What is the deal with multi frequency metal detectors?

Multi frequency is not a "trend"; its been around for at least a decade.

I am not an electrical engineer, but the general theory is that as different targets respond better to different frequencies (e.g., silver responds better to lower frequencies), it makes sense to shoot a range of frequencies into the ground to give you a higher chance to hit more stuff. I also believe certain frequencies deal with mineralized ground better, tho I am not certain on this point.

To answer your third question, I am quite happy with my E-Trac. It performs much better than any single frequency detector I have used. Moreover, it has 11 channels which let you shift the frequencies slightly, which can be quite powerful in certain situations, tho the actual mechanism is not disclosed by Minelab.

randy gave you some good information. Actually Minelab's first multi frequency VLF detector I think, was the original Sovereign which used Minelab's BBS technology and was released in 1991. Randy's E-Trac, which is Minelab's FBS technology was released in 2008. Multi IQ, Minelab's latest VLF version of simultaneous multi frequency detectors used in the Equinox and Vanquish series came out in 2018. So Minelab has been making simultaneous multi frequency VLF detectors for 30 years. White's have also made some simultaneous multi frequency VLFs with their DFX and V3 detectors along with the CZs made by Fisher. Garrett just released its ACE Apex which is a simultaneous multi frequency detector but it is nowhere near as advanced a form of simultaneous multi frequency technology as what is used by Minelab. But, like I said Minelab has been doing this for 30 years and their newest Multi IQ detectors have almost solved the big problems which for simultaneous multi frequency detectors have always been signal processing capacity/speed which adversely effected target recovery speed, target separation and at least equal depth between single and simultaneous multi frequencies on the same detector along with successfully handling really bad iron mineralization.

There is no bragging or hype involved in how these detectors actually work. It is not a secret or something magic. Simultaneous multi frequency detectors have their uses and are just part of the detecting tool box. The Equinox just happens to work really well in almost every detecting scenario. Most experienced, unbiased Equinox users that have owned and used lots of different brand VLF detectors will tell anyone that wants to know that they would pick an Equinox either first, second or maybe third for any detecting task except deep scuba diving in salt or fresh water and for detecting gold nuggets in thick magnetite or maghemite highly mineralized ground.

What Minelab marketing says about their products and any marketing department of any manufacturing company for that matter should be taken with plenty of salt however. They aren't necessarily lying but they are trying to sell a product that many of them don't know how to use at even a beginner's level.

So, what does Minelab's Multi IQ simultaneous multi frequency system do that is different from single frequency VLF detectors?

These two quotes (not hype from marketing) are from Minelab's head physicist for the Multi IQ project. Multi IQ stands for simultaneous multi frequency In-phase and Quadrature synchronous demodulation. I won't even try to translate that. Here are the quotes from Dr. Warlich:

“Within the Multi-IQ engine, the receiver is both phase-locked and amplitude-normalized to the transmitted magnetic field – rather than just the electrical voltage driving the transmitted field. This field can be altered by the mineralization in the soil (in both phase and amplitude), so if the receiver was only phased-locked to the driving voltage, this would result in inaccurate target IDs and a higher audible noise level. Locking the receiver to the actual transmitted field, across all frequencies simultaneously (by measuring the current through the coil) solves these issues, creating a very sensitive AND stable detector”

“For each frequency the detector transmits and receives there are two signals which can be extracted which we refer to as I and Q. The Q signal is most sensitive to targets, while the I signal is most sensitive to iron content. Traditional single-frequency metal detectors use the Q signal to detect targets, and then use the ratio of the I and Q signals to assess the characteristics of the target and assign a target ID. The problem with this approach is that the I signal is sensitive to the iron content of the soil. The target ID is always perturbed by the response from the soil, and as the signal from the target gets weaker, this perturbation becomes substantial. With some simplification here for brevity, if a detector transmits and receives on more than one frequency, it can ignore the soil sensitive I signals, and instead look at the multiple Q signals it receives in order to determine a target ID. That way, even for weak targets or highly mineralized soils, the target ID is far less perturbed by the response from the soil. This leads to very precise target IDs, both in mineralized soils and for targets at depth.”

I can attest to the fact that the Equinox and Vanquish have very accurate numerical and audio target IDs. There is some practice involved and these detectors cannot tell you if a target is aluminum or gold IF they respond electrically with the same target ID which they do on any detector. However, for example, if you detect a non-ferrous target with a Vanquish 440 that is a low conductor like a piece of gold jewelry, lead, aluminum pull-tab or a US nickel at 1" depth, it will also detect accurately the same way that same target if it is 10" deep. The signal might be weaker but the audio tone pitch and the numbers will be virtually the same. Most single frequency VLF detectors will do very well accuracy wise on those same targets if they are shallow to medium depth depending on the amount of iron or other mineralization in the soil. As those targets get deeper most single frequency VLFs will either read those same targets as iron or as very high conductors in the silver range. Some will just give you a tone and no numerical target ID at all. So you end up possibly not digging the target because your single frequency detector says it's too iffy, it could be iron or you spend several valuable minutes digging a deep target your think might be high conductor silver which ends up being a pull tab or other aluminum trash. It could turn out to be a nickel or gold too or actually silver or a high conductive coin, you just don't know. With the Equinox and the Vanquish you do have a really good idea if the target is a non-ferrous low, mid or high conductor no matter how deep it is. The weak point, as explained by Dr. Warlich is iron since Multi IQ basically ignores the iron In-phase part of the return signal. So iron can read as iron correctly and/or it can "false" throughout the Equinox and to a lesser degree, the Vanquish numerical target ID range. With some practice and some good use of some of the features and settings, this iron issue can be worked around. I rarely dig iron trash accidentally any more using the Equinox and Vanquish except for the occasional rusted bottle cap or really deep bent nail.

By the way, I don't know what Nokta Makro did to the Simplex, but at least in the moderate to highly mineralized soil where I usually detect, the Simplex has some of the most accurate tone and numerical target IDs I have experienced down to about 6" deep. In my dirt that is really good. Some very expensive single frequency VLF detectors, even some made by Nokta Makro, completely lose their accuracy at 3 to 4" here. So, don't bad mouth your Simplex. It is an amazing detector for the money and definitely can hunt with the big dogs.

EMI can hinder on muti-frequency detectors. The DFX you could use 3KHz or 15KHz or both at the same time. DFX had best data running 3KHz & 15KHz giving the best signal from either frequency. It also had correlate running3KHz & 15KHz where it had to agree before calling a target.

Minelab running muti-frequency you don't have a choice of what frequency you want to run.

graybeard said:

EMI can hinder on muti-frequency detectors. The DFX you could use 3KHz or 15KHz or both at the same time. DFX had best data running 3KHz & 15KHz giving the best signal from either frequency. It also had correlate running3KHz & 15KHz where it had to agree before calling a target.

Minelab running muti-frequency you don't have a choice of what frequency you want to run.

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If both frequencies had to agree to call it a target wouldn't that make it prone to missing targets they couldn't agree on? like iron masking a silver coin?

Coin-Saver said:

If both frequencies had to agree to call it a target wouldn't that make it prone to missing targets they couldn't agree on? like iron masking a silver coin?

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Running it in correlate it could make it so it would miss targets. In best data it would sound of on every target that it would call a good target.

graybeard
"EMI can hinder on muti-frequency detectors. The DFX you could use 3KHz or 15KHz or both at the same time. DFX had best data running 3KHz & 15KHz giving the best signal from either frequency. It also had correlate running3KHz & 15KHz where it had to agree before calling a target."

"Minelab running muti-frequency you don't have a choice of what frequency you want to run."

Graybeard, you do have sort of a choice of what frequency you want to run on the Equinox in Multi. Just change modes, do a new auto noise cancel and lower the sensitivity a bit until the EMI quiets down. Each mode uses slightly different frequency combinations. Plus, as you know, you can also just switch to a single frequency on the Equinox if nothing else will take care of the EMI. You don't have any choice using the Vanquish but I have not had any problems with EMI using the Vanquish so far.

I really enjoyed using my Whites DFX as long as I did not use it for detecting that highlighted its weaknesses. It was great for open areas with just a little trash, for the beach and especially for shallow to medium depth down to about 6" on most jewelry and coins. The Signagraph in best data was amazing and very accurate too on good targets. At least for the areas that I used it, it got very little depth no matter what coil I used and since salt compensation was always on it had a pretty big detection hole in the small gold jewelry and smaller gold nugget range. In my area it was also very susceptible to EMI (much worse than the Vanquish and Equinox) and its ground tracking and slow recovery speed could not handle the high mineralization around here. Otherwise, it was amazing for shallow to medium depth coin and jewelry hunting in normal dirt without too much trash.

Talk about hype......Minelab aren't the only ones that try to fill our minds with semi truths. This is from Whites 2006 catalog about the DFX.....

"Here it is. The finest all-around metal detector. DFX™ is simply unsurpassed in its ability to find treasure - older, deeper and smaller items that other detectors pass over. DFX™ brings together the ultimate combination of sophisticated microprocessor technology, and turn-on-and-go simplicity. You’re out and hunting right away, but there are dozens of adjustments available if you choose. White’s patented multifrequency method partners with the target I.D. you get only from DFX. “See through” minerals in the ground and detect coins, jewelry and relics other detectors miss. Hunt in 3 kHz or 15 kHz (the two best frequencies for finding treasure) or use both together for unequalled hunting. Choose Best Data and the DFX™ displays data from the most reliable frequency. Choose Correlate and questionable targets, including iron, are rejected. All happening automatically while you hunt! There are dozens of features that come together in the DFX™ to create the world’s best metal detector. It’s built on White’s proven digital platform, with the features that give you more flexibility to find it all!"

The DFX is one detector I really miss. I needed to sell some things during this pandemic and the DFX had to go. After all of this is over, I plan to find another one. However, when I finish detecting an area with a DFX, I always go over the same are with a Deus and an Equinox............just to make sure that I haven't missed anything important.

Are you guys saying that the equinox is NOT running all 5 frequencies at once when in multi ? If the answer is no,then why?

woodbutcher
Are you guys saying that the equinox is NOT running all 5 frequencies at once when in multi ? If the answer is no,then why?


There will not be a definitive answer to your question until Minelab decides to tell us or until the Multi IQ patent runs out.

So far, two or three different frequencies at once in each mode is what I have been told by some pre production field testers that signed NDA's. That is also been supported by some users that have done their own tests with spectrum analyzers and oscilloscopes. Minelab has never claimed publicly that all five frequencies were being used in one mode at the same time.

I am no electrical engineer so I can't answer your question about why. You could go over to Detector Prospector and ask Geotech that question. He is currently one of the engineers at First Texas and helped design the Whites V3i.

jmaclen said:

graybeard
"EMI can hinder on muti-frequency detectors. The DFX you could use 3KHz or 15KHz or both at the same time. DFX had best data running 3KHz & 15KHz giving the best signal from either frequency. It also had correlate running3KHz & 15KHz where it had to agree before calling a target."

"Minelab running muti-frequency you don't have a choice of what frequency you want to run."

Graybeard, you do have sort of a choice of what frequency you want to run on the Equinox in Multi. Just change modes, do a new auto noise cancel and lower the sensitivity a bit until the EMI quiets down. Each mode uses slightly different frequency combinations. Plus, as you know, you can also just switch to a single frequency on the Equinox if nothing else will take care of the EMI. You don't have any choice using the Vanquish but I have not had any problems with EMI using the Vanquish so far.

I really enjoyed using my Whites DFX as long as I did not use it for detecting that highlighted its weaknesses. It was great for open areas with just a little trash, for the beach and especially for shallow to medium depth down to about 6" on most jewelry and coins. The Signagraph in best data was amazing and very accurate too on good targets. At least for the areas that I used it, it got very little depth no matter what coil I used and since salt compensation was always on it had a pretty big detection hole in the small gold jewelry and smaller gold nugget range. In my area it was also very susceptible to EMI (much worse than the Vanquish and Equinox) and its ground tracking and slow recovery speed could not handle the high mineralization around here. Otherwise, it was amazing for shallow to medium depth coin and jewelry hunting in normal dirt without too much trash.

Talk about hype......Minelab aren't the only ones that try to fill our minds with semi truths. This is from Whites 2006 catalog about the DFX.....

"Here it is. The finest all-around metal detector. DFX™ is simply unsurpassed in its ability to find treasure - older, deeper and smaller items that other detectors pass over. DFX™ brings together the ultimate combination of sophisticated microprocessor technology, and turn-on-and-go simplicity. You’re out and hunting right away, but there are dozens of adjustments available if you choose. White’s patented multifrequency method partners with the target I.D. you get only from DFX. “See through” minerals in the ground and detect coins, jewelry and relics other detectors miss. Hunt in 3 kHz or 15 kHz (the two best frequencies for finding treasure) or use both together for unequalled hunting. Choose Best Data and the DFX™ displays data from the most reliable frequency. Choose Correlate and questionable targets, including iron, are rejected. All happening automatically while you hunt! There are dozens of features that come together in the DFX™ to create the world’s best metal detector. It’s built on White’s proven digital platform, with the features that give you more flexibility to find it all!"

The DFX is one detector I really miss. I needed to sell some things during this pandemic and the DFX had to go. After all of this is over, I plan to find another one. However, when I finish detecting an area with a DFX, I always go over the same are with a Deus and an Equinox............just to make sure that I haven't missed anything important.

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I never had any problems finding deeper targets with the DFX. The DFX has two frequencies if you want 3KHz & 15KHz. The Equinox 800 does not run 5 at the same time and the Etrac don't run 28 at once.

I no longer have the Equinox 800, I traded it for a different detector.

Thanks for the info guys, it don't matter to me if the equinox Is running all or just some frequencies at once,,I was only curious

Thanks all, I just wanted to know what the multi freq. is, I am going with my trusty simplex anyways, might upgrade to a full on Nox 800 with my clad.

Thanks,
metal detecto

Jmaclen you seem pretty bright and up on things and i think i remember you saying once you nugget hunt,so i always wondered why dedicated gold machines not counting pi's are single frequencies ?being that they have to handle the hottest ground,i get how well multifreqs handle conductive soils but on some ultra black sand beaches on the dry parts i've found multis can struggle as an example on my cz ihave to disc out iron and iknow other guys complain about excaliburs and equinoxes having similar problems

I've heard the secret sauce is in how the signal from the coil is filtered and analyzed. I believe Minelab has patents on that stuff too.

Metal detecto said:

Thanks all, I just wanted to know what the multi freq. is, I am going with my trusty simplex anyways, might upgrade to a full on Nox 800 with my clad.

Thanks,
metal detecto

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Multi freak works wonders in saltwater and in iron. Just saying.

The Lama
Jmaclen you seem pretty bright and up on things and i think i remember you saying once you nugget hunt,so i always wondered why dedicated gold machines not counting pi's are single frequencies ?being that they have to handle the hottest ground,i get how well multifreqs handle conductive soils but on some ultra black sand beaches on the dry parts i've found multis can struggle as an example on my cz ihave to disc out iron and iknow other guys complain about excaliburs and equinoxes having similar problems

Hi Lama,
Thanks for the compliments. I am actually pretty dumb but I work really hard at gold prospecting and metal detecting and have made every possible mistake in the process and will continue to make many more.

I will try to answer your questions.

In the past the only dedicated gold prospecting detectors that would pick up smaller gold nuggets and larger pickers were the really high frequency detectors like the Gold Bug II and the White’s GMT which operated above 60kHz. They worked great for really small, shallow gold under 1 gram in size even in pretty mineralized dirt. They would overload on the hot ground if cranked up too high but would still work well with really small coils and if the coil did not quite touch the ground. Some 15 to 19kHz detectors like the Tesoro Lobo Super Traq, MXT, Gold Bug, Minelab Eureka and X-Terra 705 and later the Garrett AT Gold did okay on small and a bit larger sized gold nuggets but like you noted, ground balancing all of these detectors on highly iron mineralized ground was next to impossible and they had to be run at only half sensitivity to keep the ground noise under control. Makro came out with the Gold Racer and XP added their high frequency coils for the Deus and Minelab released the Gold Monster 1000, but still none of these detectors could be run flat out without using some kind of iron range discrimination if they had it, and/or turning the sensitivity way down so any kind of depth was out the window. Minelab really captured the gold prospecting market with their SD, GP and GPX PI detectors which got tons of depth no matter how bad the soil’s iron mineralization was but they had little or no discrimination and would not hit most of the sub .25 gram or smaller nuggets.

So for the really small gold either you could run a single higher frequency VLF with a little iron discrimination and lose depth, run them in a threshold based all metal mode and probably listen to a ton of ground noise and hot rocks, or forget about the small stuff and just go for the bigger, deeper gold and use a PI and dig absolutely everything. The early simultaneous multi frequency VLF detectors by Minelab, Whites and Fisher like the CZs did great on salt mineralization but they too could not handle iron mineralization very well. I hear people and detector manufacturers say all the time that multi frequency detectors can handle mineralization really well. That is not true unless it is non-ferrous mineralization.

When the Equinox was being designed, two of the pre production field testers in Australia and the USA who are professional gold prospectors, quickly realized that the Minelab physicists had accidentally created a fantastic gold prospecting detector. Minelab for some reason has yet to even officially acknowledge this fact and if you go to their official model lineup, they have the Equinox in their “treasure” category. I guess they don’t want to compete with their own gold specific detectors like the Goldmonster 1000 and their small gold nugget PI, the SDC 2300. Many of us that actually gold prospect out here in the Western USA have sold our Goldmonster 1000s, SDC 2300s and most of our other gold prospecting specific single frequency VLFs. The Equinox will out detect them in iron and volcanic mineralization and will hit small and medium sized gold nuggets with very little interference from ground noise or hot rocks even down to 6 to 8” That is the same depth that most PIs will hit with 11” coils or smaller and the Equinox costs a third as much and weighs 3 lbs or more less. So, even though Minelab doesn’t want to advertise it, the Equinox 800 and even the Equinox 600 have revolutionized small gold nugget prospecting with their fast recovery speed, excellent target separation, single target ID number discrimination if it is needed, a steady threshold tone which boosts smaller and deeper target signals, noise cancelling, iron volume level controls, full range target IDs, pinpoint mode, the choice of single tone VCO or up to 50 tones, extreme sensitivity to sub .1 gram sized gold nuggets due to its use of up to 40 kHz in single or multi frequency modes, and most of all, a simultaneous multi frequency system that lets the user control the amount of iron that the Equinox will detect through it iron bias controls and single digit discrimination without losing depth capabilities and due to the way Multi IQ automatically limits the received iron signals caused by iron mineralization. I could go on, but I will just say that the Equinox when set up for even almost the worst soil conditions imaginable is easily the best VLF gold prospecting detector on the planet today. I can successfully detect with in on ground that has overloaded every other gold specific VLF that I have used on the same ground and I have used most of the ones I mentioned. Sorry this is so long, but you asked a great question.

Metal detecto said:

Okay, here is the deal with me. I'm a guy that wants to catch on to the new trend, and the trend right now is multi-frequency. I am a proud owner of my simplex, but my simplex seems a bit off compared to minelab's vanquish 440. So here are the questions.

1) What is the difference with multi frequency? It sounds cool, sure, but does it DO anything?

2) Do you feel anything different with the multi freq. detector, except the huge bragging right I guess?

3) Do you get more depth, balance, sensitivity, etc. with mult freq. detectors, if you have one?

Thanks,
Metal detecto

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It finds gold rings on the beach. Necklaces and bracelets too. It does that very well.

Thanks Jmaclen

Multi frequency is the only way to go on a salt beach. It also seems to help in trash for better TID. It helps with relic hunting, because it lets the machine be hot on low and high conductors at the same time. Other than that, it does nothing. Smile

I like multi frequency machines,and run minelabs alot. The one downfall on dirt hunting is iron falling. Etrac,any fbs and the equinox,and the vanquish all love to false on iron. Not just my results,been reading that for years from others too.