Noise Cancel Survey

[Johnnyanglo]

Here are airtest results with E-trac and 11" coil:

Deep-Off, Fast-Off, Trash Density-Low, Ground-Neutral.

Manual
Sensitivity .......... Depth
30....................... 10.25"
28 ...................... 10.0"
22 ....................... 9.25"
18 ....................... 9.0"
15 ....................... 8.0"
10 ....................... 6.5"
8 ........................ 5.75"
3 ........................ 4.0"
1 ........................ 3.0"

Tried independently changing Deep-On, Fast-On, Trash Density-High, Ground-Difficult and testing with all setting OFF while changing noise channels.

Result: No noticable difference in depth obtained on a white gold men's ring (positive two-way signal with ring parallel to coil) in any noise channel setting. In other words, it doesn't make any appreciable difference what the noise cancel setting is set to.

What does matter, and matters greatly, is the level of Sensitivity chosen. It may be the only setting that significant affects depth.

The noise cancel delta represents only the tinest of freq shift - where actual dominant power frequencies are about 25kHz and 3.125kHz, and the rest are unused harmonics and are not processed or demodulated. So, frequency is not where the action is - sensitivity settings are.

 

[BHNugget]

The noise cancel delta represents only the tinest of freq shift - where actual dominant power frequencies are about 25kHz and 3.125kHz, and the rest are unused harmonics and are not processed or demodulated. So, frequency is not where the action is - sensitivity settings are.

Probably when the ground is not a consideration. When did Minelab release this information of 2.5kHZ to 3.125 kHz information? Theres more to FBS than that. What your reciting sounds like a Whites ad.

 

[Samuel_Champlain_FTW]

;Hirschmann....

I just read an article the other day, about using chanels 2,6,9,10...

I used to always use 9,10,11... but that dime I found the other day at 7" under a nail, was on channel 2.

Channel 2 was the channel (out of the 4) that gave me the best auto recommend numbers. I do hunt in manual though, fyi.

I think I'll be using 2, 6, 9, 10, 11... exclusively now.

 

[MHirschmann]

That makes sense Samuel. From what I have read, the lower the channel, the better the machine "should" be on higher conductors, such as silver. I don't know by how much the transmitted signals are shifted by noise cancel, but it does seem like they are shifted enough to make a difference, at least for some people, in specific examples. Like I said above, I clearly need to do more experimenting/testing here to see what exactly is going on. I don't expect to discover some "breakthrough" channel or get some earth shattering answers out of this testing, but I do hope to figure out something from it that can help me get a slight edge. If I find something out, I'll surely be posting it here.

Thanks guys for all the input! -Marc

 

[Sailorman]

That's interesting. I was hunting a mineral spring swimming hole, absolutely miserable noisy ground, and the machine auto cancelled to 2. Hit a Merc dime at around 4" under a bent nail that was at 2". I was using an X-5 coil and just got a little squeak like silver on the edge of a null (using the bill_s park pattern, without it the cacophony was overwhelming). Now I wonder if that helped. Another struggling detector had just gone over the spot and missed it.

 

[earthmansurfer]

I generally hunt on NC 9 but I do noise cancel at the start of every hunt just to see where it ends up. If it is on a low number I will use it and then check again in an hour or so. If it settles on a higher number, not 9, I will manually move it to 9.

Something to consider is that since FBS is apparently using 2 dominant frequencies (Carl from Whites, AMONGST OTHERS, tested this and posted this). Of Note, the Fisher CZ machines use 5kHz and 15kHz as the two dominant frequencies. In certain conditions the CZ's appear to get better depth than the FBS machines, but the CZ's are using concentric coils and also have trouble in iron. Here is Carl's reply to me - we can't link here but you could easily find this post by a partial copy and paste:

Hi Albert,

All these detectors are true MF designs. They all have remarkably similar receiver hardware designs, in that they all split the received signal into individual frequency channels. That is, ALL of them do the analog processing on the individual frequencies, NOT a combination of them. This is very easy to determine with an oscope.

It is also an easy way to determine that the so-called 17-frequency BBS is really only 2 frequencies, and no more. They are roughly 3.125kHz and 25kHz. I haven't bothered to probe an FBS design but the identical transmit waveform dictates that it is also a 2-frequency design. The noise channels are minor perturbations of the transmit waveform, and not the selection of wholly different frequencies. That is, the channels might result in 3.15/25.2, 3.175/25.4, 3.2/25.6, etc (I don't recall the exact numbers)... the frequencies don't change much, and maintain an 8:1 ratio. DFX and V3 do the same thing with "frequency offset."

With all these designs the baseband signals from the individual frequency channels are sampled by an ADC and fed to a microprocessor. It is certain that they all process the BB signals in some algorithmic way that combines information from the individual channels to effect GB and to identify targets. It is pretty certain the 3 manufacturers all do it differently, resulting in pros & cons amongst the 3 approaches. But they are all unquestionably multifrequency.

- Carl

Now, if we consider that we are talking two frequencies and not one, perhaps only some of the time is the lowest frequency combo the best on silver and perhaps the same is true with the higher frequency sets and smaller gold. I say this because ground conditions (e.g., mineralization level) and EMI might make the equation more complicated than just frequency sets chosen. Also, the interactions between the frequencies at different KHz might create some interesting performance characteristics under certain situations. Basically, what I am saying is that we are simplifying an issue that unless we really thoroughly test, we can't truly say. So, when we find a fringe depth target for our ground, we really need to go through the NC channels imo. Clearly a high level of EMI would throw the equation out the window (as a few posters here have said), but what about those times when the EMI in between low and high?

My EMI is next to nothing, I run at manual 28-30 95% of the time. So, this talk makes a lot of sense to me as the EMI variable is not present. But, the ground variable in the form of some iron mineralization is. (In my ground, many fringe depth coins, which is 8"-9", bounce all over the screen - as you can see in many of my videos on youtube - earthmansurfer69 channel.)

Nice discussion and I would like to test this more when I find deeper targets,
Albert

 

[MHirschmann]

Great post Albert, thanks for the input!

One question I have here is now 2 people (Albert and Johnny) posted that the E-trac runs on 2 frequencies, roughly 3.125kHz and 25kHz. I know we will never get an answer from anyone in the know about this technology, but it seems that there might be some truth here to the "fact" that FBS/BBS run on a lot less frequencies than we previously thought. THIS IS NOT A COMPLAINT, I am merely trying to understand as much as I can about this machine and knowing how many frequencies, what they are and how they work, is an important part of understanding the detector. I couldn't care less if it ended up that these machines run on 1 or 50 frequencies, as they work very well either way. It would just be nice to "know" rather than speculate.

If only I had an o-scope laying around here, I could get busy, haha.

Thanks everyone for the input! -Marc

 

[Yeasty]

With a Spectrum Analyzer, all would be revealed.

 

[earthmansurfer]

Mark - Carl from Whites used an O-scope (he said so in his post above) - I do take his word for it. Would be interesting if Yeasty's suggestion would work as well. Not sure if it would pick out the harmonics (see my mention below) or just the main frequencies. This is out of my understanding.

I'm no expert here, but think about this...
How could Minelab possibly be broadcasting all those frequencies with a single core processor? FBS is notoriously slow and Minelab supposedly did the chip in the coil to help with processing. Clearly, something about the FBS/BBS
technology screams a form of time domain technology - quite a few have mentioned that as well. (The machine is waiting and you can only speed that up so much I would guess.) The way White's transmits 3 frequencies in the V3i requires a 3 core processor.

Many have investigated the FBS/BBS machines with some equipment. The consensus I hear is that the many frequencies are just harmonics (and that makes sense considering the processor). Do a Google search on
the harmonics and some Minelab keywords, you will probably come across a bit of information.

More food for thought; I contacted the owner of XP about the Deus, if in the future, it could be upgraded via software to transmit multiple frequencies. His answer was what I suspected - (Me summarizing) "We can't do it with the stock processor."

Here is something from Tom D.

Where the FBS platform attributes...........is............. they operate at a very low frequency(s). Even though the manual advertises 1.5Khz - 100Khz.......................... fact of the matter is................. it is the bottom end of its available spectrum unto which the FBS platform primarily operates. The benefits are 2-fold. Lower freq's are much more resonant to high-conductor silver........... AND ............ much less resonant to iron............. especially tiny flecks/flakes of rust. In fact......... tiny/minute flecks of rust to the (psudo/quasi PI platform) FBS units (electronic/electromagnetic decay-rate) are simply viewed upon as 'minerals'. The only way to analyze (electronically measure) "decay-rate"...... is to have a slow sampling clock speed. If only to have the attributes of FBS.......... yet...... have a much faster microprocessor clock-speed.

I often wondered how the E-Trac did better than my much faster Omega 8000 and V3i in iron. I wonder if some of it has to do with the incorporation of the time domain and multiple frequencies used...

Albert

 

[stasys]

http://www.youtube.com/watch?v=xcChyUlgPIs

 

[MHirschmann]

Thanks Stasys, so what the video is telling us is the scale is exactly the opposite from what I thought it was. The higher the NC channel, the lower the frequency and vice a versa. Hmmm.....

Also, strange how the video shows only one frequency as it sounded like we were pretty happy with thinking that there were at least 2......

The deeper we go into this thing, the more I realize I have no idea what is going on here. If I wasn't so stubborn I would walk away from this thread and just go back to auto NC and not worry about what is going on or how many frequencies there are, but I am pig-headed and now I want to know the truth about how many frequencies are actually being used! Truly used, as in sent, received and processed, for a purpose, other than marketing.

Thanks again Stasys, at least we seem to heading in the right direction. -Marc

 

[Sailorman]

Remember that meter is a single channel meter probably reading the strongest received signal. There could be several signals it's not showing. A spectrum analyser would show the whole story. I used to have access to one but not any more. Anyone else got one?

 

[looknforgold]

I read this post when you put it up. I checked my numbers on the last 2 hunts.my machine sounded sweet on my finds@ 2 & 6.

 

[Samuel_Champlain_FTW]

We'll figure it out one of these days....

 

[nge]

And to think Minelab had everyone hoodwinked into thinking that their machines actually operated on either 17 or 28 frequencies good marketing I would say. Not knocking Minelab, because they do, do an excellent job......nge

 

[MHirschmann]

I agree NGE. I hope my comments in this thread don't read as a Minelab bashing as I am a true Minelab fan. I support their company, their products and their service fully and have nothing but great things to say about them. That being said, I do wish that the truth about the "28 frequencies" could come out. I think we can all agree that there aren't 28 frequencies at play. I also think we can all safely say that there aren't even half that many. So now the question is, how many are there? We know White's uses 3 on a couple of their models. Now it sounds like the FBS machines might be using 2, although that has not been proven yet. It would just be interesting to know exactly how many frequencies are being processed and what those frequencies are.

looknforgold- I went on a 5 hour hunt today and it seemed my machine did the best in NC "2" as well. I tested the various channels on some really deep targets and on channel "2" they sounded the bost and both turned out being silver dimes in the 8-9 inch range. Of course I am not saying you should all use NC2 going forward as EMI and ground factor in to the equation, but today, in the park that I was hunting, NC2 worked the best for me.

I am sure someone will come across this thread here soon who has access to the tools required to get us the answer. I can't wait to figure this one out.

Thanks guys, Marc

 

[nge]

I also own and use (on construction sites) a Fisher 1266-X. It uses 2 freq.'s 5 khz and 15 khz. 5 is supposed to be good on coins and 15 is supposed to be optimal for gold. I've actually found more gold jewelry in the dirt with my 1266-X, but I prefer coins more.. If I ever find gold with my etrac, then it's icing on the cake. I didn't buy an Etrac to find more gold or coins, I bought it thinking that the machine had so many more freq.'s that it transmitted into the ground, then analyzed the return for better target I.D.'s, I guess not! They are pretty close to what my Fisher has, and yes, I have found extremely deep coins with my Fisher, one example a 1923 silver dollar at 13 inches, moist neutral soil. I could have found it with my Etrac also, the signal would have been much, much louder, instead of the whisper that I got............nge

 

[stasys]

With Video that I found is not everything clear for me, FBS is different from the rest single frequency detectors, but how much frequencies use FBS I really dont know, suspect is somewhere is true in earliest post where is mentioned 2 frequencies and some sort simple Minelab trick.

 

[earthmansurfer]

nge - Doesn't the 1266-X use just one frequency - 4.8kHz? I have looked everywhere and can't see that it uses 2 frequencies. I think that was with the CZ's, That said, I hear the 1266-X was one of the deepest detectors they made, nice low frequency was probably the reason and it being just a single tone.

Minelab saying there is lots of frequencies is not a complete lie. I think they are stretching the truth. Technically those harmonics do exist (as they do in CZ's, V3i's, etc.) and perhaps they are doing something with them, but clearly they can't be doing a whole lot when one considers the processor(s) used. I mean on the one hand we can take it at face value, but when you lift up the hood and there isn't some kind of "Turbo" to do all the processing, something is amiss.

Hey Mark, I don't agree with a lot of what Minelab does. I don't like the marketing hype, chips in the coils, lack of listening to customers regarding weight and I hate the secretiveness, but I do LOVE the performance and in the end that is what I come back to. I think it is fine to be critical of corporations. They need someone to keep them honest.

Albert

 

[E-Trac-Ohio]

I would think, with all the members that are posting their results - we should start to see a patten soon.

At this point - It would be great if Andy S. posted his opinion on the subject.