Operating Frequency on brands

[vefrancis]

Can someone explain what the operating frequency is about? Some brands are low some as high as 19 KHZ. What is the difference ? Higher better? Help please And Happy New Year

 

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[Treasure_Hunter]

Can someone explain what the operating frequency is about? Some brands are low some as high as 19 KHZ. What is the difference ? Higher better? Help please And Happy New Year

Single frequency detector that transmits higher freq are more sensitive to smaller targets, single freq detector that transmits lower freq gets more depth on larger targets,





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[Charlie P. (NY)]

And the question arises whether your wavelength is 62 miles (3kHz) or 6 miles (30kHz) when you are looking through 12 inches of dirt really makes as much difference as we think.

But smaller Hz is better for smaller targets.

 

[woof!]

Charlie meant well but his math was bassackwards. Higher frequency is (all other things being equal, which they never are) better on the smaller and lower conductivity stuff.

Wavelength is irrelevant to metal detectors. One real simple reason: the radiation resistance of the transmitter coil is many orders of magnitude below the ohmic resistance. Searchcoils, although often referred to as antennas, are near-field air core transformers responsive to the magnetic field and (hopefully!) not to the electric field.

 

[atomicscott]

I would listen to woof! He knows his stuff. Gold (VLF) detectors are higher frequency, usually 15 khz or more for the reasons woof mentioned. Better response to smaller & lower conductivity targets such as gold & lead. Check out the free .pdf book, "Gold prospecting with a VLF metal detector" by Dave Johnson (woof knows him well, lol). Its a great, informational read, even if you are not planning on prospecting.

 

[Professor of Engineering]

Hello Woof,

Thank you for the information.

Doc

 

[Charlie P. (NY)]

Charlie meant well but his math was bassackwards. Higher frequency is (all other things being equal, which they never are) better on the smaller and lower conductivity stuff.

I think I wrote my got all up screwed. Happily I'm not an engineer or the nurse dispensing your medication.

I was looking through some old W&E Treasure magazines and there was a Garretts ad discussing the merits of a single frequency over a multi-frequency detector. A few years later other brands were claiming just the opposite.

Does a detector do better sending and receiving a single frequency or is a broadcast more effective? Or does it make no real difference at all as they're just detecting the effects of conductive items within the coil's field?

I know ain't nuttin ever easy but it would seem the larger & higher conductive items are "low hanging fruit" and a detector will react to them regardless so a higher frequency would be desirable for the smaller items. There must be a trade-off (or ten) in penetration or signal corruption of the higher frequencies or some such?

 

[atomicscott]

I think I wrote my got all up screwed. Happily I'm not an engineer or the nurse dispensing your medication.

I was looking through some old W&E Treasure magazines and there was a Garretts ad discussing the merits of a single frequency over a multi-frequency detector. A few years later other brands were claiming just the opposite.

Does a detector do better sending and receiving a single frequency or is a broadcast more effective? Or does it make no real difference at all as they're just detecting the effects of conductive items within the coil's field?

I know ain't nuttin ever easy but it would seem the larger & higher conductive items are "low hanging fruit" and a detector will react to them regardless so a higher frequency would be desirable for the smaller items. There must be a trade-off (or ten) in penetration or signal corruption of the higher frequencies or some such?

Ok not an expert, but the higher frequency coils are putting more khz per sweep, lets say 50 khz as opposed to an F5 at 7 khz (or so) hence the ability to find smaller objects. Since gold is a lower conductor, it responds better to a high frequency, that is 'seeing' that conductivity better. Silver being a high conductor, doesnt needed as many "waves" (think 5 or less khz) per sweep; as it conducts so well, it is easier to 'see' with a low khz. This may not be exactly explained properly, but I think it's close, lol.

 

[Phantasman]

From Dave J's interview with DetectorStuff

DS: Seems specialized detectorists feel frequency/khz is so important now, claiming a 7khz Coin$trike for example is for coins not relics. Is 13khz great for all-around hunting, & why don’t we see say 25khz units for relic hunters?
"In general, higher frequencies are better for smaller and lower conductivity stuff, and lower frequencies are better for larger and higher conductivity stuff. Relic hunters are generally looking for stuff that is smaller or lower conductivity than US clad, copper, and silver coinage. However, frequency is not critical, and a 7 kHz machine can be good on relics and a 13 kHz machine can be good on coins.
Metal detector manufacturers generally avoid the 20-30kHz range because of electrical interference from military communications."

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[RockRaven]

This thread contains so much great information, the link to the gold prospecting pdf is of great value to me. It is wonderful that those with so much knowledge are here on treasurenet. Thanks.

 

[atomicscott]

This thread contains so much great information, the link to the gold prospecting pdf is of great value to me. It is wonderful that those with so much knowledge are here on treasurenet. Thanks.

Yes the .pdf is awesome. I printed it out and have read it a few times. I almost feel guilty it was free!

 

[LawrencetheMDer]

Yes the .pdf is awesome. I printed it out and have read it a few times. I almost feel guilty it was free!

The Johnson book is very informative about frequency and gold detection and urge readers on this topic to read free.
Link: http://www.fisherlab.com/hobby/davejohnson/DavesGoldbook-reders.pdf

 

[Terry Soloman]

For those of you that don't know "Woof" by his other name, Dave Johnson, he is the Chief Engineer at First Texas, and the renowned designer of many of my favorite metal detectors.

Dave Johnson's Essays

http://www.fisherlab.com/Hobby/davejohnson/DavesGoldbook-reders.pdf

 

[motohed]

Ok not an expert, but the higher frequency coils are putting more khz per sweep, lets say 50 khz as opposed to an F5 at 7 khz (or so) hence the ability to find smaller objects. Since gold is a lower conductor, it responds better to a high frequency, that is 'seeing' that conductivity better. Silver being a high conductor, doesnt needed as many "waves" (think 5 or less khz) per sweep; as it conducts so well, it is easier to 'see' with a low khz. This may not be exactly explained properly, but I think it's close, lol.

Sorry ,but I have too say Gold is a high conductor , but usually found in a smaller quanity .

 

[dirtscratcher]

Sorry ,but I have too say Gold is a high conductor , but usually found in a smaller quanity .

You need to do some research gold is not a high conductor. It's used in electronics because it never corrodes. Not because it's a high conductor.

 

[atomicscott]

Sorry ,but I have too say Gold is a high conductor , but usually found in a smaller quanity .

Wow, it is common knowledge that gold (like lead) is a low conductor & higher frequency machines are better suited for the task of gold nugget hunting. A simple google search will prove it.

 

[motohed]

Wow, it is common knowledge that gold (like lead) is a low conductor & higher frequency machines are better suited for the task of gold nugget hunting. A simple google search will prove it.

Sorry , I was thinking tone wise , not so much conductor wise .

 

[RobRieman]

Sorry , I was thinking tone wise , not so much conductor wise .

Gold is not a high tone either, it mostly lives in the mid/low tone area and is good friends with the pull tab [emoji4]

 

[motohed]

I guess that all depends on the machine you are running and having the ability to set your tones up .

 

[RobRieman]

I guess that all depends on the machine you are running and having the ability to set your tones up .

Well yeah if you look at it that way. I guess every target could ring in the opposite of everyone else's. But it makes it hard to join in on a conversation when someone asks what it rings up as.