Nice items there and I do like that silver ring.
With the large mineralised ferrous plate - I have now realised (by reading the manual for the third time - I wonder about me sometimes) that whereas a large mineralised piece of iron will fool most detectors - including the F5 - the F5 has that brilliant fe bar bottom right. If that fills then that large but clear signal one hears is sneaky ferrous .. rusty iron .. so it is 'walk away' - now how great is that!
I don't know how to run it as hot as one can - but I run my F5 like this -
I disc to 15, which just cuts out iron and small nails as I don't want to miss any small hammered coins (of which I've found many) or our tiny Celtic Pre-Roman gold coins (of which I've found none in ten years - lol).
Then I threshold somewhere between +2 and +4. Reason being that I want a louder signal and threshold acts as a volume control in the + range, whereas in the - range it decreases susceptibility to tiny items.
Gain I run as high as it will go until the machine starts to chatter - give false signals - then I reduce it slightly until it runs stable. This I monitor regularly as I try to keep it as high as I can to get deeper. I also don't want to over-flood the ground and decrease penetration so do keep an eye on it - like headlights in the fog in some circumstances too much means too little.
I don't use notch - again because of our small silver hammered coins which can give a similar reading to some pull-tabs and also thin old gold can come up in the foil range. Actually I don't know of anyone that uses notch on farmland over here.
I tend to use D3 as I find D4 too noisy and D2 too uninformative (are there three bears and a blonde girl in this story?).
I keep an eye on the phase so that I know the detector is as ground-balanced as possible.
I dig all two-way signals unless the Fe bar fills and I tend to dig faint 'scratchy' signals by taking off the top few inches of soil to see if it is a deeper good item at the limit of detection - it is, many times.
Since reading an earlier part of this thread that mentioned how much deeper all-metal is than in disc I am now experimenting with running in all-metal to see how I like it - so far it seems a little too much on iron-infested ground but much easier to use on long-term pasture, which tends to have less metal items in it.
Most UK detecting is on farmland as local councils tend to look very unfavourably on detecting in parks. From my reading of the American forums there seems to be a lot of ruined building plots searching, as well as parks and playing fields. Do any of you get permission from farmers and detect on open land? You just never know where a company of soldiers camped for a day or two en route to somewhere .. either side of a fordable stream tends to be good, as well as around a spring - even if there are absolutely no signs of previous habitation. Also, at harvest time each field was filled with people, who also had there lunch breaks there .. say 50 people in a particular field each harvest X 200 years .. that's 10,000 people ... and people drop things. In our case it is X 3,000 years of course

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