New Life For Old Coil Compatible Low Freq Whites? (QXT, 6000, Etc) Dongle To Use Fisher/Garrett/BH Coils, Which Means SEFs Too!

[Critterhunter]

First, I cleared this with higher ups, and was told as long as we don't turn this into a commercial we can talk about the possibilities and results for these dongles and adaptors here in the modifications forum, which I fully understand. So keep it tame. We probably shouldn't pot any links or "where to get" stuff. Just general talk about possibilities/results. So here goes...

Got a heads up in an Email from Mike T (thanks Mike) that sounds very cool. Said there are some adaptors that are said to allow you to run coils for certain other brands on your 6.59khz low freq Whites models of yester year. One type by the looks of it are just cables with re-arranged pin outs (perhaps?) to use other non-Whites coils on certain machines. Not too impressed with that concept if that's what it is (read below). But what I am sort of excited about are some dongle boxes that allow those coil compatible Whites (6000, QXT, etc) to use coils made for some Fishers, some Garretts, some low freq Bounty Hunters, and I think a few other machines.

I was looking into building coils for my GT a while back before the SEF line came around. Coils have to match various specs precisely for a detector to work. For instance, a 5" trash coil will have the same coil winding resistance readings of the TX/RX internal coils as a 12" coil made for the same machine. Several other electrical specs have to also be within a very tight window range identical to other coils, big or small, aftermarket or not, for that machine or it won't work or will give terrible performance and instability.

While I could swing the electrical side of it having a related background and experience, and even tracked down a schematic of the unique pre-amp circuit found in the BBS Sov/Excal coils to boost the RX signal that is not normally found in a detector's coils, I figured by the time I bought shielding tape for the inside of the coil and all the other needed materials/wire and coil casings, I'd have to make at least 3 or 4 coils to make it cost efficient over just buying an SEF when they finally rolled around, so I gave up the idea.

I don't remember off hand what the frequency range is for the Fishers one of the dongles will use coils from, but I'm pretty sure at least some of the Bounty Hunters have the same freq as the Whites, which might explain how various coils specs just happened to be within the same range of the low freq Whites perhaps using just a re-configured coil cable. I hear at least the pure coil cable adaptor for certain coils/detectors didn't give one guy too stellar of performance, so I suspect that might just be a pin re-configuration and it's not adjusting various electrical specs to make the coil match the detector precisely for better performance.

But more than likely more than just a simple pin-reconfiguration is going on with that dongles. Probably something else going on inside those, so I have high hopes those are tuning the various parameters of X detector brand compatible coils to match up and work well with your low frequency Whites detector. That's what I'd suspect is going on there, but I can find no remarks or field reports yet on those to say either way.

Way I understand it the cable adaptors have been around a long time, but the dongles look to be new far as I can tell from what I can find (or not find) on the web.

*In my soil*, up until two later/current machines I moved onto, out of all the detectors I've owned, used, or went head to head with over the years, only the low freq Whites (in particular the QXT and 6000) seemed to get the best stability and depth *in my soil* for a long time of detector hopping. I attribute that to the low freq of those units penetrating my mineralized soils/sands well. I felt the QXT, set up properly, was as good as it got for me for many years, and to this day is still right at the top of my list of favored detectors.

Having cut my teeth on those low freq Whites units, I miss them in many ways on certain days, as they were my first love, so the possibilities here intrigue me if this coil swapping with DDs pans out performance wise.

One of the reasons I sent my last QXT off on it's way was the lack of larger coils than the 9.5" to push depths deeper, and the lack of DD coils for more stability/depth/even better left/right separation in my soils/sands. I always wondered why Detech didn't make SEFs for the low freq Whites, since there are so many coil compatible units out there and even to this day they are favored among serious hunters for various things. Now, with this dongle, you could buy a 12x10 meant for say the Fishers it's compatible with and maybe push depths deeper, increase left/right separation over the stock 9.5" concentric, and run more stable in worse grounds being a DD.

I'm very tempted to bring another QXT back into my hanger of machines for various days and try a 12x10 on it. Being low freq to hit hard on silver/copper coins at good depths/stability in minerals like it did before, with a quality larger DD coil like the 12x10 on it to increase depths even in mineralized ground, it might be a contender in this modern day and age in terms of certain performance aspects *perhaps*. Same deal with your favorite low freq Whites you still love but don't take out as often as you should perhaps these days due to lack of coil selection and such.

I had always planned to bring another QXT back into my line up of machines for various days when I wanted to swing faster without the need to slow down or risk masking stuff in heavy trash, but the *possibility* of using a larger DD coil to punch deeper and increase left/right separation, along with a tiny 4" or so round DD for extremely heavy trash in the length axis...Makes this really tempting now if these coils perform well on the low freq Whites.

Wondering how pin pointing is going to do on a DD coil with the ability to de-tune the Whites a few times like you could to really zero in on stuff and pop with a screwdriver without need of using a pin pointer? They were excellent in that respect, but I'd be surprised if a DD pinpoints as tight as the concentrics did. On the other hand, detuning 2 or 3 times over the target might surprise me at how well it's able to do with a DD, or should I say how much easier it might make doing that over a DD on a typical detector with no ability to de-tune can some times be?

Also, I'm thinking of what the assignable high/low tones for various zones and the lightning fast recovery speed on the QXT might do with a DD coil working heavy trash, and of a tiny (4"?) Garrett DD trash coils for max unmasking in the length axis. The ability of the 9.5" concentric on the QXT with it's lightning fast speed was pretty impressive without needing to slow down. Just wondering how it'd do with the possible enhancement of left/right separation of a DD. Might be jaw dropping..

Anyway, just throwing it out there for you guys...These little dongles might be just the thing to breath new life in both depth and separation and stability in bad soils back into the old Whites low freq line with the DD selection at hand you could now use. Not just from the likes of Garrett, Fisher, and such, but also in the realm of aftermarket coils available for them. How about a 12x10 or Ultimate or a large coil, or perhaps a 8x6 or a small round coil for heavier trash?

Larger coils or DDs just simply didn't exist for the low freq Whites models other than the 4x6. Sure, there were two larger concentrics than the 9.5" out there, but I wasn't very happy with either of them for reasons I won't go into. Let's just say they weren't an option for me for increased depths *in my soil* on coin/ring sized targets. If this little dongle thing works it might be the answer to many of our prayers.

 

[Mike T]

I was suspicious until I emailed the guy selling them and he replied he makes them in his shop. Apparently these are not the older adapters sold a long time ago to use Bounty Hunter coils on a Whites or vice versa. These are newly made and tested on contemporary machines. I don't know how well they work But I figured it was worth ordering and I'll let you know once I get it out in the field.

 

[Critterhunter]

Mike, I'm wondering if the adaptor cables are the same as the ones said to have been around for a while that didn't perform all that well? If they are then it probably means just a pin re-configuration and not adjusting the coil to be in proper specs for the machine= poor performance. But the dongles- those are what I'm mainly interested in. Chances are it's a dongle for good reason- to adjust the paramaters of how the coil and machine interface so they match properly and perhaps equals just as good of performance as they would have on the machines they were originaly meant for. Here's hoping anyway. Looking forward to any reports on how those dongles perform, and also if the non-dongle cable jobs are more than just pin-conifigures and thus get better performance than the old ones were said to?

I got a friend who is pretty excited about the prospects himself too (like me). He's already talking of picking up a low freq Whites again and a dongle to run a SEF on it. Probably a 6000 or QXT maybe. If and when he does I'll update you on any field reports of it. I'll know right away if say a 12x10 is pushing depths deeper on say a silver dime. About 7.5" was max for that in my soil with a QXT or 6000. Couldn't break that barrier with any machine over the years until my last few machines I've owned. If a QXT or 6000 is punching a silver dime past 7.5" then it'll be something to talk about in my soil. I'm sure if he puts together a setup he'll let me borrow it to see how things pan out.

 

[Mike T]

Critter, there was a post on the Garrett forum a couple days ago wanting info on a "Garrett to Whites adapter" he wanted to know if it worked, anyways a guy answered he tried it and it didn't work that well and he got his $ back. I don't know if its related to the one I ordered, I should PM the guy who answered and ask where he got it and if its the same source. Of course that might not matter, as the Fisher F2/F4 is closer in Frequency and a better match and theres no way of telling until I try it out.
One thing for certain, these are newly built by the seller in his shop, not older stock. I have a feeling they will work, the question is how well?
I don't want to buy a SEF for $179 and find out its not usable, I need to find a F2/F4 coil to test out.
If it doesn't work out I am going to write a email to the factory in Bulgaria explaing how many Whites 659'ers there are in the world, and how simple it would be to alter the coil design on the 659k's they already produce.
Anyways one step at a time.

 

[Critterhunter]

Sounds like a solid approach Mike to checking out the dongle, and the idea to write Detech is a good idea too. If they make SEFs even for the long defunct and never super popular Musketeer line (which are great deep machines I hear), seems like they'd also want to tap into the low freq Whites models, as there are tons of those machines out there that all are coil compatible with each other. Those guys over seas seem to pride themselves in pushing the performance aspects of some pretty obscure machines long gone on the market, and not just the Detech coil makers, but hunters in general over there. They always seem to be tweaking, building, and pushing machines that others have long since moved on from.

 

[Ed in SoDak]

There's an old connection between White's and Bounty Hunter you may not be aware of. Some techs from White's broke away and formed Teknetics, among them George Payne. They acquired the old PNI Bounty Hunter company. It stands to reason George and the others were up on the White's coils designs, so no doubt they leaned on one or the other, or both in making their new coils. It's not a real surprise they'd be compatible, with perhaps just the wiring change to make them "different enough." Copycatting was and is the norm in the industry anyway, they just try to be different enough to avoid patent problems. Or pay royalties to the patent holder and do it legal that way. By now, many of these choice early patents have likely expired, making it easier still to clone them.

There's a lot of minute variations in coil-building. There needs to be some way to compensate for it. In a design, you can adjust either the capacitance or the inductance. It's easiest to let the coil's inductance land where it may, and adjust that with a small capacitor trimmer. If you had to precisely nail every coil, you'd have so many defective ones you'd never make production. Coil resistance plays little actual part, since that measurement is taken at DC, and not at the actual working AC frequency of the oscillator. So instead there's terms like inductance and reactance to describe a resistance to current flow at a given frequency.

So in practical terms, there's no reason a simple wiring change might not work between White's and BH. Maybe not with every coil/detector combination, but it might work better with the older coils. Today's BH coils, including Fisher and Tek, are not the hard and fast rule of "one-size fits all" that they used to be with the older BH units. It might be just an additional trimmer or small network would improve things - the dongle could easily house this.

My own BH coils all measure close to one another, but there is still a lot of variation, even between otherwise identical coils. The machine itself has to deal with the normal range of variations and might need to be peaked internally to the coil(s) it is shipped with. Just slapping on another coil may or may not match closely with that origina internal tweakingl, and might help explain why it works for some users and not as well for others.

Too many unknown without comparison coils and machines on hand, plus more knowledge than I possess! I'd kinda think it "should" work, but each individual combination might need it's own specific trimmer setting. A "generic" setting might work well enough, or you'd need to send in machine and coil to have the dongle fitted to them.

-Ed

 

[Critterhunter]

Ed, great info. Yes, several precise measurements must be within a certain tight window for a coil to work with a given detector model, but I do know that many of the guys building their own seem to put great emphasis on the resistance reading as well from at least all I read when researching building my own a few years back. They seemed to tweak the gauge and length of the wire used in the TX/RX windings to get the resistance right where it was for other coils for a given machine, as well as adjust the other specs within a very tight window of parameters taken from factory coils meant for the given machine. By no means did I read all respects and angles on it, so I'm not saying I've got that set it stone. Just what I gathered in my own amiture research and reading on coil building.

I would think the resistance would be easy enough to fine tune via either a fixed or variable resistor by the guy building the dongles. They wouldn't have to match any particular low freq Whites, and variations on production runs of that specific model, to a specific coil. All the low freq Whites I would figure are coil compatible because they all want to see the same window of operating specs on a coil, so the various electrical parameters for any low freq Whites coil should be (I'd figure) pretty much exactly the same as each other (or at least every coil I ever read for a given machine had the same readings as any other for that machine when I've checked the pin outs).

Overly complicating what I'm trying to say...Meaning, I'd figure all low freq coil compatible Whites want to see the same parameters as each other for any coil they share, and as a result any coil compatible with those machines (big or small) should also have the same adjusted electrical specs. If that's the case, then it's not a matter of tuning a dongle for X brand low freq Whites to X brand coil, but rather just tuning all the dongles to say run Fisher compatible coils so that they match up well with the low freq Whites models. Any of them that should be.

Far as I'm aware, there are only a few detectors out there where the individual coil they are shipped with has to be fine tuned for that specific detector. The Blisstool, for instance, I think requires that if I remember right. Probably due to it being what I expect is a highly amped inductive balance machine, which from what I understand means fine tuning coils becomes very critical on...from what little I've read a while back in the past about those types of detectors, so I might have my facts wrong on that. I think the Nautelist detectors also are tuned with the coil they are shipped with if I remember right.

PS- As an example, I've read the pin outs on my S-5 5.5" coil, my 12x10, and my 10" Tornado. All 3 have readings very close to each other. Only slight variation, so it's apparent to me they all have to fall within a very tight window for best operation, at least on the Sovereign. I'd figure it'd be a simple matter to tune a few POTs inside a dongle to get it to make a coil look to the low freq Whites like just another "Whites" coil, or so I hope, as that would open up a world of wonder to the many low freq Whites owners still using those machines to this day. And for good reason, as they are very good machines.

A dongle to mate Fisher coils to the low freq Whites wouldn't need to be adjusted on a specific low freq Whites it's on, nor to a specific Fisher coil, as that should all be the same. Just need to know what the Whites want to see, versus what the Fisher compatible coils specs are, and then a few POTs inside the dongle are adjusted so they match up properly so the detector sees what it wants to see. That should be it I would think.

My only question is...can external tweaks on specs of a internal coil still produce the same level of performance, or is there a price to pay? I'm also wondering if the low freq Whites at 6.59khz, sending that frequency through a coil designed for some other frequency, might generate not as good of a magnetic field. I don't know enough about coil field dynamics to know if there are inherent design considerations in the actual building of the coils layout and shape of the TX and RX coils to work better with specific frequencies. I'd expect at least in the case of the SEFs that's not an issue, because look at how many different detector brands they seem to run fantastic on. Not all brands though.

 

[Ed in SoDak]

Hi Critter,

I think resistance plays a part for those who are trying to clone a given coil. Since a given gauge of wire has so many Ohms per foot, one can just wind off as many feet as needed until you hit a match. If your coil is wound similarly to the original and the coil diameter and wire gauge match, you could make a reasonable copy with just the DC resistance measurement. But if you wound that same length of wire into a larger coil or changed any other parameter, its inductance and resonant frequency would change, and that's what the detector itself looks at for proper tuning.

There's published charts for achieving the same inductance for open-air scramble-wound coils that will give rough translations to other diameters, number of turns and wire gauges to resonate at a given frequency. This you fine-tune with a trimmer capacitor. Trying to adjust it with a second inductor or coil instead of a capacitor would run the risk of making a second "coil" out of it. Just more complicated than the garage coil-maker would want to mess with.

LCR meters are a lot more commonplace these days. So we don't need to be stuck with just DC coil resistance as our only measurement. A 'grid dip meter" is a handy tool to find the resonant frequency of a coil. Or you can sweep the coil with a signal generator and oscilloscope and find it that way.

Tuning on the detector end can be broad or sharp. It makes more sense for a company to design a little forgiveness into their machines to handle typical variations and not throw a fit. Too many repair returns and unhappy customers, otherwise. It's better to give up a little "maximum tweak" and precision tuning to instead lower the bar a bit to have a greater percentage of machines hit the performance mark.

I tried once to "shrink" a coil by copying the measurements into a smaller diameter. I may have been off by inches or miles, but I never got it to work. It takes a certain knack to wire a working coil from scratch, so maybe that's why adapters are a good workaround to investigate further.

I applaud the efforts. I'm just trying to say it probably isn't as precise in practice and there's has to be room for some leeway in coils. So that tends to increase the likelihood that there is at least some near-off-the-shelf compatibility, with or without dongles.

-Ed

 

[Mike T]

I got the adapter today and found out the coil I wanted to test( a modern bounty hunter) won't fit because even though its the right configuration its a male plug and the adapter requires a female.
What this means is when First Texas aquired Fisher and brought out the F2/F4 they kept the same frequency and pin pattern of the Bounty Hunters but reversed the order. So this must mean something, most likely the F2/F4 is an entirely different machine than the BH's that share common frequencies and pin patterns..
And this adapter specifically states its for the F2/f4. He sells other adapters for the older BH's and Garretts.
I am tempted to order a SEF coil, I am starting to think it might work.

 

[Critterhunter]

Ed, yes...in the threads I've read in the past guys would adjust both the length and gauge of the wire to get the resistance right. But I'm not talking of copying a coil design for that. At least what threads I read on the web seemed real keen on getting the resistance as close as possible, eve when building a different size/shape coil, and even with measuring inductance. Not saying it's the only approach, just saying that's the gist of what I was reading about 3/4 years ago or so in what I could dig up.

When they null out a coil via a little adjustment loop at the end of the coil winding, I'm wondering if that null is based on frequency, or if it'll work once done with any frequency sent through the coil? That could have a major impact, as nulling is the final and most important part of the coil building from what I gather. Any opinion on that?

 

[Ed in SoDak]

The nulling coil and how it works is over my head. There's a lot of coil info online, and maybe some sites that don't require a lot of math.
-Ed