This is for Randy or anyone else who would like to express their opinions. I am not a technical type of detectorist, but more of a trial and error person. I have had several Exterras over the years and I have found them to be great performers. A couple of years back I had an Exterra 70 and I bought the high freq. 6 inch coil for it. When I took it to the trashiest place I know of where a 100 year old coin might be hiding, I found it to ID tabs and bottlecaps exactly like a coin. I would check these targets from all directions and the tone and number would lock hard, seeming like a coin. I finally gave up on that coil. Since, I have read many posts suggesting that any dd high frequency coil will many times be fooled by modern trash. Fast forward to the last week. Last fall I bought a 505 with the intentions of getting the 6 inch medium freq. coil and leaving it on the Exterra for my trash detector. I like the Exterras because you can swing them fast or slow and slow is my method in trash. Just before Christmas I bought the small concentric coil used from one of the fine forum members and with it being winter here in NE Ohio, I figured it would be three or four months before I could use it. Last Friday we got some great weather and I found some unfrozen ground and off I went with the 505 fitted with the small concentric coil. It performed great and I dug only a couple of tabs and I knew they were not coins before I dug. The numbers and more importantly, the tones, were not high tones. The were medium tones. That day I found 30 coins with 6 being wheat pennies. The depth of the wheaties was impressive. All were in the 6 inch deep range. Yesterday I went to a place where I almost always find a silver coin or two. It was cold for me, about 34 degrees and I only lasted an hour and half. I only found 15 coins, but one was a wheat penny that was 7 to 8 inches deep. More impressive was I only dug one tab and I only dug it to confirm the boucning signal. This place is loaded with old, rusty nails and while the 505 would occasionally high tone on them, it was more of a screech. Also, many times these nails would change tones when checked from different angles. I know many really like the small dd coil with it's knife like separation and I would like to hear if they have tried both coils. For the technical people, what are the relationships between dd vs concentric and low frequency vs high frequency when hunting for coins. For me, I think the medium freq. concentric 6 inch coil is more accurate on coins. R.L.
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Small DD vsSmall Concentric Coils
- Thread starter RLOH
- Start date
I agree with what you've said.......can slaw, tabs, occassional rusty nails and some types of foil will fool you into thinking they are coins. Particularly when using a HF coil. The way I see it...... DD coils separate targets better than concentrics. If your ground is not highly mineralized, a concentric coil will hunt deeper than a comparibly sized DD coil. Higher frequency coils are better able to detect lower conductive targets.(gold, foil, alumunum etc) HF coils are better capable of detecting small targets. Lower frequency coils are better able to detect higher conductive targets. (silver, copper, brass etc) And lower frequency coils are better at detecting larger targets. Now, with all those things considered, in a PERFECT world I would like to be able to buy a small DD coil at 3 kHz for my X-TERRAS. The DD design would provide the separation I desire for trashy areas. And the low frequency would greatly reduce the amount of modern trash I had to dig. But as we all know, it isn't a perfect world and there is not a small 3 kHz DD coil currently available for the X-TERRA. So for now, when I hunt those nasty trashy areas, I'd rather dig the occassional pieces of trash opposed to missing an old coin that dozens of others have walked over, due to it being masked by adjacent trash. So with all things considered, based on the coils that are currently available, I chose the small DD for those trashy areas. I don't necessarily like the higher frequency, for the reasons you mentioned. But the DD design gives me much better target separation, which helps to make up for my desire to require a low frequency. By using multiple tones and minimal discrimination, I can hear all the targets and let my ears sort out the majority of the trash. Don't misinterpret me as I do dig my share of trash. But to me it is worth the effort, knowing that is still some good stuff out there, due to target masking. If I don't feel target masking is a problem, I'll switch to either the 6-inch concentric at 7.5 kHz or go to the 9-inch concentric at 3 khz. JMHO HH Randy
Yes Petr, I have read that also, Minelab says the 6" MF CC is the best coil for target separation. I have also said that that must be a mistake-error on Minelabs part is the conclusion I have come to because the 6" HF DD is best for that.
Also one thing that was not mentioned here was the Concentric Coils(CC) have a better TID(Randy calls it more accurate) than DD coils. For me especially at the top end of the scale towards 46 on the 70/705 to better differentiate trash from coins a CC is better. I want as much precision as possible anytime but especially when I get in the copper-silver range. The DD's seem to push up the TID numbers higher leaving less room for accurate IDing.
For the X-Terra's, Randy as well as a lot of the rest of us want a 6" LF DD to be made. I also want a 4" LF CC to be made for separation in very tight trashy areas.
Also one thing that was not mentioned here was the Concentric Coils(CC) have a better TID(Randy calls it more accurate) than DD coils. For me especially at the top end of the scale towards 46 on the 70/705 to better differentiate trash from coins a CC is better. I want as much precision as possible anytime but especially when I get in the copper-silver range. The DD's seem to push up the TID numbers higher leaving less room for accurate IDing.
For the X-Terra's, Randy as well as a lot of the rest of us want a 6" LF DD to be made. I also want a 4" LF CC to be made for separation in very tight trashy areas.
I have never used a 6" concentric coil, but then again I've never felt the slightest need to have one either. My 6" DD HF coil almost never has a problem distinguishing between trash and coins. To say that can slaw, pull tabs and foil have read the same as coins when using that coil is totally shocking to me. Honest! My 10.5" DD MF coil does sometimes get fooled on that sort of trash, but even then there are ways to tell the difference. The 6" DD HF coil almost never gets fooled because of how perfectly it ID's coins when compared to the ID of trash. It all must come down to two things: the type of ground we hunt in and how our XT was setup at the factory. I know of someone else from my half of PA who also has better results using the high frequency coils as compared to using lower freq. coils, so a lot of it must have to do with our type of ground...
Maybe I should clarify my statement a little. What I am saying is that my 6" HF coil almost never mistakes trash for a coin, but am not saying that it is the world's best at picking out coins from in among trash. It's pretty durn good at it, but not necessarily the best at it. The 6" concentric could be better at that (target unmasking) than the 6" DD HF coil is..
Mtnmn
"Almost never" sounds pretty good to me. I am interested in getting the 6"HF coil.
How does it compare to the 9" MF stock coil in trash vs. silver/clad coin and small gold target ID info?
My ground balance setting is usually between 40 and 60 on the X-70.
Red Ga. clay.
Good Hunting
Denny
"Almost never" sounds pretty good to me. I am interested in getting the 6"HF coil.
How does it compare to the 9" MF stock coil in trash vs. silver/clad coin and small gold target ID info?
My ground balance setting is usually between 40 and 60 on the X-70.
Red Ga. clay.
Good Hunting
Denny
Here is two actual case historys using the 6" DD HF coil. At a sportsman's club that was extremely trashy from so much use and at which I had supposedly cleaned out using the stock coil. I later went back with the 6" DD HF coil and actually matched the finds I had made previously using the stock coil covering the same ground. By the same token I took the 6" DD coil over ground that I had covered several times with the stock coil which had very little trash in it and the 6" DD found very few additional coins. In my case the 6" DD HF coil seems much better at picking coins out from among modern day trash (foil, tabs and can slaw) than it does at a sites heavily littered with very old iron. I don't know if this is the norm or not...
I currently have three coils, the stock coil, the 10.5" DD MF coil for covering larger areas with more depth, along with the 6" DD HF coil for high trash areas. I'm unimpressed with the depth that the 10.5" DD MF coil has in my kind of ground which may have a high salinity content as there are multiple salt licks throughout the area. Intend to order a 10.5" DD HF coil this coming week to see if it will gain me more depth over that of the 10.5" MF coil. If a coil proves over time to do a better job than the 6" DD HF coil of unmasking coins in areas with large amts. of old iron trash, may eventually get it too. What works for my area, may not work for the red clays of Georgia. Many guys swear by their MF and LF coils. Always liked the stock coil, but it too never seemed to have good depth in my ground (5 1/2" max.). If this new HF coil gets me down to 7 1/2" (in grd.) this summer that will be deep enough for this year....