Hi, new here, question/problem with my F75 LTD

Hey all,

I just got back from my first relic hunt with the F75 and things did not go as smoothly as I would have liked. I brought my Explorer as a backup, just in case I couldn't get the hang of the F75 LTD.

I read the manual many times and I felt like I knew how to operate all of the menu items. I got to the site and did a depth test, purely out of curiosity. I put a 3-ring miniball at about 10" and tried out both detectors. The Explorer produced a faint, yet repeatable signal and I would have definitely dug that target. In fact, later in the day, I dug a miniball at 11-12" with the Explorer. Anyway, I tried the F75 LTD and it would produce a repeatable, strong signal in boost mode only if I swept along the length of the miniball. Swinging the other direction only produced a faint clip, and it sounded like iron. I would have dug that target only if I approached it from that one direction. Still, I'm impressed that a VLF detector was able to match the depth of the Explorer.

Here's the settings I used for the F75 LTD.
bP mode
Disc 3
Sensitivity 90
2 tones
Eventually I was able to bump it up to 0 disc, 99 sensitivity, but it only worked in a few spots.

I don't have a pinpointer yet for the F75, so I knew I was going to be hunting with the Explorer for most of the day. I took the F75 to a trashy area that leaves the Explorer dumbfounded. As I went through the field, I was getting the "iron grunts" all over the place, and I would occasionally come across a signal that sounded good if I swept from left to right, but it would sound like iron if I went right to left. I wasn't sure how to read these targets.

THEN, I came to an area relatively free of trash that I had gone over with the Explorer many times. The LTD produced a really strong signal and the display read into the 90's. COOL! I must have missed something great........ wrong. After digging a 15 inch massive hole and finding nothing, I decided to save it until I come back with the Explorer and Sunray probe. This happened two more times before I finally gave up and got out the Explorer. I went back to these three holes and, according to the Explorer, there was nothing in the holes. I tried the probe, and then the 10x12 SEF coil that gets great depth in that area.... nothing. I guess the F75 was falsing on me. Too bad, because they seemed like really great signals.

I loved the weight and speed of the thing, and I was impressed with the depth. However, I'm concerned about the falsing. This wasn't just EMI/ground chatter, these were solid signals that sounded like something really good. Nothing there, though.

Another discouraging thing is that I can't even use it in my backyard. Interference city. Forget bP or JE mode.... I have to put the thing in DE with the discrimination at about 17 and the sensitivity at 40 for it to be quiet. I'm sure it gets OK depth with these settings, but I doubt I'm going to get the deep silver. To be fair, I can't use my Explorer very well in my yard either because it nulls out too much. I did manage to find a wheatie at 5" once, though.

I'm thinking about selling the F75 LTD. I know this is being heralded as the greatest relic hunting machine out there, but I'm worried it just isn't going to work for me. Any suggestions?



Edited 1 time(s). Last edit at 02/20/2010 06:40AM by Hwy 395.

Hi. Good to read your experience with the F75 LTD.

I have a post on here today about a hunt with my F75 LTD (Bullets and a Wheat Cent) . Sounds like we were hunting in somewhat similar conditions. I was hunting in an area with a very high iron burden and dug several bullets. None of them repeated in all directions because I always had iron in nearby soil. At the settings we were using, we both were sampling a large volume of soil. Any iron in the volume is going to affect the detector response. More so in some directions than others. I had to narrow my sweep widths, some times just 6 inches from side to side, to get a repeat on some of the bullets. At one point I reburied one of the bullets and did some testing. I did not note any problem in picking it up from the side or along its length. I didn't measure the hole but I'm sure it was at least 10 inches deep based on the length of my sharpshooter shovel in the hole. Maybe you had some iron nearby that was affecting the response when you swept the bullet from the side. If you haven't already, read Tom's article titled "Sensitivity Training" on page 13 of "Fisher Intelligence". You can find a link to the document in the left hand column on the main page of this website. More is not always better in very trashy ground.

As far as loud responses, deep holes, and finding nothing, I did have that happen once today. On Tom's video he demonstrates what a piece of complete iron oxide will do as far as masking goes. This is the stuff that's left when an iron object completely rusts away. In his demonstration, the detector doesn't give an audible response when he passes it near the search coil, yet when placed near a non-ferrous object, it completely masks out the non ferrous object. I wonder if a large enough volume of iron oxide will cause the detector to sound off and then when we dig a hole it easily breaks up into small flakes or powder that can no longer be detected. Conjecture on my part but may be a possibility. You had it happen 3 times though so maybe something else was going on. Something was down there though. It had to be. I guess it could also be related to some very localized anomaly in ground minerals. I know from what Tom has said that the F75 LTD is very sensitive, will detect very small objects with quite loud responses, and is even more sensitive to objects on the low end of the conductivity scale.

Well in any case. Please keep posting anything you find out. I'll do the same. We both will benefit. Don't give up on the F75 LTD. It's a very capable machine.



Edited 1 time(s). Last edit at 02/20/2010 02:08PM by dgc.

When i hunt with my F75. Big figure readouts like into the upper 90`s have always ended up being IRON.

Welcome aboard!

Was the 'really strong signal' continuously repeatable in one focal/pinpoint location?

I shall presume it was........and the VDI numbers continued to stay in the 90's as you rotated your body around the target whilst continuing to sweep the target.

In this case; there's one of two scenarios:

1. Oxidized sheet steel. (Steel is an alloy of iron). A tin can lid can do this.

2. Oxidized sheet steel with a small non-ferrous target in co-locate.

In either case, the Minelab Explorer will most probably remain silent (iron 'nulling').........and you would never know any metal exists.......unless you place the Exp in a all-metal mode.

A heavily rusted (almost completely disintegrated) tin can lid looks like a patch of bad dirt/minerals to many detectors (including pin-pointers).........especially if the unit has a 'iron mask' feature; subsequently, the unit will not report the metal (however, bad masking will occur)..........WHEREAS......the T2/F75 platform will report it; albeit proper ID will suffer.

Followup - I found the following explanation on another website.

We’ve all encountered "Phantom Signals" at one time or another,
and probably chalked up the experience as something crazy
happening with your metal detector.

A "Phantom Signal" is a signal which sounds good, but when you
try to recover the target, there’s nothing there. You can’t
find anything!

When a target is in the ground for a number of years, it
eventually reverts back (oxidizes) to its natural state. As
long as the ground around the original target remains
undisturbed, the matrix in the ground as seen by your metal
detector, appears as the original target.
As soon as the soil is disturbed (by digging), this matrix
is destroyed and your detector no longer sees the target.
Most of the time, if you look very carefully, you can see
a discoloration in the soil where the "Phantom Signal" was.

I have an F-75,(reads special edition on the box) been using it for 2 years and have come across this many times.I usually run my machine as hot as I can...0 disc, 85-95 sens, 4 tones, GB on average is in the 60s.
We have "hot rocks" here in SE pa & I've dug many.The VDI numbers and tones vary on the hot rocks as the audio could be low to midtone. Sometimes the signal is crisp and other times it's scratchy and odd. The hot rocks range in size from golfball to marble and don't have specific VDI or tones. I did notice many had a VDI of 16 but not all. They are the color of the surrounding dirt but when you break them open they are a glittery shiney black and look just like coal (maybe they are coal?). My Garret Pro pointer will also sound off on them.
Now my friend uses Minelabs. He has a SE & an E-trac w/ Sun ray probe. His machines don't pick-up hot rocks and he has never dug any.
When I hunt in old farm fields and get a strong signal in the 80's - 90's, high tone and dig deeper than normal, I know it's going to be a hunk of iron from an old harrow and usually is.
My experience being, if the F-75 is giving a signal, there IS something down there. Maybe it's a hot rock or a hunk of iron thats deeper than we care to dig or it disintegrated iron, like they said.

Hwy 395, my advice would be to use the F-75 another hundred hours or more to give yourself reasonable time with that machine. It's a no nonsence detector, it hits hard fast & deep. After you feel in sink with it & still don't like it, it will sell.



Edited 1 time(s). Last edit at 02/20/2010 02:36PM by ozzie.

I think you should give up and sell it to me!

I've had my LTD since early Dec. 09 Paid for it the first week, but just starting to get the hang of the machine after NASA Toms field report and the other info. Been having the same issues you have just experienced and more. But also digging some really nice relics and gold items. It's very hot on gold. Dig those signals around 20, they may be gold. Or if your back is strong dig it all. In the old days you had to dig it all, no discriminators.

I've been detecting since 71. Most of my detector experience is with Nautilus and Tesoro. Fisher Tech is a new animal to me, you should be a little ahead of the curve with your Minelab experience. I have yet to use a good detector that didn't out preform another model in some way in some condition, IMO.

The LTD definitely finds relics in my area Ctrl VA no other machine can. I've hunted some very pounded areas that have been detected by everyone and every machine ever made since the 50's, the relics are still there with the LTD. This is my experience with the machine.

I have no personal interest in whether you sell the machine or not, but if you want to find what others are missing I would give the machine more time. Admittedly it's not an easy machine to listen to and setup. But if it was easy anyone could do it. The bottom line for me is what I put in Riker/display cases at the end of the hunt. LTD is filling them up again, for me.

Sounds like a bad unit or you have really bad ground. I am sure you fast grabed sometimes you have to hunt in AM but that should be only in the worst of palces.

It may be you have a bad coil do you have any other coils?

LowBoy

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

[www.youtube.com]

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!

I have found half dollars to read in the upper 90s when relic hunting I dig it all

LowBoy

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

[www.youtube.com]

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!

Thanks for all the responses.

I want to give it another chance. I'm going to try hunting a park tomorrow and do some more depth testing against the Minelab. I can only keep one, so I need to make an informed decision. I don't want to give up too easily, because I had problems with the Explorer when I first started. I know it very well now.

I'd hate to think I have a bad coil, as this is a brand new detector. It came with a 5" coil, but I haven't used it yet.

Oh, another thing I haven't mentioned... while doing fast grab, it was ground balancing in the low to mid 80's. Isn't that really high? The iron meter was only at 0.1, which is considered "typical" according to the manual. Maybe this is part of the problem?

sounds high to me mine is awfully chattery when i hunt hot ground like that ususall y have to cut down sens to 60s to get it queit where as i usually always hunt high 90s sens

The Fe3O4 bar-graph on the F75 is what 'mostly' will tell you how bad your ground mineralization is. And this is performed whilst detecting/swinging coil.

Hi, new here also...I have similar issues with my f75. I'm not entirely sure of whats going on since I'm still very green but I think it may be very mineralized ground. Based upon your screen name I assume you live Somewhere near me, i.e. Mono County, CA. My G.B. is always in the 80s. If anybody has any advise I too would appreciate it as just the other day I dug a few of my own "ghost holes." That being said I must reiterate that I've only got about 30 hours of detecting under my belt.

BrianMono Wrote:
-------------------------------------------------------
> Hi, new here also...I have similar issues with my
> f75. I'm not entirely sure of whats going on
> since I'm still very green but I think it may be
> very mineralized ground. Based upon your screen
> name I assume you live Somewhere near me, i.e.
> Mono County, CA. My G.B. is always in the 80s.
> If anybody has any advise I too would appreciate
> it as just the other day I dug a few of my own
> "ghost holes." That being said I must reiterate
> that I've only got about 30 hours of detecting
> under my belt.

The GB reading doesn't indicate if the ground is mineralized, pump your coil and check the fe304 meter, what's it say?

Thanks for the reply,

Ground balance is at 85 and the fe304 is between -3 and 1. I seem to be getting some better success in all metal mode. However, when I'm in DE or PF im still experiencing major chatter even though i've played around with the settings. I think maybe I just need some advice for settings for a newb like myself which may be simpler as I'm still very new to this. BTW...I dig tons of 22 LR shells even deep ones so I know its pretty sensitive I just dont know how to wield the power. Thanks for any advice you can offer!