Help if you can please,... I have a 505 and a 705, and are somewhat familiar with them, and detecting in general. When I coinshoot in trashy areas, ie; older urban house yards, I find very few coins. I like to hunt in pattern 2,... 99 tones as long as I can stand it, then switch to 4 tones, with sens @ about 20-24. It seems to me that both units have a slow recovery time, (compared to some others I own).... I have been using the 3khz coil, hoping for silver. .. Is the disc. blanking hiding the coins, due to prevalent trash? I have a smaller coil on order, (6" 7.5 khz).... If I search in all metal, or one of the other less discriminating programs, I seem to have somewhat better luck, but have to put up with all the noise, and mentally decode all that is going on. I've tried turning the Sens down, and adjusting both the GB and threshold levels, etc..... I know that good depth and target ID are inherent in these units, but am I using the wrong detector for this kind of high trash detecting?, Should I get a DD coil? high freq? --- Sad to say, but I'm getting smoked by Fisher F2's --- Appreciate the advice, Thanks!
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Is Disc circuit hiding coins?
- Thread starter bigholes
- Start date
Mick in Dubbo
New member
Whenever you use disc on any machine, it starts to slow down the recovery speed. The more you use, the slower a detector recovers. The 3kHz coil due to it's frequency, will slow things down a bit more. The small DD coil is best for trashy areas.
Mick Evans.
Mick Evans.
And it could be one (or more) of several things. First of all, you are not using the wrong detector for that site. You are, however, probably using the wrong coil. Not frequency, necessarily. All three frquencies will pick up all metals. But size and design have a big impact on how well a coil will do in trashy sites. The 9-inch concentric coil at 3 kHz is a silver and copper coin killer in wide open areas. In areas with high levels of trash? Not so good. As I've posted many times, the small DD coil is your best option for separating trash from treasures with the X-Terra. If you calculate the amount of ground being analyzed by the 9-inch coil vs the 6-inch coil, you will find that when using the 9-inch concentric, the X-Terra has to process over 4 times as much "dirt" at any one time. This results in the odds of a 9-inch concentric coil having both trash and treasure under the coil simultaneously to be 4 times greater than when using the 6-inch. So from the point of view that seeing less soil at any one time is a good thing, a 6-inch coil will be better than the 9-inch. So the fact that you ordered a 6-inch concentric aat 7.5 kHz is OK. But to be honest, I'd opt for the 6-inch DD for target separation. I like the lower frequency better on the 6-inch concentric (7.5 kHz). But if I am using a small coil, target separation is my objective. Not frequency. As I said, all three freqs will pick up US coins. But DD coils separate targets much more readily than concentrics.
Detector speed? The X-Terra can produce 50,000 calculations per minute. I do not consider that a slow recovery time. I've had an F2 and found target separation to be much poorer than a properly equipped (and set up) X-Terra. And I consider target separation to be an excellent "measurement" of recovery time.
Sweep speed? The toughest thing I have to do when detecting is S L O W D O W N my sweep. I've come to the conslusion that if you are hunting in a trashy environment using a 6-inch coil, a sweep speed of no faster than 4 seconds per sweep is plenty fast. The main thing to remember is that the X-Terra is a motion dectector. Move the coil fast enough that targets will register. But go as slow as you can to isolate individual targets.
Frequency? The frequency of a VLF coil is a measurement of how many times the electromagnetic field is sent into the ground and received back, per second. Not how fast the processor works. A 3 kHz coil sends an electromagnetic field into the ground 3000 times per second. Changing the frequency of a VLF should not have an impact on how fast a processor works. Only on how responsive the X-Terra becomes to specific targets. As mentioned many times, higher conductors respond best to lower frequencies and lower conductors respond best to higher frequencies. According to George Payne, the father of today's metal detector technology, a silver dime responds best to a frequency of 2.7 kHz. Nickels and gold jewelry respond best around 16.5 kHz. All other US coins are most responsive to frequencies under 10 kHz. Gold nuggets are better served with a frequency of 20 kHz or faster. But again, I've found silver, copper and gold with each of the eight X-Terra coils.
Patterns? Yes, using discrimination can and will result in target blanking. Trash + treasure at the same time = Blanking. If you are using the factory notch rejection on Pattern 2, you are rejecting over half (15 out of 2
of the possible notch segments (phase shift) that any target might provide. Since you indicate you are hunting in a high trash area, you are "blanking out" the tone more than half of the time, when in Pattern 2. Slowing your sweep speed will help reduce the effects of target blanking. But using a smaller coil, preferably DD, will greatly improve your success.
Tones? I like running in the multiple tone mode. It allows me to hear what every target is, under the sweep of the coil. Granted, it can be confusing. But I'd rather hear the short burst of tone provided by a piece of trash as opposed to having the tone blanked out and chance missing something completely.
JMHO HH Randy
Detector speed? The X-Terra can produce 50,000 calculations per minute. I do not consider that a slow recovery time. I've had an F2 and found target separation to be much poorer than a properly equipped (and set up) X-Terra. And I consider target separation to be an excellent "measurement" of recovery time.
Sweep speed? The toughest thing I have to do when detecting is S L O W D O W N my sweep. I've come to the conslusion that if you are hunting in a trashy environment using a 6-inch coil, a sweep speed of no faster than 4 seconds per sweep is plenty fast. The main thing to remember is that the X-Terra is a motion dectector. Move the coil fast enough that targets will register. But go as slow as you can to isolate individual targets.
Frequency? The frequency of a VLF coil is a measurement of how many times the electromagnetic field is sent into the ground and received back, per second. Not how fast the processor works. A 3 kHz coil sends an electromagnetic field into the ground 3000 times per second. Changing the frequency of a VLF should not have an impact on how fast a processor works. Only on how responsive the X-Terra becomes to specific targets. As mentioned many times, higher conductors respond best to lower frequencies and lower conductors respond best to higher frequencies. According to George Payne, the father of today's metal detector technology, a silver dime responds best to a frequency of 2.7 kHz. Nickels and gold jewelry respond best around 16.5 kHz. All other US coins are most responsive to frequencies under 10 kHz. Gold nuggets are better served with a frequency of 20 kHz or faster. But again, I've found silver, copper and gold with each of the eight X-Terra coils.
Patterns? Yes, using discrimination can and will result in target blanking. Trash + treasure at the same time = Blanking. If you are using the factory notch rejection on Pattern 2, you are rejecting over half (15 out of 2
of the possible notch segments (phase shift) that any target might provide. Since you indicate you are hunting in a high trash area, you are "blanking out" the tone more than half of the time, when in Pattern 2. Slowing your sweep speed will help reduce the effects of target blanking. But using a smaller coil, preferably DD, will greatly improve your success. Tones? I like running in the multiple tone mode. It allows me to hear what every target is, under the sweep of the coil. Granted, it can be confusing. But I'd rather hear the short burst of tone provided by a piece of trash as opposed to having the tone blanked out and chance missing something completely.
JMHO HH Randy
Jackpine Savage
Active member
Your sensitivity settings look good (20-24), a nice slow sweep speed with good overlap helps a lot as well. The 9" LF coil has a nice sweet spot on tougher co-located targets but it is small so again use lots of overlap.
Tom
Tom
Thanks for all the good info. Sounds like some expert advice, I may look into the small DD coil, and spending more time in the all metal. Definitely lots of trash in the old front yards of these houses. By "old" I'm talking 75 - 100 years old, very small front yards, so both trash and any possible treasure are concentrated in small areas averaging approx 500 sq.ft. --- foil, aluminum slaw, pull tabs, nails, screwcaps, etc. I am just glad that buried broken glass is not conductive, or I would have to find a coil the size of a pencil eraser. Thanks again.......!
Have been having the same problem as you using my X-T 70 and its stock 9" coil in high trash areas. Something which helped me make more finds was besides cutting down on my sweep speed was also cutting my sweep distance in half. By cutting down on one's sweep distance, your able to concentrate on fewer signals making it easier to separate the good signals from the bad ones. Do intend to buy a 6"DD 18.75 khz. coil just as soon as my finances will allow it, not only for its good target separation abilities, but also for its ability to locate small gold.
SAGITTARIUS
New member
If you hunt virgin areas or want to find recently lost clad coins then the concentrics are OK, But if you are hunting for older deeper coins in heavily hunted parks I think the 10.5" DD MF is the best coil. What coil does Minelab put on the E-Tracs, Explorers, Safaris and the Sovereigns? DDs coil are the only ones. At 8 inches the concentrics cone shaped field is probably the size of a pencil eraser but the DDS blade shape is hot at this depth along its entire length which results in more area covered and better separation. If you want Minelab to make a better coil for the X-Terra, ask for the new Pro Coil. I used it on my Quattro and Safari and its a killer. Also do some testing of the settings yourself. With my 705 I can get a good clear signal on a long buried silver dime at 7" even with the threshold set at 20. All Metal is good but try a low level of discrimination. Switch back and forth over targets. You do not always lose depth with discrimination. With a setting of low iron mask such as pattern 4 on the 705 and a level of threshold you can hear well, listen to the nulls. This tell you when you are over iron and if the threshold just dips a little but does not null it may be a very deep coin. Rick(ND) in the Sovereign Forum has a great post on the technique. Read the other forums, especially the Explorer Forum. These guys find the silver, Read the posts of Bryce-IL, one of the best and you will notice he uses low level iron mask(disc). Testing is the best way to find out what works in your area. Coins below recently found from a heavily used and much hunted small park. Back left---zinc pennies, Back right--- clad dimes & quarters, Front left--- silver dimes, Front right--- nickels & wheat pennies, No silver and only one wheat penny found with concentric coil. I found my first silver half there in 1972. I have sold my Quattro, Safari, Elite, and GT. I like X-Terra and think of it as a baby Explorer, but faster and lighter. If the X-Terra had a Pro Coil which is also very light, I bet sales of E-Tracs, Explorers and Safaris would drop. JMHO Don
I agree that it can be very beneficial to read the other fourms, study other's methods and implement those methods that work well in our sites. But we have to recognize that there is a big difference between those FBS and BBS detectors you mentioned and the VLF X-Terra. The FBS units produce 28 simultaneous frequencies and the BBS produces 17 simultaneous frequencies. Witht the X-Terra, we have the choice (by coil selection) of using any one of the three frequencies one at a time. The FBS detectors analyze target characteristics much differently than the "one at a time" freq X-Terra in that an Etrac or an Explorer will analyze both the conductive and non-conductive (ferrous) properties of each target. As a VLF detector, the X-Terra analyzes the conductive properties. The FBS and BBS units also have the ability to implement iron mask and discriminating simultaneously. In the X-Terra, iron mask can only be implemented in the non-discrimination Prospecting mode. I've used both the Explorers and Sovereigns quite a bit over the years and have implemented some of those techniques with my X-Terra. I agree with your comments suggesting we can "learn from others". But again, we need to remember that the inherit functionality of those other detectors may be different than the detector we are using. As such, the methods used to maximize their performance may not be conducive to those best suited to the X-Terra.
I agree that there are old coins still hiding out there because they are deeper than many detectors are capable of detecting. However, in parks and well hunted areas, I honestly believe there are more old coins still hiding due to target masking opposed to extreme depth. I believe that the separation characteristics of a DD coil are superior to those of a concentric, due to the coil design. (e.g. blade) I disagree, however, that a DD coil will hunt as deep as a similarly sized concentric for everyone. In highly mineralized soil, no doubt it will. But in moderately mineralized soil, it does not. I did some testing myself, using both a concentric and a DD. Since Minelab does not make a 9-inch DD or a 10.5 inch concentric, the only two I can compare are the two 6-inch coils. And depending on the target, one frequency may react differently than the other. However, while hunting US coins with these two coils in my moderate soil, the DD does not hunt deeper than the concentric. I primarily use the DD as I prefer it's separation characteristics. And, separation is the reason I use a small coil.
With that said, here are some diagrams (and explanations) of both a concentric and DD coil. These were "borrowed" from the Garrett website. But are representative of other brands.
Note that the detection pattern of the concentric does not come to a point the size of a pencil eraser. It is a bit more cone shaped than the DD. But the DD pattern is also somewhat "bowl shaped" as it nears the maximum depth. The "blade" does not go straight down "all the way" as some might believe.
[attachment 132740 concentriccoilpattern.jpg]
Concentric (from Garrett)
The advantage of this configuration is that both the TX and RX coils are wound as large as possible within a given searchcoil diameter. This provides the largest possible detection field and greatest detection depth, making the concentric coil potentially the most sensitive configuration available. In addition, concentric coils also provide the most symmetrical detection field, allowing ease in pinpointing and consistency in target identification. For these reasons, they are the most commonly used searchcoil and will provide the best overall performance in most environments. Unfortunately, this configuration is the most susceptible to interference from ground minerals, which results in substantial loss of performance when used over heavily mineralized ground.
[attachment 132741 DDsearchcoilpattern.jpg]
Double-D (from Garrett)
The Double-D configuration is designed to significantly reduce ground interference and, thereby, recover the performance lost by a concentric coil over mineralized soil. With the Double-D, it is the arrangement of the TX and RX coils that produce a canceling effect of ground signals. This configuration is called DD because both TX and RX coils are in the shape of a
I agree that there are old coins still hiding out there because they are deeper than many detectors are capable of detecting. However, in parks and well hunted areas, I honestly believe there are more old coins still hiding due to target masking opposed to extreme depth. I believe that the separation characteristics of a DD coil are superior to those of a concentric, due to the coil design. (e.g. blade) I disagree, however, that a DD coil will hunt as deep as a similarly sized concentric for everyone. In highly mineralized soil, no doubt it will. But in moderately mineralized soil, it does not. I did some testing myself, using both a concentric and a DD. Since Minelab does not make a 9-inch DD or a 10.5 inch concentric, the only two I can compare are the two 6-inch coils. And depending on the target, one frequency may react differently than the other. However, while hunting US coins with these two coils in my moderate soil, the DD does not hunt deeper than the concentric. I primarily use the DD as I prefer it's separation characteristics. And, separation is the reason I use a small coil.
With that said, here are some diagrams (and explanations) of both a concentric and DD coil. These were "borrowed" from the Garrett website. But are representative of other brands.
Note that the detection pattern of the concentric does not come to a point the size of a pencil eraser. It is a bit more cone shaped than the DD. But the DD pattern is also somewhat "bowl shaped" as it nears the maximum depth. The "blade" does not go straight down "all the way" as some might believe.
[attachment 132740 concentriccoilpattern.jpg]
Concentric (from Garrett)
The advantage of this configuration is that both the TX and RX coils are wound as large as possible within a given searchcoil diameter. This provides the largest possible detection field and greatest detection depth, making the concentric coil potentially the most sensitive configuration available. In addition, concentric coils also provide the most symmetrical detection field, allowing ease in pinpointing and consistency in target identification. For these reasons, they are the most commonly used searchcoil and will provide the best overall performance in most environments. Unfortunately, this configuration is the most susceptible to interference from ground minerals, which results in substantial loss of performance when used over heavily mineralized ground.
[attachment 132741 DDsearchcoilpattern.jpg]
Double-D (from Garrett)
The Double-D configuration is designed to significantly reduce ground interference and, thereby, recover the performance lost by a concentric coil over mineralized soil. With the Double-D, it is the arrangement of the TX and RX coils that produce a canceling effect of ground signals. This configuration is called DD because both TX and RX coils are in the shape of a
Thanks again for all the info. I really didn't understand why the DD coils were so popular, now I do. I was under the impression that the search field was larger than a concentric coil, the illustrations really help. Definitely will be getting the 6"DD. ---- Like Abe Lincoln said, " I don't think much of a man who doesn't know more today than he did yesterday" ---------- Today Abe would like me. Thanks!
SAGITTARIUS
New member
Coil Configuration statement and images from Minelab website,
.
"A Concentric coil has an inner circle and an outer circle wire winding. Its search pattern is cone shaped and can be useful for accurately pinpointing the target. Concentric coils tend to be noisier in highly mineralised ground and require more over lap of sweep for thorough ground coverage."
"Double-D wound coils are the preferred coils for most detecting. They give a blade or chisel shaped signal that covers the ground more uniformly and once an operator becomes accustomed to the signal, pinpointing can be very accurate. Double-D coils are also preferred for their superior ground balancing ability."
The Minelab images of the two coils differs from the Garrett images. I think the Minelab statements about the two coil speak for themselves. All of my tests were on a buried silver dime and a wheat penny at 7". Tests of the concentric 3kHz & 7.5kHz showed no depth advantage for either. The 10.5 DD 7.5kHz was slightly deeper probably due to the larger coil size. Ground coverage at this depth was much greater for the 10.5' DD MF. False signals off iron can be dealt with in following way. This works well on the Sovereign, Safari and X-Terra with a DD coil. With 3 or 4 iron segments discrimination if good sound and meter signal from two directions, also listen for nulls near target. Then do the Sovereign wiggle and pinpoint off the toe of the coil. Mark the spot and rotate 90 degrees around the target and do the wiggle again. If the spot changes and or nulls are heard near target, most likely iron. I believe that the 10.5" DD MF coil is a good coil for the X-Terra
The best discussion I have seen of FBS and BBS detectors is by Bruce Candy, co-founder of Minelab titled "Metal Detector Basics and Theory", also found on the Minelab website. He states that "Multi-frequency transmitting and receiving metal detectors have a significant advantage in time constant discrimination, and to some extent ferrous discrimination capability, over the most common form of detector, the VLF detector." I have observed this technology difference when comparing target identification between a Safari or Sovereign and a Advantage or X-Terra. Minelab makes DD coils for all these detectors. And I think that many of the other detector techniques will work with the X-Terra.
.
.
"A Concentric coil has an inner circle and an outer circle wire winding. Its search pattern is cone shaped and can be useful for accurately pinpointing the target. Concentric coils tend to be noisier in highly mineralised ground and require more over lap of sweep for thorough ground coverage."
"Double-D wound coils are the preferred coils for most detecting. They give a blade or chisel shaped signal that covers the ground more uniformly and once an operator becomes accustomed to the signal, pinpointing can be very accurate. Double-D coils are also preferred for their superior ground balancing ability."
The Minelab images of the two coils differs from the Garrett images. I think the Minelab statements about the two coil speak for themselves. All of my tests were on a buried silver dime and a wheat penny at 7". Tests of the concentric 3kHz & 7.5kHz showed no depth advantage for either. The 10.5 DD 7.5kHz was slightly deeper probably due to the larger coil size. Ground coverage at this depth was much greater for the 10.5' DD MF. False signals off iron can be dealt with in following way. This works well on the Sovereign, Safari and X-Terra with a DD coil. With 3 or 4 iron segments discrimination if good sound and meter signal from two directions, also listen for nulls near target. Then do the Sovereign wiggle and pinpoint off the toe of the coil. Mark the spot and rotate 90 degrees around the target and do the wiggle again. If the spot changes and or nulls are heard near target, most likely iron. I believe that the 10.5" DD MF coil is a good coil for the X-Terra
The best discussion I have seen of FBS and BBS detectors is by Bruce Candy, co-founder of Minelab titled "Metal Detector Basics and Theory", also found on the Minelab website. He states that "Multi-frequency transmitting and receiving metal detectors have a significant advantage in time constant discrimination, and to some extent ferrous discrimination capability, over the most common form of detector, the VLF detector." I have observed this technology difference when comparing target identification between a Safari or Sovereign and a Advantage or X-Terra. Minelab makes DD coils for all these detectors. And I think that many of the other detector techniques will work with the X-Terra.
.
Try running in the all metal mode with 2 tones. Then when you hear the high tone try to zero in on it. Personally I believe the Xterra's love being run this way. I found a lot more stuff at the same places running this way. It's just something to try. Yes, the 6 inch DD coil is a nice one.
NiagracountyNY
New member
There are some good vids of the 305 being used in all metal on youtube..the recovery between targets is really fast .Neswiper does a recovery test in one of them..Good Luck
Since you're new to this forum a week, may I suggest you read through the FAQFAQ section at the top of the page, as well as some of the previous posts? If you do, you'll see that we've discussed the topics of your "analysis" many times in the past. Depth of the 9-inch coils being pretty much equal. Time constant discrimination. Sovereign Wiggle. etc, etc etc. In fact, the first link in our FAQFAQ is to the article by Bruce Candy.
As to the Minelab coil drawings you provided, comparing a concentric coil to a DD...... Artitst's conception! I've analyzed a lot of coils in my 37+ years of metal detecting and I can honestly say I've not seen a concentric coil that dropped down to a nipple end. How did he get those eddy currents to make a 180? Conical shaped and rounded corners? Sure. But certainly not down to a sagging point. And to see those eddy currents going down and up, then over, then down and up again, all while under the DD coil, goes against the laws of physics. I realize that you and I will probably not agree on what the detection field of the X-Terra coil looks like. But I spent several hours "sweeping coins and drawing lines" in an effort to create what I consider to be an accurate portrayal of the 6-inch concentric coil's field of detection.
[attachment 132890 concentricdetectionpattern.JPG]
JMHO
And in closing... here are exerpts from an article written by NasaTom that I believe fit into this discussion.
Iron Masking by Thomas J. Dankowski
When you discriminate iron with any detector (Minelab calls it "iron mask" you have achieved nearly nothing. (Simply, there will be no audio response reported in the headphones). The detectors electromagnetic signal is still disrupted by the iron. It does not matter if you transmit one frequency, two frequencies or 17 frequencies into the ground - electromagnetic energy is electromagnetic energy, and iron will always disrupt this energy. This is not a fault of any detector, only an indication of where technology is at today. There is not a detector on the market today that can "see through" iron. And I think I could safely say that less than 20% of the coins in the schoolyards and parks have been recovered because of masking, silent masking and deep depths.
If a 8" coil can 'see' a one gallon volume of dirt and the 11" coil (not 10.5" can 'see' 7 gallons of dirt at any given time, it is a fact that you are 7 times more likely to 'mask' a object with the larger coil, especially in trashy areas. It is so easy to get into trouble with the larger coil AND NEVER KNOW IT!
A true 'Double D' coil is a leap in technology and can separate targets better than the standard concentric coils; however, there are drawbacks. An 8" Double D coil will generate a signal (hypothetically) 8" long by 1" wide giving incredible adjacent target separation. As long as there is about an inch of distance between objects laterally, a true Double D coil will signal each target individually. Minelabs discontinued "CoinSearch" coil is a perfect example of a true Double D coil. The drawback is a decrease in overall detection depth. It is physically difficult to condense the electromagnetic energy into a narrow knife-like beam (directional field intensity) and achieve the same depth that a concentric coil attains. Still, no coil design can see through one metal object and reach the deeper target, then signal only on the deeper target. Why would the detector want to report the deeper, weaker target? When electromagnetic energy is used to locate metallic objects, masking is characteristically, an inherent flaw. This is where we stand today with our technological limitations.
As to the Minelab coil drawings you provided, comparing a concentric coil to a DD...... Artitst's conception! I've analyzed a lot of coils in my 37+ years of metal detecting and I can honestly say I've not seen a concentric coil that dropped down to a nipple end. How did he get those eddy currents to make a 180? Conical shaped and rounded corners? Sure. But certainly not down to a sagging point. And to see those eddy currents going down and up, then over, then down and up again, all while under the DD coil, goes against the laws of physics. I realize that you and I will probably not agree on what the detection field of the X-Terra coil looks like. But I spent several hours "sweeping coins and drawing lines" in an effort to create what I consider to be an accurate portrayal of the 6-inch concentric coil's field of detection.
[attachment 132890 concentricdetectionpattern.JPG]
JMHO
And in closing... here are exerpts from an article written by NasaTom that I believe fit into this discussion.
Iron Masking by Thomas J. Dankowski
When you discriminate iron with any detector (Minelab calls it "iron mask" you have achieved nearly nothing. (Simply, there will be no audio response reported in the headphones). The detectors electromagnetic signal is still disrupted by the iron. It does not matter if you transmit one frequency, two frequencies or 17 frequencies into the ground - electromagnetic energy is electromagnetic energy, and iron will always disrupt this energy. This is not a fault of any detector, only an indication of where technology is at today. There is not a detector on the market today that can "see through" iron. And I think I could safely say that less than 20% of the coins in the schoolyards and parks have been recovered because of masking, silent masking and deep depths.
If a 8" coil can 'see' a one gallon volume of dirt and the 11" coil (not 10.5" can 'see' 7 gallons of dirt at any given time, it is a fact that you are 7 times more likely to 'mask' a object with the larger coil, especially in trashy areas. It is so easy to get into trouble with the larger coil AND NEVER KNOW IT!
A true 'Double D' coil is a leap in technology and can separate targets better than the standard concentric coils; however, there are drawbacks. An 8" Double D coil will generate a signal (hypothetically) 8" long by 1" wide giving incredible adjacent target separation. As long as there is about an inch of distance between objects laterally, a true Double D coil will signal each target individually. Minelabs discontinued "CoinSearch" coil is a perfect example of a true Double D coil. The drawback is a decrease in overall detection depth. It is physically difficult to condense the electromagnetic energy into a narrow knife-like beam (directional field intensity) and achieve the same depth that a concentric coil attains. Still, no coil design can see through one metal object and reach the deeper target, then signal only on the deeper target. Why would the detector want to report the deeper, weaker target? When electromagnetic energy is used to locate metallic objects, masking is characteristically, an inherent flaw. This is where we stand today with our technological limitations.
SAGITTARIUS
New member
Quote Digger "Since you're new to this forum a week, may I suggest you read through the FAQFAQ section at the top of the page, as well as some of the previous posts? If you do, you'll see that we've discussed the topics of your "analysis" many times in the past. Depth of the 9-inch coils being pretty much equal. Time constant discrimination. Sovereign Wiggle. etc, etc etc. In fact, the first link in our FAQFAQ is to the article by Bruce Candy"
Does being new to this forum mean I must read all of your 2000+ posts/opinions before posting results of my own testing/opinions of coil, settings, etc? Could a newcomer maybe offer some insight that might help others? Open discussions promote progress. I have read many of your posts on your preference for the Concentric 3kHz coil and have seen impressive finds posted with this coil. However, I have read some other posts on this forum where members prefer the 10.5" DD coil. Lets agree to disagree on coils, settings, etc and move forward. If I have offended you I apologize. I appreciate your many years of contributions to the metal detecting community. Don
Does being new to this forum mean I must read all of your 2000+ posts/opinions before posting results of my own testing/opinions of coil, settings, etc? Could a newcomer maybe offer some insight that might help others? Open discussions promote progress. I have read many of your posts on your preference for the Concentric 3kHz coil and have seen impressive finds posted with this coil. However, I have read some other posts on this forum where members prefer the 10.5" DD coil. Lets agree to disagree on coils, settings, etc and move forward. If I have offended you I apologize. I appreciate your many years of contributions to the metal detecting community. Don
As to reading all the posts.......you don't have to read any of them, or the FAQFAQ section, if you don't want to.... It is not my intention to infer that my opinions are better than yours or anyone elses. Positive discussion is a good thing. But positive discussion only occurs when you support your opinions with facts pertinent to the situation. And the fact is that there is no "one size fits all" in the world of detecting. Whether it be the choice of coils or the detector itself, consideration should be given to the site properties and the targets you are hunting. If a DD coil works better for you, great. But since you haven't mentioned what levels you are able to properly set the ground phase or the types of targets you seek, making the blanket statement that DD coils hunt deeper than concentric coils is misleading to those who may be unfamiliar with coil design and the impact of soil conditions. HH Randy
SAGITTARIUS
New member
After reading the reports of good results with the 3kHz concentric coil I ordered a new one from Richard@Backwoods to test against my 10.5" DD coil. When properly noise cancelling in auto and ground balancing in auto the 3kHz coil balanced at 17. Tested the coil on the buried coins. Same procedure used within minutes with the DD coil at same metal free spot and the balance number was 43. Also tested on the buried coins. Repeated procedure several times with different threshold and sensitivity settings, in all metal and Pattern 4 disc and obtained similar results. The DD coil multiple tones signal was better at the same sensitivity and the coil would detect the silver dime at a lower sensitivity. And as I said in my earlier post the DD coil was slightly deeper probably due to the larger coil size. As one can see I couldn't use the ground balance number 28 as a reference to determine which coil to use. I too do not want those who may be unfamiliar with coil design to be mislead. This is the reason for my original post.
So let me repeat the statement verbatim from Minelab USA website on the DD coils. "Double-D wound coils are the preferred coils for most detecting. They give a blade or chisel shaped signal that covers the ground more uniformly and once an operator becomes accustomed to the signal, pinpointing can be very accurate. Double-D coils are also preferred for their superior ground balancing ability."
The statement is supported by the www.detectortest.info/ TEST 1. and the TEST 2. INGO. Don
So let me repeat the statement verbatim from Minelab USA website on the DD coils. "Double-D wound coils are the preferred coils for most detecting. They give a blade or chisel shaped signal that covers the ground more uniformly and once an operator becomes accustomed to the signal, pinpointing can be very accurate. Double-D coils are also preferred for their superior ground balancing ability."
The statement is supported by the www.detectortest.info/ TEST 1. and the TEST 2. INGO. Don
Your ground phase setting with the concentric coil was a 17. It is no surprise that the ground phase reading with the DD was 43 as the main purpose of the DD coil design is to neutralize the effects of mineralization. But back to the 17 you got with the concentric......Again, I believe that if you are able to properly select a ground phase reading of 28 or higher, the concentric coil will perform well. If however, your ground phase reading is lower than 28, you'd be better served with a DD coil.
And to address the questions surrounding the X-Terra coils, this comes from the X-705 operator's manual. Afterall, this is the X-Terra forum.
[attachment 132926 coilsofthe705.jpg]
The X-Terra 705 is capable of operating at three different transmission frequencies set by VFLEX compatible coils.
Concentric Standard (7.5kHz)
This frequency is most suitable for general detecting for most ground conditions. These coils have a label with the letter M on them.
Concentric Low (3kHz)
This frequency is more suited to searching for larger, deeper targets, higher-conductivity coins (eg. most US coins) and has improved ferrous rejection. These coils have a label with the letter L on them.
Concentric High (18.75kHz)
This frequency is more suited to searching for smaller shallow targets, gold nuggets and low conductivity targets (e.g. hammered coins, fine jewellery). These coils have a label with the letter H on them.
Double D (7.5kHz and 18.75kHz)
The Double D coil allows the detector to ground balance more effectively. It is the ideal coil for detecting gold nuggets in heavily mineralised areas or beaches with black sand concentrates.
And to address the questions surrounding the X-Terra coils, this comes from the X-705 operator's manual. Afterall, this is the X-Terra forum.
[attachment 132926 coilsofthe705.jpg]
The X-Terra 705 is capable of operating at three different transmission frequencies set by VFLEX compatible coils.
Concentric Standard (7.5kHz)
This frequency is most suitable for general detecting for most ground conditions. These coils have a label with the letter M on them.
Concentric Low (3kHz)
This frequency is more suited to searching for larger, deeper targets, higher-conductivity coins (eg. most US coins) and has improved ferrous rejection. These coils have a label with the letter L on them.
Concentric High (18.75kHz)
This frequency is more suited to searching for smaller shallow targets, gold nuggets and low conductivity targets (e.g. hammered coins, fine jewellery). These coils have a label with the letter H on them.
Double D (7.5kHz and 18.75kHz)
The Double D coil allows the detector to ground balance more effectively. It is the ideal coil for detecting gold nuggets in heavily mineralised areas or beaches with black sand concentrates.
Jackpine Savage
Active member
at your sites. It would go a long way in making sense as to why your coil performance results are not in line.
Without knowing the mineralization (Fe) reading the ground balance numbers mean nothing.
Tom
Without knowing the mineralization (Fe) reading the ground balance numbers mean nothing.
Tom
SAGITTARIUS
New member
Good suggestion Jackpine Savage, mine with original coil is 00 89 72 = mild soil and thanks to BarnacleBill for providing that hidden feature of the X-Terras.
My "original post" was to try to answer one of bigholes questions "Should I get a DD coil?" and I did not say the 10.5" was deeper but touted its advantage on deep coins in ground coverage due to its blade-like center hot zone over the cone shaped concentric. In my own amateur tests on a 7" buried silver dime when sweeping from right to left and back and moving the coil forward over the dime, the 3kHz concentric's signal covered about 4" and the 10.5" DD's signal covered about 8". This only occurs on a deeply buried coins. Anyone can test this themselves on a buried coin. Many facts have been provided in this discussion and I hope it has been beneficial. I know it has for me. Thanks to all who have read this topic and happy hunting. Don
My "original post" was to try to answer one of bigholes questions "Should I get a DD coil?" and I did not say the 10.5" was deeper but touted its advantage on deep coins in ground coverage due to its blade-like center hot zone over the cone shaped concentric. In my own amateur tests on a 7" buried silver dime when sweeping from right to left and back and moving the coil forward over the dime, the 3kHz concentric's signal covered about 4" and the 10.5" DD's signal covered about 8". This only occurs on a deeply buried coins. Anyone can test this themselves on a buried coin. Many facts have been provided in this discussion and I hope it has been beneficial. I know it has for me. Thanks to all who have read this topic and happy hunting. Don