F75 and aftermarket coils

It seems like this may have been previously covered a long time ago....but I couldn't find anything quite like what I want to find out. So here's a new thread on the topic.

I couldn't stand it anymore....I found a new F75 for a great price and bought it. I couldn't stand being out done by my buddies with their T2s and me lugging around an AT Pro that couldn't hang with them. Anyway, it has been several years since I had the F75. I got the regular one; the boost mode ones do not work well for me in this bad soil, and in addition to that, most of the sites we hunt now are in and around some form of electrical interference....be it from powerlines, fences, etc. So none of those really jive well with the boost mode anyway.

So since I have last had an F75, there are a few coils that have came out on the market that I wanna know about. I like having a little more ground coverage and depth, so I'm looking at getting a 13" or 12x10 range size coil as an addition to the stock coil. Some times we do hit big wide open fields and the extra coverage is welcome. Does anybody have any experience with the 12x10 SEF coil for the F75, or the Ultimate 13"? Those are the two that I'm interested in for now. The NEL also looks good but I'm not sure if I wanna spend that kind of money for one. I had the 15" DD Fisher coil for mine once...and that sucker was too heavy to do anything with. Those 12-13 inch coils are about as big as I wanna go. I had the Ultimate 13" for the Omega and it really brought that machine to life and didn't weigh much at all...but a friend of mine had one for his T2, and really didn't see any improvement with it. It seems like I vaguely recall one of my other buds running one on his F75, but I've slept since then and can't remember what the outcome of that was...but it makes me wonder if I would see the same thing as my buddy did with the T2.

So that's where you guys come in. Surely there is somebody out there that has some experience with these.



Edited 1 time(s). Last edit at 09/10/2013 03:00PM by Daniel Tn.

For what it's worth...when I got this new F75 and ran it through my test garden...it enlightened me to see just what all I have been missing. As a good example...I have several Civil War bullets buried at various depths in there. One is relatively shallow at around 4 inches...and another one was at 7" when I buried it eight years ago. When I got the AT Pro and went out there...I was surprised to see that it was hitting what I thought was the deeper bullet with a faint but good audio. I thought...wow...I've had some high dollar machines that couldn't hit that bullet as good as the AT Pro. So all this time, I've been confused as to why in my yard, I could get a bullet at that depth....but in the field, I wasn't seeing anything of that sort. As soon as I got the F75 home, I found out why. As it turns out...the bullet I was locating with the AT Pro was actually the shallow one, and I didn't get anything at all once I had really located the deeper bullet with the F75 and then checked that with the AT Pro...and that is exactly the same kind of thing I was seeing in the field. I should have done a better job marking out my spots...at the time I made the test area, I was into detecting a lot. Then after a year or so break and getting into other things, I could only remember the ball park area of where and what each of the items were in the yard. At one time, I had them marked with golf tees but they have long since disappeared.

I think maybe you will get more coverage Daniel, but little if any depth by using the bigger than stock coil on the T2/F75....

now the big 15 FT coil I hear is a little deeper and still sensitive but really really heavy....

I will say the T2/T2 s.e.now is one of the best detector's made in the last decade....

I have a proper F75 s.e from Tom.. But Is till prefer the T2 S.E. the most..It get's the most use...

The T2 is a relic monster on relic brass and also button's....The F75 seems to lean more towards the coin's...the T2 will dig some awfull deep button's in hunted out spots in bad dirt...

they both are excellent machine's to have on hand..Either work well..

Keith

The SE models might be good else where, but are basically useless around here. We have so much stuff that causes interference with the B.p mode, that you can't even run in it unless you run the sensitivity at around 30 or lower. Here lately, we've been finding more relics in urban areas than we have in the country away from all the power lines, houses, etc. The guys I've been hunting with have schooled me on how much stuff can come out of a 10x12 area of grass in a city lot. With overhead power lines, or underground stuff...it makes it hard on detectors as amp'ed up as the F75 and T2. Just this year alone, they have found two belt plates, a Block I button, quite a few bullets and common eagle buttons, etc. All in areas no bigger than 2,500 sq ft. One of the plates was a sword belt plate...found in the grassy area between the street and side walk...just a very narrow strip of grass. Places I wouldn't have even looked twice at swinging a coil. The guy that found the Block I button was letting his kids play on a tot lot...and decided to hunt the small area of grass under some shade trees for some coins. His first signal was a dropped spencer bullet with the case...and next thing he knew, he had found several more bullets, a complete shoulder epaulette, block I button, and US Belt Plate. Well that search led us to hunt the next little grassy area down from it...which produced about 15 drop 3 ringers, and several J hooks and triangles. It's amazing how much stuff has came out of this one little area of town....in which all of our post find research hasn't led us to any reason why there is stuff where it is. To our knowledge...that area of town wasn't anything back during the war...and didn't even have a road close by it. This isn't even close to the "old" part of town. Even as late as the 1890s, when I have much better detail maps of the city....there wasn't anything out there. No houses...no roads...just bare land.

All that to say...in some cases, the higher freq machines are handling these type sites better. One of my buddies has the G2 and runs it basically wide open with little interference...he don't get much depth but he can run without chatter. We have to turn our T2s and F75s down in sensitivity. I had to run mine on 70 the other day and flip around to different frequencies to get it to be somewhat stable...it still chattered but not as bad as some of the other settings.

Hunting with the chatter it can be done with success. Pick the best freq (there may not be a big difference) and keep the disc less than 5, if any, sens maxed, or close.

When you hit a target tone, the chatter is overridden by the tone for a split second. Uncomfortable to hunt that way but sometimes there's only two choices, stay and hunt with the chatter, or go home.

A few weeks ago I hunted that way with the 75 just to see how the unit would perform. Pulled out a dozen flat buttons and a couple coppers that were over 7" deep, and, there was moderate amounts of iron in the ground.

You have to swing slow but the target tones differ from the emi noises. When hearing a target tone (kind of scratchy), a wiggle over it will be a repeater when the coils center and tone timing matches, vrs emi garble. Not a relaxing way to hunt because you have to 'up' your concentration to maximum. I actually had fun, very challenging.

Horses for your courses....

but yes I to Ozzie at times can work through the noise...running BP 99 sens....

Urban areas do pose a rpoblem sometimes for the FT machie's except the G2...but then the G2 can get weird out in the

country around an electrical fence..

FT has a hyper gain platfrom and its Sparky and at times untamable...You see they turned the Eurotek pro down on the hyper part and in my dirt it really does not cut it....so the hyper sens is a must but is double edged...

Yet I love the Platfrom...

I know what I have pulled out of my funny clay dirt and I appreciate it even more...Still convinced the Bi-Axial is the best coil made to date by any manufacturer...

The thing about the deep buttons on the T2/f75 is they do read iron but they have slight nuances to alert you that its not a nail...ROUNDNESS of the iron tone!

Keith

The 13" Ultimate coil completely changed my G2. In my hunting area of east Tenn. the soil ranges from mild to at times slightly more than moderate red dirt soil. With the stock coil a 58 cal minie would read 6" (solid and loud) to 8" (very soft and alternating with iron tones) in the moderate ground, and I would get a max of 9" in good ground. With the Ultimate I have dug MEASURED 58 cal's at 11" in the good soil, and 9" in the moderate. That puts it's performance right at a T2 and just a little less depth than an F75...without the noise! Quiet as a church mouse. The Ultimate only comes off to switch to the 5" for super iron infested trashy spots....I have no need for the stock 11".

There was a thread on a UK forum about larger coils on the F75. Several people commented on how their T2 was improved by a moderately larger coil, so suggested the F75 should behave similarly. Then a 'representative' of UK Fisher distributor Joan Allen added that in their opinion, no larger aftermarket F75 coil gave any improvement, some even appearing to give less performance. One can only speculate on why - the coils are constructed differently (centre-tapped TX in the T2, single-ended in the F75) so there may be something related to that. Or maybe the Fisher has slightly more gain / sparkiness / adjustability / JE mode etc that it can get that bit more out of the stock coil, and so a larger coil has less to offer, just more EMI pickup.

Daniel, Steve, Keith...... good/correct performance resultant report.

Well here is an update to this older thread. I finally broke down and got a bigger coil for the F75. It will be here today, according to FedEx. I had a tough time deciding between the NEL 12x13 coil and the Ultimate 13" DD. In the end, the Ultimate won out for me. I will put this thing through the paces and give ya'll updates. There has always been some interest in these larger aftermarket coils for the F75 but nobody seemed to have any real info on it. So that's what I plan on providing. Can't wait for it to get here...we are suppose to get above the freezing mark today, for the first time in several days. And then be in the 60s by the weekend. Quite a temp differential...it was -1 here just Tuesday morning with the high of 12 degrees that day, and then a few days later, in the 60s.

Good luck!!!! I can't help but think that it will reach way down there and ping on some of those DEEEEEP buttons!!!!! Please let us know how it works out for ya!!!!! Yeah, we have had single digit temps here too. I was going to go detecting today......but I just cannot enjoy it when that cold wind whips down my collar. But tomorrow is another story.

Okay first hunt in the books with the Ultimate. First impressions are as follows:

1. It's not all that heavy, but I do wish it were black or dark grey instead of bright white.
2. In hotter ground, it is indeed a bit noisy and seems to false on the negative/hotrock spots a little worse than the stock coil does. This was to be expected though.
3. At first I was thinking this was going to be a coil that mostly gained ground coverage instead of gaining depth. But in the field, I noticed two things. First of all, was much better IDs on targets that would be considered the fringe depth area of the stock coil....the zone where the F75 starts saying everything is iron, even when it is not. Second of all...most of the time a larger coil will only amplify the depth of larger items, and lose sensitivity to smaller things. Not the case with the Ultimate. I'm not exactly sure how much "depth" I have "gained" with it...but I do know I was having to dig deeper for items that were IDing well. Example.....with the stock coil, I would get a signal that was IDing pretty decent with mid range numbers...so I would know to dig a plug about 4-5 inches and check the hole. Most of the time it would be in the plug or just another inch or so down in the hole. The Ultimate changed that up a little bit today. I would cut the same size plug, and have to dig down in the hole several more inches before the target would come out. So it is for sure, IDing with better ID on "deeper" objects. They are objects that I believe the stock coil would have detected in all metal...except it would have read them as iron instead of giving mid range IDs. What this means...is that a person could have ran the machine in disc mode, and even picked up some of the targets I dug today....in a site that I've been hunting for a while now in motion all metal, and have hunted it to the point that I was digging iron signals just to see what they were.

Here are my finds for today....not sure if this will show up. The pics are better quality than what my PhotoBucket account would show. But they might not show up since it's on my Facebook thing. [www.facebook.com]

I know one is a dropped Enfield bullet...but the other two, I don't have a clue. The shell casing may not be Civil War period either, but it is a rim fire and similar in size to the cartridge that has the bullet still in it. They may not be Civil War either...never dug one like either of them.

Which brings me to another point. For the most part, it has been my experience that the DE mode on the F75 seems to like coins/bullets pretty well. Well I tried something today that I've not really done before. I hunted one little area in motion all metal with it in DE mode. Then swapped it over the JE mode, and rehunted the same area. I dug all 4 of those targets in that area, in JE mode. They all gave mid range IDs...and all were over 7 inches deep. The Enfield was the deepest, and it was several inches past the cap of my ProPointer. When I hopped over the DE mode to check the signals out...the signal that resulted in the Enfield bullet, was non existent in DE mode. The smaller bullets...both gave iron IDs in DE mode. JE mode made them come to life for some reason. Don't ask me why....I'm just reporting what I saw.

bump

Bullets have somewhat been identified. One has a section of the skin still attached. Both are 44 caliber. One is a 44 cal Barthalow bullet. The other one is a .44 caliber Watervliet Arsenal bullet. I had never found or even heard of either one. Happy to have em in my collection though.





Edited 1 time(s). Last edit at 01/11/2014 02:29PM by Daniel Tn.

I don't put much stock into air tests. But here is what I got today in all metal mode with the F75 and both coils.

Stock coil. All metal mode. Sens 99:

Clad quarter -- 11.5 inches
Clad dime -- 10.5 inches
20 mm flat button -- 11 inches
.58 Minie -- 11.5 inches


Ultimate 13". All metal mode. Sens 99.

Clad quarter -- 13 inches
Clad dime -- 11 inches
20 mm flat button -- 12.5 inches
.58 minie 13.5 inches

This was in JE mode. It didn't dawn on me til just now to give the DE mode a shot and see if it made any difference.

All in all, this is what I really expected to see with this coil. The bigger ground coverage would be the big plus for it...and looks like typical larger coil features....i.e. the bigger the object, the more of an increase in sensitivity. While the smaller objects seem to be about the same. You note this especially on the dime...not much difference between the stock coil and Ultimate on the dime in air testing. But look at the quarter and minie ball....about 2 inches gain in air test.

I still think the most impressive so far out of testing...is the ability to ID things better at in ground depth. When you look at the data from this air test, you will say "meh...not worth it" but this is just showing the extent in which the detector makes a noise on the object. What determines whether we dig or not, is often times the ID of the object.

Scenario to ponder: What if the stock coil can detect a dime down to 10 inches....but only ID it as a dime down to 5 inches...then afterwards, transitions into iron ID the remaining distance from the coil? Well you'd walk right over it in disc mode and never know it was there if it was in that 5-10 inch range and giving iron IDs.

Then lets say you have the other coil on....it can detect a dime down to 11 inches with audio only but can accurately ID it as a dime down to 8 inches in the ground. Now you're getting some place. In the air comparison, there might only be a inch or two difference in audio signal. But ID wise....you just gained an extra 3 inches of ID on that same target.

I believe THAT is where this coil is going to make a difference from what I have already saw in the field. Does that make any sense at all?

Yep, makes sense Daniel. If you get a chance to test it over targets in the ground and report on it, that'd be sweet. Thanks for the air test!

Quote:"Then lets say you have the other coil on....it can detect a dime down to 11 inches with audio only but can accurately ID it as a dime down to 8 inches in the ground. Now you're getting some place. In the air comparison, there might only be a inch or two difference in audio signal. But ID wise....you just gained an extra 3 inches of ID on that same target."

I suspect you're being overly optimistic here, the truth is much more likely to be the reverse of this. That is "it can detect a dime down to 11 inches with audio only, but can accurately ID it as a dime down to 5 1/4 inches in the ground"
The reason a machine calls deeper targets in bad ground as "iron" is because of the strong ground signal. A bigger search-coil just boost the target signal AND the ground signal, by a similar amount, so you are no better off.
One of the reasons your new coil may work better in-ground is related to it's different shape compared to the stock coil, not so much its size.

So you are saying if the soil were closer to the inert side, this bigger coil would be the ticket? And, it would be a wash in higher mineralized soil ...any extra depth would be overcome by the higher minerals in the soil, therefore giving a inaccurate I.D.

Pimento, will you explain why they iron tone vs high, on a deep high tone target? And why can't a detector pull that together?

Two main things stop you detecting something in disc mode (with correct ID) : the detector+coil 's raw ability to see the target at that depth, and the detectors ability to seperate the target signal from the ground signal. A small coil, say 4 inch, has less raw depth, hence why they don't go so deep. A big coil has more raw depth, as your airtest shows (you could pretty much calculate this difference mathematically) but it still comes up against the problem of finding a target signal that may be 1/20th, 1/50th ?? that of the ground. So if you were in very mild ground, then, yes you would see more in-ground depth gain.

As to why deep non-iron targets can read as iron...that's a tricky one, I'm not 100% sure myself. The techniques detectors use to determine if something is there, and the way they determine what its ID is, are completely different. So it turns out to be fairly easy to say "there's something there", but finding out the nature of it requires a "better quality signal". Hence why a machine can give a clear beep, but the ID could be wrong. As to why an iron ID... this is almost certainly due to the ground being iron-like, tiny iron. As you sweep over that silver dime, the signal picked up by the coil transitions from 'tiny iron', through 'large iron', through 'nickel' up to 'silver', then reverses this, and goes back down to 'tiny iron' as you move away from the target. I think a weak target just doesn't have the strength to get beyond going 'tiny iron' to 'large iron' to 'tiny iron'. Hence the iron ID. Just my interpretation of things.
I'm sure some 'old-school' machines can cause ID to increase at depth. This is basically an artefact of the corner-cutting approximations that analogue machines use to make a viable cost-effective detector. You can't calculate arctan of ( A / B ) in analogue electronics, not without a briefcase sized detector, anyway.
Why can't detectors 'pull that together'? Well, I'm happy with the fact things drop to iron, it makes more sense to me. You could 'manipulate' things so that weak targets appear less iron-like. My hunch is that's what a certain 'deep' European machine does, but that's an aside.



Edited 1 time(s). Last edit at 01/12/2014 02:23PM by Pimento.

Pimento Wrote:
-------------------------------------------------------
> You could 'manipulate'
> things so that weak targets appear less iron-like.
> My hunch is that's what a certain 'deep' European
> machine does, but that's an aside.

THAT, in my opinion, is what the Blisstool machine allows a person to do. The plus factor of it is that you are getting crazy deep depth for a VLF machine. The BIG negative side to it is when you start making those deeper/weak signals appear to be less iron like, at the same time, you are making the real iron targets appear to be non iron like too. The depth is good but as the old saying goes...you take one step forward and two steps back. Yep, you just dug a minie ball at 14 inches with a VLF machine and an 11 inch coil. But it took you digging 30 square nails and pieces of wire that sounded exactly like the minie ball did. lol

Yes I was being a bit far fetched in my example with the dime and the coils. I hope nobody thought I was being realistic with my example; was just trying to show a contrast with a liberal amount of numbers. There was just so little info from actual users of the aftermarket coils for the F75 that I thought I would jump in and give them a go instead of just speculating what one may or may not do on the machine. I can't wait to get into the real testing and playing of the coils; signal checking and analysis. I will say this though...the ground type that makes up my yard, is pretty hot ground as far as natural iron content. For some reason I am seeing better/more consistent IDs on my deeper targets with the Ultimate vs the stock coil. These are targets the stock coil can pick up, but some of them the ID is very bouncy, hitting anywhere from iron to foil to nickel and up to tab/zinc penny ranges...with every sweep over it, it will give something different. The same targets with the Ultimate are showing a lot less jumping around and being more consistent in a smaller ID window. Actual time hunting with it is going to tell the big story.

Pinpointing with it sort of threw me for a loop. With most DD coils I've used, I've gotten really good at finding the target center. The ultimate coil is what I consider to be off center a little bit. My particular coil pinpoints to the left...if you are holding the machine looking down at the coil. If you use the detector stem as the center of the coil...it would pin point off to the side of this just a little bit.

Keep us updated on your testing and real-world hunt results, I had contemplated buying a larger coil for mine, but there's little out there to say how good or not they really are. I still might make one though....