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Rajat

Which Is Best Frequency For Detecting Gold Jewelry And Silver Items At The Same Time

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I always have one question in mind which is the best frequency for silver and gold jwellary or treassure hord at the same time i know 7 to 15 khz is for silver relics tressure 15khz to upper is for gold suppose if i find a cannal full of silver and gold jwellary which frequency is best suited for it 

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Any one frequency is a compromise. You kind of answered your own question - you want to be somewhere in the middle. Say 14 kHz give or take a little. Very many "do-it-all" detectors run at 12 kHz to 15 kHz for this reason.

George Payne was one of the engineers who patented many of the basic concepts used in VLF detectors to this day. Here is an excerpt from his article at http://jb-ms.com/Baron/payne.htm (2002):
 
"The r component acts differently. It is maximum at one particular frequency and decreases if you go up or down in frequency. We call the special frequency at which the r signal is maximum, the target’s “-3db” frequency. It also turns out that at the -3db frequency the x signal is one-half of its maximum value. This special frequency is unique to each target and is different for different target.

The higher the conductivity of the target the higher will be the targets -3db frequency. Conversely, the lower the conductivity the lower the -3db frequency. The -3db frequency of the high conductivity target will also make the r signal peak at a high frequency, normally well above the operating frequency of the VLF detector. This will make the high conductivity target have lower sensitivity on the VLF detector because the r signal amplitude drops if we are significantly below the -3db frequency. Simply put, maximum sensitivity on a VLF detector would be if we position the operating frequency directly at the target’s -3db frequency. For example, a dime and penny have a -3db frequency of about 2.7KHz. This is where their r signal peaks and would be the best frequency for picking them up using a VLF detector. However, a silver dollar has a -3db frequency of 800Hz. Nickels, on the other hand, have a -3db frequency, where its r peaks, at about 17KHz. Targets like thin rings and fine gold are higher still. Clearly there is no one frequency that is best for all these targets. The best you can do is have an operating frequency that is a compromise."

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I think the 8 kHz range is a probably the best mid range frequency for a general purpose, do it all, unit.   Once you start going above that frequency you start to loose the general purpose aspect and begin the road to specialization.   Sure, you can use the higher frequency units as general purpose detectors bu the higher frequencies start to induce inherent bias, which moves them away from a true general purpose detector.  

But as we have seen, the various engineers try to do a general purpose unit with all kinds of frequencies.  But in use, you can tell which ones are and aren't.

HH
Mike

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If you include gold prospecting as part of the definition of "general purpose" which I do, then 8 kHz won't cut it. If you exclude gold prospecting that's another thing, but is it then truly general purpose?

To me anyway the 14 kHz MXT is kind of the definitive "general purpose" detector by way of that switch in the upper left.....

IMG_1436.PNG

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Hi Steve.  I stand by my statement.   I was responding to Rajat's statement of. "I always have one question in mind which is the best frequency for silver and gold jwellary or treassure hord ".    Silver, gold and hoards, while each of which have specialty units available, can be hunted with a good 8 kHz general purpose unit.  And contrary to popular belief, some 8kHz units can make a good prospector.   The Fisher F5 at 7.8 kHz has the hots enough to prospect with and the ground balance circuit is pretty decent.   

The V3i's 7.5 kHz is no slouch either.   The V3i is probably the best around best you have the good 7.5 general purpose frequency along with the availability of the 2.5 and 22.5 specialty frequencies.

Anyway...I've spent a lot of time in that range and it can do most things acceptably.

HH
Mike

 

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