Minelab's Noise Cancellation

Is Minelab's noise cancellation technique patented? I've always wondered why Fisher, and others, don't employ a similar auto-technique.

Don't know, but my Garrett ATX seems to be doing something similar. And for a PI unit it seems to run quieter than mostPIs, at least my understanding of reading about it. And one thing you can usually say about the minelabs. If a site can't be hunted by one of them due to EMI, my experience is you are wasting your time most of the time trying another/different brand machine. One reason they are I feel so good in the town parks on the deeper coins-------stability.

Id used an Explorer for many year and have been water hunting now days. Most of the guys i hunt with we keep our distance just because of cross chatter something you cant get away from with most water machines. BUT.... i hunted with Cliff the other day and he brought along his CTX. We stood close to each other and he noise cancelled. I have to say i was really surprised and impressed. Once he cancelled i barely knew he was near me.

Great feature on a Minelab, wondered that myself....should be standard on all high end detectors.

Does anyone know if Minelab's auto noise-reduction is patented?

Minelab's FBS noise cancellation is better described as noise avoidance. It slightly shifts the transmitted and receive frequencies away from an undesired noise source.



Edited 1 time(s). Last edit at 06/15/2015 01:42PM by Yeasty.

Is noise cancellation in regards to trashy items like nails? how does it come into play in all iron? thanks

No, noise cancellation with regard to EMI, from both other metal detectors and miscellaneous man made sources.

Always remember hunting a field near a large sign in evening..when it turned on my Explorer went bonkers. Noise cancelled and ran smooth again...Would be a great asset for planted hunts but using an explorer in these would be like using a 30-06 for rabbits...Indeed a great asset especially for buddies hunting together...I imagine these companies protect their products with patents and may be the reason you don't see them on other units...

I don't think ML could patent noise cancel, as it's not an uncommon technology. Effectively they sample the available frequencies, and select the cleanest ones. Some enterprise/comercial level WLAN (WiFi) AP's (access points) employ similar technologies whereas on 2.4GHz they will use an auto-channel selection to dynamically select the cleanest channels (2.4GHz in the WiFi world is terribly polluted).

This has been discussed here before, and I too think it would be a great technology to implement on other detectors. Spectrum Analyzer circuits are expensive, so I'd expect to see the cost of the detector potentially go up several hundreds of dollars. IMHO it would be a worthwhile investment as time and time again, Tom Dankowski has proven that even silent EMI can cripple a detector without the operator being aware of it.

Speaking specifically of the Fisher F7x platform, the switching of frequencies is done through software (like Minelab), therefore it seems obvious that a similar methodology could be employed on that platform. Bottom line, I always noise cancel when running my ETrac but rarely switch frequencies on the F75. Yeah, it's my fault but the ease of automatically canceling on the ML is a big convenience.

A few summers ago I picked up a radio signal on my Ace detector, was near a tower. I guess was really hearing voices

Let's not forget that just because one does not hear EMI, doesn't mean it's not affecting the detector. I've had experience with that happening.

As I recall, the FBS variation from Noise Cancel 1 to Cancel 11 is a 20% over the range. That would be +/- 10% variance from Noise Cancel 6 (midrange).

Something like this:
...............................................HIGH FREQ......LOW FREQ
Noise Cancel Channel 1 ....... 22.560KHz ........ 2.820KHz ........... High Conductors (Silver) / Not resonant to Iron/rust especially iron flakes (due to lower freq).
Noise Cancel Channel 2 ......... 23.064 ............... 2.883
Noise Cancel Channel 3 ..........23.568 ............... 2.946
Noise Cancel Channel 4 ..........24.072 ............... 3.009
Noise Cancel Channel 5 ..........24.576 ............... 3.072
Noise Cancel Channel 6 ....... 25.080KHz ........ 3.135KHz ........... Normal / Default Setting
Noise Cancel Channel 7 ......... 25.584 ................ 3.198
Noise Cancel Channel 8 ..........26.088 ................ 3.261
Noise Cancel Channel 9 ..........26.592 ................ 3.324
Noise Cancel Channel 10 ........27.096 ................ 3.387
Noise Cancel Channel 11 ...... 27.600KHz ........ 3.450KHz .......... Low Conductors (iron, hammered coins) improved response (due to higher freq)

Fixed earlier values ... should be close to reality.



Edited 1 time(s). Last edit at 06/17/2015 04:24AM by Johnnyanglo.

So the ML FBS platform allows for significant frequency shifts (0.3 --> 5.9 kHz) that, regardless of EMI effects, fundamentally affects performance against certain targets?

There's something wrong with your numbers, there, Johnny. The high and low frequency components are at a fixed 8:1 ratio, so as one increases, the other follows in sympathy. From a discussion in one of Yeasty's earlier threads:

"Based on the timing details and the scope traces posted, channel 1 has a high-freq. burst of 22560 Hz, (fundamental = 2820 Hz) and channel 11 has hf burst of 27600 Hz (fundamental = 3450 Hz). The ratio of these extreme values is 1.22 :1. The centre-frequency (channel 6) would appear to be about 25 KHz, as previously suggested."

But this +/-11% range is helpful when you're trying to reduce EMI problems, as it's quite significant. By contrast, the F75/T2 range is much smaller (+/-1.3%), and is primarily for coping with other detectors nearby. The Minelab electronics/coil are not particularly 'tuned', so they can be forced to run at other frequencies. Whereas the FT machines are tuned for their one frequency, and running them too far off the design frequency may result in loss of depth, etc.

What's different with Minelab coils that they don't need to be 'tuned' to the electronics? Or visa versa? Interesting subject...I always thought the noise cancel was the best feature on ML units. The FT machines freq shift is barely noticeable at all around here...near useless unless hunting near another F series detector.

When using my 75 near a Minelab I can't do a shift and make it better....I have to ask/remind the ML user to clear the air.

"No, it's not a patented system but they do own the 'proprietary software' that runs the Noise Cancel system they operate through their patented FBS system software'...confusing, yes, no?

Here's a bit on Noise Cancel written on the subject when it first debuted to the world:

NOISE CANCEL

Just what is going on when we press NOISE CANCEL and what is it doing?
The BBS/FBS detectors transmit and receive a wider range of frequencies than single/dual frequency detectors. Consequently, a wider range of atmospheric electrical noise can interfere with the internal processing circuits, resulting in an oscillating ( warbling chirping) threshold and resultant loss of sensitivity. The received "electrical noise", referred to consists of electrical noise radiated by power lines, computers and some weather conditions. All electrical appliances radiate some electrical noise! Under these conditions the microprocessor is not only trying to differentiate between ground noises and target returns, it is also trying to process this 'interference', so some target and ground information is not correctly processed, hence the loss of sensitivity. (Turn one of these detectors on whilst inside a house, turn the sensitivity up and you will see what I mean)
Due to the larger spectrum used by the Explorer, at higher sensitivity settings, this may be more noticeable. The internal Noise Cancel feature overcomes this problem. This feature also allows a number of detectors to be used in close proximity.
The following Noise Cancel explanation may help in understanding this feature.
The 28 frequencies transmitted by the Explorer are all produced from one variable oscillator, and all 28 are multiples or sub multiples of this oscillator frequency. When Noise Cancel is initiated, it steps the variable frequency oscillator through its range of 11 frequency steps (thus slightly changing all 28 frequencies by the same ratio). It records the received electrical noise at each step. At the end of this procedure, it selects the quietest frequency (i.e. the one that received the least noise). It also remembers this frequency when you switch the detector off and sets it to that particular frequency when you turn it back on again. This would possibly explain why some Explorer users experience initial instability especially if, the detector is switched on at a different site on a different day? You really should do a Noise Cancel before each search. The receiver is designed to properly receive the whole range of possible transmitted frequencies, so neither depth, nor discrimination will be affected by whatever frequency the Noise Cancel circuit finally selects.
Why is it important to hold the coil very still during the Noise Cancel procedure? If the coil is moved during this procedure, the noise being picked up in that instant may change because the coil has moved. Therefore whatever frequency was being sampled at that instant will have "noise" recorded against it, and it means that it won't use that particular frequency (even though that frequency may have been the quietest).

Would love for someone to do some test on a couple of say deep undug suspected dimes. And manually change the channels to see what difference it makes on the signal. It would only seem reasonable to think electronics can hear/see EMI (noise) better than our ears can. White's, FT, Makro, Nokta, Tesors, etc all should employ something similar on their flagship units to mitigate EMI.

ozzie Wrote:
-------------------------------------------------------
> What's different with Minelab coils that they
> don't need to be 'tuned' to the electronics? Or
> visa versa? Interesting subject...I always
> thought the noise cancel was the best feature on
> ML units. The FT machines freq shift is barely
> noticeable at all around here...near useless
> unless hunting near another F series detector.
>
> When using my 75 near a Minelab I can't do a shift
> and make it better....I have to ask/remind the ML
> user to clear the air.


When I am hunting with ML users I ask them to do a noise cancel while I stand right next to them and and enable pinpoint on my F75, the ML appears to select a channel that doesn't interfer with the F75 and it's worked like a charm so far.

>Cal stated; When I am hunting with ML users I ask them to do a noise cancel while I stand right next to them and and enable pinpoint on my F75, the ML appears to select a channel that doesn't interfer with the F75 and it's worked like a charm so far.

Ha, yes. I have a friend who is very competitive....I listen through my headphones to make sure he used noise cancel, lol....you can hear it cycling through.

ozzie Wrote:
-------------------------------------------------------
> >Cal stated; When I am hunting with ML users I ask
> them to do a noise cancel while I stand right next
> to them and and enable pinpoint on my F75, the ML
> appears to select a channel that doesn't interfer
> with the F75 and it's worked like a charm so far.
>
>
> Ha, yes. I have a friend who is very
> competitive....I listen through my headphones to
> make sure he used noise cancel, lol....you can
> hear it cycling through.

I found out early on with my F75 that they are suspectible to what equates to silent signal jamming from an Explorer or Etrac type machine. I had a hunt in a small 25'x25' area that a guy and I had just cleared out the overgrowth and fallen trees on, and he was finding all kinds of stuff and I wasn't getting anything. Mind you targets were not deep, 2"-6" max. that any machine would detect. Finally I said hey let me hear the next target you get and sure enough my F75 didn't make a peep I had him do a noise cancel while I held the pinpoint trigger and viola the F75 was back in action.

Now when I hunt with Minelab users and I use my F75, this is standard operating procedure at the beginning of the hunt

Cal, I believe you posted that a while back, I remember.....not sure you posted it here though.

That's why I want to hear my friend noise cancel through my headphones....like I said, he's competitive....not that he'd really jam me up like that....I don't want an hour going by and then find out.... then hear a "oops, sorry, forgot".

Ozzie it was an eye opener for sure. BTW that signal he got that I tested and could not hear turned out to be a 2" deep silver dime....sigh



Edited 1 time(s). Last edit at 06/17/2015 03:16AM by Cal_cobra.

So if it's not patented then Fisher could write their own "proprietary code" to work with their software. The logic would be simple to program. Having a 'noise cancel' option on the menu doesn't seem too much to ask.

go-rebels Wrote:
-------------------------------------------------------
> So if it's not patented then Fisher could write
> their own "proprietary code" to work with their
> software. The logic would be simple to program.
> Having a 'noise cancel' option on the menu doesn't
> seem too much to ask.

I don't really know exactly how the detector circuits work, but a WiFi access point can do a similar function with the radio reporting the SNR, noise floor, and other 802.11 devices on the same frequency, I would imagine a similar function would be possible on the receive circuit on a detector. Perhaps it's something that Dave Johnson has up his sleeve for the CZX and Mocha (or whatever it was) that may be their latest and greatest coming out next year???

Dave J. you reading this? ><

A explorer has little depth in my dirt till I Nosie cancel then the depth comes...

Actullaly sometimes if you forget to Noise cancel and Im hunting and not digging much then do a Noise cancel then the depth comes alive..

its like the sens even in manual is detuned/attenutated..

the ATX just scans through the freqs looking for the quitest its a carry over from a infinium freq scan... the Explorer scans the freqs and OPENS up the gain it feels..

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

Quote
Keith Southern
its like the sens even in manual is detuned/attenutated..

The negative resultant of silent EMI -

go-rebels Wrote:
-------------------------------------------------------
> its like the sens even in manual is
> detuned/attenutated..
>
> The negative resultant of silent EMI -

Ive noticed upon startup unless you do a noise cancel the machien is weak on any channel...but do the auto cancel and the gain comes back..even though it may scan through and come back to the same channel..

Ive always wondered if the machien is detuned till auto noise cancle is activated to find a clean freq then ramps up???

on the XS seemed to be the most demanding for a noise cancel to be done,,, the 2's and the S.E.'s did not seem to suffer as much if a noise cancel was not done..

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

Keith have you any thoughts on the users who,,,,,,, use channel 1 for low conductors and 11 for high conductors.