F70 Sensitivity Settings.

[kt]

I noticed something curious about the sensitivity settings today on my F70. I was hunting right beside an occupied residence, directly beneath the home power line and the telephone line. Lots of emi, obviously. I was running the 11inch dd, 3 tones, -3 thresh, disc at 8 to reject most nails. I normally run sensitivity at 90, but in these conditions there was no way. Ground balanced at 62.

I remembered some posters on here talking about how they can run their sensitivity down into the 30s and still get decent depth, so I gave it a try. Lowered my sensitivity to about 36 or so. The emi chatter went away, as expected. Then, BANG, a nice round coin tone, high 70s - low 80s on the meter. Pinpointer says three inches. So I dug a plug about 2.5, 3 inches in depth and flipped it out in a more or less solid lump.

With my sensitivity down in the 30s, no signal at all from the F70 when sweeping the bottom of the plug. Turn sensitivity to 42, and the sweet coin tone rang out like a bell and my numbers on my meter screamed coin. Turn sensitivity above 80 or thereabouts, and I got the muddy blip-HONK and varying vdi numbers that I associate with junk.

Signal in question turned out to be a clad dime about an inch from the top of the plug. Nothing else in the plug. I repeatedly ran my sensitivity settings up and down enough before I broke open the plug to satisfy myself that, at least on my F70 and in those conditions, a sensitivity setting below 42 will not hit a clad dime deeper than a couple of inches. And, a sensitivity setting above 80 can turn a clear coin hit into a junky muddled hit in heavy emi.

I bought my F70 used, so there could possibly be something out of whack with my machine. Or I could simply be misinterpreting what I THINK I saw. But I ran my sensitivity setting up and down enough before breaking that plug open to convince myself that a sensitivity setting below 42 compromised depth on my machine in a serious way, and a sensitivity setting above 80 may be too prone to emi to report coins as clearly as I like. Based on what I saw today, I am going to keep my sensitivity in the mid 70s, down to about 45 at the lowest.

The next time someone finds a shallow coin in a high emi situation, I wish they would try to replicate what I think I am seeing. Maybe it's all in my head...

 

[Ed Steinhoff]

Good info, will experiment next time out.
HH Ed in co.

 

[REVIER]

I hit a dime at a measured 5" deep in the ground at a sense setting of 19.
For every 10 numbers up on the sense I could raise the coil up 2" and still get a solid hit.
This went on till I hit that dime still buried with 6" of air at 49 sense so that would add up to 11".

I have turned that sense down to 30 and still gotten way deep in areas of some pretty good EMI.
I have even hunted near power lines when the thing has been pretty quiet on sense in the 70's and 80's.

The difference in your situation is you were directly under those power lines.
Nobody here ever said you will get any kind of decent depth under those circumstances, as a matter of fact I have never read a post about anybody talking about being directly under power lines at all...or the depth problems it can cause.
Now we know, but don't worry about it or expect anything that went on under those wires to be the same in normal hunting situations.
I sure wouldn't, anyway....that is not a normal hunting situation and I sure wouldn't set hard and fast setting rules for everywhere else just because of what was coming on here.

By the way, you seem to want to hunt quietly and if that is the way you want to do it that is just fine and dandy, however...
If you can stand a little noise hunting in high EMI situations then finding targets deep is not a problem for the F70.
It is well known that even in high EMI and with settings set high, so high that you will probably get lots of chatter and some decent jumping around on the screen and maybe even with a bunch of ghost signals too, when the F70 rolls over a good target it still seems to stop most of that behavior and tells you it found a possible good target.
This exact thing happened to me hunting at the very edge of an old park across the street from some houses with power lines, WiFi and something else that always causes the most EMI crazy behavior in my F70 than any other place I have ever hunted.
In this area with the big 11" DD coil, the sense somewhere around the 80's, thresh at -2 or so in low disc and 4H tones, the severe chatter, ghosts, jumping and everything else almost stopped, calmed way down anyway, when I swung over an area about 1' square.
Still a bit jumpy with numbers in the high 50's and a few into the low 70's in slightly different areas but with solid tones as I swung the coil around the small square..
Turning and hitting it from a 90 degree angle I got the same thing and a depth reading on the screen that said 7" on most and with flashes of 8".
I had to dig this and see what it was.
It turned out to be a fantastic coin spill that contained 3 Indian heads from the 1880's to the low 1900's and one very early wheat in the low teens.
All were spread out around that square foot box and the e depth on all these coins was as advertised with 2 of them at 7" and two others a bit deeper at 8".
I am not saying you should do it this way if you really don't want to, everybody's threshold for noise is different and mine just happens to be pretty high.
I just want you to know it is possible to deal with difficult situations, even severe EMI, and still be successful if you have an open mind about trying new things.

 

[kt]

I'm not accusing anyone of giving me bad info. Basically all I'm saying is that, in a severe emi situation, I'm seeing that the sensitivity setting makes a big difference for me, on my machine. Anything below 42 loses serious depth, anything above 80 gives me a signal that I wouldn't generally dig. Just providing a little food for thought. I generally am most comfortable hunting quietly, but for me the most important thing is interpreting that coin signal. When I go from a BANG on a coin to a blip-HONK, to me that is something to keep an eye on. But, it may just be me or my machine, I dunno.

 

[IBdiggin]

Hey KT. I think possibly one of the reasons for the confusing results is the fact that removing the plug will change the detectors first image of the target. Comparing the signal, In it's natural suspension with the aura intact, to the post dug signal is like comparing apples to oranges. A good example of this is a nice high tone created by super tiny pieces of rust invisible to the naked eye, completely dissolved into the soil. The mineral itself is the target and becomes ghost like when interrupted, jumping from spot to spot as the clumps break up into nothingness. Actual ground balance itself may even have changed to the point that by increasing the sensitivity after digging the plug, you may have in fact been getting a muddled reading from the actual mineral in the soil over powering the aura from the dime within. I learned along time ago from a Mike Hillis read, on the F5 that a good way to tell if your ground balance has changed is to pinpoint in clean ground. You should get nothing but straight lines in your display. If a depth number is registered you are out of balance and I assume detecting the mineral content of the soil. This trick also works quite nicely with the F70. I personally have hit a clear one way high tone on a silver Merc at 5" set at sensativity of 30 and threshold of -3 with the elliptical coil. Nevertheless you bring an interesting topic to the forum and makes for a good topic to share personal ideas. Thanks and I hope my input helps--------IB

 

[REVIER]

I am just saying that hunting directly under power lines all the time is not a normal occurrence for most of us so adjustments need to be considered which you are doing.
I might suggest a few other things if you want good ID's at depth on targets in severe EMI situations that might also work.
They have for me.
Use all metal with jacked up sense, thresh and even SL if you want.
Tons of chatter and jumping but if it sees a deep coin target it should stop and let you know, (if just for an instant so look for quick repeating similar numbers), if you zero in on it with the center of the coil.

Use 1, 1F or 2F tone settings because they all deal with EMI better than all the others from my experience...especially using just monotone.
You might be surprised how high you can turn up that sense using 1 tone, I have found using negative thresh at -2 or lower also helps to combat noise in that situation.

Neither method will be super quiet in severe EMI, probably, but if finding and digging good targets deeper in that situation is the goal putting up with a little noise is a small price to pay.

 

[foreign object]

Just because you can raise the coil off the ground eta say 4 inches and still hit your target does not mean that you can bury it the same 4" deeper and hit it.
Just the way it is.

 

[REVIER]

Just because you can raise the coil off the ground eta say 4 inches and still hit your target does not mean that you can bury it the same 4" deeper and hit it.
Just the way it is.

If this was referring to my post I just want to say I know that, just an example about possible depth at a less EMI plagued area and I think you missed my point.
The dime was at a measured 5" in the ground and I hit it solid at a sense setting of 19.
I might have hit it at 6" or more but I will never know because that was where it was laying.
I have gone deeper than 5" on sense settings of 30 and 40 and really deep on higher settings.
15" with my sense in the 90's.
I hunt both quiet and high EMI filled sites and adjust my F70 accordingly...usually to get the best depth at older areas, maybe a little shallower and more precise in not so old areas when looking for jewelry.

My actual point is I would never let conditions at one site dictate how I would set it at another.
Rules are good, I have many, but not about blanket in stone settings for every site.
Having depth problems directly under power lines is one thing, move away from that exact area, maybe even just a few yards in some cases, or to another site also with severe EMI but not under power lines, and your settings might not be optimum for the best depth anymore.

 

[kt]

Thanks everyone for all the thoughts and advice. I wish I had a camera to film what I experienced, it struck me as odd. Sensitivity in the 30s, run the coil over the grass side of the plug, coin-coin-coin. Flip the plug over, nothing-nothing-nothing. Sensitivity in the 80s, junk-junk-junk. Sensitivity between 42 and 80, coin-coin-coin on both top and bottom of the plug.

I think you all are right, it is probably a combination of screwy emi and yanking that plug out of the ground and disturbing the halo. Really, the most remarkable thing is, you can even run the F70 in that kind of scenario. Power lines, telephone, cable tv, underground sewer and water lines, Lord knows how much wireless activity, all buzzing right on top of me, and still the F70 bangs on a coin. If you can tame the chatter or get used to it, the F70 is a pretty powerful suburban coin shooter.

 

[foreign object]

Just because you can raise the coil off the ground eta say 4 inches and still hit your target does not mean that you can bury it the same 4" deeper and hit it.
Just the way it is.

If this was referring to my post I just want to say I know that, just an example about possible depth at a less EMI plagued area and I think you missed my point.
The dime was at a measured 5" in the ground and I hit it solid at a sense setting of 19.
I might have hit it at 6" or more but I will never know because that was where it was laying.
I have gone deeper than 5" on sense settings of 30 and 40 and really deep on higher settings.
15" with my sense in the 90's.
I hunt both quiet and high EMI filled sites and adjust my F70 accordingly...usually to get the best depth at older areas, maybe a little shallower and more precise in not so old areas when looking for jewelry.

My actual point is I would never let conditions at one site dictate how I would set it at another.
Rules are good, I have many, but not about blanket in stone settings for every site.
Having depth problems directly under power lines is one thing, move away from that exact area, maybe even just a few yards in some cases, or to another site also with severe EMI but not under power lines, and your settings might not be optimum for the best depth anymore.

Well if you did know it there are a lot of guys that don't so my reply was for the ones who do not know and are inclined to think so when they read it.

 

[REVIER]

Just because you can raise the coil off the ground eta say 4 inches and still hit your target does not mean that you can bury it the same 4" deeper and hit it.
Just the way it is.

Well if you did know it there are a lot of guys that don't so my reply was for the ones who do not know and are inclined to think so when they read it.[/quote]

Yes, it would be nice if all we had to dig through was air...much easier than hard, clay filled concrete-like dirt in the middle of a drought.