Rcpt Ack of F75 Ltd prototype

Tom, with all of the current units you have tested...what is your opinion of the consistency between units? Are the EMI handling charactoristics consistent between units/batches. Are the depth abilities consistent between units/batches and is there any correlation between depth and EMI handling.

Thanks,

Kenny

Tom,

I was thinking about the fact that if we can get the detector onto the cleanest RF channel, that it will potentially detect far deeper then a dirty channel. This is a fact, we see the same results when designing WiFi WLANs, particularly on 2.4GHz which is quite polluted.

I believe Minelab has hit the nail on the head here. They seem to have implemented an inexpensive RF analyzer circuit built into their Explorer/Etrac/CTX machines. I believe when you hit the Noise Cancel, it scans the available channels, and selects the best channel (frequency) based on channel "goodness" (channel utilization/saturation, interference, etc). This channel clarity, in addition to using multiple frequencies is what I believe allows them to be incredible depth demons, particularly in mineralized soil.

This, IMHO, could very well be the next evolutionary step for VLF machines, provide them with the capability to have an intelligent frequency selection. As dynamic as RF is, take it even one step further, doing constant channel sampling, and if the initial best channel selected encounters undesirable conditions, give it the ability to switch to another clean channel.

Sounds like a patent in the works

~Brian

Cal_Cobra...Minelab also has this on the GPX detectors as well. I use it religiously on the 5000. It is quite extensive on the 5000, If I remember correctly it has over 200+ points in the range. It can be performed automatically, just push a button and it scans the entire range and sets itself to the best (cleanest) point. Takes a minute or so to run automatically. It can also be done manually. I know some people run it in a certain range say between 110 and 150. I'm not sure if there are advantages to doing it this way, I have had better results just pushing the auto button and waiting for it to complete the cycle.

The frequency scan definitely makes a difference to help get the 5000 to run as quiet as possible with minimal EMI. These things are quite touchy with any kind of EMI, multiplied even more when using the larger coils.

I think it would be pretty sweet to have this option on the F75.

Kenny

Okay......... now it's time for the F75LTD/2 with 5" DD coil report. This is with 9.0, Sens on '99', Disc '0', Grnd Bal '90'. This is with a buried clad dime in Florida inert dirt.

bp = 10.1"
cl = 10.0" (Elongated audio response)
je = 9.3"
pf = 9.2"
de = 9.2"
bc = 8.8"
FA = 8.9"

Keeping all settings the same......... but this time in 9.1:

bp = 9.8"
cl = 9.6" (Elongated audio response)
je = 9.1"
pf = 9.0"
de = 9.0"
bc = 8.5"
FA = 8.6"

Once again..... whilst in the FA mode......... the last inch of detectable range.....and the audio response is merely a audio 'tick'........ not quite the length of a audio 'beep'. This does indeed make for a more difficult audible intelligibility factor..... with the deeper targets in FA mode..... especially in the real world.... with real hunting scenarios. However, once learned...... your real-world performance will increase. And......... in the real world..... on actual hunts in FA mode........ it is difficult to find targets deeper than 6" - 6.5".

Of all the process modes..... 'bp' mode is the most intelligible....... with the best usable depth. Interesting how the 'cl' mode is not quite as deep. All of the other modes will only produce these stated depths in a test-garden under ideal conditions. Only 'bp' process mode fully carries out of the test-garden..... and into the real world..... in regards to depth.

All testing performed with Sens '99'......... due to zero EMI encountered. The 5" DD coil is a much more EMI free coil design. 'Almost' no need to test other Sens settings. But.......... for the record.......... I did test different Sens settings and (for the most-part)...... found that Sens could be reduced to '70' with minimal depth loss....... and provided more modulated audio. Go below a Sens setting of '70' with this 5" coil........ and depth does indeed start to ramp down.

When Disc is increased, depth does indeed start to (slightly) reduce...... mostly due to the audio report from deeper targets being 'clipped/shortened'. In a test-garden...... minimal depth is lost (due to "known" target in a 'exacting' pinpoint location) ...... but....... in the real world....... the shortened audio length of deeper targets will become 'awash' more readily when thrown in the mix with all of the other audio responses from ground chatter, trash, falses, audible mineralization aberrations, etc........

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

As time progresses, I will write more on real-world hunts/performance with this LTD/2. Test-garden performance data always generates a 'base-platform' unto which real-world hunts will be referenced/compared to. Test-garden performance generates live hunting (performance and scenarios) expectations. And these expectations are 'key' for maximizing real-world performance. Never underestimate the 'gained tuition' importance/level of what a test-garden will instill.

Excellent data,Tom and being able to reduce Sens to 70 with minimal depth loss is good news, also interesting that CL is not as deep as BP. I had planned to use CL on some deep cannon balls. Thanks again.

Thanks Tom, is an excellent information.
I've been testing my new F75 LTD 2 Updated (02-15), and I've noticed that now the detection distance is always the same, regardless of discrimination.
Now the F75 behaves the same in all reference range (0 to 65). Personally I think we lost depth with the upgrade.
If you had to choose one of these two (F75LTD2 or F75LTD), What would be your choice?

Thank You!



Edited 1 time(s). Last edit at 03/04/2015 07:04PM by elromano.

elromano Wrote:
-------------------------------------------------------
> Thanks Tom, is an excellent information.
> I've been testing my new F75 LTD 2 Updated
> (02-15), and I've noticed that now the detection
> distance is always the same, regardless of
> discrimination.
> Now the F75 behaves the same in all reference
> range (0 to 65). Personally I think we lost depth
> with the upgrade.
> If you had to choose one of these two (F75LTD2 or
> F75LTD), What would be your choice?
>
> Thank You!

Found this in another post...

[www.dankowskidetectors.com]

doc holiday Wrote:
-------------------------------------------------------
> Excellent data,Tom and being able to reduce Sens
> to 70 with minimal depth loss is good news, also
> interesting that CL is not as deep as BP. I had
> planned to use CL on some deep cannon balls.
> Thanks again.

something to consider. I assume Tom tested BP VS CL on coin type/size targets. I suspect that the true value of CL will be apparent on larger targets like your cannon balls.
If this is incorrect Tom, please quantify/correct.

NASA-Tom Wrote:

> Once again..... whilst in the FA mode......... the
> last inch of detectable range.....and the audio
> response is merely a audio 'tick'........ not
> quite the length of a audio 'beep'. This does
> indeed make for a more difficult audible
> intelligibility factor..... with the deeper
> targets in FA mode..... especially in the real
> world.... with real hunting scenarios. However,
> once learned...... your real-world performance
> will increase. And......... in the real world.....
> on actual hunts in FA mode........ it is difficult
> to find targets deeper than 6" - 6.5".

Tom thanks for your report.

I noticed when I was hunting a field of iron with the 11" DD stock coil that I would get these audio "ticks" that it was enough to slow you down to analyze the target, and then generally working a 360 around the target, I could bring it up to a better signal, and each one dug turned out to be a non-ferrous signal.

Thank You Bertman!

On the original F75 LTD/SE's...... the detection range/performance on a clad dime whilst comparing 'bp' ... vs ... 'cl' mode....... the 'cl' mode was ever-so-slightly deeper..... in real (Florida) dirt.
And on a very low conductive tiny Type-1 $1 U.S. gold coin...... and still...... the 'cl' mode was a bit deeper.
The 'cl' mode somewhat defy's expectations.

Hunted all weekend with the F75 LTD2. In a nutshell....... there were 4 sites that I had (subconsciously) 'wrote-off'..... several years ago...... as unhuntable. I could not remember 'why'. I started to hunt one of the 4 sites with the original F75 LTD..... and was immediately 'shut down'..... due to excessive EMI. . . . . . and instantly remembered as to 'why' these sites were 'wrote-off'. Bottom line: The LTD2 opened these sites up. I could not even hunt any of these 4 areas with the original F75 LTD....... even with reducing Sens, increasing Disc..... and selecting the best F1 - F7 channels.

Which leads me to say:

Observation = Initially.......... It appeared entirely that the LTD2 (T2 or F75) was simply a 'reduced sensitivity' unit. Subsequently...... more 'snap-shot' sampling/timing (boost process) was added/employed...... so as to mitigate the depth loss encountered by engineering/incorporating this reduced Sensitivity level.
Now......... after this past weekend experience(s)........ it appears to have more than just a simple reduction of Sens (with more 'bp' added). There is more engineering behind-the-scenes that became somewhat evident.

Also noteworthy: One of the four (previous EMI shut-down) sites has such excessive EMI that would warrant the implementation/utilization of 9.1. . . . . however, I did continue to hunt in 9.0.......... comparing 9.0 to 9.1 with each/every target detected in this excessive EMI site. I could find very little 'intelligible' difference between the two modes; yet, 9.1 was a bit more quiet ... vs ... 9.0. My only concern was the more elongated/delayed target response that 9.1 presents..... still...... was a bit disconcerting.

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

ALSO noteworthy: In my test-garden...... with the new LTD2....................... with freq selection F7, I encountered a 2.7" depth loss difference on a clad dime.... when compared to the other (F1-F6) freq's/channels. There was NO audible EMI on any one (of the 7) channels. The next day, F4 was the least-performing channel..... and F7 was one of the better performing channels. Soooooo....... How would you know that you are operating on a 'reduced performance' channel!
Moral of the story = Do not think... for one moment................ that EMI & silent EMI does not affect other detectors!

Thanks again for posting your observations Tom.

I recently took my LTD2 to a location where I had some EMI using the AT Gold and Nel Tornado coil. I only had a small area I could not hunt with the AT due to EMI. The LTD2 is affected to a much greater extent at this location. EMI was present on all frequencies (in 9.0), I had trouble identifying any frequency that was better. Switched to 9.1 and pretty much had the same results. Changed back to 9.0, set disc all the way to 6 and turned sens down to 40. Still had a little chatter but at least it was useable. This was all with the 11" coil. I have not had the opportunity to try the 5" coil at this location.

I found non-ferrous targets down to about 7"...nothing was measured but I bet that is pretty close. So far the LTD2 and the AT Gold are running neck and neck for depth in this location.

Is there a simple test you are doing in the field to verify (air test maybe) that you are on the lowest EMI frequency. Or simply the quietest one....Would be cool if Fisher would incorporate an auto scan feature.

I am still learning the LTD2....going to take awhile to see what works best for me. Sooooo many combinations.

This little test was all done in BP, sens 99, disc 1, 4H tones, I laid out a couple square nails on the ground say running East to West with a quarter in between them, heads of the nails within 1/2" of the quarter. Keith spoke of something similar in a previous post, thought I would see what happened. With the 11" coil sweeping East to West all I heard was the iron, North and South would pick up the Quarter a small percentage of the time.

Switched to the Nel sharpshooter coil that came with the package. Something interesting.....When sweeping East to West the front half of the coil would only hear the iron, the back half of the coil would hear the nails and the quarter!!

Switched to the 5" coil...it would report the quarter and iron no matter what direction the coil was swept.

I know this has all been done before and we know the 5" coil is a rock star in trash. What I found interesting was the Nel sharpshooter would only report both iron and quarter on the back half of the coil. I may send an email to Nel and ask if this is normal. If it is normal, I'm going to sell it.

Thanks again

Kenny

Tom, how would you compare the f-75ltd-2 to the GMP for unmasking with high emi in the area?....11"dd on the 75, 9" on the GMP.

Or, same detectors in medium to low iron/trash, no emi.....throw depth comps in there also, if you don't mind, Thanks.

ALSO noteworthy: In my test-garden...... with the new LTD2....................... with freq selection F7, I encountered a 2.7" depth loss difference on a clad dime.... when compared to the other (F1-F6) freq's/channels. There was NO audible EMI on any one (of the 7) channels. The next day, F4 was the least-performing channel..... and F7 was one of the better performing channels. Soooooo....... How would you know that you are operating on a 'reduced performance' channel!
Moral of the story = Do not think... for one moment................ that EMI & silent EMI does not affect other detectors!


Could a person after a target is acquired in a particular site, say moderately deep, then switch channels and compare signal?? And maybe find the best channel to work around the silent EMI????

ddmk = Very good question....... and ........ time permitting ........ would answer. SO..... I'll answer it now:

When all (F1 - F7) channels are quiet..... how do you know which channel presents the best depth/performance level.
FIRST: Yes, an air-test with a clad dime. Coil MUST be parallel to Earth.
SECOND: I will then find a deep target...... (prefer a higher conductor)...... then verify if the best air-test channel/Freq still remains the same. . . . with the deep dirt target. IF NOT....... the Freq/Channel that works best with the dirt..... remains the trump card.

ddmk = Your 7" max depth performance/resultant in real dirt.....with said settings......... is exacting. With the amount of (stated) EMI...... in concert with Disc 6 and Sens 40 (which is still a lot of power/Sens/performance) is right on target. Remember..... If you are encountering EMI that is causing the detector to audibly chatter (probably like crazy!)..... with according low/mid/high tones....... and is emulating targets with a signal strength/intensity of targets that are 7" deep: .......... guess what? You must then detect targets that produce a signal strength of 7" deep and/or STRONGER....... in order to override the strength of the existing EMI...... in order to detect any targets.

You will be surprised as to how powerful/deep/sensitive the 5" DD coil is. You will also be surprised as to how well this factory little coil will 'adjacent target' separate.

((( Your finds/discoveries with the NEL coil..... are on-par ))).

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

Steve. Funny you should ask. I performed just exactly this. Also prompted a epiphany. Stand by.

Thank you Tom.

I gave this a try today at one location where EMI was silent. I did in fact observe one of the frequencies had less depth during airtest.....I didn't use that one :-) It was an obvious, noticeable difference. I appreciate the tips.

So many things to learn with this machine. I have 12 pages of F75 topics printed off for review while I'm getting familiar with this unit. Been running it pretty steady for the last week, I'm still not clicking yet.

Kenny

Time to catch up with questions.... and more data.

Steve: I am finding nearly identical EMI handling capabilities between the F75 LTD2 with 11" x 7" coil ... vs ... GMP with 9" coil. And this is in fairly heavy EMI areas. The difference is........ the LTD2 is substantially deeper than GMP......... but the GMP unmasks substantially better than LTD2. Put the 5" DD coil on the LTD2...... and the unmasking "difference" reduces quite a bit ..... but is still not matched. GMP is...... by far ........ the best unmasking detector on the open market. This includes iron and aluminum unmasking.

This past weekend, I hunted a particular area where a bit of electronic information became exceptionally clear/evident/obvious. With a standard LTD...... EMI was fairly heavy, requiring some drastic EMI reduction methodology to be implemented. Sens on '45', Disc on '5' and best F1 - F7 freq selection required. I was (limited to) capable of finding coins to 9" depths. Switching over to the LTD2....... and I could run Sens on '99' and Disc '0'...... with no EMI issues audibly noticed. This is also to say...... the LTD2 was very quiet, stable...... and a pleasure to hunt with. Still, I could only detect coins to 9" depths. Marking several of the deeper (9" coins)....... I then tested the GMP. No joy. Not detectable. A couple of the 9" targets would give a audible report...... but exceptionally faint/weak audio...... that merely sounded like a minute' false chirp/chatter. Two thoughts come to mind; Although the GMP was very stable/quiet........ EMI (in silent fashion) was operating at a reduced performance level. And....... possibly........ the GMP operates/performs better with a different type of soil.

This particular dirt..... especially the top 6" - 7"..... has the texture/consistency of cool-whip/marshmallow-topping/miracle-whip/whipped-cream. It is a very light, aerated, low density type of soil. One of the dimes found at the 9" depth strata was a nearly uncirculated 1985 clad dime. And same with a 1985 nearly uncirc quarter at 9" deep. This dirt is undisturbed..... and the surrounding houses dates back to 1877. Disheartening to know the 1985 coins are 9" deep...... and no idea how deep the 1885 coins are.

This is also why the GMP has limited application/usage/capabilities in Florida's fast sink-rate soil,,,,,, due to it's lower depth capabilities. F75's, CZ's and Minelabs are still the 'depth' trump-cards.

Hi Tom,,,once again very good info for me to absorb....Boy your sink rate is phenomenal in your area....In order to pull older coins etc. you must seek out areas with a low sink rate if they are available........JJ

Sink rate must very a lot. The 1906 Indian I found was only three inches but the retired golf course old stuff is at least 8 inches or more. 5 miles same terrain.

jimmyjiver Wrote:
-------------------------------------------------------
> Hi Tom,,,once again very good info for me to
> absorb....Boy your sink rate is phenomenal in your
> area....In order to pull older coins etc. you must
> seek out areas with a low sink rate if they are
> available........JJ

Bryanna - Nebraska

Current - New to me but not new MXT Pro and T2 SE2 - Previous Minelab Sovereign GT, Minelab Safari, Whites DFX, Whites Eagle Spectrum
Smile its a good for you!

jj & Bryanna = Exactly & Exactly!!

Bump

> * In air-tests............... switching through
> any/all of the process modes (then invoking All
> Metal mode)........ and there is a very minimal
> gain/loss. Nearly the same air-test distance
> performance. In the ground...... the resultant
> differential is dramatic.
>

Hi Tom,

I have been reading and re-reading all of your data. Incredible amount of effort you put into this "hobby". Thanks again for sharing. Any chance you can expand on this? I have a hard time comparing my results with anyone's because my soil is pretty tough. Stick a magnet on the groung and you will come up with a handful of rocks lol.

Just wondering what differences you are seeing from say BP mode, to all metal, airtest and in ground.

Thanks,

Kenny

Hi Kenny,

Glad all this stuff helps. I'm still testing (for more definitive results)...... the differences between all-metal vs ID (especially bp) mode.

Thanks Tom, definitely interested in your findings.

One reason..it seems like BP is not carrying over to All Metal on my machine. In all metal (air test) I can hear a nickle at 13" max. Disc mode, BP I get a good tone at 16".

But.....in the ground (my horrible test garden dirt) I can hear a dime in BP, 99 sens, 1 disc, 4H tones....6" max. I used your wooden dowel trick when planting my coins so I would know how deep they are. If I lift the coil 1/4" I can not hear the dime.

Much stronger signal in All metal mode on the 6" dime and the ID is still hanging in there as well. The only downfall to having the deeper all metal mode in my dirt is once I get past the 6" mark I start losing visual ID. (which makes sense because I lose tones at that depth) So it kind of becomes a beep and dig after 6" in all metal.

Something interesting, the AT Gold all metal ID's better and deeper in my dirt, but it is greatly effected by hot rocks. If I switch over to disc one...the hot rocks disappear but, sadly, so does about 2.5" of depth.

Now the F75 I can run in disc 1, BP, 99, 4H and I know anything past 6" is a crap shoot but hot rocks do not effect the F75 one bit. I can hear them clearly in all metal. but not a peep in disc.

My GPX 5000 with a mono coil is also effected by these hot rocks. If I run in the fine gold timing the effects are very minimal but I can hear them if the coil is right on them.

I find it interesting that the F75 can breeze through these hot rocks in disc mode with nary a whimper. The AT and the GPX both struggling with them.

Sooo......I'm still playing and learning to see how I can wring the max performance out of this F75 in my dirt :-)

Kenny

Kenny,

On page 14 of this thread/post....... there is a 'bp' all-metal mode test results on a buried clad dime. Did that info help you any......... give you a base-reference?

Yes Tom, it helped a bunch. I was just wondering if your testing is trending the same as what I am experiencing.

In airtest, my disc mode is much stronger than all metal, by 3 to 4 inches. However, in ground tests it seems my all metal may be performing better than disc. I just lose any kind of accurate ID past 6" in all metal. I haven't had time to see exactly how much deeper all metal is yet.

Plus, I'm trying to figure out if my all metal is really working 100%. It seems a little weak compared to disc (in airtest). I think in my soil, all metal is going to be my best bet. Want to make sure it's up to par.

Kenny



Edited 1 time(s). Last edit at 04/16/2015 11:43PM by ddmk6.

Shame this post can not be kept as a sticky for all those needing this great info. I find it hard to believe there is no means available to make this most informative post readily available ?????????????

silverhound Wrote:
-------------------------------------------------------
> Shame this post can not be kept as a sticky for
> all those needing this great info. I find it hard
> to believe there is no means available to make
> this most informative post readily available
> ?????????????


It would be awesome to see all of Tom's test data posts extrapolated into a separate sticky that way we wouldn't have to wait 30 pages of stuff to get to the relevant points

I'm leaning more and more to the quiet DE and JE modes rather than the BP mode on my LTD2. It seems to me that the audio has been compromised on the upgraded units running high sensitivities in BP. CL in disc mode sounds terrible.

Has anyone else experienced that?

I just dusted off the big white Fisher 15" DD and found it to be nice and quiet in JE pounding my deep targets in my test bed with ease. Mount it backwards to improve the ergonomics.