F-75 Advice please

I have owned my F-75 for just over a month and so far I have been very happy with its performance. However, there is one thing that totally drives me crazy. I recently have been detecting an old fair ground that dates back to the early 1920's. I have visited this same site many times over the last 10 years and have found that the older coins are in the 5 to 8 inch strata. The soil in the park ground balances neutral around 58-60. I have been using the F-75 in DE process, Disc=6 Tones = 1 Sens = 85. Since I am most concerned with coins between 5 to 8 inches I am paying careful attention to the F-75's on-the-fly depth meter. If I get a solid repeatable tone that ID's in the middle or lower segment of the depth meter I usually dig. Now here is where I am having a problem. Many times the F-75's depth meter indicates a mid-scale depth reading and when I pinpoint the F-75 says the target is 5 inches deep. The grass is very short and I press the coil against the ground using firm pressure while pinpointing to get an accurate depth reading. Since the F-75 is indicating a 5" target I dig a 6 or 7 inch plug only to discover a new coin around 1 to 2 inches deep. Dam, this is frustrating. Does anyone else have this problem? Does the machine need to be re-calibrated. I know many of you don't put total faith in the actual depth readout; nevertheless, the F-75 should be able to correctly id the depth of a 2" coin. This is the best forum on the net hands down so know I will get some good info and suggestions.

Thanks,
Leo

Are you using the standard DD coil?

Yes

hi there..
this is normal,-nothing wrong with your F.
a coin on edge or a coin masked by something will always disturb the depth
meter. A small coin will not read the same depth as a big coin or vice versa..
---mineral content,man made iron,aluminium thrash...can explain the difference
in the depth reading in P.P versus the direct "on the fly"reading...
I have experienced the same myself and use the depth reading only as an
estimate...
trond



Edited 1 time(s). Last edit at 08/22/2009 05:19AM by trond.

I`ve never bothered with the depth meter since i`ve used the F75.
Why bother. The idea is to find the target then dig the target. Why bother trying to work out how deep it is ?
We use spades with the blade cut down to approx 8 " deep by a tapering 8" x 5". Find the target Dig the spade depth ,look in the hole if its still in there continue digging ,if not its in the soil or Sod. By the time your wondering how deep it might be, you could have retrieved the coin and be on your next target in the time spent analyzing how deep a target may or may not be.

Most commonly........ a small piece of trash in extreme close proximity to the coin (or target) will cause this.
A secondary cause is: IF you invoke the pinpoint whilst the coil is over another target (or very close to)....... then you bring the coil over the desired target.... your detector has been partially 'detuned' to the other/initial target; subsequently giving you a incorrect depth reading. You may be unaware that you have done this....... as the target that you are over...when you invoke the PP.... may be BELOW the Disc setting............................so you hear nothing.....and have no idea of what just took place.

I to, experience a significant error in the F75's dept indicator. Now, I am very pleased with the overall performance of the F75, and, I am aware that a depth indicator, perhaps much like the VDI indicator, is only a "guess-ta-ment." But, even with new batteries,a precise manual ground-balance, and using the standard coil, the depth indicator (using the pp function) will almost always indicate 5" when the flat coin (any coin) is just below the ground's surface enough to obscure its appearance. This might not be an issue for many, but 95% of my targets are within 4" of the surface, so a slightly more accurate depth indication would be very helpful. I have talked with Felix about this and may send it to FT soon.(I read another person having an identical problem.) Can you estimate, Tom, the percentage of accuracy I could reasonabley expect from the depth indicator (20%,40%,etc)????

Thanks guys, I knew I would get some good information. I most always use the "detuning" technique when pinpointing. I have known for a while that detuning while pinpointing can make the depth reading unreliable; however, at this particular park I use the standard method first to get an idea on the true depth and then use the detuning technique to more easily zero in on the target. Jeb, you are right to a point, and there are days when I will dig everything that gives me a good tone even when I know its a new zinc penny. However, there are days when when I try to go for deep coins and try to ignore shallow modern coins which is precisely what I was doing the other night. Tom, thanks for shedding some light on why this is happening. I must admit that this particular site is littered with ferrous and non-ferrous junk targets. Seinohio, I concur with your post. What you described is precisely what I have observed with my F-75. Having owned the F-70 with the same coil as the F-75 first, I don't recall having the same problem. I will take both machines to the testbed later today and do some experimenting.

Thanks again guys,
Leo



Edited 1 time(s). Last edit at 08/23/2009 02:33AM by Leo234.

"Why bother. The idea is to find the target then dig the target. Why bother trying to work out how deep it is ?"


Hmmm - this means you're digging the memorials while your partners are skipping them to move on to the Indians or deep silver. If you're hunting a manicured lawn or well kept park, digging 3 holes a foot to pull out clad is a little irresponsible - during the summer anyway. A too good to be true tone and ID on an F75 at 3" is probably a bottle cap in my area. At 6 or 7" --- you're heart starts racing to find out what cool thing you've found



Edited 1 time(s). Last edit at 08/23/2009 02:01AM by Shambler.

when I hunt even for relics I dig it all if it is the VDI I am looking for. And depth means nothing I have found more old coins three inches or less then I can remember

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!
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Shambler Wrote:
-------------------------------------------------------
> "Why bother. The idea is to find the target then
> dig the target. Why bother trying to work out how
> deep it is ?"
>
>
> Hmmm - this means you're digging the memorials
> while your partners are skipping them to move on
> to the Indians or deep silver. If you're hunting
> a manicured lawn or well kept park, digging 3
> holes a foot to pull out clad is a little
> irresponsible - during the summer anyway. A too
> good to be true tone and ID on an F75 at 3" is
> probably a bottle cap in my area. At 6 or 7" ---
> you're heart starts racing to find out what cool
> thing you've found


I`m in the UK friend. we don`t dig manicured lawns here ! Farm fields & pasture only .

As you can see, there are MANY variables. In my test-garden...... all of the dimes depths are reported properly to exacting depths.....9", 10", 11" 12". This includes a dime that is buried 13" deep. The detector will give a depth reading correctly on this dime......... but the detector will not detect it in the ID mode. (It sounds like ground chatter in the A.M. mode). The test-garden was not an easy task, as it had to be sanitized of ALL metals initially...... before commencement. The detector works per-design (perfect) in the test-garden. NOW........... out in the real world........... infinite variables enter into the equation. Because of this, I cannot give a 'percentage' of depth-accuracy in the real world.
I will say this........as I have run in to this scenario multiple times; a target that is grossly in error as far as F75 depth bar reports........ a concentric coil CZ will not even detect this target. Food-for-thought.

Over the last two days I have switched from 1 tone to 2F. Using Tones = 2F I can audibly tell the difference between a shallow target and one that is deeper than 4 inches. Tom is correct about the accuracy of the depth indicator in the test garden. In the "clean" test garden my F-75 gives the correct depth every time but out in the real world it struggles frequently. Based on the responses I have received to my original post I now realize that my F-75 is working properly. I have only owned the F-75 for about a month so I am still in the learning curve.
Speaking of the "learning curve" I used JE process with Disc = 0 for first time this morning. Ditching the headphones made the constant chatter and low tone grunts more tolerable. Looking back, I think I could have just turned the volume down on the headphones and left them on. Anyway, using JE and Disc = 0 I found four silver dimes all over 8 inches in an area that I had hammered numerous times. Dude, I got to ditch the hand trowel and get a shovel if I am going use the F-75 in this mode. I left a few good sounding targets in the ground because I could not reach them with my 8" hand trowel.

Leo