Smaller Coil For Trash

[Monte]

18 hours ago, Flydog said:

So I somehow discovered a fresh water beach that looks like its never been hunted. Yeah!

But I now realize why. The trash is INSANE! A large building burned down here in 1930. Great place for a beach right? LOL

#1.. Makes as much sense as me just ordering a 5 inch coil so I can collect a small handfull of coins.

#2.. Although I will know soon enough.......will a small coil be a significant help? Or,  it will help but dont expect miracles.

#1.. Yes, a smaller-size search coil can or might help, but only to the limits of the detector's circuitry design combined with the operator' sweep technique and coil control.  Additionally, regardless of the coil SIZE, you also have to factor in the coil SHAPE and coil TYPE (such as Concentric Vs Double-D) along with how a particular detector model was designed and/or is capable of functional well with.

#2..  'Miracles' don't seem to happen in an electronically-controlled hobby such as metal detecting.  You do things right or you do things wrong.  You get lucky or you miss out.  There are good days and there are bad days.  But one thing for sure, if detector selection and coil applications are in your favor, a 5" or similar small-sized coil can be a significant help.

 

2 hours ago, Flydog said:

#3..  Us knowing what your swinging would be a great help!

#4.. Gold Bug with 11 inch coil.  Some say it has good separation. So far I have only "accidentally" dug one piece of iron. 

#5.. How does knowing which detector I am using help with a question of smaller coil size? Would not the answer be the same for all detectors? Honest question.

#6.. I have been running just enough discrimination to eliminate iron but still the strong iron targets blow though.

#7.. Annoying to listen to but the bigger problem is iron masking.  I can see how a small coil will be trying to identify less, or only one target at a time. What I've seen is....brief coin signal/TID, scan back and forth 10 times an 9 of those swings its saying iron, should move on but OK I'll dig, out comes a coin. Need to stack the odds in my favor.

#8.. Boy I don't think cleaning up all the iron sigs will work, take too much time and place will look like a battlefield. Maybe on the sandy beach but no way in the grassy park areas.

#9.. Cranking up the disc to eliminate all  below copper penny/dime for an initial attack may be a good idea. Or will it? I'd still have to go back over everything again ( time) and the iron is still there. Only benefit would be to get the high conductors before someone else comes along and beats me to it. I am curious to find out though if higher disc will reduce the large iron blow though. Haven't had this detector very long and it would be an interesting experiment.

#10.. Yesterday got a silver earing, rust bubbling though the plating, junk. Nice condition gold necklace, no karrot markng, the chain is magnetic but the pendant is not. Both "visual" finds on surface.

Got me wondering, SMALL/FINE gold necklace chains, are they always plated steel for strength or are there solid gold chains? I suspect in the smaller sizes even say 12k might be just too delicate but I don't know.

#3..  Yes, knowing what make and model detector as well as what size and type of search coil you are using is important.  One reason is because regardless of coil size, some makes and models do no handle things like dense Iron Nail trash conditions well, while on the other-hand, some makes and models work exceptionally well.

#4.. Are you referring to the Fisher 11" BiAxial coil which is close to about a 7X11 DD"  The "BiAxial" simply means it is a Double-D design.  That coil, like most others of a comparable size, can sometimes do reasonably well in 'separation' as long as the site isn't too heavily covered with undesirable metal targets that are positioned too closely to 'keepers'.

#5.. Good question, and NO is the answer when it comes to matching search coil size and type on different makes and models, even within the same brand.  Some of the reason has to do with the type of trash and hunt site as well as the close-proximity masking effects.  Folks need to know what causes "target masking" and then learn to deal with it.  Although you can consider a detector's Operating Frequency, Sensitivity Level, Discriminate Level, and other functions of some models, such as Reactivity or Iron Bias, etc., etc., in the end it really gets down to how well the circuitry was designed to handle both ferrous and non-ferrous audio responses, their effects on a total received signal, and how well they can respond-to and recover-from audio responses from ferrous-based targets.

A quick example:  I can use my Nail Board Performance Test with 4 Iron Nails that surround an Indian Head Cent just as initially discovered / encountered in a Utah ghost town.  I can sweep the 4 marked routes, from the left nd from the right which makes a possible 8-out-of-8 hits.  I can get 8 solid, repeatable hits with either of my Tesoro models with their 6" coils, or with a 7" Concentric or 8" Concentric.  I can get 8 solid hits with a Nokta FORS CoRe or FORS Relic with their 5" DD coils, and 7-out-of-8 with their mid-sized 5X9½ DD coils.

I get 7-out-of-8 with a Nokta / Makro Simplex + w/5X9½ DD, and also with a Garrett Apex with their mid-sized 'Ripper' or 'Viper' DD coils or their larger 'Raider' DD coil that measures 8½X11.  My XP ORX w/5X9½ DD can also get 7 or 8-out-of-8.  I used to use a Teknetics T2+ and with their smaller 5" DD coil I would get 5-out-of-8 for sure, nd sometimes 6-out-of-8.  A Minelab Vanquish 540 with 5X8 DD would hit on it usually 6-out-of-8 times unless swept too fast, then it dropped to only 4 or 5 good hits.

However, put a small 5" DD on a Teknetics Omega 8000 or 8500 or Fisher F-44 and you'd be lucky to get more than 2 good hits out-of-8.  A friend bought a Tesoro Tejón w. Tesoro's 6X10 DD, 8½X11 DD and a NEL 5X9½ SDD Sharpshooter coil.  On the NBPT he used a Barber Dime, GBed, and checked the target out.  All three coils failed to produce more than 1 or a questionable 2 hits out of a possible 8.  He figured he needed a smaller coil, but I encouraged him to check the 'standard' 8X9 Concentric.  That gave him a good 8-out-of-8 ... but their 6" Concentric would have been better for the nasty Iron-littered ghost towns we were hunting.

#6.. Discrimination has its limits due to a target's size and shape.  For example, the crown-type Bottle Caps that tend to produce a high VDI read-out on most of today's modern detectors.  They suggest a Dime or Quarter.  Part of that is due to more modern circuitry design.  I never run my Discrimination higher than to just knock-out a Nail.  More often it is just barely low enough to Accept the Iron Nail.

#7.. The only way to "stack the odds in your favor" is to also accept the fact that you are going to miss a lot of d=good targets.  You can 'cherry-pick' and go for the higher-conductive targets and trust they are plentiful, but the more Disc. you use, the fewer good targets or partially-masked targets you'll find.

#8.. City  Parks, private yards, beaches or plowed fields, the only way to find the most good targets is to systematically recover ALL targets, good and bad.

#9..  High Discriminate Levels will reduce some of what you HEAR, but that Iron and other rejected trash is still going to have an effect on the EMF, and the higher you go, the more risk of impaired performance.

#10.. Congrats on a couple of OK finds.  I have found a lot of smaller-size good and costume jewelry with most of the detectors I enjoy using.   Typically, they have a smaller-size or a mid-size coil mounted, and a low Disc. setting.  Site selection is a key.

Monte

[GB_Amateur]

3 hours ago, kac said:

When I used the Gold Racer I used the ID filter to adjust base filter to discriminate out targets from a base point then used the tone break to adjust the tone break point.

 

3 hours ago, kac said:

You should have similar controls on the Gold Bug....

The 'new' Fisher Gold Bug was, true to its name, designed first and foremost as a native gold detector.  That is exhibited by its All Metal mode, which is VCO (effectively tone pitch and tone volume indicate strength of target).  The discrimination half of the GB's operation was a reluctant afterthought.  Part of the consequence is that although there is an adjustable threshold to silence low conductivity targets, it is intimately tied to the 2-tone breakpoint.  You can choose where to set the silent threshold or where to set the low-->high tone break, but once you decide on one, the other comes along for the ride.  (BTW, this feature was relaxed when Fisher released the sister F19 model.  That allows the silent threshold and lo-to-hi tone break to be chosen independently.)

[kac]

22 minutes ago, GB_Amateur said:

 

The 'new' Fisher Gold Bug was, true to its name, designed first and foremost as a native gold detector.  That is exhibited by its All Metal mode, which is VCO (effectively tone pitch and tone volume indicate strength of target).  The discrimination half of the GB's operation was a reluctant afterthought.  Part of the consequence is that although there is an adjustable threshold to silence low conductivity targets, it is intimately tied to the 2-tone breakpoint.  You can choose where to set the silent threshold or where to set the low-->high tone break, but once you decide on one, the other comes along for the ride.  (BTW, this feature was relaxed when Fisher released the sister F19 model.  That allows the silent threshold and lo-to-hi tone break to be chosen independently.)

Thanks, I didn't know they don't have independant control on discrimination and tone break. None the less upping the discrimination will narrow the target range. Cherry picking out the copper and silver is possible on most machines and trying to cherry pick gold from aluminum is difficult on just about any machine.

Monty has an excellent response with coil control. That is key in isolating target signals.

[Monte]

4 hours ago, kac said:

Thanks, I didn't know they don't have independant control on discrimination and tone break. None the less upping the discrimination will narrow the target range. Cherry picking out the copper and silver is possible on most machines and trying to cherry pick gold from aluminum is difficult on just about any machine.

Monty has an excellent response with coil control. That is key in isolating target signals.

►► Discrimination use and 'Cherry Picking' higher-conductive targets is an interesting concept and discussion on its own and still gets down to he particular detector circuitry design.  True, it is possible to increase the Disc. setting so as to audibly reject lower and mid-conductive targets to try and isolate only the higher-conductive targets such as Copper Cents plus Clad and Silver Dimes, Quarters, Halves and Dollars.  As a rule, most of the available targets when rejecting a lot of lower-conductive trash also suggests the desired targets are relatively shallow and free of good-target masking.  That's good because with most detectors, a higher Disc. setting is often going to reduce the potential depth-of-detection to some degree, and it will also have an effect on the response-potential for targets close-to the Disc. break-point for acceptance an rejection.

I was out detecting for an hour or so this afternoon here at the 88 year-old house I'm at, and due to the heat and my health limitations ... combined with the abundance of discarded trash such as pull-tabs, pry-tabs and bottle caps ... I just worked sections of the yard and was 'cherry-picking' in search of Wheat-backs and Silver.  Today I used my Garrett Apex w/'Ripper' mid-size DD coil and had my Disc. set to accept everything from '20' on up in my Custom program.  I also swapped over to my XP ORX with its mid-size 5X9½ DD HF coil and the Discrimination was set to my saved '7' setting.

So, how was that 'cherry-picking' some would ask?  With the Apex I had my Iron Audio Volume set at '2' and working Volume maxed out at '8'.  Also, with the 5-Tone Apex nd 3-Tone ORX, I relied partly on listening for the mid-high and high tones, and my 'cherry-picking' was handled by me glancing at the visual VDI display and simply ignoring all target responses that suggested they were Iron or in the lower Foil to Tab range.  Simply ignoring undesired targets by audio Tone and visual ID read-out.  I didn't want to increase the Disc. rejection to the point that it would inhibit good-target detection.

►► Search coil selection, for the best size and shape and internal design, combined with search coil sweep speed, over-lapping, and coil-control to thoroughly cover a site, are far more important than many might believe.  Especially since about 1988 when we saw a new 'trend' to make detectors with larger-size 'standard' coils, and that was soon followed by another 'trend' to make more coils a Double-D design rather than Concentric.

I started using  DD coils when they were first introduced by Compass Electronics back in '71, and on the conventional TR's they worked quite well.  The TR-Disc. models, however, didn't perform as well when it came to Discrimination as the Concentric or Co-Planer types which became more popular, at least for a long time.  Due to the DD coil's overlapped winding orientation we often get different target responses from a left-to-right sweep than we do from a right-to-left sweep when compared to the more consistent audio response and behavior of a similar-size Concentric coil.  But the 'trend' continues and many manufacturers do not make Concentric coils for many or any models, plus quite a few detectors were designed for a DD coil design because that was all that was available.  Kind of sad.

Worse yet, in my opinion, is how so many detectors are offered with larger-size search coils.  So many think about 'depth and wanting to 'go deeper' when, in reality, they can't due to having too much shallower trash targets to contend with.  Good-target masking is not handled well with bigger coils, but by smaller-size coils that are definitely smaller or maybe a mid-size coil. A full 5½ decades of very successful detecting, finding more coins, especially in those earlier days from '68 to about '85, when lost coins were so plentiful, and the vast majority came my way when I was working a smaller-size to maybe a mid-size coil.  Very, very seldom did I opt of a bigger coil, simply because they were not all that necessary, or functional when hunting dense debris sites.

Guess what?  They still are not that necessary because our more modern detectors can sometimes work better, the coils might work better, and they increased the detection-depth for many detectors with the right smaller-to-medium coil.  I still favor smaller-size coils to a mid-size coil as long as the detector provides the needed performance.  I very seldom swap coils, and keep each unit I have at-the-ready with the coil it will most often use.

I have 8 detectors in my regular-use outfit as follows, from smaller-size coil to that largest size:

Nokta FORS Relic w/5" DD

Garrett pex w/NEL 5" DD

Tesoro Bandido II µMAX w/6" Concentric

Tesoro Silver Sabre µMAX w/6" Concentric

Garrett Apex w/'Ripper' (5X8) DD

Nokta / Makro Simplex + w/5X9½ DD

XP ORX w/5X9½ DD

and my one bigger-size combination, Garrett Apex w/'Raider' (8½X11) DD coil.

Some of these circuitry design can offer a little faster sweep speed, but most often I prefer a slow-to-moderate sweep speed, overlap a lot, and take my time covering an area thoroughly.  The smaller and mid-size coils can work quite well.👍

Monte

[GB_Amateur]

Two great posts, Monte, and as typical for you, lots of details as to why things work (or don't work, or sort of work but not optimally).  Even though I also started metal detecting very early (~1970), other things (aka 'life') caused me to detour for 45 years.  As a result I missed a lot of the evolution that you experienced, and it has cost me.  (Not to mention all the good targets that were vacuumed up by other detectorists while I slept....)  Reading isn't a substitute for swinging, but it helps.

When I atteneded the WTHO last month (thanks, again, to you for inviting me and Gregg and others for making me feel welcome, but I was disappointed you couldn't be there) I took your advice from many previous posts in my choice of detector and coil.  Although I didn't use it exclusively, the Fisher F75 with 4"x6" concentric was my main tool and it worked very well.  BTW, I have built a nail board and tested this combo on it with good success (6 or 7 positive results) but I'm still unsure if I'm performing the test as intended so I haven't publicized that (much).  I had planned on bringing it along to WTHO to get some tips but forgot. 

I still need to sort through and photo my finds from the WTHO.  Then I'll make a detailed post here as well as posting photos on your site.

[Joe D.]

Agreed GB!

   Monte, your a walking, talking, and posting encyclopedia of detecting knowledge!

   I'm well behind GB, and many others here, but I appreciate any info you are willing to share! I will work at unraveling all that you impart! Thanks!!🤯😁

   And by the way, I will email you to get on the WTHO contact list! One of these days I would like to get out there with you all!!👍👍

  

[Flydog]

Monte. Fantastic, well thought out, concise information. And thanks for not yelling at me with an explanation mark at the end of every sentence.

I need to make a correction. I had mentioned "large iron blowing through the discrimination".  In hindsight I now realize it was operator error, the disc was NOT turned up far enough and it was giving low grunts on iron, perfectly normal and I would not want a future reader to think the GB has poor iron disc.

Just for fun I made a short video of the ground trash. The worst I've ever seen, cant even find a clean spot to ground balance on and its like this everywhere. No way I'm gonna clear all that iron, I'll leave some targets for someone else. Be interesting to see what others think of it, if they have seen worse.

 

 

[kac]

I got a few spots that are much worse, pile of coal and coke under river bed gravel full of bog iron with lots of emi.

Kick that discrim up till much of the small iron is dscriminated out. Should make your head spin less.

Saw you had a spike in the 60's might be a pull tab maybe or a zinc penny? Not familiar with the GB id range.

[Joe D.]

Flydog,

   I'm very fond of exclamation mark's at the end of every sentence! But I'm not yelling, it's just my thing!!😁

 

THIS IS YELLING FROM ME!! 

Of which, you will never see!!

(Well, just this once, for exclamation purposes)!🤣👍👍

 

[rvpopeye]

Monte

Interesting info , thx for sharing that !🤔

 

WOW   Flydog   , beepady beeb beep !

I noticed the target ID changed on every one too .....

I thought ALL CAPS was yelling  and exclamation points was just excited ? LOL

I'll try and remember that when replying to ya .

( I'm annoying enough as it is already🤪 ,,,I studied english in school but have more fun not following those teacher's rules)