Jul 22, 2012, 03:41 AM
MD Frequencies - Which is better for what?
Looking beyond brand names, all the whistles and bells, and coils and accessories - each operate at a different frequency. I have seen the frequency range from 1 kHZ to 100 kHZ, the majority are specific such as 6.8 kHZ, and some I've seen have a even more specific frequency like 8.25 or even more so.
I've read the higher frequencies such as 50 kHz is great for gold, but not on coins. It seems the lower a frequency is, the more it detects ferrous metals, the higher frequencies are for non-ferrous metals.
The most common general purpose/coin detectors run somewhere in the 6 kHz to 15 kHz range I've found. I have to ask which frequency is best for what type of coin (clad, silver, or value (nickle, dime, etc.)) or relic?
A Garrett Ace 250 is 8.25 kHz and my Bounty Hunter Discovery 3300 is 6.7 kHz. What truly is the difference in the two frequencies - is one better for silver than the other, better for relics, or is there no real difference?
Many different brands seem to use specific frequencies not used by any other brands - is this simply to allow them to copyright/trademark/corner the market on that set frequency or what? For example White's Coinmaster Pro uses 8 kHz and Garrett Ace 250 is 8.25 kHz. Surely there is not much change in 0.25 kHz for one brand to use one frequency than the other.
Then the obvious question is why doesn't every brand/model use the same frequency for the same purpose? For example 7 kHz for coins, and 18 kHz for gold.
Beyond the set frequency in a MD, several MD's allow the user to switch the frequency. Oddly it isn't marketed to allow people to necessary find different items, it is often marketed as a option for electric interference problem solving or for competition events to prevent overlapping other MD signals. Surely jumping from a 7 kHz to 15 kHz for example would vastly alter the person's outcome while detecting.
Bottom line - are there frequencies better suited for finding clad coins, silver coins, jewelry, or gold nuggets? If so, anyone have any recommendations which frequency is better suited for which? Or is it simply nothing more than a brand technology or copyright/trademark/or such issue?
Obviously the technology/electronics backing up a frequency will make a world of difference between two similar MD's in depth capabilities, target information, and such - but there has to be some rhyme or reason for the differences in frequencies.
Thomas - BH Tracker IV, Mod HF Cen-Tech PP -MDing Since 6-4-12
-Number of Coins: 302 -Jewelry: 8 -Pull Tabs: 307 -Fun:100%
Jul 22, 2012 03:41 AM
Jul 22, 2012, 08:21 AM
Pre S.P.D. motion machines it was pretty simple. Garrett for instance produced the Master Hunter VLF/TR Deepseeker running at 5 kilohertz for super depth but more junk had to be dug. The Master Hunter VLF/TR Groundhog sold alongside ran at 15 kHz and offered improved discrimination but less depth.
many other brands did the same thing. Almost identical detectors but one high and one low frequency.
Minelab had and still have detectors like the Eureka Gold. 60, 20 and 6.4 kHz. Just flick a switch and switch into a different frequency and see the results. Compass had the Challenger X-100, this offered two different frequencies.
Where things have changed is that nowdays they can produce a detector that goes a long way towards giving the best of all worlds from one frequency. I've a feeling that Dave Johnson (MXT, Fisher Impulse, T2, F75 and a load of others) said on this forum that careful coil and circuit design gets round many of the old limitations. Then add that Blisstool claim their frequency of choice (8 or 8.5 ?) is only a carrier frequency. This suggests that something is then done to get round single frequency problems though how this works is anyones guess.
You ask about your Bounty Hunter 6.7 kHz frequency. I thnk the answer here is that the first motion detectors, the Bounty Hunter Red Baron's developed by George Payne ran at a similar frequency then he moved and worked for Whites and they ended up using 6.592 kHz as it was a good middle ground frequency. To avoid interference they needed a slightly different number than the competition but not to far off 6.5.
Your problem in selecting a "best" frequency is that some brands high frequency machines go deeper than others low frequency ones and still other brands low frequency models can be more sensitive to small items so its all the exact opposite of the "rules" we could once safely follow. An example that might further worry you is that the DFX (or a similar twin/triple frequency design) should in theory be used at its lowest frequency, in the Whites case, 2.98 kHz to find silver coins. Come to Europe though and our hammered silver responds better to the DFX's higher frequency of 14.91 kHz because most of it is so thin. Likewise with gold. Size, thickness affects the best frequency to be used. Detectors read conductivity not composition and size can make low conductors into high and vice versa. It also skews discrimination I.D. unfortunately.
The answer should be multifrequency but you don't have the frequencies claimed as the numbers they put on the advertising is arrived at by using harmonics and the use of harmonics brings in its own range of problems.
Jul 22, 2012, 08:58 AM
i "think" what UK Brian was trying to say is, these days operating frequency is not as important as it once was because of advances in electronics and circuitry. Here is just one example, the Tesoro Lobo Super Traq, and the Fisher Goldbugg II. Both of these machines have a reputaion as gold nugget hunters than can get a BB-sized piece of gold at 7" in depth. The Lobo works at 17.8kHz, the original Goldbug II worked at 71.1kHz (the new model operates at 19.2kHz).
The bottom line? There isn't one. This hobby relies on personal preference, just like fishing or golf. Everyone has their own opinion on what the "right" reel, club, or frequency is. My advice is to decide what you will be looking for 90-percent of the time, and in what conditions and soils, and then buy the machine that suits your needs best. I use 14.1kHz for coins and jewelry; 17.8kHz fow raw gold nuggets and thin gold chains, and pulse induction for everything else.
Operating frequency has become a sales tool, more marketing hype than a real concern in modern metal detectors. Just look at the XP Deus (4 kHz, 8 kHz, 12 kHz, 18 kHz). Seriously? My Lobo Super Traq can find anything the Deus can, for a lot less money..
This is my OPINION. Looking forward to others..
Jul 22, 2012, 11:36 AM
Brian and Terry are right,the newer detectors has gone ahead and things have changed considerably. The power is one worry and ID and tactile or knobs are another. After 42 yrs of detecting and asking the same question to myself I find that a 2 or 3 freq. detector which uses all 2 or 3 at the same time (DFX-V3) works better for me in junky spots for coins and rings. The older whites like 4900-5900-6000 had a hot rock setting and it was to my advantage to use it here in SW. missouri around stores and schools as they used COAL for heating and clinkers were are a problem. With the depth issue they were not real deep but got the job done. I'm not sporting any certain make of detectors just saying what I have found out while detecting,as I have used them ALL in the last few years.I find for some reason the Minelab (E-trac-705) are deeper in some areas than other makes. And after using a Blisstool for justa few minutes on my testing plots looks like its a killer. But I don't think the frequencies are a matter anymore as Dave Johnson made or help make most of the detectors no matter what make it is, whether its whites or tesoro or fisher etc. jmho.
Jul 22, 2012, 11:53 AM
The simple answer is that YES, for some detectors the frequency makes a big difference.
On some of the latest technology detectors, frequency isn't an issue.
Jul 22, 2012, 12:22 PM
Low kHz is good for conductive targets and higher kHz for less conductive targets, most fixed GB units are a low kHz mostly for the coin hunters.
Jul 22, 2012, 02:12 PM
Detecting fever comes and goes.
You see that many manufacturers lately use a 14-17Khz frequency for multi purpose MD That is a very good mid frequency, in my opinion.
Jul 23, 2012, 06:12 AM
A/C has missed the point on this but you do have to consider that not all detectors had enough thought put into their design so the old rules may still apply. The Lobo Supertrac being old school (even the follow up Wolftrax) have extreme sensitivity but the price paid is lack of depth which is where XP who had been manufacturing detectors for years saw a gap in the market and stepped in with the Goldmaxx, Power and Deus which combined sufficient sensitivity with more depth.
Jul 23, 2012, 08:47 AM
Just said what you said with less words, some have combination of frequencies with advanced ground tracking to be an all around detector some detectors don't , is according how much you want to spend,
Jul 24, 2012, 02:48 AM
What you said was the old and still in some cases correct wisdom (though size of target is also important) that has now been overtaken by better modern detector design in single frequency machines without having to resort to multifrequency and its range of drawbacks.
Jul 25, 2012, 01:49 AM
Another two bits. While there is some validity in thinking that lower frequencies 6 or so may be better for higher conductivity and higher 18 to 70 better for small gold, most general purpose detectors run from around 8 to 12 and serve quite well for coin shooting and general hunting. That's why most of the detectors are manufactured somewhere in that range. While I have no doubt that serous, controlled tests may show a slight difference on some metals for instance, I'm betting most of us could never tell the difference in our detecting unless we're prospecting or have a very specific need for a certain frequency range due to the desired target. For coin shooting and general detecting it's more profitable IMHO to grab one of the many good general purpose detectors out there and start swinging and finding regardless of minor differences in frequency.
Jul 27, 2012, 12:36 AM
Sorry for a late response, it's been a busy time lately. Thanks everyone for the well explained answers. The more I looked at the specs of detectors in the various catalogs I have got, the more I wondered what was going on with the different frequencies.
After reading the responses and doing some digging I found some more details. One of the most prolific MD designers, George Payne, has articles online about frequencies. Here is one quote, "...an operating frequency between 10 and 15 kHz does the best job on a wide variety of targets, from relics to gold nuggets." It seems the best specific frequency is in the middle at 12.5 kHz; however, specific frequencies for US coins is also given as..
US coins. A silver dollar = 800 Hz (below 1 kHz), Dime/Penny = 2.7 kHz, Nickel = 16.5 kHz, thin rings & fine gold = above 17 kHz, Gold coins & other coins = below 10 kHz.
With all that said George Payne goes on to say this...
Contrary to popular belief, there is no one best frequency for any specific metal or metals. Any VLF-style detector that is operating between 3 and 30 kHz will do a fine job for any type of hunting that is done. This frequency range gives good depth, target separation, and is not overly affected by ground mineralization.
The ability to pick up good targets and separate trash from goodies is more due to the design of the detector, type of coils used, and several other engineering points that are brought up during the R&D phase. Comparing feature points of the detector model to the type of hunting you are planning to use it for will help you more than just comparing frequencies.
Thomas - BH Tracker IV, Mod HF Cen-Tech PP -MDing Since 6-4-12
-Number of Coins: 302 -Jewelry: 8 -Pull Tabs: 307 -Fun:100%
Jul 27, 2012, 01:20 AM
George, though considered the father of motion detectors has dropped off the scene in the last few years whilst other designers have pressed ahead and thought more out of the box. Your quote from him in the box is more in line with current thinking though even that has to be considered in relation to what you are hunting for with small gold for instance still requiring a very high frequency. Another complication to detector choice regarding frequency is soil type/dryness. Some detectors start to fail as the soil gets drier and there performance becomes distinctly average. Some older detectors running down as low as 1 kHz seem to be much less unaffected so that could be a consideration if you live in a hot, dry area.
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