How reliable is the notch system?

[opus]

Should I invest in a multi-tone instrument? And if so, what's the best buy? I'm mainly a coinshooter and I'd like to know how these detectors preform in trashy areas; coins hiding under pull tabs, what object would it respond to? I know that without practice, you're not gonna get good with any detector, but I'm thinking more coins, less pull tabs!

 

[BarberBill]

Well, whether it's notch or dial in discrimination, if you've disced out pull tabs you've also eliminated most gold jewelry and all nickels.
As soon as the detector reads a buried pulltab it will miss any good target underneath and/or near it. I'm not sure how well notch disc works on the targets on either side of the notch, but I'm thinking you'll likely miss many good targets if they're close enough to be masked. This is easy to test by putting a coin under or very near any junk target, then passing the coil over it to see what happens. Some machines do better than others in relation to the proximity of the two targets so it's worth testing on your machine and using different coils . If you read through the different forums back aways you'll read that those that find the most jewelry and the deeper, better old coins use little or no discrimination and dig everything, including pesky pull tabs. Just a sad fact of detector physics.

As to multi tones, some love them and some don't. I'm inclined to think that more than 3 or 4 tones would become confusing. It's something you'd have to try and decide for your self.
BB

 

[slingshot]

The reliability of ANY id system suffered a serious blow when the newer square tabs were made since they're in the nickel range. Also,any combo of different metals and ground metals cause error. The biggest factor, as you point out is where gold rings fall. They are in the iron, foil, pulltab and square tab range-and some have been found in the coins range.I only use one in the heaviest of trash and leave the foil accepted. Otherwise, I'm just above iron nail reject. One ring can make up for a lot of trash.

 

[Elton]

To take out a persistent pesky target and still leave in most good things. It was never designed to hunt with on it's own merit..... Just a tool to assist you in making the best of your detecting outings. If your hitting a gazillion one type tab to one good target then you notch out the bad target so you can hunt the area without digging the gazillion bad items..



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EL

Digging the past !! ..."Preserving for the future"

 

[Elton]

n/t

 

[UK Brian]

Re the notch there's good and bad systems but all suffer the same problems. Fieldmaster had "auto -notch". Terrible. Then there's the original + cheper machines systems where the notch width is pre set. Not really much good. Then followed the machines where the notch width could be adjusted. This was better as you could just take out an item and still recover items that come in each side of the rejected item. Last came the notch "accept" and "reject" systems as used by Whites. You could notch out a certain size of ringpull by sweeping it in front of the coil and getting the detector to learn its target signature or notch out everything but get the detector to learn say a lost earing signature by sweeping the other earing across the coil. Looking for lost items this really speeds up the hunt.

The system will allow dozens of "notches" both accepting and rejecting items if thats what you require.

All suffer the same problem. If its ringpulls you are bothered with there's small and large, anodised or not, square and round, plus any of these sitting at different angles to the coil all of which changes the target signature. Widen out your notch setting to allow for these variations and you lose so much good stuff its hardly woth bothering and the masking of items that are lower in the ground makes things even worse. Better to dig and remove them.

As mentioned in a post below not many can cope with lots of tones. There's also an experiment any one with a test bed consisting of the same target set at different depths can try. If you have a machine where you can select either tones or just "beep and dig" all you have to do is run along until the audio starts to become a little iffy. From this point the coins will still be located but the beep and dig setting would have you digging the target out in the field whilst the tones will start to I.D. as iron meaning you would ignore a good target. Worse the ground mineralisation the worse the effect.

 

[Mike Hillis]

n/t