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steel bottle cap problems on my F75, will a small coil help?

B

Byron (TX)

Member
I've been using an older model F75 with the stock 11" DD coil extensilvely for about a year. Really great machine, found a lot of cool stuff with it. But the steel crown bottle cap that will stick to magnets will fool this detector every time. I cannot disc them out, seems like these would ID very low in the iron range below 10 on the target ID, but in 4H mode I get an eratic bouncing tone and the ID number jumps from the 70's to 90's and won't lock on. The aluminum bottle caps lock onto a number usually in the 50's or 60's with a mid tone or high tone. I hunt a wide variety of sites, most are older demoltion sites with loads of metal trash, but many good targets too. Also have the same problems on steel washers. Some of these sites are wall to wall junk metal, but also have a few old relics and coins there too. Most are shallow, less than 5" deep.

Discussed this with Mike at Fisher tech support, he said concetric coil would do better on at the trashy sites.

I'm thinking about either buying the 6" eliptical concentric coil, or the 5" DD coil. Which small coils are y'all using with the F75. Does this disc out the steel bottle caps better? I've got a few old demos sites that used to be bars and fairgrounds that are practically plated in bottle caps. I'm sure there's a lot of good stuff hiding amongst the trash.

Also have not got any gold jewelry yet with the F75, I hunt in very low disc, and lower the sensitivy to calm the chatter.
 
Bottle caps (and some pull-tabs) are a PITA on the F75/F75 LTD. I've tried the 11" DD, 6.5" elliptical concentric, and 5" DD. They pretty much sound great on all of them, even in the supposed BOTTLE CAP mode. Yes at times they'll be jumpy TID's, but so are many coins, so even though at times I'm fairly certain it's going to be a bottle cap, I still dig it just in case it's a jumpy coin (and often times it is). If anyone has a fool proof way to vet out bottle caps, I'd love to hear it.

I sincerely hope that FRL will work on this in their next flagship detector line.
 
saying on the bottle caps. I use the standard 11" DD coil as well and have been fooled many times by those stinking bottle caps. I also have the 6" elliptical and it isn't much better. However........................I have tried a bunch of different things trying to get these stinking things to sound different so I can identify them. Try this. When you get a quarter signal that jumps all over but stays a high tone, pinpoint the target and place the coil where the target is centered and just in front of the coil. Place the coil right on top of the grass and move the coil forward over the target until the coil has moved over the target and actually clears it. See if you get the 'iron crackle' at the 'heal' of the coil. Dig up the target and if you got the 'iron crackle' the target will probably be a bottle cap. If you did not get the 'iron crackle' it will probably be a quarter. I have practiced this so many times that I can tell, MOST of the time what the target is. Read page 30 in the owner's manual. It gives good info. This isn't a foolproof method but I find it helps me. Bottle caps will usually jump all over the place on the TID and if the target is shallow it is usually a cap. Deep quarters will also give varying TID so be careful. Try this method and see what you think. Post your results here so I will be notified or email me. I am interested in your findings. Man, I HATE those bottle caps!!!!!!
 
Most DD coils that I use have difficulty working out steel bottle caps...if you are in an area littered with them, try a co9ncentric coil if you want to decipher between the bottle caps and higher range (VID) targets.
 
It's not the F75's problem, as it is the coils problem. One of the negative points about using DD coils are the way they respond to bottle caps, certainly rusty bottle caps.

Suggestion, use the coil off the F70. It's a concentric design, and should give you a bit better performance with the caps. You also may notice a tad bit better discrimination with it also.

If you go that route, stop back & let us know how you do.

Mr. Bill
 
n/t
 
Thanks,

I've noticed that on other detectors DD coils too. On the tot lots I use a DD 5" x 10" elliptical coil on my Troy Shadow X5 the steel bottle caps will sometimes fool it in low disc mode when knocking out small iron. My old Tesoro Tejon with the 5 3/4" DD hot head coil has problems with the steel bottle caps too. Some of the stainless steel or nickel foreign coils produce the same problems as steel bottle caps with the DD coils on all 3 of these detectors.

On the F75 I can usually tell the difference between the steel caps and quarters, the caps bounce all of the ID readings, the quarters will lock solid in the low 80's. It's a real pain at a solid trash site, that just happens to have lots of coins. Got a couple that I want to redo, I'm sure I missed good items because of this. One site was a huge 70+ year old former Military/Govt housing site that produced incredible amounts of coins, most were pennies. But it's also loaded with steel bottle caps and other metal trash. We had a couple of big club hunts there, hundreds of coins were dug amongst the junk. Each time we went more coins kept being dug in the same general area. Several costume jewelery items were dug, and a few silver and gold rings too.

I'm leaning towards buying the 6" elliptical for the F75, hoping it might increase my gold jewelry finds in the junky areas. I still use the Shadow X5 and Fisher 1236 at the tot lots and volleyball courts, both seem to hit better on the small jewelry items at a fast sweep speed. I'm also using the tot lots as speed practice for competition hunts for quick recovery. Don't like fooling with the meter when I'm in that type of hunting. Most of the tot lots bark mulch / sand/ gravel play grounds lack the junk at the schools here in Texas.
 
Thanks,

Hoping the 6" will help fish through the junk to the good stuff. Did it help improve your jewelry finds?

I did dig a big .925 silver nugget ring 2 weeks ago with the F75 11" DD coil. The ring was smashed, gave solid high tone in 4H, and steady ID at 81. Thought I had a silver quarter. I found 2 merc dimes, some wheats and a V nickel nearby. Had several of those darn steel bottle caps fooling me too, always wondering if it might be a silver or gold bracelet or big necklace.
The big ring had several steel bottle caps near it. I dug it about 3 inches deep next to a busy city sidewalk & street. One of my hunting partners walked right over it too, the steel caps masked/fooled the DD coil on his Garrett Ace 250.
 
I've kind of been doing the same and the broken signal/ bouncing ID numbers is 90% of the time a steel bottle cap or washer.
This works great if the site has scattered caps. Some of the sites I'm hunting in are really thick with these. I missed a really nice aluminum Texas Good for token, that one of my hunting buddies dug behind me with a Minelab detector. It was shallow but had a lot of steel caps near it. I had been over that small area 3 times, finding several nice old coins, but a lot of junk too.
 
Thanks!

When I spoke with Fisher tech support, Mike says he's got around this by lower sensitivity and using a concentric coil at trash infested city parks.
 
I've tried the 6.5" concentric coil and it still LOVES bottle-caps :ranting:

I'm going to try my 10" concentric from my F70, as I don't recall the F70 having an affinity for bottle-caps and it may just be that specific coil does well with them.
 
Cal_Cobra said:
I've tried the 6.5" concentric coil and it still LOVES bottle-caps :ranting:

I'm going to try my 10" concentric from my F70, as I don't recall the F70 having an affinity for bottle-caps and it may just be that specific coil does well with them.
Click to expand...

Bottle caps and penneys sounding/iding like dime is one of the reasons i gave up the 75. Love the machine for open plowed fields. Ive made some super nice finds with it when i had it too.
 
hi there Byron..
-suggest you go for the small eliptic coil , try to slow down sweep speed a bit, and try use the straight 4 tone and not the
the 4H. Use criss-cross when in pin point and check the read out-- rusty steel b.caps tends to give sharper high tones than coins will do....
happy hunting
trondr
 
According to the F4 Manual the F4 using the same 11X7 DD coil as the F75, Steel bottle tops are a problem and advises that . If a repeatable ID 68-72 it should be a dime or copper penny.
A. If ID not in the range of 68 - 72 Then sweep the ( back edge ) of coil over target if tone changes from medium to lo it is prob a bottle cap..

B. sweep coil faster over target if tone & ID drop = bottle cap faster you sweep lower tone.
 
Thanks everybody! I'm going to buy the 6" concentric elliptical, from your comments and advise from a dealer here in Texas. It's supposed to have a smaller slice footprint than the 5" DD coil. Probably loose some depth, but I don't think that would matter at some of these incredibly metal trashy sites. I'll let y'all know if it makes a difference.

I hunted yesterday at a small house demo site with the F75 and stock 11" DD that must have had a few pieces of small junk metal per square foot ! I did manage to dig a 1945-D Merc dime at about 4", and junk kids ring, clad quarter and one modern penny there. This was a 1940's home site, doubt it had been hunted before. It should produce more, it's an urban site on a busy street next to old railroad tracks. I'll go back and hit it again, when I get the small coil.
 
Mr.Bill said:
It's not the F75's problem, as it is the coils problem. One of the negative points about using DD coils are the way they respond to bottle caps, certainly rusty bottle caps.

Suggestion, use the coil off the F70. It's a concentric design, and should give you a bit better performance with the caps. You also may notice a tad bit better discrimination with it also.

If you go that route, stop back & let us know how you do.

Mr. Bill
Click to expand...
I have 2 detectors from different companies and both have DD coils. My f 75 likes the rusty caps and I never dig any rusty caps with the E-trac. Why is that ,and they both have DD coils. It does not seem that the DD coil is the issue.????? I like and use both units but am puzzled about the rusty caps. I just use the one that fits the site best at the time. HH
 
Sonny, The ET sees both FE and CON values. That's the reason we can tell the difference between a copper penny and a silver dime. Bottle caps have a different FE value than say a silver coin of the same size. There is only so much a company can do with a single frequency detector.

EZ
 
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