it does get great depth in discriminate–taking rings at an easy 18″-plus.  It’s also stable.

Now the Equinox is one of the hardest detectors to tune with a big coil that I’ve used.  My usual 2 Tone method works–but is unstable and gets only moderate depth.  My super-sharp responding gold magnet “Undertune” (GB -9 / tone “25”) method is out of the question.  Without Ground Balancing–the threshold is lilting, uneven and requires careful coil control.  I’ve seen videos of guys running down at “14” Gain–unacceptable.  Why bother with a big coil to run that weak of a signal?  The sense I have is that this detector has a hard time supporting a coil that size.  When I run near-preset B2 with 5 Tones–it seems more balanced and stable. This is about the only time I’ve ever been driven back to the pre-sets to balance a detector.  It’s a good coil–but hard to balance–just saying.  I see a detection signal as being kind of like an arithmetic sum.  When you keep subtracting with say, fast water, Gain too high, (in this case) Recovery Speed too fast, high saline conditions  bottom contours / inclines and the work a detector does with a highly processed signal like that of the CTX or EQ–what’s left is not always enough to get any more depth than the stock coil.  I’m still learning with both of these detectors / coils but am really struggling to get any respectable depth–especially with the EQ.  I’ve a lot of great signal balancing “tricks” up my sleeve–including smoothing out the threshold with a “1” discriminate setting or even bringing up the Tone Break–but have yet to find anything that convinces me that a narrower–more manageable detection field drawing less interference would not perform better.    I’ve also been instructed on the forums to  keep the Recovery Speed low–down at “4” with the big EQ coil. This is just not that stable in salt conditions unless its absolutely still.  Of the two, the CTX wins in terms of stability–but for coils that size–even compared to the WOT–the depth just does not seem to be enough to justify the extra swinging effort–at least not in salt water.  I’m open to Equinox big coil salt water suggestions.  Otherwise–next trip–the coil at least–is staying home.

cjc

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I don't have an advice, but would like to know more behind the balancing challenges, as in, how they were determined, the noise, stability, depth? This is just for my own education. 18" sounds very impressive, but with EQX I can't even think hitting anything small at that depth. I did notice however, that slow recovery can extract small items from deeper, but using anything below recovery 3 is rather difficult, to me anyway. I think the 15 inch coil being elliptical is made to rather cover more ground and not the depth. If only they made it round! 

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One main design goal in the Equinox was to increase the sensitivity to low conductors compared to FBS and BBS detectors. Multi-IQ is hotter on small gold and therefore inherently more reactive to saltwater. Simply getting it to settle down in saltwater via the beach mode was challenging.... keep it as hot as possible while not being overly reactive to saltwater. It was tuned for the 11” coil.

The larger coil is “seeing” a far larger volume of saltwater, in a giant globe around the coil. The detector becomes more reactive to the salt, requiring reductions in sensitivity by various means to stabilize the machine. If reducing recovery speed too much makes the detector too unstable then you have to up it again.

Salinity levels vary at different locations and what works for one person may not work for another at a different location. This scenario is similar to what prospectors face running large coils in extreme ground. The bottom line in both cases is getting the large coil stable my leave you with little more depth than what you have with a smaller coil. For gold prospecting in the worst ground a VLF can get less depth with a larger coil, which is why so many prospectors go PI to run large coils, since PI detectors are less prone to the problem. However, even if the large coil on a VLF gets no more depth it’s often still worth it just for better ground coverage.

While prospecting with Gold Mode in extreme ground I run at fairly high recovery speeds, 5 - 6, or coil knock becomes an issue at high sensitivity levels.

Long story short I have no specific tips other than higher recovery for you Clive but I’m not surprised by what you are reporting. I’m not expert at running the Equinox in saltwater but I can understand why running coils larger than the stock coil would be problematic. For huge Florida type beaches I personally still might do it even if I ended up with no more depth just for better coverage, but as you note the big coil is also harder handling in the water.

It’s this sort of stuff and decisions that make detecting fun for me... the strategy! :smile:

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The large coil is a real favorite of mine and I just loved it for UK style field detecting. Going to an 11” under those circumstances was like taking baby steps. I would use the 15” on the dry beach for the same reason. In water though I’d also probably stick with the 11” personally. I’d actually like an 8” or 9” for water use as my tendency would be to go smaller, not larger. But the 6” is a little too small.

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W

19 hours ago, Steve Herschbach said:

The large coil is a real favorite of mine and I just loved it for UK style field detecting. Going to an 11” under those circumstances was like taking baby steps. I would use the 15” on the dry beach for the same reason. In water though I’d also probably stick with the 11” personally. I’d actually like an 8” or 9” for water use as my tendency would be to go smaller, not larger. But the 6” is a little too small.

Which brings me to my sore point on the Vanquish coils.  All I am going to say is big opportunity missed by Minelab not including some degree of cross compatibility across their Multi IQ line.

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8-9 "coil on Equinox would be great .., well I don't understand why minelab has not yet made it ... when the competition has me.
  According to me the advantages of 8-9 coils:
  1.Excellent 2D and 3D separation while maintaining excellent depth ..8-9 "for round coil ... is the size of coil where it begins to separate perfectly in the iron ...

2. Sensitivity to small objects., And possibly improved ground mineralization work.

3.Light weight = Better balance and excellent handling of Equinox in difficult-to-move conditions.

4. On this size of coil we can count increased resistance to Emi ..

 :wink:...EQUINOX deserves another good coil ..

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Steve and Clive,  Since Florida beach hunting is my life, I’ll add the view from my foxhole to this interesting discussion.  

Without rehashing the good points brought up by both Steve and Clive, I’ll just say that I’ve used both large coils and the stock coil searching our beaches and the surf.  In the end, I now use the stock coils exclusively.  Yes, the larger coil covers more ground with each swing but with less ease of use and reduced sensitivity as I’ve seen.  As Steve says, the EQX was tuned for the 11” coil and I believe I’ve proven that...at least to myself.
 I know other well accomplished detectorists use the large coils on the beach and in the surf and with some success.  To each his own, but for me, I prefer the enhanced sensitivity on low conductors the 11” coil seems to give me...as I always say however, that’s just the view (and preference) from my foxhole.

Good job to both Clive and Steve.  Salute!!

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I share a similar understanding of the 15, 11 and 6 for the Equinox.  That can be shown in some of my posts from the beginning.  I hunt 90+% of my time on beaches around Santa Monica Bay that has a black sand line from the waves and a wet zone where the wave energy leaves some of the heavier good targets.

My large CTX coil seems to do 'better' than the Equinox 15 but I rarely use the 3030 any more.  I should because I think I would walk faster with it and not 'miss' targets.  I have mentioned to Simon on a number of occasions that I think the 15" Equinox coil is a finicky coil.  I think it is better with the latest update but as has been noted I don't know that it gives me much additional depth over my 11" coil.

I have upped my volume for negative targets and on my beaches I can dig quarters at 14-15 inches.  In order to do that I also dig a lot of bobby pins and iron trash like tent stakes which are nearly invisible as they don't have massive response even tho they are big.  I can eliminate some of the black sand by staying 'quick' at around 6 and I keep my sensitivity almost always at 23.  I have learned to swing speed hunt certain beaches.  If I find a target (the waves make some pockets) I really slow down for that and crusty quarters.  My gridding will find more that patch hunting.  I do look for the patches and then swing differently.

Last night I found a couple of cheap rings and they were 'tiny targets' that I would have missed walking faster.  I listen for the fringe signals and bring my 11 back to a good target better than the fringe of the 15 I guess I would say.

All that being said, I've found some good targets with a limited amount of time with the 6" coil on the same beaches.  It provides a target ID with less variance than the other two coils and I can dig down to 8 inches.  I do it once in a while just to have 'fun' and I extend the handle length and swing it over a wider arc so my 'footprint' is larger because the fringe works for me also.

On rare occasions I'll set up down to 4 but normally now I like the 11, 23 and stay at 6 with FE and F2 off and stay in Beach 1.  Sometimes I'll go into 1 ft of water but that is about the max.

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I have nowhere near you all's experience with detecting!  Let alone with the Nox!

But i just had my 800 out yesterday, after a few months of sleep! At a well eroded beach, and did fine with the stock coil and settings! Beach 2 for the wet sand, for the majority of a 2 hour hunt!

  There were 4 other detectorists working a fairly small area of beach with mid to higher end detectors! And i worked the area behind them that they had been thru!  I looked to be the only one with a Nox! And still found 2 rings, and several older encrusted coins! I ground balanced several times, and was hitting some pretty deep stuff! Including some very small copper and lead pieces!

I agree with "if it ain't broke, dont fix it"! And i try not to mess with my settings at this point! I appreciate the thought and experience that went into the Nox's program's, and i; at my experience level; would be wrong to think that i could "out program" the software engineers!

That being said, i do appreciate you  "Yoda" guys pushing the envelope and finding "never thought of" tweaks that could get more productivity! That is, after all, how the detector companies got to where they are in the first place!

Thanks for Testers and Innovator's! 👍👍

 

 

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