frequencies?

[emubob]

when hunting for coins and jewellery,which is better a single frequency or multiple frequency detector in beachs,parks,etc?emubob

 

[stalker1]

Multi wins hands down .

 

[Steve O]

For one all around best single freq, I believe it 12khz.....remembering correctly.

 

[hunter_46356]

Invest in a Minelab FBS detector, The Etrac or Explorer. This technology analyzes a target with 28 freq, from 1.5kHz to 100kHz at the same time. The lower the freq. used the deeper you detect. the higher the freq. used the smaller the target you detect. What else could you want in a detector?

 

[Mega]

I personally would have said both can be used successfully inland on both coins and jewellery,the beach is another ballgame as the multi freq machines would win hands down on the wet sand,if the plan is just occasionally say when you are on holiday once a year then its possible to use a single freq but with limited success.

Of course it also depends on if you are loyal to multi freq machines like Minelab etc then of course the weight and cost problems could also come into play as well.

You dont give any indication on what machine you currently use or even if you do mainly inland with a few trips to the beach.

Me personally in a situation that you have described i would use my DFX as that offers dual freq that will cope with the wet sand,its the wet stuff that seperates the men from the boys as very few single freq machines work well on the wet sand.

So basically as you have mentioned beach use my vote would go for the multi freq option.

 

[Larry (IL)]

Not really true Hunter, Minelab only claims to transmit 28 frequencies. All detectors transmits many frequencies when you include the harmonics of the primaries. Explorers and E-Trac are believed to process two of those 28, both in the 2-3 KHz range which makes them very good on high conductors like silver and copper but lacking in small low conductors like gold chains. There are no metal detectors known that processes more than three frequencies at the same time, none that I have heard of anyway.

 

[hunter_46356]

I stand corrected. I have obviously overstepped my technological experience with my comment. I've only been detecting for four years and only with four different detectors. This amounts to a small percentage of equipment available and there are definitely more experienced persons who do know more than I. I probably should have stayed out of this thread. I guess my opinion could come from the fact that over that four years not only have I learned more about detecting in general, I have upgraded to higher quality machines. Maybe this is why in my opinion the FBS technology of my current detector is better than single freq. technology. Thanks Larry for setting things straight as far as how FBS works. We all like to think we've invested in the latest and greatest detector but I agree with you, none of them do it all. Hunter.

 

[Larry (IL)]

A common misconception Hunter due to misleading advertising hype by Minelab. Don't feel bad, a lot of people believed in the 28 frequency thing.

 

[ironsight]

Not really true Hunter, Minelab only claims to transmit 28 frequencies. All detectors transmits many frequencies when you include the harmonics of the primaries. Explorers and E-Trac are believed to process two of those 28, both in the 2-3 KHz range which makes them very good on high conductors like silver and copper but lacking in small low conductors like gold chains. There are no metal detectors known that processes more than three frequencies at the same time, none that I have heard of anyway.

Larry, can you provide a published technical article on that?
I've read posts where some people try and measure the frequency output of FBS detectors with a frequency counter and come up with similar conclusions. Ain't gonna work.
The only true way of analyzing the frequency spectrum output of an FBS detector is with an expensive spectrum analyzer.

 

[MarkCZ]

Not really true Hunter, Minelab only claims to transmit 28 frequencies. All detectors transmits many frequencies when you include the harmonics of the primaries. Explorers and E-Trac are believed to process two of those 28, both in the 2-3 KHz range which makes them very good on high conductors like silver and copper but lacking in small low conductors like gold chains. There are no metal detectors known that processes more than three frequencies at the same time, none that I have heard of anyway.

Larry, can you provide a published technical article on that?
I've read posts where some people try and measure the frequency output of FBS detectors with a frequency counter and come up with similar conclusions. Ain't gonna work.
The only true way of analyzing the frequency spectrum output of an FBS detector is with an expensive spectrum analyzer.

My questions for this would be,

Why doesn't MineLab state those frequencies?
What is the detector doing when you first turn it on and its searching for the clearest frequency to operate at, if its operating at the same 28 all the time?
Why can't you do more with frequency selection for specific purpose hunting, if they have 28 frequencies?
Do they actually have 28 output channels and 28 receiving channels processing each channel?
In these questions without answers I wonder why units like the E-Trac are so well know for deep silver coins, but also known to do so poorly on smaller gold items? (does those 28 channels not include one for gold?)

Mark

Mark

 

[Larry (IL)]

Not really true Hunter, Minelab only claims to transmit 28 frequencies. All detectors transmits many frequencies when you include the harmonics of the primaries. Explorers and E-Trac are believed to process two of those 28, both in the 2-3 KHz range which makes them very good on high conductors like silver and copper but lacking in small low conductors like gold chains. There are no metal detectors known that processes more than three frequencies at the same time, none that I have heard of anyway.

Larry, can you provide a published technical article on that?

No
I've read posts where some people try and measure the frequency output of FBS detectors with a frequency counter and come up with similar conclusions. Ain't gonna work.
The only true way of analyzing the frequency spectrum output of an FBS detector is with an expensive spectrum analyzer.

Even a spectrum analyzer is not much help because of the complex digital signal.


My questions for this would be,

Why doesn't MineLab state those frequencies?

They are very secretive with that info
What is the detector doing when you first turn it on and its searching for the clearest frequency to operate at, if its operating at the same 28 all the time?

Doing just what it says, searching for the clearest operating frequencies (primaries plus their offsets) Just like using offset frequencies for EMI on other detectors except it is automated.
Why can't you do more with frequency selection for specific purpose hunting, if they have 28 frequencies?

With only two primary frequencies, there is not much to chose from.
Do they actually have 28 output channels and 28 receiving channels processing each channel?

Two primaries plus their non functional harmonics =28. Minelab only claims to transmit that many frequencies, not to process them all.
In these questions without answers I wonder why units like the E-Trac are so well know for deep silver coins, but also known to do so poorly on smaller gold items?

They are low frequency detectors designed to detect high conductors.(does those 28 channels not include one for gold?)

No, only their gold detectors operate in the higher frequencies.

This subject has been hashed over for at least 10 years on this and other more technical forums. Do some searching, much of this info is coming right from the engineers who design detectors.

Mark

Mark

 

[NiagracountyNY]

I own several minelabs ,se,etrac,ctx.I also recently purchased a Notka Fors cor (Induction VLF) .I personally feel the vlf is better for depth and very tiny foil/or gold.Also works way better on chains which are hard to get.My fors cor uses 15 khz i believe. I noticed alot of very deep seeking vlf machines use 17.5 khz.Im not sure if this is fact,just me personaly noticing the diffrence between the two types of detectors(fbs/induction vlf).

 

[ironsight]

This is developing into an interesting thread.
First of all i disagree that the transmit output of the coil cannot be quantified with the right sensor and the right spectrum analyzer. I've used a variety of spectrum analyzers to measure the frequency domains of complex waveforms in addition to analyzing pulse parameters with storage scopes.
Breaking down a complex waveform into its fundamental frequency domains and related harmonics over a given band width is what spectrum analyzers do.
Having said that, i don't know how useful that information would be for cracking Minelab's FBS secrets as their is a lot more going on behind the curtain.

As stated Minelab is secretive regarding their patented FBS system.
They do give some clues however in one of their technical notes. Apparently they use a multi period rectangular wave train to accomplish their FBS transmit energy as explained in the pic below. Is that multi period wave train comprised of 28 separate and different periods (frequencies)?
The article stops short with additional info but IMO it suggests so as there is no mention of harmonics. The article goes on to state that and i'm paraphrasing that the resulting different frequency R signals (from the target) can be used to determine the target's time constant (target's eddy current duration) at various frequencies.
Given that description, it sure looks like FBS machines transmit and analyze at various frequencies but is it 28 frequencies?..... they don't say.

http://i122.photobucket.com/albums/o273/moparado/FBS_zps6d28d00e.jpg

 

[hunter_46356]

So it appears to me that there is a possibility that some detectors (ML included) that may transmit and receive multi frequencies after all. I guess my question would be why would anyone develop and market a detector saying what they've said about FBS and not be able to back it up? The possibility of learning their secrets or stealing technology?.......Maybe. The possibility that they're trying to smoke and mirror the consumer?....... I'd have to question that. Wouldn't make much sense for a successful company, that has a proven line of detectors to take a chance like that in my opinion. All of this technical information is very interesting but doesn't really matter to me as I am completely satisfied with how ever many freqs my Etrac transmits and receives. It's seems to get the job done.

 

[ironsight]

According to Minelab advertising, FBS transmits a band of frequencies simultaneously and processes multiple frequencies. The key to understanding FBS is the word simultaneous. While its easy to transmit 28 frequencies, how do they receive and process or analyze those 28 frequencies simultaneously?
One possible method off the top of my head would be to take period spectural snap shots of both the receive energy and possibly the transmit energy in some pre-determined time domain then run that data through a DSP. If that or something similar is the case, then they would be simultaneously transmitting and receiving a band of frequencies but analyzing that data far as i can see would not be simultaneous with the transmitter/receiver sequence. In a sense Minelab could honestly say FBS detectors simultaneously transmit 28 frequencies and receive receive those 28 frequencies but to analyze those frequencies simultaneously not so much. That would take a 28 port parallel processor DSP chip and even then it wouldn't be simultaneous with the transmitter/receiver sequence.

Some of the information Minelab releases in their technical notes appears to be contradictory only because they leave out key technical details which us owners have to fill in the blanks by guessing. For example, do they use harmonics to generate 28 frequencies or do they use a multiple period rectangular waves mentioned in one of their tech. notes to generate those 28 frequencies which at first glance would seem to be contradictory to the word simultaneous.

From Minelab advertising:
Generally, high transmit frequencies are more sensitive to small targets and low transmit frequencies give more depth on large deep targets. FBS simultaneously transmits and analyses a full band of multiple frequencies from 1.5 kHz to 100 kHz and is therefore sensitive to both very small and large deep targets at the same time. This means you only need to cover the ground once and can be confident you

 

[MarkCZ]

According to Minelab advertising, FBS transmits a band of frequencies simultaneously and processes multiple frequencies. The key to understanding FBS is the word simultaneous. While its easy to transmit 28 frequencies, how do they receive and process or analyze those 28 frequencies simultaneously?
One possible method off the top of my head would be to take period spectural snap shots of both the receive energy and possibly the transmit energy in some pre-determined time domain then run that data through a DSP. If that or something similar is the case, then they would be simultaneously transmitting and receiving a band of frequencies but analyzing that data far as i can see would not be simultaneous with the transmitter/receiver sequence. In a sense Minelab could honestly say FBS detectors simultaneously transmit 28 frequencies and receive receive those 28 frequencies but to analyze those frequencies simultaneously not so much. That would take a 28 port parallel processor DSP chip and even then it wouldn't be simultaneous with the transmitter/receiver sequence.

Some of the information Minelab releases in their technical notes appears to be contradictory only because they leave out key technical details which us owners have to fill in the blanks by guessing. For example, do they use harmonics to generate 28 frequencies or do they use a multiple period rectangular waves mentioned in one of their tech. notes to generate those 28 frequencies which at first glance would seem to be contradictory to the word simultaneous.

From Minelab advertising:
Generally, high transmit frequencies are more sensitive to small targets and low transmit frequencies give more depth on large deep targets. FBS simultaneously transmits and analyses a full band of multiple frequencies from 1.5 kHz to 100 kHz and is therefore sensitive to both very small and large deep targets at the same time. This means you only need to cover the ground once and can be confident you

Whatever they're using isn't unknown in the field of the engineers who work with this stuff! listed it or not, or even how specific for clarification its listed, its known!!! the only way for them to keep it locked down is to keep up the patent or copyrights. Restrictive printed information only limits it to the industry for a short period of time, (their FBS is now old technology) now to the consumer it leaves us forever confused and forever debating over it. In turn the byproduct of that is rewarding from a market strategy standpoint. People are drawn into the mystery, the unknown, we can build whatever we want filling in the blanks. From the marketing side of things, threads upon threads, forum upon forum the mystery keeps the name "Minelabs" a hot topic, its been a great way to achieve FREE ADVERSTIING!!!
However good or other their detectors are, what they've done is very innovative and effective in the area of marketing, its nothing short of genius!!

Mark

 

[Nauti]

Whatever peoples views are about minelab multi frequency machines,the fact is that they are very effective detectors over a wide range of conditions.However,in certain situations they can be beaten by some single frequency machines and as for wet sand on the beach,i would pit my Bh300 up against any minelab multi frequency machine and it would hold it's own comfortably.I've used minelabs extensively on the beach but I prefer the BH.....it's an excellent machine but most give up on it because it is not the easiest machine to learn to get the best out of.......but it will pick up tiny bits of jewellry the minelabs will just pass over.

 

[Larry (IL)]

I am very fond of Minelab, I use the CTX, my wife uses the E-Trac and I have owned many of them in the last 14 years, but most of us know their limitations. Even the $150 Tesoro Compadre, 12 KHz runs circles around the E-Trac, CTX, SE on fine chains and other small gold.

To answer the original posters question, there is really no best answer, it depends on many factors like what targets are you looking for, what are your depth expectations and especially what is your budget. There are many very nice single frequency general purpose detectors out there but the selectable multi frequency detectors are the cream of the crop IMHO, but the learning curve is usually very long. Two of my favorites for small jewelry and general purpose hunting are the White's DFX and especially the V series. The V series can be set up as a single, dual or three frequency detector and is very good from prospecting nuggets to deep relics. IMHO, it is probably the best general purpose detector on the market but it is costly and complex.

The best detector for me is the Minelab CTX because I hunt high conductor targets most of the time and I do some fresh water hunting at times. I also have the White's V3i as a backup to do the things the CTX can not when the need arises.

 

[tarajudy]

I'm now using the Garrett AT PRO , IN STANDARD MODE 0 DIS SET AT 25, SENS AT 3 BARS FROM TOP AND NOTCH OUT FIRST BAR. It has picked up stud earrings up to 6" deep. It is one of the best detectors I have had and I had a lot of mid
too high end doctors over 40 years. Stick with one and get use to it's sounds

 

[ironsight]

I'm now using the Garrett AT PRO , IN STANDARD MODE 0 DIS SET AT 25, SENS AT 3 BARS FROM TOP AND NOTCH OUT FIRST BAR. It has picked up stud earrings up to 6" deep. It is one of the best detectors I have had and I had a lot of mid
too high end doctors over 40 years. Stick with one and get use to it's sounds

Yep, this is where a single freq. machine has an advantage detecting 'some, certain' jewelry the eTRAC has problems with.
When i first got my eTRAC i tried an air test over a small gold plated semi open-ring earring and a gold chain. The eTRAC could not detect either of them. I switched to all metal mode and the eTRAC barely and i mean barely detected the chain but with that same earring..crickets.

Tried the same air test later on when i picked up an ATPro and it had no problem detecting both of them.
After using both detectors, the eTRAC has a definite coin advantage over the ATPro...no contest, not even close.