It seems the many have obviously overlooked the fact that the X-Terra is not just another VLF, with the added capability of utilizing 3 different frequencies of coils. It is so much more than that. The X-Terra is based on a whole new concept in metal detectors, called VFLEX. The X-Terra utilizes state of the art digital and mixed signal components to enhance standard single frequency technology. One of the most beneficial advantages of VFLEX technology is the microprocessor in the detector housing that communicates over a data link to a microchip in each coil. Having the coil communicate over a data link, as opposed to sending electrical impulses up the coil cord, provides more dependable performance and greatly reduces the influence of outside interference.
If someone was truly interested in understanding the differences between the three frequencies of X-Terra coils, they would only have to search this forum for past posts. As many of us have proven over and over again, all three coil frequencies will detect copper, silver and gold. In my opinion, the frequency of coil I chose has as much to do with target size as it does the target's metallic composistion. My higher frequency coils are more sensitive to the smallest targets than the lower frequency coil. The lower frequency of coils hunt deeper for me. And frankly, just because one frequency performs better at detecting targets with a higher conductivity, for example, doesn't mean that it still isn't good at detecting targets with a lower conductivity. The minimal difference between 3 kHz, 7.5 kHz and 18.75 kHz probably won't matter to most detectorists. But it matters to the guy hunting gold nuggets, the guy hunting for those rings on the beach and those of us who like to hunt old homesites and were tired of digging up chunks of iron.
All metal objects, whether ferrous or non-ferrous are conductive. To understand why certain frequencies of detectors perform better than others, on specific targets, we must first understand the difference between ferrous and non-ferrous properties. The term ferrous is derived from the Latin "Ferrum" which means "containing iron". Common ferrous metals include the various irons and steels. Common non-ferrous metals include aluminum, tin, copper, zinc, and brass, an alloy of copper and zinc. Some precious metals such as silver, gold, and platinum are also non-ferrous. Silver has the highest electrical conductivity of all metals. Even higher than copper. Better electrical conduction implies more loosely-held valence electrons; more loosely-held electrons allows for better metallic conduction. (The exception to this rule is silver and copper. Although silver is a slightly better electrical conductor than copper, it is less chemically reactive. that is why the old copper coins we dig up are more deteriorated than old siver coins) Gold is often used for electrical contacts not because it is the best electrical conductor but because it is the least chemically reactive of metals. Metal oxides and sulfides (the tarnish on copper and silver) are insulators and disrupt electrical connections.
Generally speaking, VLF metal detectors operate in the 3 kHz - 30 kHz range. We have all been told that the lower the detector's frequency, the deeper it will penetrate. But we also recognize that lower frequency detectors may not be as sensitive to smaller targets. On the other hand, the higher the detector's frequency, the higher its sensitivity to even the smallest targets, but it may not penetrate as deeply. If you take a look at the marketplace, gold detectors operate at a higher frequency for locating small gold nuggets. Coin, relic and treasure hunting detectors generally operate at lower frequencies for greater depth penetration. Over the years, engineers have figured out that higher frequencies were more suited for detecting targets with lower conductivity, like gold. And likewise, lower frequency detectors were better suited for detecting higher conductive targets such as silver and copper. To give you an idea of the differences between these three metals, the electrical conductivity ratio of Silver is 63010000/ohm.m. The electrical conductivity of copper is 59610000 /ohm.m The electrical conductivity of gold is 45210000 /ohm.m. Based on this data, it is obvious that gold is less conductive (more resistant to current flow) than either silver or copper. A target that conducts electricity easily (is inductive) reacts slowly to changes in the current. A target that does not conduct electricity easily (is resistive) reacts quickly to changes in the current. For metal detecting, this means that an object with high inductance is going to have a larger phase shift, because it takes longer to alter its magnetic field. An object with high resistance is going to have a smaller phase shift. As well, the impedance of an inductor will increase proportional to the frequency being induced. So, based on this very brief description of frequency and metallic content, you can see that silver, gold and copper will all respond differently to any given detector frequency. And by changing the frequency of the detector, whether by a coil or chosing a different detector, you will alter the response produced by any given target.
I'm not going to get into a technical discussion about single frequency VLF detecors vs. BBS or FBS. Just realize that the frequency a detector operates is only one factor in determining the depth of detection or how sensitive it might be to specific targets. Other factors include mineralization, sweep speed, target response speed and coil size and design, to name a few. As well, depth and sensitivity are only two aspects some of us consider when chosing our detector. It all depends on where you hunt and what you are hunting for. And in the case of the X-Terra, VFLEX technology, being very light weight, well balanced and the option to chose any of 3 different operational frequencies, are other factors most folks consider. Providing a 7.5 kHz coil as a stock "all around" coil is the only coil that some folks will ever need. To have the option of connecting an 18.75 kHz coil for prospecting is something that no other manufacturer has done. Allowing another person to put on the 3 khz, in an effort to help "sort out the iron" from the old silver coins at an old homesite, is another. And having DD coils for those who hunt in highly mineralized soils is yet another. HH Randy
If someone was truly interested in understanding the differences between the three frequencies of X-Terra coils, they would only have to search this forum for past posts. As many of us have proven over and over again, all three coil frequencies will detect copper, silver and gold. In my opinion, the frequency of coil I chose has as much to do with target size as it does the target's metallic composistion. My higher frequency coils are more sensitive to the smallest targets than the lower frequency coil. The lower frequency of coils hunt deeper for me. And frankly, just because one frequency performs better at detecting targets with a higher conductivity, for example, doesn't mean that it still isn't good at detecting targets with a lower conductivity. The minimal difference between 3 kHz, 7.5 kHz and 18.75 kHz probably won't matter to most detectorists. But it matters to the guy hunting gold nuggets, the guy hunting for those rings on the beach and those of us who like to hunt old homesites and were tired of digging up chunks of iron.
All metal objects, whether ferrous or non-ferrous are conductive. To understand why certain frequencies of detectors perform better than others, on specific targets, we must first understand the difference between ferrous and non-ferrous properties. The term ferrous is derived from the Latin "Ferrum" which means "containing iron". Common ferrous metals include the various irons and steels. Common non-ferrous metals include aluminum, tin, copper, zinc, and brass, an alloy of copper and zinc. Some precious metals such as silver, gold, and platinum are also non-ferrous. Silver has the highest electrical conductivity of all metals. Even higher than copper. Better electrical conduction implies more loosely-held valence electrons; more loosely-held electrons allows for better metallic conduction. (The exception to this rule is silver and copper. Although silver is a slightly better electrical conductor than copper, it is less chemically reactive. that is why the old copper coins we dig up are more deteriorated than old siver coins) Gold is often used for electrical contacts not because it is the best electrical conductor but because it is the least chemically reactive of metals. Metal oxides and sulfides (the tarnish on copper and silver) are insulators and disrupt electrical connections.
Generally speaking, VLF metal detectors operate in the 3 kHz - 30 kHz range. We have all been told that the lower the detector's frequency, the deeper it will penetrate. But we also recognize that lower frequency detectors may not be as sensitive to smaller targets. On the other hand, the higher the detector's frequency, the higher its sensitivity to even the smallest targets, but it may not penetrate as deeply. If you take a look at the marketplace, gold detectors operate at a higher frequency for locating small gold nuggets. Coin, relic and treasure hunting detectors generally operate at lower frequencies for greater depth penetration. Over the years, engineers have figured out that higher frequencies were more suited for detecting targets with lower conductivity, like gold. And likewise, lower frequency detectors were better suited for detecting higher conductive targets such as silver and copper. To give you an idea of the differences between these three metals, the electrical conductivity ratio of Silver is 63010000/ohm.m. The electrical conductivity of copper is 59610000 /ohm.m The electrical conductivity of gold is 45210000 /ohm.m. Based on this data, it is obvious that gold is less conductive (more resistant to current flow) than either silver or copper. A target that conducts electricity easily (is inductive) reacts slowly to changes in the current. A target that does not conduct electricity easily (is resistive) reacts quickly to changes in the current. For metal detecting, this means that an object with high inductance is going to have a larger phase shift, because it takes longer to alter its magnetic field. An object with high resistance is going to have a smaller phase shift. As well, the impedance of an inductor will increase proportional to the frequency being induced. So, based on this very brief description of frequency and metallic content, you can see that silver, gold and copper will all respond differently to any given detector frequency. And by changing the frequency of the detector, whether by a coil or chosing a different detector, you will alter the response produced by any given target.
I'm not going to get into a technical discussion about single frequency VLF detecors vs. BBS or FBS. Just realize that the frequency a detector operates is only one factor in determining the depth of detection or how sensitive it might be to specific targets. Other factors include mineralization, sweep speed, target response speed and coil size and design, to name a few. As well, depth and sensitivity are only two aspects some of us consider when chosing our detector. It all depends on where you hunt and what you are hunting for. And in the case of the X-Terra, VFLEX technology, being very light weight, well balanced and the option to chose any of 3 different operational frequencies, are other factors most folks consider. Providing a 7.5 kHz coil as a stock "all around" coil is the only coil that some folks will ever need. To have the option of connecting an 18.75 kHz coil for prospecting is something that no other manufacturer has done. Allowing another person to put on the 3 khz, in an effort to help "sort out the iron" from the old silver coins at an old homesite, is another. And having DD coils for those who hunt in highly mineralized soils is yet another. HH Randy