Whats the difference bertween BBS, PI etc???

[wreckrat]

Hi,
Im confused with all the technical infprmation on underwater detectors. Of course each claims to be the very best and those who use them also claim the same. Can anyone give me a simple explaination as to the differences between the technology used, in the Minelab and Garrett underwater detectors for example? Or point me to a site with some info on the prosd and cons of the different operating systems.
Or....is it a case of 'they all work' so it doesnt matter what you use
thanks

 

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[seas1to2]

http://websearch.cs.com/wm/boomfram...com/gadgets/other-gadgets/metal-detector2.htm this site does a fair job on explaining it. for the BBS...BBS and FBS Metal Detectors transmit signals in multiple frequencies simultaneously, instead of just one, as with most VLF machines. BBS technology transmits in 17 frequencies from 1.5 - 25kHz simultaneously and FBS transmits in 28 frequencies from 1.5kHz to 100kHz....these help when hunting in saltwater

 

[wreckrat]

Great link thanks it really explains VLF and PI systems well, but what is the BBS system is it a type of PI but with multiple frequencies or is it a totally different system??

 

[Michigan Badger]

The above posts give you the technicals so I need not go into all that.

In true Badger bluntness let me say its basically a gimmick game today.

I've been at this hobby since the early 60's and have seen many so-called new developments in metal detector technology.

The fact is that since the 60's the real working technology of the hobby has had few genuine changes that seriously affected the finds of those truly devoted to the hobby.

Some of the few are:

1. Change from BFO to TR
2. Change from TR to VLF
3. Development of discriminational abilities
4. More comfortable designs
5. Advances in coil designs and great choices in sizes
6. Advances in target ID (meters, tones, etc.)

7. And now today...great advances in target separation with improved depth (mega fast target processing)

The above are the developments that have impacted the hobby in significant ways. Most of the other stuff has been fluff.

The machines that will totally revolutionize the hobby today are the Fisher F75 and F70. While not the deepest (Nautilus still carries the banner there) they have rendered obsolete most machines due to their super fast processing of target data while maintaining good depth with excellent target separation.

Look for tremendous changes in the competitor designs in the very near future.

Badger

 

[thompy]

MB i would like to see a explorer with the f-75 recovery speed and weight, now that would be sweet

 

[bakergeol]

The Garrett Infinium is a PI which has limited discrimination. Minelab Excalibur, Sov, Explorer are not PIs and have excellent discrimination. Minelab nugget machines used for nugget hunting (GP & SD series) are PIs which are quite deeper than VLFs(also lack effective discrimination). GPs are far superior in mineralized ground than VLFs and as many nugget hunters don't need discrimination- the Minelab PIs are King of the PIs used for nugget hunting.

Don't be confused by the number of frequencies advertised for muti-frequency detectors. It is more of a marketing ploy. Minelabs Ex, Sov may transmit all those frequencies but what they don't tell you is that these machines just don't receive them. It is what 2 or 3 frequencies received?Heck a PI such as the Infinium(or my GS5) may transmit over 90 frequencies which is normal and means nothing.

There are advantages for single as well as multiple frequency machines and it depends of your useage. For example, some of my gold specimens ( you may try gold chains with your Ex, Sov or Excal) were completely undetectable with my Minelab Ex but were detected at 9 inches with my X-5 single frequency machine. Determine your useage and concentrate on the reputation and feedback of the users involved more than advertising claims. Indeed the Minelab Ex and Sov are tested great performers.

George

 

[wreckrat]

Thanks for all the great info so far. This board really is a wealth of knowledge. Great to hear from people with so many years experience.

Im interested in a detector that can find brass, gold, silver etc on iron hulled wrecks that lie mostly on a sand bottom and sometimes on rock, so it would need to be able to discriminate out the iron hull of the ship.

Im also occassionally on ancient wooden hulled wrecks that lie on sand or gravel bottoms mostly buried under a few feet and containing very little metal apart maybe from some nails and/or utensils, coins etc so no real need to discriminate but would be good.

I guess something that can detect metal when the coil is a few feet up off the sand would be good as it is not as easy to sweep the coil over a rugged ocean bottom as it is on a smooth beach and the could may be 6" or so above the bottom when searching.

Need something that can detect a foot or so into the sand but much deeped than that is pointless as it wont be able to be dug out.

What would be the best style for this? A PI or a BBS style (If Minelab Excal isnt PI type then what type is it classed as?? VLF>??)

Im leaning towards the Excal at the moment but have been told the Aquascan is used by a lot of professionals and also the Garret and Fisher underwater detectors are on my radar. Any advice much appreciated.

thanks again for all the info so far.

 

[thompy]

vlf, and in the water that is probably the machine you want, the other would be the fisher cz21, but most perfer the excal.

 

[Willy]

If the hull is iron.. good luck. There's no such a thing as iron 'see through' when talking PI and VLF detectors. In fact, if the iron is even cose (and it's large), the detector will most likely be overloaded by the iron signal. Don't believe me? Get a sheet of tin roofing about 3-4' square and stick a big ol' silver dollar under it; now try detecting that dollar. Go on.. I dare ya.. double dare even. You might be able to get somewhat close to the iron, but that's it. Another thing to take into consideration is the mineralization. If it's highly mineralized, I'd go for a garrett Infinium. Tested an Infinium, Excalibur, and Sov. on a highly mineralized freshwater beach w. a LOT of iron and found that my 'cash to trash' ratio was about the same. Difference was, the Infinium spanked the BBS detectors when it came to depth. ...willy.

 

[steve from ohio]

If the hull is iron.. good luck. There's no such a thing as iron 'see through' when talking PI and VLF detectors. In fact, if the iron is even cose (and it's large), the detector will most likely be overloaded by the iron signal. Don't believe me? Get a sheet of tin roofing about 3-4' square and stick a big ol' silver dollar under it; now try detecting that dollar. Go on.. I dare ya.. double dare even.

I did that with a piece of rusted 18 gauge sheet steel. Put the silver eagle dollar on top and also tried it under the steel and used my E-trac.

Guess what..........the E-trac read the silver dollar just fine. Incredible. I tried it also with my Excalibur 800. It found it just fine. Incredible. I then tried it with the Fisher F75......overloaded out. My White Eagle Spectrum....nulled out. My Ace 250......nothing. My DFX....overload.

I then tried it with a piece of aluminum plate.......1/8 inch thick......the silver eagle read 01-39 just as it would in the field. The piece of aluminum would read 10-01 with nothing near it. The E-trac would read the aluminum and when it was over the area where the silver eagle was...weather on top or underneath, it read the coin at 01-39. Freaking amazing.

Thanks for the idea. It was an interesting test.

 

[Tom_in_CA]

Steve from ohio, excuse me for being a doubting Thomas, but try your test again like this: test the silver dollar SOLO, and then with your piece of sheet-iron covering it. Now try the sheet iron alone (with no silver dollar underneath it), then with the silver dollar. Etc.. etc.. etc... Preferably with side by side examples (if you have multiple silver dollars and multiple scrap metal sheet plates). I think you will find that you are not getting the same signal in each case. I simply can't believe the signal of a silver dollar is not degraded (if not out-right masked) by the size sheet metal you're talking about. You're simply hearing a targets that "over-blowing the disc".

I mean, you know how an entire aluminum can might read "quarter" or "half" right? So if I put a quarter or half "behind" the aluminum can, and subsequently get a "quarter" or a "half" signal, I'm not "seeing through" the can, since it had some sort of signal there to begin with, even up into the range. Yes I know that's a case of 2 conductive targets, but even large enough iron (esp. with a new tin coating on it) can go into the conductive range, albeit a cr*ppy signal.

 

[steve from ohio]

Steve from ohio, excuse me for being a doubting Thomas, but try your test again like this: test the silver dollar SOLO, and then with your piece of sheet-iron covering it. Now try the sheet iron alone (with no silver dollar underneath it), then with the silver dollar. Etc.. etc.. etc... Preferably with side by side examples (if you have multiple silver dollars and multiple scrap metal sheet plates). I think you will find that you are not getting the same signal in each case. I simply can't believe the signal of a silver dollar is not degraded (if not out-right masked) by the size sheet metal you're talking about. You're simply hearing a targets that "over-blowing the disc".

I mean, you know how an entire aluminum can might read "quarter" or "half" right? So if I put a quarter or half "behind" the aluminum can, and subsequently get a "quarter" or a "half" signal, I'm not "seeing through" the can, since it had some sort of signal there to begin with, even up into the range. Yes I know that's a case of 2 conductive targets, but even large enough iron (esp. with a new tin coating on it) can go into the conductive range, albeit a cr*ppy signal.

I did the tests exactly as you stated. I was able to detect and get the correct numbers on a 2008 US silver Eagle no matter how I placed it using the factory coin setting on the E-trac.

The funny thing is that the E-trac and the Excalibur were able to detect the US silver eagle under and on both sheet steel and aluminum plate. I never would have thought that it was possible for any machine to detect a coin of any size under those conditions.

Will it do it out in the field when buried? I'm not sure but the air tests with the metal was an eye opener. My thanks to Canadian Willy for the idea. It made me realize how GREAT both the E-TRAC with FBS technology, the Excalibur with BBS technology really is.

 

[treasurediver]

LuckyLarry,

good to hear the comments from an experienced engineer. Gives me something to compare with.
Out of curiosity and because I just have a front-end circuit on the bench, I decided to look at the problem.
So I put the coil in reverse position, then set a 6" plastic can on top. On the plastic can I set a steel bottle top.
Ground balanced.
Then put a 0.3 gram gold ring into the bottle top. No signal.
Then I added a 3/4" plastic spacer between the bottle top and the gold ring. Observed on the scope.
I got a 7mV signal, this is now a distance of 6 and 3/4" from the coil.

So what is happening here?

The detector does not "see" through the steel bottle top, but it "sees" around it. The bottle top and the gold ring both cause a distortion in the magnetic field of the coil. If they are separated sufficiently, then the difference in field distortion can be measured.

I find these problems fascinating and always welcome a serious discussion about them.

Treasurediver

 

[Lowbatts]

Seen the Etrac finds from some folk I know, they'e getting great target separation with those things. But as I noted, the real promise these machines have shown is finding targets in normal depths, 5 to 10 inches, that machines with concentric coils tend to mis-identify due to co-located trash or iron.

But no one gets target separation as described, Steve. Sounds more like those orginal marketing hypes from Minelab, all about BBS and FBS, ignoring the fact that just about every machine that outputs your basic analog signal ALSO puts out a theoretcially infinite number of harmonics.

Are you familiar with the standard loss rate among harmonics? If, that's IF the Minelab guys were to attempt to use the 15th or 21st harmonic, you need a rx side the size of a radio telescope, maybe Arecibo?

No, they don't "see through ground" but like any other machine they get some useable signal phase shift on the rx side when there is something like a target there.

 

[steve from ohio]

OK folks. I know it sounds crazy.

But if you do not believe me, then try it yourself.

Find someone who has an E-trac or Excalibur and see for yourself. Or buy one and try it. Whatever.

To say it is not possible without doing it yourself reminds me of the persecution of Galileo or the notion many many years ago that if anyone went over 60 miles per hour they would die because they would not be able to breath.

I do not post BS or hype. I do not work for Minelab and have no pecuniary interest in anything to do with Minelab. I just own their products. And I make it a habit of knowing everything I can about them. I read everything I can about them and what is getting some people angry at me is because I am passionate about the E-trac and Excalibur and try to give out valid information to try to fix misguided notions. I know some people take that as being conceited but that is not the situation in my case.

I only did what one post said to try. They even double dared me. I thought it was a good idea. I did it and was able to read the coin over the ignoring of the steel and aluminum by the technologies available with the Minelab products. I am not and would not attempt to post to just get attention or to get anyone angry. I only did so at the request of the poster and I posted my results.

So the question becomes....Did you try it or are you sitting there saying it is not possible without even trying it yourself?

I will say it is possible that it did see around the metal. I put everything on a cardboard box. Raised about two feet above ground. The steel was about 3 foot square and the coin was placed on top of it and also underneath it. Same with the aluminum plate.

All I know is that the Excalibur with just the steel would buzz as it always does when it finds steel or iron and gave out a very nice dig-able bell like sound when the coin was there.

The E-trac with nothing would null out the steel in the audio, but still give out the C & F numbers for an iron/steel target. With the coin it would at first read the steel correctly with no sound but then the coin would read as it should with the nice silver sound that Minelabs have.

With the aluminum, it would read at 12-01 with a good sound ( I would not have dug it) , and with the coin on top or on the bottom would read 01-39 with the nice silver sound. (diggable)

 

[Tom_in_CA]

Steve, thanx for staying with this. I am an Excaliber & Explorer fan too. But no, they can not "see through" iron and/or aluminum. You say you: "[were] able to read the coin over the ignoring of the steel and aluminum" You are merely hearing the over-blow signal of the surface target. Ie.: if you scan a garbage can lid (for example) you will get a target (maybe even a conductive one!). But does that mean if you put the silver dollar behind that lid you might still get the same signal?

And the analogies to Galileo, etc.... are a mute point. I mean, since people once thought the earth was flat, is that proof-positive that anything, no matter how absurd, is therefore legitimate (afterall, they thought the earth was flat once)?

It all boils down to a sound test, swing test, etc.. Because we all know that when one person says "I heard such & such", it's a question of sounds. And no one can describe a sound in print. That's like saying "please describe the sound of C-minor in print" It can't be done. It has to be heard.

 

[steve from ohio]

Steve, thanx for staying with this. I am an Excaliber & Explorer fan too. But no, they can not "see through" iron and/or aluminum. You say you: "[were] able to read the coin over the ignoring of the steel and aluminum" You are merely hearing the over-blow signal of the surface target. Ie.: if you scan a garbage can lid (for example) you will get a target (maybe even a conductive one!). But does that mean if you put the silver dollar behind that lid you might still get the same signal?

And the analogies to Galileo, etc.... are a mute point. I mean, since people once thought the earth was flat, is that proof-positive that anything, no matter how absurd, is therefore legitimate (afterall, they thought the earth was flat once)?

It all boils down to a sound test, swing test, etc.. Because we all know that when one person says "I heard such & such", it's a question of sounds. And no one can describe a sound in print. That's like saying "please describe the sound of C-minor in print" It can't be done. It has to be heard.

It could have been any number of things that caused it to read correctly. Not sure and I know it sounds incredible to be able to read a coin through a piece of steel. All I know is that it did and I could repeat it. The Excalibur was able to give me a good dig silver sound and that is what I found. I could not repeat that with a silver dime or quarter. I think the mass of the silver eagle may have had an influence in my little test.

Not saying it is repeatable in the field. I would think that the targets being on a cardboard box may have a lot to do with what I saw. It probably wrapped around the steel to detect the coin but I am not an engineer and it is only speculation.

The Galileo comment was meant to show how an idea not in the mainstream is often met with resistance.

I did try the garbage can lid idea and I found that I could not see the coin on top and underneath. If I got too close it would overload. I think it is because it is galvanized and we all know how zinc reads to almost any detector. (Damn Zincolns) !

 

[steve from ohio]

Could be and your explanation sounds as good as any I can think of or heard of.

 

[steve from ohio]

Don't believe all that misleading Minelab hype and garbage about running all it's frequencies all at the same time. You would need separate coils to match all those different circuits and freqs too, and that would be absolutley silly..

LL

What? How do you figure? It is not really that hard to do. I am a ham radio licensee and I know a little bit about radio frequencies and how they work.

Separate coils are not necessary just as separate antennas are not needed for a multi band antenna. After all a coil is nothing more than an antenna.

Hype and garbage? I am sure that there are far superior minds to ours who are metal detectorists that would have come out saying that what the engineers at Minelab were saying is as you say hype and garbage. So far you are the only one who said that. I have read the papers on the technology and it is valid as far as I can see. How would it look if a major company like Minelab would advertise a technology and then have a group of engineers say that what they are saying is not so and prove it. You can bet their sales would drop to nothing.

I've yet to see White's, Tesoro, Garrett, and all the others come out saying what you say. Their engineers are now looking into using the technology that Minelab engineered and pioneered. White's even obtained a license to use multiple frequency technology from Minelab and use it in their DFX.

I see these type of arguments just like in ham radio. There are those who prefer analog tube radios. And there are those who prefer the digital radios and their almost infinite adjustments and filtering ability.

And it has been my experience that the Minelab products have so far shown to me that they are a superior technology for MOST situations because of the technology that they have. I don't own them because I can, but because they do what I need them to do. And after all, that is all that is really important.

That will be it on my comments. I have work to do and things to find.

 

[Carl-NC]

OK, so I took an E-Trac, a 12" piece of 30 gauge sheet steel, and a silver dollar. I could not detect the silver dollar under the steel. Nor on top of the steel. I tried a 20-ounce silver bar. I still only "see" the steel.

Some other clarification... Minelab introduced MF to hobby detectors, but MF techniques go back to at least 1948. Also, both BBS and FBS are two-frequency only, 3kHz and 24kHz (they are identical). Yes, you can run MF using a single coil.

- Carl