Your 10K / 100K idea mirrors some of my thoughts. As you probably recall, I'm a Geotech1 regular, and there has been some general discussion about BBS multi-freq over there. But it's pretty ambitious for home-builders to recreate. I said on a thread there that I'd be interested in making a 12kHz / 48kHz BBS-style rig, and to make the seemingly obvious step of making both freqs individually selectable, so you have a 12kHz machine, a 48kHz machine, and a 12/48 multifreq-er. But a more interesting variation would be to run at 12k & 48k, but NOT in BBS-mode, but in a 'mixed-mode'. That is: 12kHz in one ear, 48kHz in the other (though maybe some subtle blending may be productive).
For this to work, it would probably have to be dual-tone operation, Ferrous and Non-ferrous, but with a different Non-ferrous tone for each operating frequency. Example:
Left ear: 48kHz operation, Iron-tone & low non-ferrous tone
Right ear: 12KHz operation, Iron-tone & high non-ferrous tone

It always puzzled me why MineLab never offered single-freq operation on their FBS/BBS machines. Maybe it's a marketing problem, if multi-freq is so good, why are you offering the single-freq option? And why have they stuck to the same 3.125kHz / 25 kHz freqs all the way through? It seems a fairly easy step to make a 30k / 90k nugget-hunter, or other variants.

Nerdy Stuff:
The two frequencies used by BBS/FBS are 8:1 ratio (25kHz & 3.125kHz). This isn't anything special, in principle, any two freqs could be used. It just makes the electronics timing simpler if integer multiples are used, so 3:1, 4:1, 8:1 could all work fine.

In theory...... it should work; yet, there is a fairly large disparity in the EMI variable delta. I would like to think that modern filters could help correct; but, this would be fixing the 'effect'...... and not the 'cause'. However; all is not lost. There's other options. Some have already been discovered........ and some have yet to be discovered.

It is my strongest recommendation that Mfr's 'standardize' semantics/definition.

MULTIFREQUENCY = Simultaneous transmission of two or more frequencies.

SELECTABLE FREQUENCIES = Single frequency operation; with the ability to select other individual frequencies.

Detech Chaser is this weeks flavor!

NASA-Tom Wrote:
-------------------------------------------------------
> It is my strongest recommendation that Mfr's 'stan
> dardize' semantics/definition.
>
> MULTIFREQUENCY = Simultaneous transmission of two
> or more frequencies.
>
> SELECTABLE FREQUENCIES = Single frequency operatio
> n; with the ability to select other individual fre
> quencies.

Funny that you wrote this, NASA-Tom. I just got done having this discussion with someone on another detecting forum just a couple of days ago...

Steve

It's gone TOO far........ and needs resolve.

I agree but I would amend that:

MULTIFREQUENCY = Simultaneous reception and processing of two or more frequencies.

SELECTABLE FREQUENCIES = Single frequency operation; with the ability to select other individual frequencies.

The thing is that to be a true multifrequency detector it is not even required to receive multiple channels absolutelly simultaneously. It just puts some limitations on width of the spectrum you can pass through the channel. Until you "motion" spectrum is well within the given limitation It is completely fine. It is very similar to processing signals from Bayer matrix in image sensors, the only difference difference that it resolved in time but not in the space.
Also people need to stop confusing terms "frequency" and "demodulation channel". While for vlfs demodulation channel receives only single frequency component transmitted it is not always like that for other types of detectors.



Edited 1 time(s). Last edit at 10/31/2017 11:59PM by Gastro.

steveg Wrote:
-------------------------------------------------------
> NASA-Tom Wrote:
> --------------------------------------------------
> -----
> > It is my strongest recommendation that Mfr's 'st
> an
> > dardize' semantics/definition.
> >
> > MULTIFREQUENCY = Simultaneous transmission of tw
> o
> > or more frequencies.
> >
> > SELECTABLE FREQUENCIES = Single frequency operat
> io
> > n; with the ability to select other individual f
> re
> > quencies.
>
> Funny that you wrote this, NASA-Tom. I just got d
> one having this discussion with someone on another
> detecting forum just a couple of days ago...
>
> Steve


Like I said Steve, I think these terms fit.

Rich (Utah)

------------------------------------------------------------------

Just one more good target before I go.

I am just finishing up a Phase-2 site recovery with a Regional Archaeologist and a State Archaeologist on a small 1653 Spanish settlement.

- Conclusion: Nominal/median/average depth of 'era' implements: 47".

Tom - That sounds truly interesting. What sort of era implements are you finding? And, sorry if my math is a little off ........but essentially 7" of sink a year?

NASA-Tom Wrote:
-------------------------------------------------------
> I am just finishing up a Phase-2 site recovery wit
> h a Regional Archaeologist and a State Archaeologi
> st on a small 1653 Spanish settlement.
>
> - Conclusion: Nominal/median/average depth of 'er
> a' implements: 47".


Tom,
Have you also calculated an 80/20 rule, like what is the depth range of 80% of the items, and the extreme outliers (other 20%) of object? for example, are 80% within 15" of that...from 32" to 62", or is it flattened, like most of the objects are right at the 47" with few below and few above, etc?

This topic actually makes me want to dust off my statistics textbook....

TN, you divided into the wrong number. Comes out to be about 1/8" per year or about 3.276 mm per year.....according to my deciphering.

2017 - 1653 = 364..........47 / 364 = .129.......or a tad over 1/8"

Oh yea, wanted to say, that sink rate is fast for around here in SE PA....especially for coins.



Edited 2 time(s). Last edit at 11/22/2017 03:46PM by ozzie.

Thanks,Ozzie. I knew it was off, just had a quick moment to type this morning.

I come up with about 1.3" per decade, which is slower than what Darwin calculated for England (2.4"/decade). However, Darwin's rate was calculated over a much shorter period. The sink rate should decrease with depth (and time) due to the greater earthworm activity at shallower depth. Very interesting Tom. Please keep us posted on the recoveries.

...dug a 7' x 10' x 22" deep pit.

Tom, the pit would have a volume of 128.3 cubic feet.

Assuming the 5"DD coil could recover 100% of non-ferrous targets in the pit to a depth of 10", the coil illuminates a total of 58.3 cubic feet of soil or 45.4% of the pit.

That leaves about 55% of the pit soil unsearched by the coil.

Assuming a homogeneous distribution of non-ferrous targets (which probably was not the case), then the 141 non-ferrous targets were evenly distributed, then 64 non-ferrous targets should have been recovered by the 5"DD coil. That gives the 5" coil a success rate of 6.3% (4 / 64). Not good.

But, if the actual sensitivity of the 5"DD coil is overstated at 10", rather we'll assume it identifies 100% of larger non-ferrous fragments to only 5".

The 5" DD with 5" depth illuminates 29.2 cubic feet of pit soil or 22.8% of the pit. Then the coil finds 100% of the 4 non-ferrous targets in about the first 5" of soil, there should be an additional 5.6 times more similar sized targets in the pit (5.6 times more volume unsearched with the coil). The expectation would be that about 23 more non-ferrous targets were laying deeper in the soil beyond the reach of the coil (5.6 x 4).

It is inferred then, of the 141 non-ferrous targets evenly distributed, 32 targets should be within range of the 5" coil with 5" depth capability (141 x 22.8%). It found 4 of the 32 targets or a 12.5% success rate. Still not good.

But, if the sink depth of targets affected the distribution, such that 80% of the non-ferrous targets had sunk beyond the 5"DD coil capability (~5" depth), then only 20% would remain discoverable. Based on that assumption, there were only 28 non-ferrous targets within range of the coil, of which 4 were found, with a success rate of 14.2%. A bit better.

But again, assume those non-ferrous that didn't sink beyond 5" were mostly smaller non-ferrous target pieces that the 5"DD coil was not particularly sensitive to, and had only a 50% recovery rate (due to their tiny size).

Then, with an expected 50% target recovery rate, and with 80% of the targets beyond the 5" range, that leaves of the 28 non-ferrous targets in the pit's first 5" of soil, only half or 14 were conductive enough to be found. Therefore, the 5"DD coil had a success rate of 28.6% on detectable targets in the first 5" of soil.

What does that mean? It can be inferred that under optimal sink rates of non-ferrous targets, when searching with a small 5"DD coil in fields of nails, that masking would restrict target recovery so that out of every ten detectable targets in the soil, 3 would be recovered and 7 missed. It could also be inferred that for every ten detectable targets there are another ten (50% non-recoverable) that the coil can't find due to their lack of conductivity and/or small size. It could also be inferred, that of the ten detectable targets, there are about 121 non-ferrous targets of various sizes beyond detection range (141-20), and of those, half or 61 would be detectable if the overburden of dirt were systematically removed in 5" increments and the coil swept between removals.

In other words, as you swing the coil over the ground, walking 20 feet forward (similar areal coverage to the test site) you would recover 3 targets that can be illuminated by the detector (missing 7 others) and walk past an additional 61 non-ferrous targets that the detector could find if they weren't so deeply buried. That means the 5"DD coil is recovering only 4.9% of all buried non-ferrous targets (that leaves 95.1% of all targets undiscovered with a 5"DD coil).

john



Edited 1 time(s). Last edit at 11/22/2017 05:48PM by Johnnyanglo.

Calibrating the depth curve to the measured 47" after 365 years, I come up with a depth to bedrock/hardpan/sand etc. of 60 inches.1653 Sink Rate. Of course this assumes that the site is not in a sediment depositional or erosional area (next to a stream or other body of water).

Kent



Edited 2 time(s). Last edit at 11/22/2017 06:59PM by BigSkyGuy.

Wow. I had no idea my data would trigger THIS much interest/passion!

TNdd = Just to list a few of the implements/items recovered during this excavation: buttons, coins, pottery, clasps, buckles, clay pipe stems, BB/bird/buckshot, clay pipe stems/bowls, an uncanny/disproportionate amount of forks, skeleton keys, fish/animal bones, beads, bottles (black glass shards), various tools........etc................

Rod-PA = Yes. In fact, it was the Regional Archaeologist of whom documented/computed/calculated the depth-strata data. 83% of the implements were in the 45", 46", 47", 48" depth range........ with a slightly heavier data/number % at the 47" depth range. This is what allowed him to 'target' the 47" average depth claim for the period/era of this site. All targets of this 1653 era/habitation ceased to exist past 58". About 9% of the targets/implements recovered .... were in the 48"-58". The remainder 8% of the targets is what I found to be interesting......... as a detectorist. Less than 1% of the implements were in the 0"-12" top-soil. . . . . . . yet......... this still collectively attributes to 11 targets of era...that were within modern-day metal detector range. For what ever (variables-induced) reason(s).......these 11 targets (which is statistically normal)...... did not sink to proper depths of the stratification era. These are the targets that we 'detectorists' will find...... and will generate 'hope' of finding larger quantities of 'era' stuff. . . . . . . . , , , , , , , . . . . . . . never realizing that the bulk of the implements that we dream/choose to find.............we are merely walking right over......by just a couple/few feet deeper....... and never knowing it. ..... The remainder 7% of the targets were very linearly disbursed from 12"-45"........... and with the heavier part of the concentration increasing.....as you approached the 45" depth strata.....in linear fashion. ((( Please understand that I am converting all of this data from Cm to Inches.......... as Archaeologists work in Centimeters. )))

Looking at the striations/color of the dirt at the varying depths...... the State Archaeologist made the claim that........... and one point-in-time....... this exact area was woods (wooded).......then became a field again. There are different sink-rates related to 'wooded' areas...... vs....... open-field conditions. (A lot to do with subterranean life-form "differences" between wooded vs. open-field. Flora & fauna make a 'sink-rate' difference.) However......... even with all of this data,,,,......... the sink-rate depths would still fit within the 'norm' parameters of Florida (and South Eastern U.S. climate).

John........ Your data is ALWAYS enlightening!!! Yet........ I feel I wasted a lot of your laborious time/labor/effort...... by NOT providing additional/amplifying data in a timely manner; due to MY incremental limited time! If only I had the time to convert all of my notes/sheets to digital format........ I would give you ALL of this data...... for your perfected computed mathematical stat's!!!

BSG = My test-garden (now with 31 years of collected data) has a nominal/median average sink-rate of 1"/4.5-years. This equates to 10" in 45-years. The data that I do NOT have ....is............. once a target reaches greater depths; say: 15" or 20"......... THEN what does the sink-rate become?
Because of this sink-rate........would cause my test-garden to require re-validation every few months...........and............... subsequently................ required me to change my methodology as to 'how' I would create a test-garden....for a 'variables-REMOVED' standardization......in order to generate valid/accurate comparison data. ((( I now use Schedule-40 PVC pipe cut to exacting lengths.......gluing coins/targets to the bottom end of the PVC pipe........,,,,,,,,,,......... so now I know the exact depth of each/every target (without fail/error).....to an exacting depth; hence/via....keeping the top of the PVC pipe 'flush' with the surface of the dirt. )))
Also...... I do not have a hard-pan bedrock at 60" in my region.

Recently...….. I was returning home from an all-day detecting excursion. I had found a 110-year old Barber dime. Whenever I come home with a Barber...… it has been a very successful day. If I come home with a 140-year old Seated dime...… its been an extremely successful day. When I come home with a 200-year old coin...….. it is a major/monumental/triumphant historic success in epic proportion. . . . . . as ……. a coin that is 200-years old.... is 'nearly' a once-in-a-lifetime 'find'. I have very few 200-year old coins.
The epiphanictic moment happened..... when a friend of mine (Archaeologist) exclaimed: Its been a good day....if he came home with a 2000-year old item. Its been an extremely good day if he comes home with a 20,000-year old item. Its been a major/monumental/triumphant major success day...…. if he comes home with a 2-Million year old item.
Hmmmmmm. Really made me 'think'..... and ……. really put things into perspective.

----------------------------

How ironic when many folks exclaim that their detector is 'as deep as they would ever want to dig' ((( 12" on a dime ))); yet, on the contrary...… are all excited about possible new detector/technology...… that'll acquire a Nickel at 17".

Tell me: Depth is not important! Let's keep pushing the technological-advancement envelope!!!

It's interesting that two years ago, one year before the Equinox was launched we were discussing that Simultaneous Multifrequency detectors should also provide the capability to choose to run the frequencies implemented as individual frequencies. Perhaps Minelab is finally listening (how many years did it take to get the SMF detectors weight down to a reasonable amount?).

Tom D. I can relate to what you're saying, but the archeologist also has an entirely different perspective, per-historic vs historic era relics. Unless you're lucky to live in a region that had copper/bronze age era technology, you're looking at stone tools and pottery, none of which a metal detector is beneficial to find. Whereas metal detectorists are mainly looking for contact period relics of European influence. I doubt most archies care if they excavate a seated dime or real (akin to pull-tabs to them?), as they tend to have the disposition that European influence on the indigenous population only brought about disease, slavery, and war. At least that's my take from my experiences with archeologists on the left coast.

Yeah Cal that European influence is viewed as Bad world wide---even when they turn on a light bulb,talk on the phone,ride in a car,plane,train----you get the idea.

Depth is important....but man Tom...I’ve got to know it’s worth my time digging it. I know I can hear a nickel about 10” lets say...after that i might still get a signal ...but that first thought is iron move on. I guess depth and sensitivity/TID are kind of all the same.

When folks go to the extreme...... and are willing to use a PI in locations where iron is present/problematic.,.,.,.,.,.,., a genuine reality...starts to sink in. Folks are willing to go to extreme efforts..... in order to fill a quest...…. with the utilization of a detector that poses severely inhibiting handicaps. Hmmmmmmmmmmmmmmmm. Opportunity knocking?

Advancement. Have we made some technological advancements? Are we trying to make technological advancements. Are we stuck in the confines of 'evolutionary'...… and have yet to achieve 'revolutionary' technological advancement status.

We have been playing with (inductive coupling) metal detectors since 1931/1937.

What if we could think outside the box...… and figure out a way to use 'sound'...… to check the 'density' of objects in the ground? Would it see rocks and tree roots? Yes...… but rocks and tree roots are very low density..... as compared to metallic objects. Would there be drawbacks? Yes. ---- But would the drawbacks be worse than a guy using a PI (of which has severe inhibiting handicaps) at a Civil War battle-site with plenty of nails/iron implements in the ground?

Any lightbulbs?

So size maybe and density vs conductive properties.
Makes me think somewhat of this new thingy Nokta has.
What’s it called? Oh yeah, the Invenio.

Or a fish depth finder in water maybe.

Or sonar.



Edited 2 time(s). Last edit at 07/02/2019 07:35PM by tnsharpshooter.

Ultrasound,...what they do for pregnancies. These days they are very clear compared to when my wife had them.

Detector using a magnetic field. A magnetometer detector?

Throughout all/entire metal detector history...…… technology has had us incarcerated into finding (nearly) only the 'annular' gold jewelry targets......in a wet-salt environment.
This is about to change.

Is there a naming competition for it?
I'll have first guess: MDT-8080 ; reminds me of the microprocessor.

Well i hope you are talking about the Fisher AQ....... if NOT someone spill the beans. Seems i keep buying new detectors. People are starting to talk about me on the other forums lol. BUT ...... i sure do hear you about chasing recent drops... or annual targets within the depth of our current detectors. Money drives the train. Companies work within their ability to sell and produce the next model. Making cheaper machines may hurt other companies ... and help us.... but if you are going to do that you best be sure of the machine. New Tech is even more a gamble. It helps when the military NEEDS a new design.

Pimento...…. 8080-Alpha sure would be cute! (((But sounds 'old'.... and 'slow'))).

There is another particular door that metal detector Mfr's have yet to open.
Without the 'vision' ……. it remains unforeseen.

(Forward-thinking..... is unsuspectingly difficult).