Rcpt Ack of F75 Ltd prototype

Fascinating answer, sir! So much info there, which by the way answers so many tangential questions I had (for instance, I had NO IDEA an elliptical DD, and that "narrow" footprint I love, is a "severely reduced" depth coil, compared to a round DD or especially a concentric. I don't like the "less narrow" footprint on the round DD Minelab Pro coil, as compared to the Fisher coils, and I wondered why in the world Minelab's engineers didn't make it a narrower-footprint elliptical; now I know -- to maximize depth capability while staying with the DD design!!)

So, to theoretically put a DD on a CZ, and then to get the same depth, you would end up having to jack it up into "chatty" territory, sensitivity-wise. Now, I get it. BUT, you have me intrigued by something...you alluded to an F-75 running at the CZ frequency. A fascinating thought...

I imagine an F75 LTD -- except altered, to run a second frequency simultaneously with its normal 13 kHz -- the second being the absolute optimum frequency to "resonate" (if that's the right word) with silver...and matched with the best coil for the job...

Anyway, back to reality -- thank you for a most informative answer...

Steve

Your "fascinating thought" (s)..........may ascertain fruition.

Thought I provoke this with an interesting question. Why does the Omega go slightly deeper or about the same with the 11" DD coil than it does with the concentric coil? Shouldn't the depth of the 11" DD be reduced with everything else being the same on the same machine, and the coils are very close to the same size as well.

Thanks

NASA-Tom...most interesting. I await with bated breath...

Steve

Sensitivity...here's one for the books. Went out today with the T2 (standard model). Using stock 11" DD coil. Usual Idaho .1 to .3 Fe iron rich dirt. "Sensitivity set to 50". "Disc at max...80"......tones at 3. The T2 is being chattery as hell from EMI with coil stationary....so we know its EMI interference. Blip......get a high tone. Dig down to 9"...yeah....I verified the distance.......and no the coin wasn't a drop back down in the hole situation. Get this.........its a 1940 nickle.......not a partial silver war nickle....just a plain o'l nickle. How in the Sam Hill did the machine pick up this disc'd out coin. And yes, the hole was thoroghly scanned after nickel extraction.......with the T2 & Garrett's Pro Pointer......no other metal in/by hole.
Tom D......care to venture an opinion?

I'll venture an opinion...your T2 ID'd that nickel NOT as a nickel, but as a high-tone coin, and thus, while it was a nickel, it was NOT disc'd out.

I remember my F-70 would sometimes ID a deeper nickel in my test garden with a much higher VDI/tone that in should have...and if I recall, the Gold Bug Pro is capable of that, I'll have to double check...

Anyway, I know that's only a partial answer at best to your question, as my opinion offered here only changes the question slightly -- the question, to me, is now, WHY did the nickel ID as a high-tone coin?

Steve

Sounds like its just going after a round shaped object.......not metal content, past a certain depth. Makes sense. Maybe First Texas programs the machines that way.

Interesting finding about the nickel, all I can say is that my T2 will give a high tone for a nickel in 3 tone, but if it was discriminated out I am not sure why it would give a tone at all.

But we are getting a bit off topic, so I will repost the question so Tom doesn't miss it, as i would like to know more about DD vs concentric coils.

"Thought I provoke this with an interesting question. Why does the Omega go slightly deeper or about the same with the 11" DD coil than it does with the concentric coil? Shouldn't the depth of the 11" DD be reduced with everything else being the same on the same machine, and the coils are very close to the same size as well."

Thanks

could it be that in your soil, which is much like mine the T2 can not accurately ID past about 6"-7". Anything beyond that it sees just as a ferrous target.
So the disc would also not work at that depth. Put the nickel at 6-7" and you don't see it.

Last 2 pages have been really interesting guys. Steveg - I don't have one (I have an Omega 8000 - great coin machine) but you might want to check out White's V3i. It is a bit overwhelming (though the new Vx3 isn't - essentially a reduced option V3i) but it seems to have what you are looking for, except for the light weight design. But well balanced from what I have read and it has a round DD coil. I guess I understand now why White's did what they did with the coil.

I have read that the great depth of the V3i is not due to power alone, but rather very nice discrimination and sensitivity programming (I forget exactly what I read.) It ID's very well at depth. Further, overpowering the unit will hurt your depth - no shock. It's a complicated unit that would need lots of playing and testing to understand. Have you seen the V3i air tests? Absolutely insane. (12" on a quarter - with ID, 10" + on a dime). And the kicker is, it gets incredible depth in the ground. From the whites forum I quote "I have pulled silver dimes at 9-10", quarters at 13", rings at the beach in wet sand at 10"."

I'm on the fence about getting one but it sure has the capability to do what one wants. The recovery speed and filters are very adjustable and I would imagine it's in the same group as the F75Lmd and Deus, but better on depth no doubt.

Also, the V3i has 3 simultaneous frequencies as well as 3 separate frequencies. That coupled with the programability means you could set up programs to be "checks" in other or multiple frequencies. A guy out here in Europe (England) just release a short book on it too. If you like fidgeting around, it sure is the detector to pick.

Would love some V3i guys to jump back into that V3i thread...

Fringe-depth nickel.......and some mineralization can cause that nickel to 'up-average' on the ID scale. This has happened to me numerous times. Once the nickel is out of the ground........it no longer ID's as a high-conductor. Also .......some fairly low conductive targets that are not nickels......have 'up-averaged' (primarily due to fringe-depths).......that have prompted me to dig.

!0" elliptical concentric...................vs........................11" DD coil. In theory............it sounds like ONLY a 1" difference. . . . . yet, if you hold the coils back-to-back ..to each other.......you will start to see the difference. There is a large size differential. The 10" coil is quite a bit narrower in physical size........quite a bit smaller in physical size. This is also to say 4/3-PI-R-cubed.....whereby the 'cubed' portion of the equation is what exposes the real answer. The elliptical concentric coil is QUITE a bit smaller than the 11" DD coil.

Hmmm, Thanks for the info Tom on the DD vs concentric, I think i am going to stick with the 10" concentric on the Omega, and will have to look into one of those huge DD Neil coils for the Omega vs the 11" DD as I will be traveling in the city they are being made in a month or so. Maybe I will pick one up, will see, not yet sold on their overall value though.

hey earthman...

Thanks much for that input. And it's funny, you are spot on, in that right now the two machines I am most intrigued with are the CZ-3D, and as you suggested -- the V3i. This machine has had my interst and attention for a little while now. The V3i does -- just as you noted -- seem to have many of the features I've mentioned, but the complexity sure does intimidate. I felt the same about the Minelab FBS machines for the longest time, before I got one -- the difference being that I had several hunting partners using them -- which helped to shorten the learning curve.

Anyway, so as to not take this thread off into the weeds any farther, I will stop here about the V3i, and go visit the V3i thread. But I thank you earthman, and really appreciate your input and help.

Steve

I have been asked the exact same question (via PM) from two independent individuals regarding loss of performance from EMI; hence, my 'bumping' this thread to the top. Start with page 4 of this thread..... and read forward. This 'should' answer your question. If not..... PLEASE ask your questions on this forum.... and not with a PM. ...Share!

NASA-Tom Wrote:
-------------------------------------------------------
> Your "fascinating thought" (s)..........may
> ascertain fruition.

Vision of the (hopefully near) future?

Bite your tongue!

Since this thread is difficult to find...... let me just 'bump' it to the top........... per request.

Yeaaahhhh

I have had a white 15" DD coil for the F75 (F70)..... for some time now. A few incomplete things to state for the record:

Installing this large coil on a standard F75...... presents virtually no 'realized' performance gain. Nearly no depth increase/decrease.... on a wide spectrum-of-conductivity of targets.... and of varying sizes. In fact, the additional ground coverage is not linear..... as you would perceive.... considering the extremely large differential between the 7-11 stock coil vs the 15" coil. There is not much increase in ground coverage.

Also..... about a 15% increase in EMI is realized with this larger coil. Large open areas/fields in the country is where this coil can be utilized.

Onward to the attributes:
When you enter the boost-process mode of the F75..... many things change. As long as mineralization is fairly low.... a very noticeable performance gain is realized in the 'bp' mode. Even more gain is realized in the 'cl' mode. (((I have a proto F75 LTD with yet another boost process timing circuitry..... that also shows yet another gain in performance; but....thus far.... is hardly usable))).

As I am waiting for Florida's tropical fat/swollen/thick/tall grass to die-down for the winter......... I will report more data on the attributes of the 15" coil. . . . when conditions allow.

I had a F75 Ltd, I used the 15" dd coil on it & it had a depth advatage over the stock 11" coil. I hunted a civil war camp with the stock 11" coil & didn't find much then the 15" coil & I found reilcs. It allmost gave me the same depth as my CZ 3D. All I know is I didn't find anything deep with the 11" coil. I found things with the 15" coil & none of them has the depth of the CZ detectors. Thats my observation. The ground here in PA where I hunt has a good amount of iron mineralized ground.

It may be that the multi-freq CZ-3D compensates for your dirt conditions better.

I really think that's it. I hunted this same camp with a Spectrum XLTbefore I got a CZ 7a pro. The first time I hunted this camp with the CZ 7a pro I would sware I had never hunted this site. I know I dug things at least 3" deeper than my whites.

Have you used the Sunray 12" coil & what's your oppinion about it? I have one It's a little unstable on my 3D. At times I cant use it & have to go back to the 10.5" stock coil. It runs smoother on my CZ 7a pro. The CZ 3D seems to be a more sensitive machine.

So, what I am getting out of this is the F75 LTD and the F75 regular do not differ appreciably at all, except the fact
there are 2 different modes on the LTD, and in BP mode on the LTD you get +0.2 inches more depth on a dime?

Is that right?

So, what I am getting out of this is the difference between the F75 LTD and the F75 is the fact the
LTD has 2 extra modes, and in BP mode you get +0.2 inches on a dime?

Is that correct?

Reading over some of this exellent information, a question comes to mind: How does the 5" coil on the f-75 compair to the 4" coil on the cz3d for unmasking?

The reason I ask is: Through reasearch, I located a baseball park that was there in the 1920's and is still there today. It's at the end of this little old historic town. Today it looks more like a sandlot ballfield with soccer fields added where the far outfield use to be. The backstop has old wooden posts still in the ground with a newer chain link stop. The base lines are gone (grass grew in) because of little or no use of the field but it is still cut.

I took the old f-75 there one late afternoon with the 11" coil, leaving the cz at home. I don't have the 5" coil but I do have the 4"x 6" (left at home also). I have the 4" for the cz.

As you can imagine, detecting around the backstop, I was getting hundreds of tones. I was able to squeek out two 1918 wheats and a barber dime. I'm not sure if the field has been filled over the years, my guess is it has been, because under the sod, it's sand. Anyway, I have good hopes for this field and want to bring the best tools for the job.

If the 5" coil for the 75 would be the ticket, I will purchase one.

If the 4x6 (for the 75) or the 4" (for the cz) will do as well, no need to buy the 5".

The f-75 ran nicely until I got close to the street, then it picked up emi.

This was just a test run on this field, next time I want to go loaded for bear. Thanks Guys!

Well Oz...when I had the T2 Standard model, its 5" could easily hit a dime at 6" in heavily mineralized Idaho soil. I think Tom prefers the 5" over the 4x6 for depth & seperation.

I still want to find more concrete/definative data on the boost-process modes of the F75 with 15" coil installed before making too many claims. I will also keep this data in this thread.

As for the 5" coil on the F75 vs 5" coil on the CZ..... the F75 5" combo is superior.... and by a large amount...... in regards to extremely enhanced adjacent target separation characteristics. Depth is nearly the same..... with a slight lead going to the F75 LTD (whilst in 'bp' mode).

Back when I purchased the 4x6 coil for the 75, there wasn't enough info to sway me either way, so I did the eeny meenie miney moe way of choosing. That worked out well, at least for the dealer.
Thanks Terra, Thanks Tom.

Hey Tom, have you any preliminary test results on the big white 15" coil? I love swinging it for the 5-10 minutes till my arm falls off.