Rcpt Ack of F75 Ltd prototype

I love these tests

LowBoy

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If you don’t dig it, then how are you going to know what you’re missing!
How can you have your pudding if you don’t eat your meat!

IMPORTANT PERSPECTIVE:

On the bottom of page 2 of this long thread is a link that connects you to a photo of a tiny aluminum 'blue dot' resting on a dime. The F75 LTD will detect this tiny blue aluminum dot to approx 1" in ideal conditions. The Gold Bug-II will detect this same blue dot to nearly 4". (((The Gold Bug-II is MUCH more sensitive to "micro" targets due to high 71Khz operating freq))).

Now.........under ideal air-test conditions; the Gold Bug-II will detect a Type-1 U.S. $1.00 gold coin to approx 9". Under these same ideal air-test conditions, the F75 LTD (in 'cl' mode) will detect this same Type-1 $1.00 gold coin to nearly 17".

This is a huge 'usable' attribute for serious relic hunters.......as you do not want to find 'micro' targets; rather, you need to be able to find very small low-conductor 'relic' targets with tremendous sensitivity abilities.

Tom

Limited "F75 LTD" is now discontinued. It may be a little while before a new release. Hold on to your current LTD's.....if you have one. And don't worry; 'bp' & 'cl' lessons learned!

I have made a VERY concerted effort recently with the LTD ...to hunt BEHIND a standard F75 at 11 different locations (and 11 different days) in a COIN HUNTING 'focus' (capacity) only. More specifically.....for lunch money at old schools. Lunch money IS nickels. In 1930.....school lunches were 5-Cents. You lose your nickel.....you lost your lunch! These 11 sites were old schools.....of where I have found voluminous amounts of early Buff's and 'V' nickels. The low conductivity of nickels is very important to the F75/LTD.
Results (compared to standard F75): NO JOY.
Summation: IF you are a coin hunter ONLY...........and you are contemplating upgrading from a standard F75 ... to the LTD......it is not necessary. HOWEVER, if you are a relic hunter.....the LTD is a tremendous boost over a standard F75. There is a HUGE difference on smaller low-conductor targets with the LTD. The TYPE-1 U.S. $1 gold dollar coin is still the bench/standard......and with stunning differential/delta.

Tom,

Why wouldn't the lower conductivity of nickels and gold coins give the advantage to an LTD over a standard F75 ?

Thanks.

Wouldn't the boost mode and air gap help in hunting tall grass? Some parks and schools or fields have a few inches (3") before you are hiting the dirt I would think the LTD would offer more help?

LowBoy

TAKE A LITTLE TIME KICKBACK AND WATCH SOME OF MY DETECTING VIDEO'S BELOW ON YouTube

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If you don’t dig it, then how are you going to know what you’re missing!
How can you have your pudding if you don’t eat your meat!

Of course remember Tom brings out the best in a detector due to his expertise and your results may differ in your neck of the woods as conditions vary from State to State or for that matter area to area. I tried the F series from the new Fisher
and the EMI drove me crazy so went back to my old favorite the CZ. Having said that remember the old Fisher 1265-1266 would drive one crazy with its snap-crackle and pop but was and still is a favorite of many detectorist old technology or not...

All I can say is I am finding more gold than I have in 40 years of detecting with my LTD. It's really amazing. Don't know the W's but I'm digging it.

The machine is a beast and has many many setups.

In a natural setting.....the F75 LTD would acquire a nickel to depths just barely over 12". A standard F75 would be right at 12". YES......definately......IRT a larger air-gap w/LTD is there/available/advantageous. You can have a several-inch air-gap and still acquire a 11" deep nickel with the LTD. Not so with the standard F75. And Yes......the LTD is MUCH hotter on conductors that are lower than nickels.....such as thin/small womens gold rings (usually adorning stones). A thin wire-band 10Kt white-gold size 4 ring at 10" may not be detectable to many detectors........but the LTD in boost process will slam out a audio response on this target.....and with a several-inch air-gap. TRY IT! Make sure you test your other units on this same target.

However, as I've proven to myself in my silver test bed... my LTD in BP mode trumps the same unit in juiced DE mode on deep silver that read as fringe targets with the original F75.

In my red clay soil, my two dimes buried at 7" and 8" appear and disappear during the summer depending upon the moisture when testing in DE mode.

So far, checking in BP mode, the dimes always hit well and always hit harder compared to any of the original F75 modes.

So, in my soil, my LTD is an improvement in "coin hunt mode alone", compared to my original F75.

That's good to hear. Yes, soil mineralization and moisture content DO play a role.

NASA-Tom Wrote:
-------------------------------------------------------
>
And Yes......the LTD is MUCH hotter
> on conductors that are lower than nickels.....such
> as thin/small womens gold rings (usually adorning
> stones). A thin wire-band 10Kt white-gold size 4
> ring at 10" may not be detectable to many
> detectors........but the LTD in boost process will
> slam out a audio response on this target.....and
> with a several-inch air-gap. TRY IT! Make sure you
> test your other units on this same target.

Just curious, do the particular settings used during your LTD "micro gold experimentation" alter automatically if you switched into a prospecting mode?
And if they do, once in the prospecting mode, can you alter those earlier settings back to the processor, while keeping in the prospecting mode?
If so, then the LTD would also slightly out detect the F-75 as a prospecting machime, unlessthere are other varients such as if, let's say, the F-75 supercedes in particular soil conditions...Otherwise the LTD should also beknowfor it's greater performance as a nugget hunter...tbhis might sway a buyer to the LTD direction if they live in areas with gold deposits.
-Mike



Edited 2 time(s). Last edit at 03/08/2010 01:07AM by PanMan.

Mike,

The LTD in the new 'bp' mode .....is QUITE a bit hotter on small gold....vs....the 'je' mode. Time-and-time again......I keep testing/proving the 'bp' mode OVER the 'je' mode; so much so......that I have NO NEED for the 'je' mode any more................making any setting in the boost mode(s) ... transferable to the 'je' mode.... a moot point.

Tom, the JPG file link mentioned in page 2 seems to be DOA, at least last few times I tried. Can you put it back on the site. TIA - Gary

I'm not sure which link?????

NASA-Tom Wrote:
-------------------------------------------------------
> I'm not sure which link?????

I believe it to be the small blue dot which depicted the F75 LTD's ability to signal on very small targets. Link didn't work for me either.

Hmmmmmmmmmmmm. Let me hit-up my web-master on this.

NASA-Tom Wrote:
-------------------------------------------------------
> I have made a VERY concerted effort recently with
> the LTD ...to hunt BEHIND a standard F75 at 11
> different locations (and 11 different days) in a
> COIN HUNTING 'focus' (capacity) only. More
> specifically.....for lunch money at old schools.
> Lunch money IS nickels. In 1930.....school lunches
> were 5-Cents. You lose your nickel.....you lost
> your lunch! These 11 sites were old schools.....of
> where I have found voluminous amounts of early
> Buff's and 'V' nickels. The low conductivity of
> nickels is very important to the F75/LTD.
> Results (compared to standard F75): NO JOY.
> Summation: IF you are a coin hunter
> ONLY...........and you are contemplating upgrading
> from a standard F75 ... to the LTD......it is not
> necessary. HOWEVER, if you are a relic
> hunter.....the LTD is a tremendous boost over a
> standard F75. There is a HUGE difference on
> smaller low-conductor targets with the LTD. The
> TYPE-1 U.S. $1 gold dollar coin is still the
> bench/standard......and with stunning
> differential/delta.


Tom, can we take this statement about being a coin hunter and upgrading from the F75 to the LTD is mainly for the soil where you live?

Soil does play a important role...........and the LTD will take more 'snapshots'........possibly giving a better edge in bad ground........yet, , , if the standard F75 can not detect a certain-depth coin..........the LTD will most probably not 'bring it to light' either..........HOWEVER, , , coins that are 'somewhat' difficult to ID due to bad dirt.....of which give a heavily bouncing ID........may/should have a better chance at a more accurate ID with a unit that can take more snapshots of the coin.

Bringing to front.......per request.

After reading the post below and pondering the entire event for several hours a thought came to me.
What if while hunting with the LTD you have a location that has above average EMI the particular day you are hunting. Switching out to a smaller coil, either the 6 1/2" Elliptical or the 5" DD and check if the EMI is eliminated or reduced to near zero. By all reason the performance loss due to EMI might be regained by switching to a smaller coil. On occasion I can switch to my 5" DD coil and run the machine completely maxed out with no EMI that I can hear. Thoughts welcome.




NASA-Tom Wrote:
-------------------------------------------------------
> I have been remiss on providing certain info.
> After a hard-core detecting
> reiteration/experience.... I have positively
> verified serious performance gains with low EMI
> vs. extremely low EMI...... and this is in the
> real world. I have witnessed/experienced/verified
> this with the T2 several years ago.... then with
> the original F75...... and now with the Ltd. This
> should seem/be 'common sense'... but well worth a
> write.
>
> Several weeks ago, I reported finding 141 more
> non-ferrous targets in a ...beat-to-death....
> small area with the new Ltd. ,,,,,,, I went to
> the exact same spot a few days ago to try one
> additional experiment with the new Ltd. The last
> time I hunted there...and found 141 more
> non-ferrous targets...... I could run the Ltd
> wide-open w/Sens on '99', Disc '0', 'bp' & 4-tone.
> There existed a moderate amount of EMI when the
> coil was stationary...and not flat/parallel to the
> ground. Whilst sweeping the coil on the
> ground......the EMI went away.... and 141
> non-ferrous targets were located.
> NOW...............fast-forward to just a few days
> ago. Exact same spot. I set up the detector to try
> the 'cl' mode......and noticed that NO EMI was
> present. Immediately, I switched over to 'bp'
> mode..... and STILL no audible EMI. . . . . and
> this is w/Sens on '99', Disc '0', 'bp',
> 4-tone.....everything max'ed out.......AND,,,,THIS
> IS WITH THE COIL IN THE AIR AND STATIONARY.
> Because of this.... I decided to cancel my intent
> to try 'cl' mode .... at least for a while......
> and hunt in 'bp' mode. Something seemed wrong with
> the detector....as if Sens was nearly zero....and
> the unit was operating at a severely reduced
> performance capacity......due to such low EMI.
> Sweeping the coil.....and in the exact
> direction/footprints as from when I had located
> 141 more non-ferrous targets......and my
> suspicions would instantly be invalidated..... as
> I found ANOTHER 92 more non-ferrous targets.....
> in this exact same location. Low EMI vs. near-zero
> EMI made a tremendous difference. Percussion caps
> were detected down to 12". I've never seen this
> type of performance before.
>
> It's in the finite details.
>
> Tom

Yes, this can be true.

BUT


What is usually the 'norm' is: If the F75 is limited/inhibited to detect a certain/specific target to only 9".......due to EMI..................((( but could otherwise detect this same/exact target to 12" when no EMI is present ))) then...........switching to a smaller coil, you mitigate the EMI.......but (now) can only detect this same target to just barely 9" (not restricted by EMI....but, rather, max detectable range of the small coil)...........and acquire this same/exact target. Your end resultant is that you achieved the exact same depth performance...........but with substantially less fatigue/EMI.

Clear as mud?

Upon receipt of a G2..........due to the nature of its operating characteristics...........I will (somewhat) tie the field-test report to this thread.

Does "no joy" mean these modes did not report the gold coin with a beep?





"BURIED 9" deep. Settings: SENS '90', G.B. '90', 4-tones & DISC '5'

pf/de = no joy
bp = 9" + 0"
cl = 9" + 2.1"airgap
----------------------------------------------------------

Buried 9" deep. Settings: Sens '90', G.B. '90', 4-tones & DISC '4'

pf/de = no joy
bp = 9" + 0.6"airgap
cl = 9" + 2.7"airgap
----------------------------------------------------------

Buried 9" deep. Settings: Sens '90', G.B. '90', 4-tones & DISC '0'

pf/de = no joy
bp = 9" + 0.8"airgap
cl = 9" + 3.0"airgap "

Mark...........yes............"no joy" means: "Not Detectable".

A topic well worth revisiting. F1 - F7 EMI mitigation. I know I have touched on this topic before......but now, I have much more amplifying information. I know I should utilize a U.S. $1 Type-1 gold coin.....as this is the perfect resonance (pinnacle performance) of the F75/LTD......yet, I used a common clad dime for better audience understanding.

Taking a U.S. clad dime to a area that presents near perfect conditions for testing. Here is the importance of Freq Shift (F1 - F7) .... so as to achieve maximum performance. At a local park, , , burying the dime @12"......in sanatized dirt........and virtually no EMI presence......the F75 will (just barely) detect this dime. Changing the frequency from F1 through F7........no EMI change of status (no audible EMI present on any channel).......... and also no change in performance of 12" dime detection with F75 LTD. The CZ-3D will also detect this dime with zero problems.

Moving 75-feet away from this location......where EMI is "moderate"......and a huge (and measureable) delta occurs. With the dime buried at only 8"...... a dramatic incursion ensued. Selecting the BEST frequency that provides the least EMI......and this dime can be detected with ease......AND this is to include over half-a-foot of air-gap over the ground. Yes.....this is to say that the coil is 6"-plus inches above the ground PLUS the 8" that the dime is buried. A total of 14"-plus inches between coil and dime.
Now........Selecting a different frequency that provides/presents a noticable amount of EMI (and this is NOT the worst channel/freq selection; rather, a 'middle-of-the-road' selection).......and the detection of this 8" dime is COMPLETELY undetectable. Here...........The CZ-3D still poses extreme audible stability.........absolutely no idea there is any form of EMI what-so-ever....BUT, BUT, BUT......the CZ will only detect this dime to 10". This is categorized as the most dangerous type of (electronic related) hunting......because the operator has ABSOLUTELY NO IDEA the unit is operating at a reduced performance level. Unsuspected and undetected/unknowing reduced performance. The operator would NEVER know it; subsequently, never suspect any form of performance reduction.

THE BEST WAY TO REDUCE EMI: Place F75 in all-metal mode with max Sens ('99'). Hold coil about a foot above the ground.....very still......and perfectly parallel with the ground. Select F1 through F7.........one at a time...... and listen to each channel/freq for about 4-5 seconds. Find the one freq/channel that provides the least interference. Now you can switch back over to the ID mode......and.....yes......this Freq/channel selection will stay the same whilst switching over to the ID mode. If you are running the unit 'wide open'....and you still are encountering EMI..... you can change Disc to a setting of '5'. There is a huge difference between Disc '4'....and Disc '5'. You should not have to increase Disc to higher numbers. If EMI is still present.... you now can start to drop Sens .... until EMI is gone. Remember; you are already on the best possible F1 through F7 Freq/channel selection...and must employ other methods so as to reduce EMI... if it is still present.

If you look at your LCD depth bar-graph......and EMI is causing it to jump all the way into the middle bar-graph (medium strength signal) ............you will only be able to detect targets that are (at least) as strong/powerful.....OR STRONGER (shallower) as that middle bar-graph. This is also to say that......if you want to get rid of audible EMI......you would then be required to reduce Sensitivity to the point where targets in that middle bar-graph (and deeper targets)... would no longer be detected. What you are doing is.....reducing the sensitivity of the detector to 'just below' the signal strength of the EMI. Said differently; If EMI is so strong......that this specific EMI "looks like" a 7" deep target................then the detector will only be capable of detecting targets up to 7" deep....and no deeper... in this hunting area.

Some of the best days to hunt.....as far as EMI is concerned......is at the very end of a hard rain........or shortly after a hard rain......as this is what washes the salts off of nearby powerlines.

If you are 'beating' an old/hunted-out area again.......and you suddenly learn that you are finding a lot more targets........it may very well be that you are encountering less EMI on this specific day.

I can only stress the level of importance of EMI mitigation. USE THAT F1 THROUGH F7 OPTION.

Thanks, that is some very good information. That explains why my f75 is super deep, but only some of the time.

Great info Tom . I dont use the Freq shift, instead back off the sens, that will change now.
In a hunt with my Gold bug at 19,2 and a Troy running about the same and Omega at 7.8
The O8 had a deep dime hit, checked with GB and it hit, when the Troy got close to the GB
both machines started to chirp . I backed off till machines whent quiet . The Troy would not hit
target untill i shut off the GB. Silent EMI i guess you could say.

Tom, since your dirt is basically inert or no minerals can a person expect to get near air test results in ground depth?

Mark,

Yes. And here in Florida........where every metal detector fails to Grnd Bal...(there's no mineralization to Grnd Bal)......nearly all detectors will present virtually the same depth in the ground.....as what the unit would present in a air-test. This (initially) sounds like a major 'PLUS' to most folks.............but...........the trade-off is; this soil is SO soft.....that targets sink exceptionally fast......to .. 'out-of-detection-range'......much quicker than States with bad mineralization. (( In general )).

Back to EMI. Some folks may want to try this test = Find/detect some fairly deep targets. Then......swich to a bad EMI channel. See if you can still detect these deep targets.

Also...............you may find that.......as the day wears on........more power is demanded from the overhead lines; subsequently producing greater EMI........AND of a different frequency. This is where you may be required to change the F1 - F7 frequency AGAIN.....whilst still hunting the exact same area.



Edited 1 time(s). Last edit at 11/08/2011 01:11PM by NASA-Tom.