Fisher F70 and rusty bottlecaps?

[88junior]

How's the F-70 do on rusty bottle caps? Does it do pretty good at discriminating them out or does it scream out quarter on them? In my ground conditions I have to use DD coils due to the ground minerals. I know concentric coils are better at discing them out but they don't get very good depth for me.

 

[Dave J.]

Various people use different techniques to ID steel bottlecaps. The F70 uses the same basic discrimination system as the T2 and F75 so anything you read about them in this regard will also apply to the F70.

With respect to DD's most of the techniques rely on the fact that a shallow coin will usually give fairly consistent ID regardless of whether you sweep over the middle or over the heel or toe of the searchcoil, and will give similar ID if you do the 90 degree X-the-spot maneuver. In lighter mineralization, bobbing the searchcoil up and down slightly over the target will usually drive ID down, but steel bottlecaps will usually go into the iron range. A coin will usually give an ID on a fast sweep fairly close to what it gives on a slow sweep, but a steel bottlecap will have a tendency to drop the ID the faster you sweep. This is more noticeable in the "slow mode" (F70) or "boost process" (on most T2 and F75 models).

My personal preferred maneuver is to turn the searchcoil on edge (i.e. in the vertical plane) and sweep over the target that way. A shallow coin will usually give an ID fairly close to what you got in normal sweeping, but the steel bottlecap will usually drop 'way down and bounce around a lot.

The foregoing applies more or less to concentric searchcoils as well, although they usually do a better job of bouncing steel bottlecaps around in a horizontal sweep.

Some people can hear the difference in the "shape" of the signal between a steel bottlecap and a coin. In all metals operation or searching with a low level of discrimination, a coin or ring will usually give a tight, crisp response whereas a steel bottlecap will tend to have a broader sound footprint.

The whole subject has been discussed quite a bit on this forum.

 

[REVIER]

What he said.
I use the wiggle and pull back method, when the edge of the front part of the coil moves over these there is a drop 99% of the time.
A few flat and real rusty shallow ones might stay in the higher numbers and not drop but most will.
Sometimes a drop from the 70's-80's down to the 20's-40's, the steel ones down into iron.
Whatever happens there will usually be a drop.
Good targets like coins and rings don't drop.
This technique works so well that I never fear or get frustrated wading into trashy areas with tons of these using DD coils.

 

[88junior]

Thanks Dave J and REVIER for the answers that helps a lot on my deciding on which machine to get! I hate those things!!

 

[mudpuppy]

I have zero problem with the F70 on bottlecaps..I have the 11"dd coil....You can hunt right through a big park plastered with them and pull all sorts of loot and leave the caps in the dirt...

This is a very good thing! Most of those trashy places are too hard and frustrating for other people to hunt on account of the caps...everyonce in a while, a flattened rusty one thats 3" deep gets a stab on account of it will hold that Q ping just enough to make a guy curious, otherwise, they are so obvious its stupid easy...when you do stab one with a driver, you can tell by the feel its a cap and not a Q..so you dont have to dig it if you dont want to... F70 set up accordingly for general purpose park hunting for fresh drops jewelry and shallow finds, you will not dig a cap...

In fact, I'm fixing to head out in a few minutes to ransack a park as stated...big party there last night, and I want to be there predawn...
Mud

 

[88junior]

Good luck Mud I hope you find a ton of goodies!!

 

[dbax]

Bottle caps, bottle caps, and more bottle caps. I have been searching with my F70 for five years now -- out of warranty -- I have dug my share of bottle caps. Hey, Mudpuppy, guess you have not run into any of those aluminum bottle caps or those fancy ones covered in a golden foil? What I have notice is that a fast swing rate will skip over most caps but you have to stay alert as dimes will give a very narrow signal. If you hit an aluminum cap and slow down for a better reading it will sound off like a dime -- not a quarter -- the rusty steel caps tend to give the quarter signal. What I have noticed is that you can usually determine a cap from a dime or quarter with the use of your Garrett pinpointer. If the target seems to be larger than a dime or quarter. What I mean by that is that a bottle cap will always have a wider reading across the ground as you sweep your pinpointer over the target. A coin will be much smaller and more exact. The F70 is really good a target ID but not perfect. Deep buried aluminum cans will read like dimes. Aluminum pull tabs will read like nickels. It seems anything aluminum is going to give a reading. If you tune all of the aluminum out you will be tuning out some signal range that would include gold rings. There is another problem with reading bottle caps with a variable signal ID. Some have developed a method of scanning causing the bottle cap signal to bounce around, while a single coin will repeat. Problem is, I have found a bouncing signal say, 67-81, many times ends up being a spill of coins. I do not believe this is a Fisher problem only. I have an F2 that seems to ignore bottle caps but chunks of aluminum and buried aluminum cans. Chunks of aluminum? Park lawnmowers chopping up cans. Someone might also be wondering about the mention of "buried aluminum cans" -- this may not be much of a problem in most places but in my town beer drinking is banned in the parks and teens prowl the parks at night and rather than getting caught with the empty cans they crush and bury them. I have found crushed cans as deep a 8". Oh, and those old Brass Sprinkler heads read like Quarters and are usually about 5"-8" down. Seems that when the parks re-turf they do not bother with ripping out the old sprinkler systems and just cover them over. I don't dig so many bottle caps these days except for one park that is loaded with aluminum. One final observation -- pennies will mask bother clad quarters and dimes if read first and if a penny is close to a clad you will get a busted up reading. A true copper pennies will give a dime signal. It is really amazing these machines do not read clad coins as trash -- oh, wait, they are. When you hit a silver target it is sharp and steady, be it a silver coin or ring. That is my one cent worth of observations. I hunt at least once a week with a buddy. I have paid for my $700 machine three times over and have 80 silver rings (4 gold) and several silver coins two of which are standing liberty halves, 1945 and 1939. It is good exercise and don't let anyone tell you different. Peace, Dan

 

[lytle78]

Good info Dan. Reading it made my head hurt however. Throe in a "return" now and then - it breaks the several hundred words up into much more readable chunks. Just a thought -

Thanks again!

 

[dbax]

Yeah I hear you lytle78 -- I just read a book, where there were no breaks for a whole page or more and this was a best seller, so I thought I could do that as well, ha, ha, no best seller here. Remember, too, that was my first draft and we know how rough a first draft can be. Thanks for the positive reply -- mudpuppy is the guy I have followed over the years, between him and revier they have made me the success I am today.

One thing that has always bothered me, though, are the depths others say they get with their F70 and F75, and other machines as well. I think my F70 will pick up a buried car at a couple of feet, a steel culvert pipe for sure, but a quarter at a foot? I have tired everything and the best I can get is 7-8" but not in the field, counting swing height and some grass most of what I find is within 4-5" of the top soil. One guy I saw on you tube was saying he had just dug up a silver quarter at 11" -- but his 7" trowel was sitting in the hole when he was showing the coin off and the hilt was at the edge of top soil.

I don't mind if my wife wants to exaggerate about inches, but guys, really? Please, the ladies have been told that 6" is really more like 8 or 12 for so long they have come to believe it but for the guys to begin to believe their own lies? If we are really digging coins at 12" or even 10" we would all be using shovels not trowels. Okay, now I feel better.

Went out the other day and dug up 17 nickels. Went out again a couple of days later and dug up 2 nickels and 20 pull tabs. Go figure. This machine has so many possible settings I am still messing with it. My hunt buddy has an XL White and we have a bit of a contest at who finds the mostest and loser has to by coffee. Peace, Dan