depth question

[findit]

how come if the lower frequency goes deeper you get better depth
with the tejon which is on 17 than say a golden which is on 10.
are the newer machines just better and does frequency really not matter that much when it comes to depth. I know about higher being able to detect smaller targets better and all that, but does frequency really help it go deeper. If someone could explain how that works and if they
know of a comparison from the older and new. Also anybody know of a true
accurate depth chart. don't get me wrong i know all the machines will get to depths that most are looking for and are good enough, just looking for an explanation on how some go deeper than others.

 

[gregl01]

Wow, I've been wondering the same!!! Heres what I've concluded so far.... the higher the freq. will go deeper on smaller ferrous items, while lower freq. is deeper on small non-ferrous. I may completely be wrong and hope somebody will correct me and/or elaborate on this subject. I guess this explains why my Cibola loves lead,brass and copper that my other machines have ignored. Good post!!!
Greg

 

[Mike Hillis]

Here is a link with some info to help answer your questions.

http://www.jb-ms.com/Baron/payne.htm

Scroll down toward the bottom to where it has the heading "Why a VLF ground balanced detector has less sensitivity to higher conductive targets in the all metal mode"

Good reading.

HH

 

[Les in the UK]

OPERATING FREQUENCY
Most metal detectors operate on a relatively low signal frequency, between 5kHz and 20kHz. The theory behind frequency selection can be compared to the behaviour of sound waves. Think of the way that the sound of music escapes from a building where a band is playing or when a party is in full swing late at night....... the sounds which you hear most clearly are the low bass notes. This is because low frequency sounds are more able to pass through dense wall materials whereas the high frequency sounds are absorbed. So it is with metal detector signals, the VERY LOW FREQUENCY signals penetrate the ground deeper than the high frequency ones. These detectors are sometimes called VLF machines.
Relatively high frequencies, above 50kHz are sometimes used in metal detectors but they are only of practical value in the search for tiny nuggets of gold in mining areas. This is because of the phenomenon by which low frequencies go deeper into the ground but they are not so sensitive to very small objects. High frequencies penetrate the ground hardly at all but they are sensitive to small objects. The vast majority of objects which treasure hunters in Europe and Asia want to find are ring or coin size and larger. An operating frequency between 5kHz and 20kHz is absolutely ideal for a treasure hunting metal detector because you get optimum depth and optimum sensitivity to the typical target. So called multi-frequency machines have come onto the market in recent years claiming advantages in depth penetration and with some very high prices. Some manufacturer's claims of higher depth capability are overstated because commonsense dictates that the machine will only go as deep as the deepest probing single frequency

 

[findit]

makes perfect sense, great post.Do you happen to know the probing frequency for some of the multi machines. I heard it is 17kHz for one of them.Also I heard coin hunters use an ideal frequency of around 10 to 12kHz then what are the 15 to 20kHz frequency ideal for . Is one frequency better depending on conductivity, then what would be ideal for jewelry and what would be better for coins?

 

[Scully]

Thats why most gold specific machines are at a higher frequency. Thats also why the Tejon hits better on nickels than on silver in an air test. Most machines geared towards coins are usually lower freqency ranges. Coins are at the high end of the scale and gold and nickel (and iron) at the low end.