Calibrating a metal detector for certain metal?

No detector is perfect, nor will any always always tell you EXACTLY what is under the coil. Experience with a certain detector has enabled many of us to get better at ID's before we dig by learning the combination of the VDI numbers and the tones. I'm sure some F75se guys will chime in and give you valuable advice, but there is really no substitute for experience. Best of luck.

Deeper targets are harder for the machine to ID correctly. As for EMI, if your machine has a frequency select like the AT Pro where you can slightly shift the operating frequency, that's your best bet. Otherwise, back the sensitivity off to see if it will settle down.

Papa

If your finding Gold Coins in a certain area ? I'd go Wide-open/ FULL THROTTLE on that thing and dig all,,,

sounds like a great spot i'd dig everything that hit solid. hope you find alot there.

Thanks everyone!

Thanks guys. You've been very helpful. I appreciate it. The findings are my friend's, truth be told. I'll make him take pictures and post it for you. You deserve it. As for your answers, yes you guys are right. I think experience and getting familiar with the combination of the ID number along with the heard tone is his best choice. I don't think you can change the freq on f75se though. And yes, he should be digging the whole place up. The problem seems to be that the land owner isn't back in town yet. Waiting never been harder.

You have 7 choices of frequency settings I believe. To change hold trigger and hit menu it should go from 1 to 7. It should be in the manual on how to change if this isn't correct.

The main operating frequency dictates the coins/metals that respond best to the machine. Lower frequencies (2.5khz to 5khz range) hit on silver better, and higher frequencies (15khz+) hit on gold better. Frequencies in the middle are kind of the jack of all trades master of none. If you are after gold, you want a higher frequency machine.

An example of this would be on the V3i, you have the option of 2.5khz, 7.5khz, 22khz, or all three at the same time (multi-frequency). When in 2.5khz mode, it obviously hits on silver hard and deep, getting 10"-12" on a silver dime, but only like 8" on a nickel, and it won't see a 14k earring back. 22khz mode on the other hand, it air tests nickels at 14", and can see a 14k earring back at 4", but only hits a silver dime at like 8".

So it's all in the operating frequency.

Where it gets confusing... is that the bigger the gold, the lower the frequency that will respond best to the large gold. For example, on a big 15.5 gram 18k gold ring, it actually hits hardest on the 7.5khz frequency on the V3i.

If you want a machine that can choose a wide range of different operating frequencies, look into the DFX/V3i.

Another option when strictly looking for gold, would be to buy a dedicated high frequency machine. There are quite a few of them... AT Pro, AT Gold, Vaquero, Tejon, Gold Bug Pro, Gold Bug 2, GMT, etc. All of them will hit on gold harder than silver, and will see gold that a lower frequency passes right over, like thin gold chains/earring backs. A few of them can be found for about $300 used, and will be worth it if you are finding gold coins in your area.

The frequency change on the F75 is called a frequency offset, it changes the operating frequency very slightly to try to quiet down EMI. It isn't a frequency change like the DFX/V3i.

Set the F75 up on a table, and do some air tests with an older nickel, and some gold rings/chains if you have a few. That will give you an idea of how it will respond in the dirt, because generally air tests are the best case scenario.

No metal detector can actual test metal content, that's a different sort of machine, which deals with a sample to be tested. Metal detectors simple detect conductive materials. There are some subtle differences between metals, size, shape, unfortunately can be the same or very similar. They aren't completely unique to the detector, it can only give you suggestions. Learning the tones, will give you better accuracy in what you want to dig up, or leave behind. Not everyone can train themselves, or hear well enough.

Environmental factors influence the signals we receive, and will effect the ID numbers. There won't be a single number for each type of metal or target, just a range of numbers. Some target can ID as most anything. Multiple targets under the coil, can also mess up ID numbers, even if you discriminate out some trash, it still gives off a signal. The detector wants to identify a single target, gets confused a little with multiples close together.

Coins are great though, solid, uniform sizes and shapes, pretty easy to learn the tones, machines have something consistent to work with. They aren't always laying flat, could be other conductive materials close by. Gravity wants to make them lay flat, and they will tend to eventually settle that way, if possible.